Printing Industry generates a wide range of products which require in every step of our everyday life. Starting from newspapers, magazines, books, post cards to memo pads and business order forms each are the products of printing industry. Printing is a process for reproducing text and image, typically with ink on paper using a printing press. There are various types of printing process for example offset printing, modern printing, gravure printing, flexographic printing etc. Offset printing is a widely used printing technique where the inked image is transferred from a plate to a rubber blanket, then to the printing surface. When used in combination with the lithographic process, the offset technique employs a flat image carrier on which the image to be printed obtains ink from ink rollers, while the non printing area attracts a film of water, keeping the non printing areas ink free. Gravure printing is a printing technique, where the image to be printed is made up of small depressions in the surface of the printing plate. It is divided into three broad product areas; packaging printing, publication printing and speciality printing. Printing technology is often carried out as a large scale industrial process, and is an essential part of publishing and transaction printing. This is the age of hi fi, jets and computers. Rapid advancements in science and technology have made their impact on the printing industry of the world too. The old techniques of printing have become obsolete and made way for the new technology. The printing industry is just one example of an entire industry movement that is changing while keeping up with the development of new technologies. The proliferation of emerging technologies has dictated a rebirth of the printing industry. The Indian Printing Industry is well established and presently growing at 12% per annum.
This book majorly deals with typographic technology, photo scanning systems, sequence of steps in the printing processes, size and scope of the printing industry, high volume printing technologies for the production of polymer electronic structures, inking system, film high contrast printing, principle of planographic printing, modern printing process, ink jet etc.
The book contains the latest printing processes like web, gravure, flexo, security and offset printing. This book is an invaluable resource for new entrants, technicians, craftsmen and executives working with printing industries.
MODERN PRINTING PROCESS
In the past, the quality of- ink-jet printing has not been good enough to prevent the recipients of direct mail products from throwing them unopened into the dust bin. If the mailshots are accompanied by the wrong name, house number, or post code, one can hardly expect a positive response to the advertising messages contained there in. No wonder then, that the main experts (technologists) in ink-jet systems for graphics arts applications, including Domino, linage. Scitex Digital Printing and Videojet, are Constantly striving to improve speed, quality & accuracy.
Now-a-days, the majority of personalised direct mail ink-jet printing, has been in mono with the occasional use of spot colour. However Scitex Digital Printing, is emerging as the pacesetter for developments in highspeed, high quality, four-colour ink-jet technology. The other manufacturers are showing evidence of lower-cost developments.
Scitex Digital Printing demonstrated a prototype full-colour (CYMK) digital press, based on continuous-flow ink-jet imaging. This technology will result in full-color 100% variable printing systems, that will provide fast set-up, quick turnaround, letter quality, direct-to-paper digital printing with variable output.
Colour images are produced by printing droplets of Cyan, Magenta. Yellow and Black on top of each other. This technology prints with multiple dots, at each pixel location, giving exact control ot colour and density.
Colour depth and saturation are also said to be enhanced by this process. A potential single row of jets is provided to enhance edge definition, registration and positioning.
Suppliers have already promised for a device with low operational costs and speeds, That will considerably exceed the 200ft./mm. demonstrated Development is in the early stages.
Benefits include complete variability of layout, contents and graphics, compatibility with industry standards for page layout and data transfer; the flexibility to set up and print jobs, ranging from short runs to high volumes on the same equipment. In addition, it gives the ability to personalise every document and to offer high-volume production at a low cost per page.
However, not every one will have a requirement for four-colour ink-jet print, nor be able to afford the press, which is expected too costly. Of greater concern the other ink-jet suppliers is improving the speed, resolution and flexibility of existing technology.
Until the new press is available, ink-jet equipment prints only black-and-white or spot colour. It serves the commercial printing, business fon-ns, direct mail, promotional graphics, catalogue magazine, lottery and gaming industries, as well as inplant printing and mailing operations. This is taking white paper at one end of the production line and transforming it into a full-colour, personalised and innovative leaflet or mail shot. Because -this takes place in one continuous operation, optimum cost-effectiveness is achievable.
The ink-jet print head have been added to Zirkon eight-page four & five-colour mini-web presses. Digital printing offering customers the benefit of two komori 16-pages web presses able to personalise products, as well as an 8-pages Heidelbery-Harris. It is able to print, personalise and inline finish in excess of 45000 products an hour, all in one pass. The three systems can all personalise in red & blue as well as black on both sides of the web. Most continuous stationery producers tend to personalise on just one side, due to cost implications and finish as a separate operations.
Ink-jet had come a long way from its original application for straight forward product identification. Ink-jet is no longer confined to Coca-Cola bottles. The technology has left this market and is offering versatility and creativity to markets previously not involved in ink-jet. With the capacity to print upto 40 inch width from a combination of one and 4.25 inch heads at speeds of 1000 ft. a minutes the quality and flexibility can now offer is out standing.
Magazine publishers are now able to personalise their products on the outer wrapper and inside and have a full-selective capability. Postal codes and addresses are printed on the wrapper, while two personally-addressed coupons are added to the back cover containing e.g a 10% discount on any tickets and a special offer for a Sunnyâ€™s cricket bar.
Such capabilities could also be of benefit for subscription renewals or to encourage a higher reader response to advertised products, by supplying a ready printed card containing readers details so that they donâ€™t need to spend time filling it in themselves.
This level of sophistication is only possible through powerful control systems, which operates ink-jet printers to provide inside/outside addressing, personalisation, numbering and postnet bar coding.
Suppliers also offer the smaller editor 2 multi-position ink-jet controller for up to 24 print-heads, providing upto 48 lines of print, An extensive range of fonts and graphics is available, enabling numerous messages to be printed. One of its advantages is the ability to control multiple print heads located in different areas of the production line.
Ink jet print-head can be used to reproduce a veriety of bar codes, fonts, usergenerated graphics, logos and photographs.
Image also acknowledges that the way forward for addressing or using ink-jet, is to achieve higher resolutions, and multiple fonts, readable in postal, equipment, which are becoming essential with the higher speeds of mail handling system
As ink-jet improves in accuracy, resolution and speed, of mail handling system the only limitation to its wider use in commercial printing applications is the imagination of.the end-user.
Image sprayed on to the paper with water based inks.
Many different ink formulations including inks with etching or acid bases for printing on coated stock.
Problems: since they are water based, the images will smear if they were to get wet.
Since ink is water based, sometimes it is absorb ed into the paper, resulting in a weak image.
Since ink jet produces bar codes through a sprayed image, bars formed at higher densities (closer together) become more difficult to read correctly. Upto700sfm.
Light impacts on photo-sensitive, hollow cylinder or drum. Laser beam hits and comes off a 6 or 12 sided prism and rotating mirror.
The beam of light rotates to the drum, swinging from the operators side to the gear side for one full, line of image, usually 240 dots per inch in both height and width.
The image, exposed to light, is on the drum. Drum rotates to a hopper containing toner with developer, then rotates to the paper, and, usually1 a corona wire (on the reverse side of the papei-) pulls the image off the drum onto the paper.
Image is then treated by heat (either a pad from the back side or infrared light above the printed image).
Images are usually more on the gray side. Image sits on top of the paper and does not impregnate the paper.
To protect image, coating the bar code is recommended.
The printed image is light black or gray. The larger the image, the grayer it will be because of the inherent nature of the photo sensitive drum.
Average, speeds from 90 to 130 pages per minute.
Image cylinder holds the image to the surface with an electrical charge.
The image head is a-hollow tube or chamber, with a small hole in the bottom. The air in the Chamber is electronically charged separating plus and minus Ionâ€™s. The minus or negative Ionâ€™s leave the chamber through the hole in the bottom.
The (-) negative ionâ€™s, place strokes or images on the image cylinder to create a negative image.
The image cylinder rotates to a hopper containing toner. The negatively charged ionâ€™s attract the toner to form the image.
The image cylinder rotates and transfers the image to the paper as it passes by.
- Under pressure: 200 Ibs per linear inch.
- Shears: There is 1 degree angle between the impression cylinder and the image cylinder, so that the character image is sliced off on to the paper.
- As in the laser process, the image sits up on the paper and should be coated for protection.
Speeds run from 90 to 130 pages per minute and much slower.
Honey well bull engine is the hardware Print head (Coil) generates a square spot on a drum which rotates to a chopper containing toner.
Toner is then magnetized in the hopper and applied to the image on the drum.
The drum then rotates to the paper, at which point a corona wire with an opposite charge will pull the image off the drum on to the paper. It is then heat set.
Problems: When the toner is fused, it will fuse to itself.
The image sits up on the paper and will not impregnate the paper itself.
Image can chip or break off.
Sometimes there is teflon in the toner to help in the fusing process. This prolongs the life of the print head, but the chemical reaction harms the corona wire.
Finish the form with a protective coating. 90 pages per minute (approx. 82.5)
Led-Light emitting diodes
Similar to the laser. Has a photo sensitive drum. Image head is similar to a bar print head with pins or grids, The diodes light the readout in a sequence as the drum passes by.
Image cylinder sees the image and takes it off the drum. Voltage is either increased or decreased. The cylinder rotates to a hopper with an electrically sensitive toner, which is attracted to the image charge.
It transfers the image to the paper using a corona wire with the opposite charge. It is then heat set.
Very slow. Only one company (Japanese) selling in the U.S. Breaks and chips. Only 5 to 7 pages per minute.
Special heat sensitive paper. Print heads are a series pins that heat up and once heated, the pins impact on the paper burning a black dot where they touch the paper.
- Customer/Lose time heating the pins in the print head.
- Only a narrow imaize area (Approx. 4").
Uses a wax or poly-based ribbon. Normal papers can be used. The image head is heated and image released to the paper from the ribbon.
Advantage over thermal direct is the lower cost of paper and its shelf life. Very, Very Slow; Much slower than the laser.
Film Plotting Machine
This is the final station of the process. Once the design is approved for.printing, plate film must be created. This machine uses a small laser beam to expose film a resolution of 2,540 lines per inch. It produces negatives upto 34" x 48". Digitized information from the electronic imaging unit is networked to the, film plotter, where it exposes each negative to produce each colour of the design. This is the first point at whicfifilm has been created throughout the entire process.
Basically there are two types of plotters: (1) flatbed plotters, where film is laid flat and then electronically laser exposed and (2) drum type platters, where film is hung and then wrapped around a large drum that spins and is laser exposed while turning.
Each of these electronic stations, when net worked, form a complete design-to-platcready film system.
Suppose a customer has an idea for a design. The customer can draw a rough sketch. If the customer is in Calcutta or Varanasi and the engraver is in New Delhi, the customer can fax the sketch to the engraverâ€™s electronic art station.
Fax in hand, the design station operator can scan the black and white fax into the electronic art system of the desk top scanner and send it to the design station. The image is now on the screen in a matter of minutes. The operator now can smooth rough edges, set type and position the type in the right places. Type can be curved, wrapped around irregular shapes or set flush left or right.
Once all the copy is in position on the screen, the operator assigns colours to the elements. The screen on the design station has all colours available to it. A colour wheel can be displayed on the screen, allowing the operator to mix and match his own colour.
Once colour are assigned, the design is ready to be proofed. The digitized information is sent from the design station to the digital proofer, where a proof is generated depending on the complexity of the design, this can be done in less than an hour.
The customer has a colour proof very quickly, with a minimum of time and money invested because no film, stripping or separation have been made.
Another benefit of the electronic art system, is the ability to design on 3,1/2" floppy disks. If a design requires promotion or revision, the previous version can be called upon the system, revision made and either proofs or plate-ready negatives created.
Once the proof is approved, we can begin to create a high resolution file on the computer. Remember that what we scanned in on the desktop scanner was low resolution and only for design.
Now we can scan in transparencies or reflective art on our high-resolution, four colour, scanner. The scanner then networks the colour separation to the electronic imaging unit, where itâ€™s colour enhanced. The separating is then sent to assembly unit, where it is electronically stripped together with the type and art created on the design station.
Black & White mechanical elements that were low resolution scanned for design on the desktop scanner e.g. company logos, must now be scanned in on the high-resolution scanner and net worked too the assembly unit for positioning in the design.
The design is now ready to be digitally networked too the ink jet proofer. The important thing is that now we have made a proof of four-color process and line copy without generating any negatives. If changes are required, we simply manipulate computer information and can then generate another proof. Once the proof is approved, the design is ready to be made into film negatives. The design is now networked to the high resolution computer film plotter.
Some customers are setting up low resolution design stations in their own plants and through a telephone and modem are looking into the trade shopâ€™s high resolution electronic imaging system. This technology allows the printers to do their own design in the shop, by using the inexpensive desktop scanner and design station.
The best thing about the electronic system, is the ability to hook up low resolution, front and equipment that is cheaper to run rather than the very expensive, high resolution computers and film plotters.
This systems takes a lot of the graphic burden off the high-resolution equipment and puts it on the front-end, low-resolution equipment, where designing is cost efficient.
COMPUTER TO PLATE TECHNOLOGY (CTP)
Today big printers are investing in computer (CTP) systems that by pass film entirely. With electronic imposition of complete flats, it makes sense to go a stage further and expose plates instead of film, eliminating several prepress production stages.
Imaging directly to plate also does away with the distortions introduced in film-based plate making. It is possible to resolve fine image detail more consistently, which is a special benefit with frequency-modulated screening where very small spots are being imaged.
Offset plates are quite thin. If the base material is flexible enough, they can be loaded in an imagesetter in roll form and exposed. Alternatively, dedicated plate exposure units commonly known as platesetter can be used for metal plates. These systems can in corporate automatic register punching.
Sometimes CTP loses out to conventional film-based platemaking due to the speed and low capital costs of conventional platemaking equipment. e.g. When duplicate plates or reprints are needed, a CTP system has to repeat the imaging process, while a conventional platemaking system has only to re-expose the film. Film is a convenient storage medium that is cheaper than archiving rasterized data on magnetic media. Proofing can also be a problem unless digital proofs are accepted as contract proofs.
It is not possible for every element in a job to be supplied a digital form, and then it is necessary to combine film produced conventionally with the digital data.
The platesetter receives the imposition instructions and exposes the digital information, masking the areas that are missing. The device then uses the register marks as a guide to position the films & expose them conventionally.
Computer-to-plate technology (figure Y) eliminates the film output and stripping stages (Figure X) in the production workflow.
Alternatively, film or artwork can be scanned and converted into digital form, Very high resolution scanners are used to avoid image quality loss on line artwork, such as type with fine strokes and to avoid the need to descreen halftones, which risks changing color values. One type of scanner designed for this purpose converts the scanned data directly in postscript code, which can then be inserted into a postscript CTP workflow.
Film is a convenient storage medium that is cheaper than archiving rasterized data on tapes or optical discs.
When alternations are required the new matter is either stripped inmanually or the films are re-output. It is more or less impossible to edit rasterized CPT data. Changes must be made to the customer files and new plates produced whenever alterations are required.
Platesetters are usually very large as they must be able to handle the full plate size for a given job plates cannot be assembled from strips like films). Some models incorporate automatic plate handling mechanism ana can accept plates upto 48 x 66 inch i.e. 1200 x 1650 mm. They ay incorporate work flow management, including queing in and preparing files while the previous job is being exposed, automatic compensation for shingling and placement of colour bars, register marks and fold and trim marks. These systems at the very end of the prepress production workflow, are installed at printers or occasionally at larger trade shops.
In contrast to conventional photographic method in which the whole plate is exposed from film simultaneously, in direct - to plate system must be more sensitive. Such containg are to sensetive to handle in daylight and unlike convention plates, they must always be handled and loaded in the dark.
By using high-sensitivity plates and multiple blue laser exposure heads, exposure at 4000 dpi can be similar to those for conventional diazo and photopolymer plates.
Computer To Plate
It is not all that long ago since publishers supplied manuscript Or typescript for the typesetter to re-key. Indeed some still do - but with the advent of Computers and universal languages like Postscript an increasing number of authors and publishers do their own key-stroking and page make-up and supply the printer with a disk for outputting on to bromide or film.
A number of prepress houses are now able to offer a CTF (computer. to film) facility which involves outputting eight pages of AS on one piece of film already imposed with correct heads, backs and gutters. Four of these are then exposed on a Stoesser print down frame for platemaking in very quick time. Some imagesetters are able to go from disk direct to 70mm film for automatic imposition. One of the problems are the moment is that generally speaking image setting film is much more expensive than negative film for platemaking. However, that situation is unlikely to continue. The aim has got to be to avoid the use of film altogether.
This brings us to a consideration of CTP (computer to plate) and as the technology evolves so some platemakers are struggling to keep up. CTP involves the customer supplying an electronic disk in Postscript or similar so that the prepress supplier can use this to go direct to plate thus avoiding the use of bromide and film altogether (see Figure 1).
There are at least two solutions available on the market that address large format press sizes and these are from Krause and Misomex. Interestingly they approach the problems in quite different ways. The essence of such solutions is that the disks supplied should be as Postscript files created using QuarkXpress, PageMaker, Ventura and other software packages. When disks are supplied they should be accompanied by laser proofs to ensure there are no conflicts between systems and no surprises when the job is printed. No doubt, as confidence in CTP grows laser proofs will be redundant and publishers will use unaccompanied data transmission â€œover the wiresâ€.
The Krause solution involves RIPing individual rates and storing the subsequent bitmap on the PSU (page storage unit). At that point the information is read onto exabyte tapes each usually containing one complete book. The tape is then kept until the plates are required at which point it is read onto the IPU (imposition processing unit). Once the imposition parameters have been installed the plates are loaded onto the platemaker and the plates exposed and processed ready for use on the press. The exabyte tape can be stored in a tape library for future use as required for reprints.
Nervous publishers will be able to see a proof before plates are made but obviously this will slow down the whole process and the use of a large plotter is necessary to produce the proofs.
The approach taken by different manufacturers in exposing the electronic bitmapped data direct to the printing plate is interesting. The Krause solutions involves a large and heavy platesetter with about 5 tons of granite in the framework to give stability to the laser. The plate, up to SP65 size, is loaded on the concave bed and slowly moves underneath the laser which exposes the image through a prism onto the plate. The technical data and plate exposure times for the Krause Laserstar are presented in Tables land 2 respectively.
The Misomex solution is based on their step and repeat system. The laser head is clamped by vacuum on to the plate and four A5 pages can be exposed at one time. The head then moves (rather than the plate) andexposes the next four pages. There are of course pros and cons for each solution but at this stage Misomex claims that their system is almost twice the speed of the Krause system. That of course is not the whole story Misomox are working with Cascade in developing pre-platemaking protocols and hope to have an actual system to show shortly, while of course Krause already has systems in the USA and Europe working in printing plants.
Savings are achi avable in time and cost due to fewer people being needed, of course, without the intermediate film, higher quality can be achieved as well with help from Misomex, Create Publishing Services and Redwood Books (both BPMG companies) cooperated to produce their first CTP book in the sununer of 1994. This was a book of old photographs and text and the quality achieved Was mi than similar books produced conventionally.
A continuing and unresolved problem is the limited suppliers of plates and the price being asked. The main supplier to users of existing Krause systems is Kalle, but they propose to market their plates in the UK at about 50 per cent more than the price of conventional plates. The same plates are available from the same supplier however at very much cheaper prices in Ireland and even more so in Germany and Sweden!
However, other suppliers are working hard to break this present monopoly and these ind)ude Polychrome, Ou Pont, Horsell,,Fuji, Agfa and others. However because of plate technology some will work better than others on the two systems. For example the laser on the Krause platesetter is strong enough to be able to penetrate and expose onto the N90 plate but could be too strong for other plates. No doubt as systems are installed increased demand will drive down prices as will increased competition and both Misomemx and Krause will develop their systems to work with the various plates.
This then bodes well for book manufacturers and for book publishers who will need, to work closely together to extract the major advantages this front end revolution has to offer.
A short while ago CD ROM was unheard of but now everyone has the word on their lips. Purchasers of home computers insist that the facility is available on their hardware and publishers of books are now among those rushing to fill the newly created opportunity. A number of large UK publishers including Dorling Findersley and O.U.P. are now producing titles on CD ROM. DK published five in 1994 and a number are already on stream for next year. Part of the excitement will be, for example, to see blood flowing through veins in the diagrams of the human body.
On the other hand having seen this sort of thing once who will want to see it again ? Overall the CD ROM facility will best be used for journals and for dictionaries, directories and other works of reference. This is servicing a new, and growing market and should not impinge too strongly on the traditional book market. It is estimated that strong growth over the next three years will mean that many books will be marketed through this medium.
Digital printing for monochrome and colour is now offered as a solution to very short run printing requirements both for loose leaf and conven-tionally bound products. Suppliers such as Indigo, Heidelbery, Exikon and Agfa are now offering presses which are able to accept digital data. The first Indigos for bookwork in the UK are at Eastern Press and other companies are watching this initiative with interest.
The Rank Xerox Docutech is now well established as a means of producing short run books. A number of these are in operation at book printers engaged in printing small numbers of publishers out of print titles, which are finding new in the market place.
The more conventional means of book production on large perfect-ers and web offset presses seems to be growing too. While no longer available the perfecters are nevertheless still being built. Both the Sovereign and finding purchasers too. Second hand presses are still in demand.
Short run colour, around 4,000-10,000 copies, is an area yet to be fully exploited Jarrold are investing in this market and will shortly be joined by one 4 companies aiming at producing short runs of the very highest quality print, of stochastic screening and waterless printing will continue to drive quality stan even higher. Webs for monochrome and two colour books are now also well establish. The front runner is of course the Timson T32 press and developments are am from Strachan and Henshaw who have not really been able to convince the rr that the Variquik press is the way forward.
CTP is not a separate, stand-alone technology. It is a part of an entire electronic operation. CTP can simply be thought of as an advanced output application printers with largely conventional prepress operations will experience massive work-follow distribution, trying to step into CTP in a long or To ensure a smooth transition and high probability of success, conventional prepress operations would be well-advised to implement a gradual chantre over process. There are three stages in this process-two page film image setting (composed single pages & spreads, imposed full-size signature four or eight page) film image -setting, and plate setting.
Each stage requires a certain technology, and the technological infrastucture is cumulative the technology of each stage builds on that of the previous step.
The first step towards CTP is proficiency with baste colour electronic prepress, including output of composed single page and two page spreads Requirement for the are as follows:-
Colour image input bringing a colour image into the system as an image file requires a digital scanner of some sort of a digital catnera.
Simple networking. Image setters and their RIPS require a networking environment in order to exchange files with one another. Either is the most common protocol for small networks such as the baste electronic prepress operation. It provides theoretical speeds of up 10 million bits of information per second, though typical real world throughputs are much slower.
Trapping. Traps can be applied by desktop trapping packages, RIP-based trapping modules or high-end work stations. -
Post script capability. Virtually all major desk top programmes and output devices employ the postscript page description language.
Digital page assembly. This is where layout takes place, since the purpose of all these stages is the output of complete pages, digital page assembly is essential.
Digital colour correction. Simple image retouching is the most common form of colour correction. It is a prerequisite for any type of sale able commercial colour.
Next is the out put of imposed film files, which requires the addition of a large format image setter to the system. In terms of learning and capabilities. This is probably the largest single step. For many printers, this stage will actually comprise two stages-formatting and eight-page film setting. However, printers who plan to use only, smaller formet presses like 20 Ã— 28" sheetf ed or eight page webs, will stop at the four-ho plan to use only 40' sheetf ed and or 16 page web will probably want go directly from 2 page image setting to 8 page imposed film.
To be effective, the large format image setter must be supported by several new capabilities.
Open prepress interface (OPT) refers to the ability to use a low-resolution version ned colour image for page make-up and image-placement, replacing it with full-out resolution scan at the moment of out put. This is essential for efficient operation is a largely Macintosh or PC environment. High resolution colour large for Macs & pcs to handle comfortably and will show a typical ethemetlocal area network) to an unacceptable, level, ition capability allows the correct placement of individual pages within a master s operations find themselves handling both desk top pages and pagesprepared by a high-end system. It is, therefore, desirable that an imposition prograrmme to be able to handle both types of pages in a single imposition.
Up to this point, colour proofing needs can be adequately met with a conventional (analogue) colour proofing system, possibly bolstered by a desktop digital f. Before taking the final step into direct-to-plate production, however. Dupont believes it will be necessary for the printer to install contract digital colour proofing and educate customers in the use of these proofs.
The most courpicuous difference between the imposed film stage and full CTP is totally reliant or a proof.
At present, some printers are dealing with this by running parallel analogue and digital proofs of the same job and showing them both to customers. This assumes that the digital and analogue proofs are tightly calibrated, which is absolutely essential. They must both also give a close match to the final press sheet. Of the pioneering printers Using CTP methods, many claim that moving to computerized platesetting, while a major step, is not as critical as the imposition and digital proofing stages. Itdoes, however require the addition of its own enabling technologies:
A platesetter is essentially an imagesetter capable of handling metal plates.
Advanced networking. As platesetters are integrated into the production network, the volume of data increases dramatically. Standard Ethernet networks arc inadequate for high-volume operations, which should use higher performance networks such as fast ethemet, ATMs and FDDI.
Electronic press control bars are an important requirement of the CTP work flow. In a CTP environment, they are generated electronically and must be exposed in the proper position an each plate. In addition to their traditional functions as devices to monitor print conditions during a press run, these colour bars will also be used for calibrating the platesetter to ensure consistency between plates.
Undoubtedly, CTP is the wave of the future. To use its maximum benefits printers need only take care to approach computer to plate methodically and with fuH awareness of the steps involved.
TP or not ?
The number of computer-to plate systems on offer is growing almost daily. Brand name identification in some cases is becoming confusing. Even competitors on the supplier side are earning OEM agreements. Gerber uses pressetech for the latest unit which, like systems from Greo (Trendsetter) and optronics (Aurora) are bringing prices for CTP systems, albeit primarily in the smaller A3 format, down to under USD 100000.
Du point study in North America has found that more than 60 per cent of printers there have no plans at present to invest in CTP. The companies switching over are mainly large groups like Donnelley, Quebecor, publishers.press and specialist book printers and producers of manuals. Black-and- white users for the time predon-dnate.
PDI announced a CT system for bimetal plates.
Polyesters plates have gained in plate life, quality of images and should be considered for CTP applicationsâ€ says Denis Mason, a US print consultant. In his view these plates, together with the new budget price systems, could appreciably speed the spread of CTP use,
Misomex-5040, SR, as well as systems from Krause and pump are specially designed for CTP applications in package and folding box printing.
Creo and Mitsubishi printing presses have linked up to offer complete colour profiling and management from digital platemaking via ink setting and press control to even integrated finishing operations. Heidelberg Data control is also -like MAN Roland pecomcovering the whole gamut of controls from pre-press to finishing.
Telecom giants like AT&T and sprint offer communications systems for CTP user so that from one digital entry point remote platemaking at print centres worldwide become instant.-Donnellely have developed an interface program for such applications.
Plates & Films
Specially formulated to meet the requirements of stochastic SC reening are Anitec Craftsman Ultra offset plates. Western Lithotech, now part of Mitsubishi Chemical, has a new range of Diamond two-side coated plates for â€œalmost waterlessâ€ printing and LAI and LY-1 laser/exposure digital plates for use in imagesetters and direct platemaking.
Polychrome has teamed with Toray in Japan to offer CTX thermal plates, made by the polychrome plant in Columbus GA. The waterless plates are available for both conventional ard laser exposure.
Brazilâ€™s IBF plate and film manufacturing company, celebrating its 25th birthday, has developed good markets especially for plates in North and South America, as well as Britain and continental Europe.
Gerber, Creo and optronics offer CTP systems for thermal plates for these systems for an those Kodak and (soon) 3M, too.
Dry film processing, pioneered by xerox verde and now polaroid is on the M-7-i-ch. Linotype-Hell introduced the Drysetter for the latter system. This manufacturer also presented a 16 -page CTP system utilizing Delta technology including post script Level 2 interpretation and screening. The system is available initially for Herkules. Quasar, Drysetter and Chromagraph R3060. The German manufacturer also announced thatover 1500 Topaz colour scanners have been sold so far. The new Topaz Robot flatbed transparency scanner allows batch scanning.
ECRM introduced the knockout 4550 laser imagesetter for colour work, apparently based on a Konica engine Monotype/Scangraphic Express Master that enables complete colour newspaper pages to be produced within 40-60 seconds.
Dalim, who have gained Dr Lutz Thiele, who was formerly on the board of LinotypeHell, as CEO, offer systems facilitating ideas, such as Twist, which permit different prepress systems to be run compatibly.
Eschar-Grand, of Canada, who have just opened a European branch in Belgium also (offer systems solutions. Pantone Hexachrome, the six-colour system, can now be proofed via Agfa.
Select Scanâ€™s high density range of 3.6 0 and maximum resolution of 4000 ppi enables it to produce scans comparable in quality to that of top-of-the line drum or CCD scanners. Its 6000-element, linear array CCD registers 16 bits per color data capture, providing superb detail even in the darkest of shadow areas. Select scanâ€™s convenient flatbed design and offline mounting capabilities allow it to meet the high productivity requirements of commercial printers, service bureaus, color trade shops, and others, Incorporating the most advanced CCO technology and specially designed optics and lenses, Agfa Select Scan delivers superior image sharpness and color fidelity with every scan, making it the perfect scanner for producing high-quality advertisements, magazines, and catalogues.
Select Scan provides two levels of scanner driver software applications: Fotolook for simple yet effective scanning operations, and Select Scan 1.0 for sophisticated scanning controls, like selective color corrections unshap masking and smoothing etc.
Selective color corrections during scanning to minimize the need for subsequent image manipulation.
- 16 bits per pixel for deep shadow detail.
- State-of-the-art aspheric illumination lens for scratch and dust minimization.
- Unique custom lens system to scan images at any resolution up to 4000 ppl.
- Single or batch image scanning with simultaneous off-line mount ing using additional slide holders.
- Slide holders that handle various film formats.
- Extensive documentation including Agfaâ€™s acclaimed An introduction to Digital Scanning guide.
Horizon plus is the impressive successor of Agfaâ€™s popular Horizon scanner, which is in worldwide user by thousands of prepress professionals. It has been developed using the latest electronic and optical technology.
The Horizon plus is a versatile flatbed CCD scanner, designed both of reflective originals up to A3 forinat and transparencies as large as 24- cm x 34 cm. The ability to â€œbatchâ€ scan multiple color positive and negative films, color, grey scale and lineart reflectives, and even screened originals,provides outstanding flexibility and productivity.
Horizon plus scans color originals even faster than its predecessor. Set to speed mode, scanning .sup to 200% faster than the normal mode.
With a resolution of up to 1800 ppl in color, significant enlargement of originals is possible without noticeable quality loss. Thanks to its 36 bit color depth and 3 range, Horizon plus captures even the smallest tonal variations in any color images need to be printed in black-and-white a neutral density filter provides perfectly balanced results.
The redesigned focusing mechanism and improved optical components transfer maximum image detail into digital format. Where sharpness is lacking in original images, variable unsharp masking (USM) is adapted to scanning resolution, contrast levels and image density. Details are sharpened without emphasising grain or running shadow areas. The Agfa Foto Look scanners interface provides automatic or manual contracts in aimplaiogical menus to achieve the best possible results.
Horizon plus is delivered with a frame with rotating holders for 35 mm, 6 Cm Ã— 6 cm and 4" Ã— 5" films. Optional holders are available for batch scanning, uncut 35 mm strips and framed 35 mm slides.
Technological development is only of interest when the final product remains affordable. Horizon plus adds features across the board. Top performance in terms of cost, productivity, quality and flexibility make Horizon plus an ideal scanner for the price-conscious profession.
Arcus II dominates the A4+ desktop color scanner market. Successor to the awardwinning Arcus family, it features 36-bit pixel depth, a true density range of 3.0 D, resolution up to 2400 ppi for continuous tone pictures and an astounding 3600 ppi for line art. Clearly this is the desktop professional.
A transparency scanning unit is built into every Arcus II, taking full advantage of the impressive CCD technology, which is capable of registering 68 billion colors; No details are able to hide in even the darkest shadow areas.
Such an impressive range of leatures and additional bundled software might appear to be outside your budget. You will be surprised to find that the cost of professional -quality scanner is reallyâ€ desktopâ€.
Duo Scan New
- Flatbed and slide tray-twice the functions. Not the cost
- Twine Plate Scanning Technology
- One-pass 36 bit color scanner
- 2000 Ã—1000 dpi-optical resolution
- Mac/PC compatible.
A New Large Format Imagesetter From Scangraphic
The most obvious effects of the continuous change in the printing industry are shown in the pre-press area. Digital work procedures become increasingly accepted and demand a consistent realisation of the companies regarding the input and output of digital jobs. Highest productivity and high throughout with simultaneous rationalisation of complex and manual work procedures determine the work process of modern and future oriented pre press companies. However, print house which in the past years were often only specialised in montage, copy and print, now also require an increased supply of modem imaging systems to achieve a more efficient work flow. Because instead of film, digital data is increasingly supplied -also to print houses, which therefore begin to invest in pre-press equipment again.
High demands on imaging systems
High performance, throughput, quality, precision and flexibility are the increasing demands placed on todayâ€™s imaging systems. These are the criteria which determine the economic viability of such systems.
The scangraphic family of drum imagesetters, first introduced to the market in 1966, has always possessed these characteristics, thus ensuring productivity and quality for typesetting and reproduction tasks. The new Scantext Apollo laser imagesetter is also based on the tried and trusted internal-drum technology onto stationary material, a technology which scangraphic established for the Post script output, thus setting a standard which has become world-wide for colour imagesetters.
The Principle of exposing images onto stationary photographic material within a drum guarantees exceptional precision, register conformity and reproducibility, an extremely rapid and thus optimal dot structuring and overall conformity of dot density.
The geniality of this principle is as simple as it is effective. To deflect the heliumneon laser beam onto the photographic material in the drum, a rotating mirror is used to deflect the beam to every point at the same distance and at. the same angle. During this process, the material is not transported nor is the laser beam modulated, two factors which could lead to errors in the dimensional stability. Thus, it is the tried and trusted Scangraphic indrum principle which fulfils the high demands of a colour imagesetter. Then geometrical accuracy and high reproducibility are the indispensable characteristics of the exposure of colour separation.
Continuous Progress in quality....
On the grounds of its comprehensive experience in the manufacture of drum imagesetters and vivid exchange with its customers, seangraphic has always continued to improve performance and quality of its imagesetters. The scantext Apollo thus now offers six different exposure resolutions with which the spot size can be varied between 8 and 22 my. These resolutions of 10 1 6,1270,1905,2540.38 1 0 and 5080 dpi and the variable spot size are the guarantee for optimum recording quality and the very best reproduction of the entire tonal value scale in black and white, colour and the frequency modulated scantext High Fidelity screening process. This high quality, however, also profits fonts, including those with the finest serifs, graphic elements with hairlines as well as negative, text and graphic elements.
During the construction of the new imagesetter, the main goal was to establish a balance between recorder speed and performance and to also ensure the highest throught put from the creation of a complete sheet to the final exposure. The overall consept of scantest Workstation and imaging system likes into account that tje capability of one component may not be blocked by another.
The main objective here was to reduce the total output time for a typical Al color
Sheet (eight A4 pages) to approximately four minutes, which corresponds to a maximum exposure time of less than one minute per color separation, and all this at a resolution of 1000 lines/cm or 2540 dpi. The typical recorder speed is 145 seconds at 1270 dpi for the full imaging format of 1072 Ã— 770 mm. At the highest resolution, this results in an exposure performance of 56 seconds per A4 page.
On the one hand this does, of course, require enormous RIP performance such as that offered by scangraphicâ€™s current Raster image processor, the scantext Prestoa software RIP developed on the principle of the Adobe CPSI and furnished with Pixel Burst hardware accelerator.
On the other hand, however, an output engine is required which can transpose the high RIP performance of the Presto into exposed film.
The scan text Apollo drum imagesetter, built to leading edge design specifications, fulfils these demands with the highest precision and at the highest speed. In combination with the new scantext combo RIP concept this has been achieved in a completely new way. All data which is made available for the generation of fully imposed sheet exposure is first transferred to the scantext combo workstation, which is a combination of server, imposition station and software RIP on one platform. The data is imposed and then calculated on the combo hardware. The Special feature of the scantext combo work flow is the ability to generate the high-resolution bitmaps required for the exposure in the background, and to thus minimize the time previously caused by the RIP process. Scantext Apollo exposes the complete sheet at its writing speed, as no further calculation times are needed for the postscript generation.
To cater for the increasing demand for imposed exposure, scangraphic has constructed a new drum designer the Scantext Apollo which features an extended circumference. This enables the Apollo to process jobs with a maximum hight of 770 mm. The 770 mm corresponds to an effective drum area of 85 degrees.
The exposable format was conceived on the basis of the facility to e xpose eight impsoed A4 page including all additional elements such as register marks and cut marks. The exposure format of 1072 Ã— 770 mm fulfils these requirements and covers the Af oversize format. This means that an Al poster in oversize format, four A3 jobs, eight A4 pages or 16 AS pages car all be exposed on a single film.
The scantext Apollo is capable of processing different types of material (film or polyester plate) which are stored in exchangeable supply cassettes and allow the imagesetter to be rapidly adopted to the various fon-nats without any complicated mechanical adjustments being made.
Photographic material can be selected in any intervals and in width between 460 and 1082 mm. According to these material widths, scantext Apollo allows the application of various imaging formats and the use of polyester plates that conform to most popular printing plates.
Punch systems compatible to printing presses up to Al oversize
The scantext Apollo is equipped with a punch system that supports the Bacher 2000 or stoesser film register. The new feature of centered material feed allows centered register punching of film or polyester plates for all printing formats within the range of 460 up to 1082 mm punch side width.
By using the integral punch system, the user can copy directly form the exposed film to the printing plate without having to carry out time consuming work of remounting the exposed film for the subsequent copy process to the plate, or repunching.
The laser system of the scantext Apollo is based on the tried and trusted heliumneon laser which is already in use on other scantext laser imagesetters. The use of a helium-neon allows the application of cost -effecfive, standard film material. In comparison with laser diodes, helium-neon gas lasers are characterized by a better consistency of intensity anO considerably enhanced dot sharpness. The latter is becoming increasingly important for output quality in connection with frequency modulated screening techniques, and in particular for the application of scantext High Fidelity screening.
The high rotational speed of the mirror drives required for high exposure speeds placed extreme demands on the mirrors themselves. They must be light, stable, and must retain their optical characteristics even at high speed. With an eye on future developments, scangraphic has departed from the conventional all-metal mirrors as these are simply too heavy. The use of beryllium, on the other hand, is extremely hazardous due to the high toxicity (beryllium oxide). Instead, a solid glass model of scangraphicâ€™s own design was used with the mirror surface composed of vacuum metalized aluminium with a special optical coating and protective covering.
RIP and RIP Interface
The performance of the scantext Apollo imagesetter is considerably influenced by the high mechanical speeds, the resolutions and the raster image processor, for these reasons, Scangraphic offers exclusively external software RIPS for the Apollo. The most powerful software RIP, scantext presto, is based on the adobe CPSI concept which enables interpretation of post script data on a software basis and uses a computer running on a standard platform (Spare technology). A special ASIC, the pixel Burst accelerator board, is utilized to accelerate the process of pixel calculation.
The scantext presto covers the entire spectrum of applications used in modem publishing systems. It can process all Level I and Level 2 Post script jobs and in addition to the original type I fonts contained in the scantext Digital type collection, can also process all original Type I forts irrespective of the manufacturer coupled with the high performance of the scantext Apollo, this facility to utilize toutilize proprietary DTP programs and fonts gives the user decisive advantages in speed and system independence.
The scantext Apollo is equipped with two RIP interfaces as standard the Li2/Li5 interface and the FPI fast Pixel Interface, the scangraphic standard for control of scantext imagesetters. The Li2/Li5 interface enables the connection of the scantext presto and Scantext Rip Express. For connection of the Rip Express, the Laser Bus interface is required as an option. All of the recent RIPS from scangraphic support the fast FPI which allows a pixel clock rate of upto 125 MHz.
For the electronic control elements of the Apollo imagesetter , scangraphic has departed from the now outdated VME bus, for reasons of better serviceability, flexibility and the promotion of EMV, scangraphic has implemented the principle of distributed intelligence on the the basis of CAN bus technology ( Controller Area Network). The individual components can be tested independently of each other and the main system, thus simplifying service aspects. Of the nine components contained in the electronic systems of Apollo, five are absolutely identical, achieving rationalisation of spare part management, in addition, this concept enables remote diagnostics of the imagesettter, which involves considerable saving in time and costs.
Every scantext Apollo is equipped with an internal data bank containing parameters relevant to the materials and which can be expanded and modified at any time. If a new material for printing plates is utilized which, due to its mechanical stability requires other speeds, for the transportation of the materials to and from the drum, the parameters for this material can then be defined by the user and entered into the data bank.
The scantext Apollo embodies scangraphicâ€™s experience in the development of hightech products for the graphics industry. In combinationwith the scantext combo workstation, the output on film or polyester plate meets the demands of a modem and efficient work flow. Scantext Apollo combine the tried and tested scantext Apollo corfibines the tried and tested Scantext in-drum principle with state-of-the art mechanical and electronic technologies.
The Scantext Apollo is thus the ideal output medium for fully imposed sheet assemblies, and offers completely new perspectives for the digital work flow in the pre-press industry.
Scantext combo: optimum job Management through combination of Workflows
Prior to the introduction of the Scantext Large imagesetter, Scangraphic had defined the basic principles for a new RIP concept. This concept is based on the understanding that recorder speed and RIP have to be adjusted such that neither component in the production chain has to wait for the other. As the slowest element of the chain determines the throughput, the speed of both RIP and imagesetter had to be adjusted with each other. This concept is currently successfully applied with the scantext Presto software RIP in combination with the scantext Apollo and Scantext Largo imagesetters.
Combo combines several work procedures
Scangraphic has now added a unique and productive feature to this RIP philosophy -simultaneous imposition of complete sheet assemblies and ripping on one work-station prior to the imaging process. This extended concept, called scantext combo, runs on a Unix workstation with spare technology, and combines server functions, imposition software and software RIP in an extremely economical way-all on one plateform.
Data output is rationalised considerably, and complex calculation procedures are reduced to a minimum bits is an important requirement for efficient and highly productive application of large format imagesetters.
The combo Philosophy
Scantext combo may be explained very easily by a Practical example very easily by a Practical example during the production of printed matter such as magazines and periodicals, the work flow may be interrupted due to missing pages or because of last minute correction of a single page. Why should the Production have to wait until the missing pages are available?
The philosophy behind scantext combo is to take into account these missing pages in the layout sheet of the imposition software, but they are not relevant for the continuing production process. All available pages of the job can be imposed and ripped for the final exposure. The RIP renders the data as bitmaps in the final imagesetter resolution and saves them temporarily on the system. When the missing pages are available, they will be ripped and included into the complete job.
The whole job, stored as bitimaps on the system, is then sent to the imagesetter. There is a considerable saving in time, because the imagesetter only outputs the data as precalculated bitmaps. The RIP process during exposure is therefore unnecessary.
Imposing with scantext
Production in the pre-press area demands imposed sheet assemblies including au control elements such as cutmarks and colour control strips. The last step prior to the plate copy, the generation of the monttage films, is not to be made manually at the light table but electronically at the monitor using an imposition program. PostScript data form applications such as page Maker, Quark X-Press and Freehand are entered into the program, analysed and automatically checked for completeness by the program. The previews of the pages are included into the imposition layout, and the complete imposed sheet is stored for the exposure. For the assembly display on the monitor, new resolution previews with a resolution of 72 dpi are generated by the scantext RIP.
Scantext combo uses the advantage of the imposition software and includes them in the combined concept of imposing and ripping. Comboâ€™s special feature is the ability to generate the high resolution bitmaps exposure in the back ground, and to thus minimise the time by the RIP process.
Preparation for the Exposure with scantext combo
The sheet assembly is carried out at- the imposition terminal by using the lowers file generated by the RIP. An automated work step of scantext combo-program, the bitmap control, checks whether the high-resolution bitmaps needed for the exposure are already available or whether these data were still have to be calculated by the RIP. Once all data (bitmaps of the page) is submitted, scantext combo starts the actual output process. The complete sheet can now be output at the writing speec or the imagesetter, without additional RIP times.
Imagesetters are for imaging
With this technique, Scangraphic has optimized the RIP Process to such a degree that the customer is unaware of the lengthy Processing time of several colour Pages. 7ber RIP process is carried out as a background operation so that the imagesetterâ€™only has to image.
This procedure is especially suited for large formes or multiple copy exposures output on scantext Othello imagesetters (eight A4 pages each) for output of fully imposed sheet assemblies.
DIGITAL COLOUR PRESSES & COMPUTER TO PRESS
There is no universally accepted definition of the term â€œdigital printingâ€. Probably this is why it is a subject of discussion. In fact there are two basically different points of view are those who in the computer Industry and another the printing industry.
For the computer Industry, every printout of data on paper is an example of digital printing, whether it is in black and white or colour. As result the digital printout machine is known as â€œprinterâ€ which to the prirting industry means the technician w o runs a press.
The printing industry speaks of digital printing when the computer is connected to the printing press and the digital data produce. The printing forme directly in the press. This means plateless information transfer or non impact printing.
How did it Start- Heidelberg unveiled the worldâ€™s first digital printing machine at Print 91 exhibition in Chicago in the form of the GTO-DI, thereby initiating a new direction to the development of printing machines and the printing industry.
At Ipex 93 in U.K. two innovative machines were introduced but only could print up to A3 size and did not become available until 1994. They are the E-print 1000 from the Israeli firm Indigo and the Chromapress from the Gerinan-Beigian firm Afgo-Gevaert. The latter machine has been developed by Xeikon, a firm established by Agfa-gevaert Xei tonâ€™s own channels of distribution under the name of DCP-1 Digital Colour Press).
The computer industry has an urgent need of digital printing for the continuation of its growth. To enhance the value of the computer and promote its sales it must be possible to print out the colour screen display, including pictures, cheaply & rapidly on paper.
At the 1992 Seybold congress in San Francisco, the then president of Apple Computer, John Scultey pointed out that conventional offset printing was unacceptably costly affair for the short runs required by the Computer Industry. He almost challenged the entire suppliers of printing machinery to develop further a means of printing off colour pages at much lower cost, other wise the computer industry would have to develop such devices for. itself.
Digital Printing for the Printing Industry
As a matter of fact the whole subject of digital printing runs counter to the interest of the progressional printer. The question is why should user spend more money to buy an additional machine simply to sell shorter runs ? Should he/she split, up his/her long runs into a number of short onesâ€™! His/her customers would gain the advantages of reduced stock and rapid up dating. But again would they pay extra for these ?
Would customer be prepared to pay an express charge for same day delivery of a few hundred sheets, as it is acceptable in the photo business ?
Naturally there are some good reason for adding a digital printing service to conventional printing.
Digital-printed jobs can be delivered more quickly, short runs can be produced more cheaply.
Digital Printing for pre-press companies
Prepress services have far more reasons than printing companies to take up digital printing. They control the production of data and the process. They already have data. With digital printing, they can extend their services and increase their turnover. Production can be ultra-rapid if one makes use of the synergies of the chain of digital data.
A page can be created, imaged and printed in fifteen minutes from the digital camera and text entry to the finished print.
These possibilities are, of course, dependent on the purchase of a digital printing machine plus finishing equipment, which represents a high investment.
To day printing technology has become an industrial process. With standardization and automation, prices have come under pressure. Anyone who wants to make money out of print must lower his costs, both on press and pre-press stage. From the cost point of view it makes little difference if savings are obtained in the manufacturing process or new markets opened up by digital printing.
Several other possibilities are open to the printer such as
- automatic imposition
- digital platemaking
- automatic platechangc
But in any discussion of digital printing it should be made clear within whether one in speaking of small A3, medium A2 to Ai or large formats, because the Price/performance ratio is different in each case. It is known that digital printing in A3 size from single copy to long run, is already available in the International market with a variety of machines.
Gravure periodical printers, who engrave cylinders directly from digital data, can witness that the disproportional organizational effort involved, could hardly be justified in offset, with its comparatively single platemaking procedures. Rapid automatic plate change, on the other hand, will certainly reduce offset production costs.
For medium size, whether suitable digital printing machines will be an offer, or whether the combination of computer-to-plate and quick, automatic plate change will bring the required cost reduction for cheap, short colour runs.
It we look at from the offset printerâ€™s point of view, a reasonable requirement would be the hybrid digital printing machine, capable not only of imaging plates produced off-line, whether by conventional or digital means.
Making digital plate production cheaper
Printers and pre-press People will have to Consider whether digital plate imaging in the printing machine kes economically viable or not.
It is reasonable requirement to be able to carry Out plate exposure within the imagesetter, which could then Optionally expose either to film or to a aluminium plate.
For longer runs, electrostatic systems are currently the most successful technologies with speeds that approach those of conventional lithographic printing. In future it is possible that ink jet may emerge as the most viable digital Printing technology, but at present the difficulty in achieving acceptable resolution at high Production speeds excludes Inkjet from colour printing at speed.
In order to compete with conventional printing presses, digital colour printers combine some features of conventional press configuration with innovative imaging methods in a hybrid design, that resembles neither the same-scale office printer nor the conventional production press.
Since high production volumes are essential to recover the relative! high capital costs of digital presses, it is importent for uselessrs to consider work flow management, including the preparation of pages.
In some cases, the press may be unable to handle the amount of data needed to change the whole image an each impression and only, a part of the page can be variable on each copy.
Digital colour presses are faster to set up the than conventional presses, since there is no need to adjust position or inking levels. Proofing is done by print run. The proof, and exact fasimile of the production run is in effect a production press proof.
The drum technolgy used in electrostatice digital printers in essentially the same as that used in laser printer and photocopiers and it must be replaced regularly. On a high volume multicolor printing systems annual maintenance costs can be very high.
Xeikon DCP-i-This is developed by Xeikon of Belgium, use dry electrophotography and employs a multi process approach to enable fully variable data to be processed. It is reel-fed printing to 2000 pages per hour, The maximum sheet size is 12 x 17 inch (307 x 438 mm).
Eight seprate printing, units print cyan, magenta, yellow and black on each side of the palper. The imaging heads, operate resolution of 600 dpi, but are able vary the amount of charge imported to the drum by the LEO spot. The greater the charge, the more toner and thus a variable spot density, can be achieved up to Offset.
Barco and Agfa developed front ends of the Xeikon engine. The Agfa Chromapress sophisticated workfow planing functions, together automatic imposition.
Indigo E-Print:- The indigo E-Print has only one printing unit, but by feeding the sheet back through after each consecutive pass, it can print upto six Colours On each side. Liquid electrophotography allows the E-Print to- use pigment particles of 1-2 microns in size, giving improved resolution with smoother solids and better highlight detail in companâ€™son with dry electrophotography. The liquid ink polymerizes instantly on contact with the paper, printing a very sharp image with no physical dot gain but optical dot gain is still present.
THE DIGITAL OFFSET COLOR REVOLUTION E-PRINT 1000
Affordable short-run colour printing is possible for the first time with E-Print 1000, the worldâ€™s first Digital Offset Color press.
Digital Offset Colour combines the professional quality and high throughput of offset printing with the flexibility and ease of use of electronic printing. Indigoâ€™s unique Electro Ink technology, enables brilliant magazine-quality glossy colour images. A fully electronic imaging process produces just-in-time, on-demand printing without films, plates, proofs or make-ready.
E-Print 1000 brings the printing industry to the best of both worlds.
Printing directly from digital data, accepting industry standard formats like Postscript and Scrtex, E-Print 1000 can operate as a stand-alone unit or network with pre-press and desktop publishing systems.
E-Print 1000 accepts a broad range of coated paper stocks as well as uncoated paper up to 320 Ã— 464 mm /1 2" x 18" size. At a process speed of 120 feet per minute, it can print 2000 fullcolor (or 8000 single color) lettersize images (two-up) per hour. With a standard printing resolution of 800 dpi, E-Printâ€™s proprietary image enhancement technology achieves outstanding, crisp, brilliant images, both for text and color graphics. The standard configuration is capable of printing In full colour, using four process color inks. An optional feature is six colour printing. This enable the user to add special purpose inks or coatings.
E-Print 1000: Combining Simplicity with Power
Printing with E-Print 1000 does not involve the tedious, complicated and expensive operations required by conventional color printing. The entire process is automatic
- E-Print receives the input data.
- E-Print processes the data for printing.
- The job is printed
Itâ€™s that simple!
E-Print 1000 eliminates the expensive materials, the time-consuming processes, and the skilled labor requirements associated with conventional offset.
No Films or plates: Electronic data is received directly from the publishing system.
No proofing : On- demand single prints replace proofs, instantly-on the-final paper, using the final inks.
No press make-ready: Perfect registration is assured and colour balance is automatic.
No expert operators required: Quality is assured electronically, without dependence on press operator skills.
Because E-Print 1000 is so easy to set up, and easy to use, quality color printing is more economical than ever-even for very short runs!
Beyond saving time, materials, and money, E-print 1000 offers new printing capabilities never before possible.
Electronic Collation: With no plates required images can be modified electronically-at full printing speed, even from page to page. This option enable even complex publicators to be printed in their entirety, with each page in its correct sequence.
Automatic Duplex Printing (Perfecting): Each page can be automatically printed on both sides. This option, together with electronic collation, means that an entire multi-page document can be printed-ready for finish-ing-fulfy automatically.
Booklet Maker (Automatic Booklet Making): This automatic finishing option enables the production of fully-finished booklets-folded and stapled-with no manual intervention.
Personalization: One-of-a-kind full colour documents-with variable text and images on each page-can he created in real-time for.targeted direct marketing driven by database profiles. This option opens up new markets for short-run printing, facilitating on-demand colour, economical distributed printing, and even individually personalized publications. By combining the power of Digital Offset Colour with electronic collation, automatic duplexing (perfecting) and automatic finishing, the E-Print 1000 can deliver fully-finished printed products-just-in-time. From pre-press to finished product, at the touch of a button on demand! This makes even the shortest runs economical, for the first time.
Many colour printing jobs such as product brochures and promotional materials, are now printed on the E-Print 1000 as multiple, on-demand short-run jobs. By printing on demand or â€œjust in time jobs on the Indigo E-Print 10.00, you can make last minute changes in order to update, modify or customize the finished product.
Printing speed is 8000 pages per hour for one colour, but every subsequent colour halves output speed. A four-colour duplex job is outpt at a speed of 500 copies per hour. Print resolution is 800 dpi, and the resolution enhancement technology used make the print appearance similar to conventional offset at a 150-lpi screen ruling.
A 640-MB buffer stores upto 100 compressed and rasterzed pages at a time. For to very it for each copy. However, it can rasterize the variable data and combine it with the constant page elements at the full production speed.
The single-unit design calls for the ink to be removed from the printing blanket after each revolution. To achieve this the ink has to be formulated with relatively low adhesion, which also means that as a result. It can be rubbed off some printing papers.
Digital colour printing technologies will continue to develop. Some will represent radical departures. Some will be evolutionary changes to current systems and others will be novel hybrids of existing and new technologies.
Short- run colour printing, using technologies and devices designed to replicate proms colour work at speeds of at least 2000 A4 pages per hour, or 900 pages printed on both sides. The devices concerned code (usually postscript), interpret the data in the form of a bitmap by way of aâ€™ raster I image processor, expose this onto an intermediate carrier and finally replicate the result on paper or other substrate.
Major economies are promised by this all -digital procedure, which eliminates digital data and the printing process: not only film and plate materials but also imagesetters and chemical processors. Make ready times and start-up waste are reduced and almost instant register is achieved, all without the need for any traditional craft skills.
In addition to technical simplification digital printing offers publishers the advantages of â€œjust -in-timeâ€ orâ€ on-demandâ€ production to meet the needs of reduced inventory and frequently changing content.
Two radical changes made possible by the digital printing methods are the reversal of the publishing procedure from â€œprint and distribute â€œtoâ€ distribute and printâ€ and the ability to change the image on each revolution of the press.
Distribution of digital data over a computer network enables the digital press to be regarded as a peripheral device for printing the quantity and version of the images required at any remote site, thereby practically eliminating the need to transport any finished print work.
Variable data printing not only allows the output to be localized or personalized but opens up the possibility of printing a series of pages in the correct reading sequence so that finished multi-page documents emerge from the press, other ingenious uses of the new facility could include interrupting the press run for the production of an urgent proof of another job, or indeed a complete rush job â€œon the flyâ€ without any waste of materials.
Digital printing as the final step in the evolution of print production form a craftbased to a technology-based business. There is no technical reason why it should not be undertaken by publishers, designers, corporate offices and other traditional clients of the printing industry. The inhibiting factor is the high capital cost of the machinery. Which ranges from US $ 200000 to $.500000. The consumable needed for digital printing are also 4 major cost factor, especially the tonner, which can cost forty times as much for a process color set as the equivalent quantity of litho inks.
Other major disadvantages of digital printing as comparedwith modern offset-litho are (1) the speed of output, which is anything form three to ten times slower, (2) the maximum sheet size of SRA3 or a little larger, and (3) the quality of the colour print, which although impressive is undoubtedly inferior to the best that an offset-litho press can produce.
To increase the speed of output and maximum sheet sizes of digital presses would call for a signifcant increase in data transfer speeds, which at present do not exceed 600 MBs,
Two factors favourable to the rise of digital colour printing the growing demand for colour in all communications media and an increasing intrerest in short runs, tending towardsâ€ print on demandâ€. These factors have stimulated the development and installation of machines such as the Agfa Chromapress, Xeikon DCP-1 and the Indigo E-Print 1000. At the same time these machines, however impressive their perfomance may be, do not automatically qualify for a significant slice of the printing market. Runs from 50 to 1000 copies, which would seem to be their natural target, are under fierce competition from below i.e. from better, cheaper and faster colour copiers, and above, i.e. offset litho presses with automatic features such as wash-up plate change and computerized press settings.
In consequence, Agfa and the other suppliers are now giving greater importance to the unique selling proposition of variable data printing. Which digital imaging offset presses cannot offer. The tremendous success of Heidelbergâ€™s new Quickmaster Dl 46-4 owing to its rapid imaging, speed and print quality , does not alter the fact that the plates can be imaged and used only once the Quickmaster Dl essentially embodies computer-to-plate philosophies, but applied on-board to a printing press.â€ Its technology is therefore quite different from that of the true digital press, which as already mentioned is basically a computer peripheral.
The market for digital colour printing will comprise average run lengths and order values much smaller than those in other sectors of the industry. This means that far more jobs will have to be found to keep these new machines busy and profitable. Which implies a completely new approach to print selling. Digital press users will also need to have an associated pre-press system in order to meet the need for an all -digital workflow.
A detailed description of five s%lstems for short-run colour printing : Agfa Chromapress
Xeikon DCP-1, India E-Print 1000. Scitex spontane and Heideioerg Quickmaster Dl
46-4. The main specifications are summarized in the Table which accompanies complied by Lawrence Wallis.
All except the dry-offset quick master are based on the electrophotographic process, which allows for variable data printing.
The xeikon engine constitutes the output portion of the Barco Digipress and the IBM Digital colour printer, in addition to the Chromapress and xeikonâ€™s own machine. Differences between the systems relate to front -end control, data, management and image processing equipment.
Xeikon -based machines are web-fed and equipped with a set of four process-colour print heads on each side of the web: a configuration most effective when producing two-side printed sheets. Work of this kind can be produced at 2100 A3 pages per hour, which is about four times faster than the equivalent production on the Indigo print. On single-sided printing the output is more equal, with 1050 A3 pp/h from the Xeikon engine and 1000 from the Indigo. (For A4 output, simple double all figures.)
E-print 1000 is one of several Indigo products, including the omnius for packaging, labels and decorating and the Mobius for publishing applications. It is based on the design of the Ryobi small offset press, as can be seen from the blanket and impression cylinders. There is also the less familiar electrophotographic cylinder fitted with a photo imaging plate (PIP). With a single, sheetfed printing unit, four cycles of the machine are required for single-sided process colour printing and eight cycles for perfecting the same-which accounts for the relatively low output compared with the web-fed Xeikon engine.
Indigoâ€™s patented Electro Ink is a vital element in the E-print process. When transferred from the photoconductive cylinder to the blanket by pressure, Electroinics are slightly heated and become tacky, but when they are offset to the paperthey peel away completely from the blanket and instantly harden, paper sheets from 60 to 250,gsm can be handled without difficulty.
Scitex introduced its spontance digital printing machine at a price of approximately US $ 220000. Spontane undercuts Indigo units by some 50 per cent and xeikon-based systems by about 40 percent. Output is 450 perfected A3 pages per hour. The machine consists of a Fuji-xerox electrophotographic print engine driven by a scitex RIP and data control system, with a print head for each process colour. Speed is achieved at some expense of resolution, which is 400 dots per inch as compared with the 600 of xeikon and the 800 of Indigo. On the other hand, a spontane pixel has a variable density of up to 256 levels, while an Indigo pixel has two and a xeikon pixel 64 levels. Paper substances from 64 to 220 gsm are accepted by trays holding 250 and 1000 sheets and automatic two-sided printing is built into the equipment.
Digital but not variable data
Heidelbergâ€™s quickmaster is the successor to the same companyâ€™s GTO-DI but retains the proven Presstek plate technology. It offers more streamlined operation than the previous machine, with automatic plate cleaning after imaging and automatic blanket washing at the end of a run.
Change -over time between jobs has been greatly reduced by the introduction of rolls of polyster plate material, housed with in the printing cylinder and rewound on another interior spindle after use. thus never being cut. One plate roll accommodates 35 jobs.
Bearing in mind that it does not accept variable data, the Heidelberg machine is superior in all other respects: maximum sheet size 460 x 340 mm, runs up to 20.000 impressions per plate, speeds 3500 to 10,000 A3 sheets per hour and above all offsetlitho quality. The manufacturers describes the quickimaster as being suitable for runs from 200 to 5000 copies. The price of the machine is naturally higher, being quoted at US $ 500,000 in the UK, or about 12 to 36 percent more than a digital press accepting variable data.
Latest of the high-speed non-impact printers from the French company Nipson Printing system (a member of the Bull group), Nipson 7000 is based on a magneto-graphic motor printing at 60 metres/min with a resolution of 240 dpi. The manufacturer promises an improvement to 480 dpi in 1996.
Magneto-graphic technology. First developed by the Bull -roup in the early 1980s, is based on an array of writing heads which compose, dot by dot, a latent image on a metallic drum. The image is revealed by contact with particles of magnetic ink (also a Bull product) and is then transferred to paper and fixed.
With its high speed of 60 mmin (compared with the 45 mmin of the fastest laser printers), Nipson 7000 accepts standard paper reels of 520 mm width to Orint up to a width of 45 mm. This width allows for the personalization! of large forms used in direct mail campaigns and also the printing of two A4 portrait formats side by side for subsequent splitting and finishing on standard A4 post.-press lines.
Nipson 7000 also benefits from a new technology of fixing the toner by flash at 50 C, a much lower temprature than the usual 160 to 180 C. This eliminates the problem of deformation by heat and extends the range of acceptability of fragile materials and those subject to complex conversion processes, for example labels, window envelopes. Pre-glued envelopes, self-copying papers, plastic materials and so on.
A unique optional function, to be released in 1996; is the single Engine Duplex (SED) features for the perfecting of A4 pages at 400 images a minute, also suitable for oneside printing in double format.
Already available for perfecting is the use of two synchronized printers in line, producing 800 images a minute. Each printer can also be used separately for one-side printing.
The printing system has as extensive range of possible connections, up to three at a time, with data processing systems from IBM, Token Ring, Ethernet, Data products , etc. As an autonomous station it can readmagnetic tapes, enhance the raw data and control the print output. It can also be easily integrated irto any pre-press or post-press production line.
Feed is by reel unwinder or from a pile of up to 10,000 sheets. In-line delivery possibilities include rewinding sheet splicing, folding and cutting stacking with conveyor belt.
While Nipson 7000 can produce complete monochrome documents in black, red or sepia, its main application will be the printing of variable data, including bar codes and numbering, on preprinted documents such as continuous forms, direct mail and labels.
It is also the printing element in the new Nipson Vary book press for the production of monochrome books on demand.
Running costs are low at 250 FF (about USD 50) for I kg of toner enough for 40,000 A4 pages, but the basic price of the full width printer with software and paper feed and delivery components is high at 1.5 million FF or about USD 300,000.
The automation of bindery processes and functions is advancing rapidly. Pre-setting of machines is becoming available for the mainly European equipment ranges from ferag, Kolbus. Mueller Martini and Polar, to name but a few. Civiemme, Ferag, Mueller martini and Rima presented complete mailroom automation systems, Baldwin offer systems solutions for mailroom handing, print finishing and value-added production processes. Other manufactures with this â€œvalue added approachâ€ are Gaemmerler and Hunkeler.
Quad-Tech FCS is a print finishing management system especially suited for demographic (split) edition work. Up to 1000 different personalized targeted inserts or imprinting (including inkjet printing) can be input and controlled electronically, This immense variety of demographic possibilities is not unusual in North America. One farming weekly offers advertisers 1000 demographic â€œsplitsâ€ via the bindery.
Bourg and Duplo have teamed up with digital pressmakers to offer integrated print and finishing solutions.
Bobst, having just introduced the Masterflex 160-Amatic multi-colour flexo system, presented the medium-format SP-6 BM foil embossing and diecutting machine for primarily short run work. The machine is touch screen operated and also allows production of holograms at a sped of up to 000 sph from the reel. Formats are up to 560x60 mm. The new Autoplate SP 104-ER offers automatic blanking. Up to 8000 sph to a max. Width of 1040 mm in weights from 80-2000 gsm (or corrugated board up to 4 mm thick) can be handled.
Technology Trends Pressroom
Komari have made a real comeback in North America in the sheetfed market. A 10-unit press has gone of Jefferson Smurfit at Greensboro NC. The Luhrone 40 has eight printing units and two coating towers, plus extended delivery. Consolidated press is installing an eight-unit (4+4) perfector in Chicago II. Color graphics in California is installing six and eight-colour Lithrone 40s for waterless offset. A sixth Komori machine, the worldâ€™s first Lithrone 844 RP, is being installed by H]M Smyth in St. Paul MN. The machine prints labels with two-colour perfecting.
Speedmaster CDs and the new SP range from Heidelberg, but also the roland on have gained exceptional sales successes in North America. Smaller A3 formats are gaining increasing colour printing market share. Speedmaster 54 and Roland 300 machines attracted large crowds during print demonstrations. Sakurai (Oliver) and other Japanese manufacturers are following the international trend to up to six colour configurations for smaller formats. Sakurai also introduced integrated CTP for their machines.
King Press and Tensor Group report excellent export results for their single width newspaper and hook presses. King press have also created a sizeable quality heatset colour market for their presses. Tensor have more than 180 press units operating in Scandinavia and Italy.
Two British manufacturer following the earlier success of BakerPerkins (now Rockwell Graphic Systems)-have gained excellent markets in North America: strachan & Henshaw, who claim that the lionâ€™s share of US pocket book in produced on their machines, and Timsons. S&H are shipping a variquick to king printing in Boston MA
Where the machine systemâ€™s interchangeable printing cassettes (with off-press unit make ready) will be used. Timsons, in cooperation with Kolbus, demonstrated integrated printing and binding on the T 32 press Rockwell Graphic systems presented the BPG-25 and the World 16 E 16-page web offset press ranges.
All over the world, sophisticated sheetfed and web offset presses are operating which were installed before electronic ink setting and adjustment became standard. Many of these presses have been and are being retrofitted by US supplier perretta who report installations in North and South America, Southeast Asia, South Africa and Ofcourse Europe. The system 21 00 offers ink setting and adjustment, as well as management control.
Colour master is Rockwellâ€™s ink and management control system for web presses that reads both proof and press copies. Re -setting and adjustment are fully automatic. QuadTech CMS -together with Light sources Colour torn offer the CMS system for automatic ink setting and adjustment based on density measurement.
Computer-to-plate step by step
Today many printers are investigating the possibility to expand their pre-press departments to handle digital dita. The reason for this being the dramatic increase in jobs received in digital form
This increase is specially noticeable for commercial, magazine and catalogue printers, where the amount of digital pages have generally been doubled during the last year.
The book and directory printers have had the access to digital data for several years, but over the last two years the need for handling digital data has increased, mainly due to financial and efficiency demands.
The packaging industry will probably be the next market segment to be influenced by the trend of digitatisatioii.
What production models are then available for digital data handling today? There are three different methods, namely
- Hybrid system
- Computer to large film.
- Computer to plate
These techniques as well as their advantages and disadvantages will be described below.
Hybrid system means a production environment that can handle both convention film originals and digital data. Although many companies will assembly pages in computers in the 1990â€™s, the conventional method of using film will not be neglected, especially for magazine and commercial products. Ads arc received from outside as films or are to be reused From earlier issues, these ads can certainly be converted into digital form by scanning the images. The printer, however, does not have a high quality scanner the graphic result is often not accepted by the advertiser.
This system creates the flexibility to handle different types of media and the printer can, at the same time, utilize the products already has in the production. Another important benefit with this system is that it is not necessary to change the production organization radically in order to begin production with digital data.
What is the Hybrid system?
The main components in this system are an imagesetter which is equipped with are gister system, a film handling system for rational handling of conventional films and a step-and-repeat or imposition machine for plate making. All components are controlled by plate planner, an impo-sition program which handles imposition of digital pages in an imagesetter, controls the flow of films via a-film checking system and controls the plate making.
The production flow through the hybrid system occures in the following.manner; The digital pages ire exposed in imposition order with necessary register and press marks in the image setter. Postscript imagesetter is equipped with register and can expose up to 4 Ã— A4 pages, controlled by the plate planner program. After processing, these pages are ready for plate making i.e. no further page preparation is necessary.
Ad pages and other pages which are available as film originals are register punched and/or assembled in a film handling system. This system mainly consists of a mounting table Autopunch for automatic register punching of the film originals and possibly a Dual Page system which converts the double page spread films from readers pairs into printers pairs.
All films are then loaded to Pre-load Cassettes and are controlled by the film Checking system to eliminate the risk of incorrectly imposed plates Finally the pre-load cassets are loaded in the imposition machine and the printing plates are exposed.
A more flexible and rational system for hybrid production is not available today.
All data in digital form
Before discussing the various computer-to-plate solutions, we shall examine how to successfully use this technique. There factors have to be attained to make a workingreality of CTP.
- All material must held in digital form in computers.
- Correct electronic proofing
A powerful computer network.
One very important reason for going directly to plate is that all data is available in digital form in the front end system. This is the first, and for many, the largest problem to overcome, when investigating the possibility to convert from conventional to digital production.
Book, manual and catalogue printers are the most successful users of modem CTP technology and the main reason for this is that one source creates the complete product and that there are usually no ads in these products.
With all material held in the computer digital proofing is needed. For black and white products this is easy, because laser printers can produce satisfactory proofs. For spotcolour pages, a colour laser printer is also acceptable.
With four-colour pictures, everything becomes more complicated. Most companies will have to output four separation films and produce a conventional proof, even though the corrections are made afterwards in the computer.
Fully digital proofing is possible today, although expensive. A large company producing top-class colour work regularly on a three-shift basis may profit from a earn digital proofer, but smaller companies have to wait years for affordable versions.
Scanned pictures, page layouts and text demand a lot of disk space. For efficient production, avoiding constant disk handling, a digital network is needed. Normally, dividing the production process into four sectors is recommended.
- Text entry
- Interactive make -up for individual pages
- Automatic imposition and job planning
When the scanner and text entry operators have finished their jobsthey store the material on the file server, where other operators can access it for page make-up,
Although modern networks are powerful, it is not practical to have more than 20 operators logged in at the same time on the same network. Even with 20 operators waiting time for data file transfer is often irritating. To build up an effective network is complicated, but a lot is happening in this area. Good, high speed and not too expensive solutions are already available and new techniuqes are constantly being developed to increase performance.
When all pages are sorted in computers, the problem with digital proofs has been solved and the network is in place and running, one can start to look at imposition programs and imagesetters or platesetters.
There are different general imposition programs on the market. A unique user interface has been developed in the Plate Planner. One of the more intresting functions is that a sheet is folded on the computer screen as it was made by hand. With this technique important advantages are obtained in the next production step; pagination and calculation of shingling and creep. The program also handles the generation of bar codes which can be used for film or printing plate identification at a later stage in the production process.
Imagesetter and RIP
When evaluating different imagesetters it is very important to test that the registration accuracy is within specification, in other words that the productâ€™s mechanical stability and repeatability is perfect. Furthermore, it is important that the RIP is powerful since it normally determines the productivity and is therefore an important part of the system.
A few years ago all RIPs were hardware units. For increased speed or functionality, new hardware had to be designed. Today. RIP is a software package loaded into a computer, i.e. the power ofâ€™the computer that determines output speed. It is very simple to upgrade the RIP to achieve higher performance and new functions with this design.
It is based on external drum technology and designed lor exposure of both printing plates and film material.
It can handle image formats of up to 16 A4 pages (max. size 1016 x 1270mm or 50 x 40"). This provides printers with the ability to impose plates and films electronically, which are large enough for most common press sizes-.
In this machine it will be possible to produce approx. 6 printing plates or films per hour unattended.
If plates or films are to be exposed. it is mainly a question of printrun, production flexibility, last-minute changes, proofing method and accepting time for remaking printing plate. These questions are very important to be answered and dependent on the type of production and internal organization.
Hoechst and Dupont are the two plate suppliers, who, until today, have introduced laser plates with an AL-base, However, some of the other large plate suppliers are doing intensive research work on new type of laser plates, thus can expect to see other high quality, long-run plates for CTP systems.
QUALITY & PRODUCTIVITY
Shows the process chain for the production of printed products. Starting from an original copy, via the prepress processes and colour separation techniques, etc., the printing plates are produced that are required for the printing process in the press. The press has to be supplied with additional materials, such as paper, ink, fountain solution. The printed paper becomes the final product via the finishing process (e.g. cutting, folding, stitching, binding wrapping).
The printing process itself is determined by the type of printing technique that is used, e.g. letterpress, lithography or offset, or gravure. The majority of printed products worldwide-more than 60%- is produced by the offset process, with gravure and letterpress having approximately equal shares. Printing can.be done on sheetfed or webfed presses. The quality, efficiency, and productivity of offset, are determined mainly by the press design, the process steps, as well as automation and measuring techniques and equipment. Quality and productivity are the main themes in the following. Production is carried out mostly on sheetfed offset presses. Sâ€ shows a four-colour press, with integrated coating unit, shows a web offset press such as is used for higher run lengths. In web offset, a continuous paper web is printed and usually transformed into the finished product, e.g. folded advertising brochures, in an in-line operation.
An overview of the influences on the production of printed products
The offset process
A typical original for colour printing is, for example, a photographic picture, which, with the aid of colour separating and scanner techniques, the selection of the colour separation for the cyan, magenta, yellow, and black inks used in offset is carried out, on which basis the corresponding printing plates are produced. These four colour separations are printed in sequence on the paper in the press via four different plates, thus producing the colour image.
Sheet-fed offset press. Four color with coating unit, model: specification 102 V+L Heidelbereger Druckmaschinen AG.
Web-offset press. Model: Web 16. Heidelberger Duckmaschinen A.G.
Shows the diagram of a four-colourpress built in accordance with the superior modular design. The paper to be printed is supplied to the first printing unit by the feeder, where the first colour separation is printed. The printed sheet is then transported via a cylinder system to the second printing unit, where the second colour is printed. Printing of the third and fourth colour is done in the same way, The finished sheet is subsequently forwarded to the pile in the delivery via the delivery system. The elastic, unstable sheet, in a typical size of about 70 cm x 100 cm, must be transferred with maximum precision from cylinder to cylinder at printing speeds up to about 13,000 revs./h, or3riVs respectively. Consequently, this makes very exacting demands on the mechanical design of the press, in order tp ensure the control of the â€œpaper flow.â€
Diagram of a Four colour Sheet-fed offset press. Model: Speedmaster 72.
Similar exacting demands are also made on the â€œink flowâ€. A finely adjustable ink transfer to the plate is made possible by an optimized design of the inking system and dimensioning of the inking rollers-a typical required ink layer thickness on the plate is about 3 m, and this must be consistent across the entire plate surface (see Fig. 5. And Fig. 6).. The offset process is based on physical/chemical surface effects on a flat printing plate and, for the separation of the ink-carrying and ink-free parts of the print images, requires the preparation of the flat plate by the preparation with a very thin (about 2 m) consistent fountain solution filmâ€”such as is made possible by the today given modem film dampening systems.
In line coating unit with IR or UV drying in sheet-fed offsets model: Speedmaster CD.
Offset is an indirect printing process, i.e., the image of the plate is transferred firstly to a cylinder on which a rubber blanket is mounted, and only then to the sheet that ion cylinder. This is possible only by an optimal matching is transported by the impress teristics and the materials concerned : ink, dampening of the physical surface characteristics and the materials concerned : ink damping solution, plate materials (e.g. diazo varnish and aluminium), as well as the rubber blanket and paper.
The quality of the multi-colour printed image is determined mostly by resolution, inking, and register. It is the screening of the colour separations that mainly defines the resolution. Today, printing is usually done with a resolution of 60 lines/cm, i.e., the interval between screen dots is 160 m. The quality of the press also permits the printing of considerably finer screens, e.g. 240 lines/cm can be produced without any difficulty. The ink supply and its consistency across the sheet, as well as throughout the print run, is most important. This is not at all a simple requirement of quality! The ink layer thickness, print-out of the screen dots and their edge definition as well as dot gain (i.e. enlargement of the screen dots by the printing process) and ink trapping (i.e. the interaction of the superimposed ink layers) are some quality-determining characteristics. The slightest position deviations can lead to unacceptable colour deviations. In multi-colour printing, production in-register is essential for a high quality standard. The individual colour separations must fit on top of one another, with an accuracy of 1/100 mm. Deviations results in bluffing and colour deviations.
Sheetfed printing press, are currently supplied with up to eight printing units (this is required, for example, when using additional special colours/spot colours as well as for perfecting printing) and an additionally integrated varnishing unit. The presses can be equipped also with different types of drying systems. Built-in perfecting devices permit the perfecting of the sheet in the press for printing both sides at full production speed (perfecting printing).
In recent years, in-line coating has become increasingly important in connection with the continuously growing quality demands on printing products, especially in the packaging market. The coating unit shown in is suitable for the large-sized printing of a thin coating application of a thin coating layer, but also for spot coating. For this purpose, a-letterpress plate prepared to suit the parts of the print image to be coated is mounted on the plate cylinder. The coating unit shown in is integrated into an offset press that is designed especially for processing cardboard of about I mm thickness. The special feature of this press, is the size of the paper-transport-ing cylinders. These have an especially large diameter in order to reduce the bending strees on the cardboard and to guarantee a non-smear paper run. High printing speeds, and fast finishing as well as the quality requirements often given rise to the need for in-line drying shows a dryer in the delivery area of the press. By application of energy, the. drying of the ink is accelerated, or wholly realized, before the sheet is collected in the pile. Both IR and UV dryers can be used and adapted in the press.
Sheeters were developed to permit the use of reel paper on sheetfed presses.
The reel paper is wound-off with a special device, cut to individual, correctly-sized sections, and supplied directly to the feeder for the online finishing as a typical feature of sheetfed presses.
Productivity is determined mainly be, the downtimes of the press. Such downtimes or unproductive times are due mainly to plate changes carried out from one job to the next. During the last two years, the press manufacturers have turned their attention especially to developing concepts aimed at simplifying plate supply and clamping. Already in 1991, at an international exhibition in Tokyo (IGAS9 1), Heidelberger Druckmaschinen AG presented a highly-automated sheetfed press. In this press, the individual printing units are equipped with cassettes in which plates prepared for several jobs can be stored. Upon completion of A job, the plate is removed automatically from the plate cylinder and the plate for the next job supplied automatically.
It is due mainly to electrical and electronic engineering that todayâ€™s presses can produce at their high standards of productivity and quality. Electronics support and, impart, replace mechanical functions and permit the safe, comfortable, and centralized press operation, shows the central control console of a multi-colour sheetfed offset press. The ink flow, circumferential and lateral colour register are set from there.
Remote Control Console for a small-colour sheet fed press. Model CPC with CP Tronic.
Measuring and control tecniques
Shows press automating components. The CPC I control console was explained already in Fig. 7 (CPC stadns for Computer Print Control). The simplification and precission on ink-key presetting considerably reduces makeready times. For this purcpose, plate readers are used (at Heidelbery. CPC 3 as shown in Fig. 8 Before plating in carried out in the press, an opto-electrical measuring device calculates the ink requirements for the individual in keys. The corresponding data are written on a cassette that is then read-in at the CPC Control console for press presetting.
Components for measuring printing quality are the CPC 2-S print quality, measuring system and the CPC 4 register mark reader for the objective calculation of the printing quality and press control. Special small register marks are printed in the sheet. These are measured there by the CPC 4 register reader (fig.9). The measured values are transmitted to the computer in the control console as infrared signals for setting the circumferential and lateral register of to the reference values. The sheet, pulled by the operator, by means of the CPC 2 or CPC 2-S print quality measuring system as part of the CPC system.
CPC 4 register reader for measuring and controlling colour register.
The measuring of the ink feed in the press is carried out on the basis of a control strip that is also printed on the sheet indicated in go by means of the scanning measuring head of the print qualitymcimuring system. A large number of measured values is recorded for the zonal ink control. Until recently, the evaluation of the ink feed was carried out exclusively via the optical density measuring e.g. with the CPC 2 measuring system as in The layer thickness of the printed ink is recorded and indicated by the optical density 0. The drawback of density measurement is that the measured values do not correspond with the colour perception of the pressman, i.e. human perception, and can be misleading, for example where different materials are used for proof and production printing. This can be demonstrated by the example shown in Fig. With conventional density measurement, the two highly different colours of blue and green Produce the same density value!
â€œfingerprintâ€ of the colour (measured denesty values and spectral reflactance of two different colours.
The fingerprint of the colour is not the measured density value but, from the physical point of view, the spectral reflectance in the wave length range of the visible light. With the aid of calorimetric evaluation, a colour difference of E can be calculated that acts as the gauge for colour deviations. In the example shown in this value is E=39. (Human colour perception recognizes colour variations already at a colour difference of E=l). To develop a measuring system with which colour is recorded in a way that the change of the measured values corresponds with our colour perception, a model of the seeing process is necessary. Important here is that, to describe the colour, not one measured value but three measured values are necessary : e.g. colour tone, saturation, and brightness. Colorimetric evaluation offers the mathematical basis for this. Three independent numerical values are calculated from the reflectance spectrum that describe the colour gamut unequivocally in a three-dimensional colour spaqe. Since 1990, for the first time Heidclbery customers have had at their disposal the new spectral photometric print quality measuring system which, working in accordance with the principles of calorimetric evaluation, can be used for measurement and control. Measuring is done from 3-coloured, overprinted screen patcheseven the â€œadditional process colour of paper is taken into account!
The preceding information already contained numerous measures and concepts aimed at enhancing productitiy. High production speeds are especially important in long print runs. A printing speed of about 13,000 revsjh in sheetfed presses and about 40,000 revs./h in web offset presses may be considered currently as the optimized technological state of the art, depending, or course, on the material used, especially paper. Above all, it is the reduction in the makeready times that has made a major contribution to increasing productivity.
Model of colour perception
Logistics and information flow
The main material flow to and from the press is represented by the paper. The feeder must be supplied, the printed pile must be removed at the delivery. By realizing suitable mechanical and electrical interfaces at the feeder and delivery, it is possible to automate the pile transport 1" shows a sheetfed press in which the pile transport is largely automated with the aid of modern automatic pikle transportation systems. An automatic stacking rack can also be seen in It permits automatic pikle change at the delivery without interrupting production. The Heidelberg Logistics System contains a specially developed automatically guided vehicle.
The plant-wide information flow, i.e. the data recording and connection of production equipment, production and management areas, is becoming increasingly important.
Information systems, such as management information and production planning systems, provide organizational clarity and allow efficient planning and utilization of plant equipment. The press with its control and data processing technology as explained before-is prepared for integration into the information flow of the overall printing plant.
Paper and printing quality
It has been pointed out in the preceding comments that the paper is subjected to a wide range of stresses and quality demands in the printing process, provides an example of the paper stress that occurs during the-printing operation on the basis of a finite elements simulation calculation. The different coloured areas, as shown indicate the tension distribution on the sheet. The grid lines indicate the deformation degree, the press manufacturer can design the mechanical systems in such a way that the stress and load on the sheet will be as consistent as possible. A precondition for this, is that the paper itself has constant mechanical characteristics.
Tension distribution and deformation of a paper sheet under the grippers (finite elements simulation calculation)
Described in the following are several influences of the paper relating to production disturbances and loss of quality: detachment of the coating can cause hickies and imperfect printing; non-homogeneity of the physical characteristics of the paper can lead to doubling, poor register, inconsistent print-out, and colour fluctuations, faulty geometry, such as angularity and waviness, is responsible for downtimes and finishing problems; Poor chemical and physical characteristics can had to poor inking and drying.
Shows the material flows in the printing process. It is shown that also different auxiliary -materials are required, e.g. dampening solution and washing agents, that are not included directly in the finished product. The printing process itself also involves disturbing emissions, i.e. emissions of pollutants, gases, and also noise. As a press manufacturer, Heidelberg has also set itself the goaf of reducing damage to the environment. Already at the development stage by optimum press concepts major improvements can be achieved, but also by offensive cooperation with partners in the graphics industry, especially the material suppliers. What innovations in printing technology will the future bring, what expectations exist, what are the prospects? Within this report, the following are but a few comments concerning the technology of the offset process itself.
A higher resolution by finer screening. To achieve -this, the prepress sector must optimize materials and techniques; materials such as paper, ink, plates, must be further improved e.g. with regard to stability and resolution as well as satisfying environmental regulations; work will continue on dry offset, i.e. offset printing without the use of the plate? How much longer will we work with films in the prepress departments? Finely, the concept of computer-to-press or computer-to-cylinder, i.e. the transmission digital data from the prepress operations, directly to the press and the writing of text and image information on the plate cylinder in the printing unit, is fascinating.
The preceding comments have provided a brief overview of the performance capacities of offset printing as well as the major influences on quality and productivity. Communication and cooperation between the different areas within the graphics industry are, essential. Only if all those concerned in the process chain, from the original up to the finished product, take due consideration of the market and customerâ€™s wishes.
Computer to press, model Heidel berger druckmaschimen AG.
State-of the-art & Prospects For Keyless Inking
In 1979, the American Newspaper Publishers Association, started a project to eliminate the complicated ink-key technology with costly electronic presetting systems and develop a less complex marking unit for printing. Working towards this, Koenig & Bauer-Albert AG, concentrated on anilox offset and has become the leader with 10 years experience, on keyless inking for multi-colour printing.
THE OUTLOOK is bright for economical multi-colour newspaper targeting. Anilox offset could soon become the established process for the economical and standardised mass production of newspapers, because it accommodates virtually all the current trends in newspaper production - the digitisation of prepress (computer-to-plate), edition splitting ,for group targeting, more process and spot colours and improved press ecology. More Than 2,000 Keyless
Offset Inking Units In use
Till date, over 2,000 printing units with keyless inking systems for newspaper offset have been sold worldwide. Most of these units are already in operation - half of them outside. Japan. However not all keyless units currently offered can be described as short-train inking systems in the true sense. Japanese and US manufacturers, in particular, offer relatively complex units with numerous inking falters and more components than the few essentials specified in the original short-train inking concept -ink trough, chambered doctor blade, screen roller and forme roller. Nevertheless, these systems do dispense with ink keys.
With the sale of 17 anilox offset web presses totalling 415 printing couples, KBA is the technological and market leader in anilox offset and has more than 10. years experience, in keyless inking for multi-colour newspaper printing, which is more than any other manufacturer in the industry. The handling and functioning of its keyless systems have been optimized in years of real daily production. All the leading manufacturers of newspaper web presses have since adopted this innovative inking concept-some after persistently disputing its merits. Their acceptance indicates its huge market potential and a willingness in the trade to move on from the classic roller inking units with ink keys which have been the norm in newspaper printing since Friedrich Koenig invented the cylinder printing press in 181 1.
Short And sharp
The initial impulse for the development of anilox technology in newspaper printing was given in 1979, by a research project proposed by theAmerican Newspaper publishers Association (ANPAO now called the National Newspaper Association (NAA). The aim of this project was to eliminate the complicated ink-key technology with costly electronic presetting systems and lengthy ink trains with friction grears from the printing units. The basic idea was to develop a less complex inking unit for newspaper printing, which would automatically guarantee the correct and continuous inking of the printing forme, even in extremely long print runs, with no manual intervention.
Incidently, the ANPA aslo provided the stimulus for the development of the four high tower configuration for printing newspaper blanket-to satellite configuration with reverse gears, complicated web leads, etc., which dominated at that time. Today, more than 80 per cent of all newspaper presses, ordered from the big manufacturers are four-high towers.
Koenig & Bauer started developing short train inking units for flexo and newspaper letterpress back in the early 1980s. In the late 1980s the worldâ€™s biggest flexo web press (a Rexi-courier) was sold to associated Newspapers in London, the biggest anilox letterpress installations to the Guardian in London and (lie Neue-Zurcher Zeitung (NZZ) in Switzerland. In the meantime Albeit Fraiikenthal, now the Frankenthal facility of Koenig & Bauer-Alber AG, concentrated on anilox offset.
Premiere in 1984
A single -width, one configured experimental printing unit was demonstrated at the IPEX international trade fair in Birmingham in 1984. The upper inking unit was fitted with conventional rollers and ink keys and the lower unit with an anifox system.
In order to launch any new technology in the market, the manufacturer must first find a pioneering user. For Albert Frankenthal, Oruck and Verea gshans Frankfurt am Main in Neu-lsenburg were the first users. In early 1987, a Y-type experimental printing unit with keyless inking was put into operation on a conventional newspaper web offset press and tested tinder real production conditions until mid-march 1989 . More than 40 million newspapers were printed on this experimental unit. In 1987, long before the experiment had been completed, this pioneering customer ordered the worldâ€™s first fourhigh offset press, the ALFRA CX, with keyless inking for four colour printing. It went on-stream in December 1988. In May 1989, demonstrations of high-quality four-colour newspaper printing were given for an international trade public. Press extensions in March 1991 and September 1992 increased the capacity to 96 pages. Frankenthal delivered anilox offset presses in the late 1980s and early 1990s to newspaper printers in Germany, England. Finland, Belgium, Israel and Switzerland.
At DRUPA in May 1990, Koenig & Bauer demonstrated four -colour printing on a four-high Anilox commander web press with arch-type printing units, in the autumn of 1990, Druckhaus Dieriches in Kassel, put an Anilox commander with 40 printing couples into operation and was later extended to 48 couples. The know how gained high colour content, such as with this installation in printing complex newspaper with a Die Woche, was used to eliminate the teething troubles of this new technology. Subsequent installations with third-generation inking units at Darmstadter Echo, the South Bend Tribune in the USA and Magdeburger vol)lksstimne are evidence that anilox offset is now a mature and well proven inking technology. Orders for anilox offset four-high towers have since been received from the schweriner volkszeitung, the Tiroler Tageszeitung in Innsbruck, the Windsor Star in Canada, the offen bacher post and the Kreisboten-Veriag in Weiltheim.
Increase in service life of screen Rollers And doctor Blades
In todayâ€™s anilox inking units, KBA uses abrasion -free ceramic screen rollers with line engravings, the laser-engraved lines in the ceramic layer are first filled with copper and then etched to the specified depth a Process which, is already familiar from the manufacture of gravure cylinders. The specified ink density can be set either by postetching the copper-fillings (Plus correction) or by grinding the ceramic cell walls deeper (minus correction). The necessary manufacturing standards for this type of roller have been Precisely defined during actual operation.
The new screen rollers have a service life of more than 100 million cylinder revolutions to reduce changes, once every two to four years, depending on the load. The current changing time is approximately 30 to 40 minutes. Tie same screen is used for both, black and colour inks. In addition, worn screen rollers can be recoated for approximately $7.000 to $8,500. Price will drop as the system becomes man widespread.
Another advantage of these new screen rollers is their broader dampening solution width- without the risk of emulsification. According to KBA, anilox ink can be printed with no problem even at a dampening content of 20 to 25 per cent. The optimised crosssection of the chambered blade (compared to initial installations) plus two small bridge rollers added by KBA, also increase the dampening range.
The service life of doctor blades, which in 1990 was approximately 150,000 to 180,000 cylinder rph for black printing, has also been increased significantly to more than 700,000 cylinder revolutions for black printing and more than I million for process colours. As a rule, doctor blades need only be changed once a week (changing time in the press, is less than one minute) They are cut off a roll and do not need to be fitted. Since there are no perforated inking rollers ink KBA short -train inking units, double-spread printing is possible at any position.
Optimised Handling And Functions
Handling of the other systems has also been optimised to improve changeover times, reduce weight and facilitate operation. For instance, the chambered blades are thrown on and off the screen roller. A new type of support and clamp allows the complete doctor-blade bar to be changed in less than 60 seconds without the aid of tools. The quarter-or half -width ink troughs with integrated ink pump, can be used in all printing units (filling volume: 3-61/5-10 pts, connectable to an automatic ink feed) and simply plugged into the drive system via a high-speed coupling. The cumbersome hose connections between the ink trough and doctor blade on earlier inking units, have been eliminated in the new generation. Ink changes have been cut to just two minutes.
Positive Ecological Balance
Tie ink trough with pump (weight when empty kg/13-15 Ibs) can be cleaned in a washing unit outside the press. During job changes the inking unit can be cleaned fast by the paper web without cleaning agents. Because (if the low number of rollers only 50m (164 ft.) of web is needed. This saving in cleaning agents and the sharp top in changover waste are a Positive contribution towards Press ecology. Only during extremely long running times is an occasional washing of the inking units to be recommended.
A further advantage of keyless inking over conventional film inking is that there are fewer splitting points and therefore, less ink mist, in addition the reduced energy consumption of anilox presses (fewer rollers = less mass moved) is also more ecological in comparison to conventional presses.
Despite rumours to the contrary, anilox offset operates with standard lithos, printing plates, blankets and dampening additives. The ingredients of the printing inks are similar to those of conventional offset inks, only the viscosity is slightly different, Anilox viscosity: at 20 degree C 3,000-6,000 mpa.s (mpa.s = Millipascal seconds): at 35 degree C 1,5002,500 mpa.s; conventional viscosity: at 20 degree C 4,000-1 0,000 mpa.s: at 35 degree C 2,500-3,500 mpa.s Anilox inks are no more expensive than conventional printing inks and can be used for conventional offset printing.
MORE ECONOMICAL FOR FREQUENT PARTIAL EDITIONS WITH HIGH COLOUR CONTENT
After carrying out detailed economic comparisons, KBA reached the Conclusion that because changeovers are shorter and there is less waste anilox offset is generally more economical than conventional offset, if the print run is split into partial editions and, at the same time, a lot of colour is to be used in the editorial and advertising sections. Some anflox products, for example from Druckhaus Dierichs Kassel, could not be printed in the specified time on a conventional press with the same capacity due to the higi number of partial editions and /or the high.colour, content.
Because it has fewer inking rollers, an anilox inking unit runs upto a uniform inking of the printing. Plate much faster than a long conventional inking unit. However, the inking system has less influence on total waste levels, than colour register and cut-off register. The waste rate depends to a great extent on the proficiency of the press crew and on the speed with which register deviations are corrected at the console. Shrink wheels to compensate for fan-out, in conjunction with ink-register controls (particularly in four-colour recto/verso printing with the now dominant four -high tower configuration), can make a positive contribution towards reducing total Waste. A uniform paper quality is also an advantage.
Of course, quality demands (which vary from job to job) and problems in manufacturing the printing, forme also play a significant role. If job changes in multicolour printing are frequent, anilox keyless inking allows waste to be reduced to the lowest levels possible in conventional offset printing (that is when ink keys are set via film or plate scaner) and with very much less effort, Moreover automatic inking eliminates the risk of humen error inherent in the remote adjustment of ink keys in conventional Offset. Unnecessary ink consumption through flooding does not occur.
Experience with anilox. offset installations in the USA shows that manning requirements are significantly lower than with conventional installations of a comparable size. However, regulations in Germany (and some other countries) governing press manning make it difficult to reduce personnel costs at the press. Even here, however, personnel not required for the actual printing process can often be usefully employed elsewhere (for example, to prepare job changeovers).
Consistently High Quality
Investigations by independent research institutes have shown that, with ani lox offset print.The density is uniform not only within each signature but also through out each printing run (irrespective of length), that the final print is true to specifications and that tonal values deviate only minimally from the proof, remaining consistent even during long print runs, Newspapers printed in anilox, for example, Diewoche, prove this, whether purchased at a kiosk or by subscription, even several different copies of this all colour weekly newspaper, will reveal virtually no differences in inking or print quality.
Standardisation Must Continue
Anilox offset was an early step towards the economically logical standardisation of newspaper production. Increasing digitalisation and standardisation in prepress (computer-plate), for example, for the most recent K13A anilox installations in Magdeburg (Aniloxcolora) and Innsbruck (Anilox- Express), point in the same direction. In the final analysis, this is where the quality of a newspaper is determined. He situation is no different in conventional printing.
Standards must be clearly defined and observed, both in repro and by external creative professionals who deliver the finished print work (four-colour comps). In view of the continuing pressure to extend editorial deadlines, it is illogical to waste valuable time in correcting prepress errors in the press hall by adjusting the ink keys for better result on one page at the expense of print quality on the following one.
WATERLESS ANILOX OFFSET
A perspective for the future
The applications of anilox offset newspaper printing are by no means exhausted, For example, KBA beleives that as legislation forces newspaper printers to become more environmentally oriented, waterless anilox offset offers enormous potential for helping them to comply with regulations while. At the same time maintaining a high print quality. Screen rollers on KBA presses are already temperature-controlled to ensure consistently high print quality even during long print runs, improved ink chemistry and newgeneration waterless offset printing plates, with much longer service lives are paving the way from the materials point of view. Dispensing with dampening units-apart from eliminating the need for ecologically sensitive dampening additives would significantly reduce other problems such as fan-out caused by dampening the web eight times in four-over-four printing on a four-high tower, which currently necessitates complex technology to correct it.
New generation keyless units offer greater flexibility in colour impositions and easier handling for faster change-overs when printing numerous partial editions.
LETTERPRESS, OFFSET, FLEXO, AND ANILOX
The rapid rate of progress in newspaper printing during the past few decades will continue into the future.
When Export -Polygraph first appeared in the spring of 1953, the world of newspaper printing was relatively routine, with newspapers almost everywhere printed in the classic letterpress process with lead stereotypes. Then, in the sixties, sweeping changes in prepress triggered off a Period of turbulent development, as photosetting rapidly drove stereotypes from the market and paved the way for offset to challenge the letterpress supremacy.
Revolution in the press hall: offset storms the letterpress stronghold
Although invented at the end of the century and successfully marketed in its country of origin- the USAâ€” by Goss, the leading supplier of that time and now a member of the Rockwell group, it was not until 1964 that offset spread to Europe, in the form of a double-width newspaper web press for a customer in East Berlin. Having secured this foothold in the European market, however, offset soon gained wide-spread recognition, and many sales were recorded in subsequent years by press manufacturers such as Koenig & Bauer, MAN Roland, Wifag in Switzerland and Plamag in East Germany.
Offset printing plates were less expensive than lead stereotype plates and could be produced faster, Parallel to the introduction of dedicated offset equipment many newly delivered letterpress machines were converted for photosetting by retrofitting saddle plates onto the cylinder to take BASF nyloprin! or IMAPP photopolymer letterpress plates.
While other manufactures in the early seventies were abandoning the construction of letterpress machines, one company, which decided to retain this sector was Koenig & Bauer. In addition to expanding its offset activities, it developed high-speed web presses with wrap-around plates and an output up to 40,000 iph. The nyloprint or Grace plates were clamped magnetically directly onto the plate cylinder.
A spectacular machine which is still fresh in the memories of many newspaper printers today was the Kocbau-Jaumbo-Courier delivered to the Gazet van Antwerpen in 1974. The press had three folder formers side by side and web width of 2.52 meters (8ft 3 in), making it the widest newspaper web press ever built.
Tailor-made technology is the trend of today
Today between 80 and 100 per cent of all newspaper web presses delivered by leading press manufacturers MAN Roland/MAN Plarhag, Koenig & Bauer (KBA), and Wifag in Europe. Rockwell Graphic systems (Goss) in the USA, and Mitsubishi, TKS and Ikegai-Gocs in Japan- are offset presses with conventional film inking units and brush-type, turbo, or spray dampening units. Different performance classes, from less than 30,000 to more than 40,000 iph, and a variety of printing unit configurations available. There is growing demand for customized solutions to individual and co flexibility, number of pages, size of circulation and automation, Leading press manufact satisfy this demand with modular built machinery offering a wide choice of options.
Rapid progress has been made in the development of inking and dampening drive systems, reelstands, folders and-above all-automation equipment. The benfits are reduced makeready and waste, increased output, improved quality in multicolour, printing and easier operation. Whereas the fundamental laws of mechanical engineering (highest manufacturing quality of the cylinder, gears bearings etc.) still hold true for top-quality printing, the electrical systems in the press hall and mailroom have undergone just as revolutionary a transformation over the past 15 years as other industrial areas, and have been outpaced only by the speed of technological change in prepress.
Cumbersome mechanical controls for protective devices, vast cabinets packed with relays and switchgear and often as long as the press itself, huge operating panels with a phalanx of push-button and display instruments-these have all long since vanished from the press hall. Whereas in 1971 measuring values for ink keys were still being transferred from drum or flatbed film scanners into punched tape and conveyed to the control desk together with a punched job card, by 1973 press manufacturers were already installing contactless semi-conductor controls. These were followed in 1975 by programmable logic controllers (PLCS) and, from around 1977 onwards, a move towards decentralized press controls.
Advanced console technology Is now standard equipment
Modem console technology for press presetting, remote control and computerized monitoring of the printing process was introduced in the early eighties and is now a standard feature on high-performance presses. Today many control functions are integrated into the printing units, reelstands, and folders. Data buses link the decentralized process stations with the operating and systems stations. Thanks to the electronics revolution the-entire control system can now consist of a single computer with a range of peripherals Standard interfaces provide an EDP link between press and related areas, logistics, and accounting. Production data, malfunctions, waste-copy totals and much, much more can all be logged by computer and printed out as hard copy.
Electronics can tap enormous productivity reserves
While promoting fierce competition to newspapers from the audiovisual media, the boom in electronics- frequently described as the third industrial revolution-has also mobilized previously unimagined productivity and quality reserves in press manufacture through the invention of increasingly powerful electronic components. Electronic equipment now accounts for 20 per cent or more of the production value of a newspaper press-confirmation that challenges also create opportunities. The resulting improvements in print quality, colour and immediacy of news coverage (through later editorial deadlines) have helped newspapers compete more effectively against satellite TV, videotex!, the home video and other new media.
Developments since the mid-seventies have led to ever faster machinery in a wide variety of satellite configurations, with reversing gear and numerous web-lead variations for adde flexibility in colour and production. Although almost anything demanded by newspaper industry is now technically possible, economic consideration shaveresulted, in a growing trend towards less complex technology and greater standardization in industrial newspaper printing.
Counter-trend towards less complex technology
Manufacturers have responded to this trend, by developing less complex press configurations. These include four-high towers with H-or arch-type printing couples for four-colour perfecting: stacked Y-type units for printing two colours recto and one verso or four colours recto and two verso: or stacked satellites without reversing gear for four-colour perfecting. Anilox keyless inking technology, i.e. anilox letterpress and offset with oil based inks or flexography with water-based inks, are further examples, In comparison to the familiar and proven satellite units, the four-high tower configurations has the advantage of dispensing with impression cylinders and reversing gear while still being able to print four colour on both sides of the web, four-high towers are available both in the classic configuration, with four identical arch-type units and four operating levels and in the Hversion where the second and fourth units are up-ended and there are only two operating levels.
The benefits to the printer are considerable: simple webbing-up, straightforward web leads ( with no web-guide rollers between printing couples), easy access to the units, ergonomic operation and full flexibility in colour leads for each individual page. Additional advantages are the shorter maker ready and wash up times and longer service life, while the less complex drive technology reduces initial investment costs.
In the US newspaper industry, flexographic printing with water-based inks has gained a significant market share of more than 20 per cent with over 1300 printing couples sold. At Associated Newspapers in London, the worldâ€™s largest flexo newspaper installation, comprising eight KBA flexo-courier presses with a total of 144 printing couples, prints more thantwo million newspapers with a high colour content every day. Flexoâ€™s big advantages lie in the rub-resistance of its inks, the absence of.show-through on thin stock and its extreme brilliance in four colour printing. In Italy over 180 Cerutti flexo printing couples are currently in operation most of them on single width presses. Elsewhere in Europe, however, flexo has still to make the breakthrough.
The last bastion to fall to keyless inking was multicolour newspaper offset printing, with its inherent risk of ink emulsification due to the need for dampening. In may 1989, after several years of testing and optimizing an experimental printing unit. Koenig & Bauerâ€™s subsidiary Albert-Frankenthal demonstrated multicolour newspaper printing for the first time on an anilox offset press, with a four-high tower configuration. There are now around 1500 anilox offset printing couples in operation worldwide, some 800 of them in Japan. Japanese keyless inking units, a number of which are also in use in the USA, are not, property speaking, aiiilox units since they do not incorporate the basic essential-an anilox roller- and have so far been limited exclusively to black and white printing.
Technological and market leader in multicolour anilox offset newspaper printing today is the K-BA group, which to date has sold twelve anilox offset presses (with a total of 294 printing couples), including a giant installation for a newspaper publisher in Indiana, USA. Nine of the one million high quality four colour newspapersevery day. MAN Roland is due to deliver a large anilox offset Press I to Finland in the autumn of 1994. Other European and American manufacturers are still at the development stage.
Anilox offset has made tremendous progress and has matured into a viable and promising alternative process for economical, high-quality multicolour newspaper printing.
The newspaper technology of tomorrow
The rapid rate of progress in newspaper printing during the past few decades will continue into the future, with press manufacturers fast becoming suppliers of â€œcompleteâ€ systems. Automatic roll stripping and splice preparation stations are now available from most leading press manufacturers. Within the web press itself, rationalization is in full swing, as is the replacement of manual activities by robots and other automation modules. Automatic plate change, computer to plate (i.e. plate exposure directly in the press), remote conversion of folders to different types of production, customer targeting of newspapers through new technologies in the folder and mailroom-all these have become reality, and many other developments are in the pipeline. Only time will show which are worthwhile. Technical progress, while continuing to present a tough challenge, will also help strengthen the position of the newspaper as one of the leading vehicles of advertising and information.
ANILOX - OFFSET
The unmistakable trend now-a-days towards more colour is news paper printing has led to the use of printing towers with up to 8 inking units. This means that as a conventional (imported) 80-page newspaper press with five towers and e.g. 40 inking units the operation tearm must pre-set upto 1600 ink keys, may then have to adjust them after proof-printing and must also keep a check as them during running -on.
In order to present and control the inkkeys comprehensive electronics and a link to the pro-press stage, via plate-or film scanner are necessary. Higher investment costs and more expensive maintenance and service are the inevitable result.
In contrast to conventional offset inking systems, where extensive automation is the rule, the anilox inking system uses a technologically less complex concept which dispenses with the need for a comprehensive ink-roller frame and ink keys: a constantly even film of ink on the printing cylinder plates is ensured by means of a doctor system together with an anilox rofler and forme roller. Thus to a great extent the printer is relieved of the need to check and regulate the ink unit and can concentrate as the dampening unit.
Except for the inking system an Anilox offset printing unit consists of the same basic components of the same basic components as a printing unit for conventional offset.
Layout of an anilox offset arch-type printing unit
- Ink trough with pump
- Chamber doctor
- Anilox screen Roller
- Ink forme roller
- Ink rollers
- Plate cylinder
- Blanket cylinder
- Dampening duct roller
- Brush Roller
- Dampening distributor
- Spiral roller
- Dampening forme roller
- Paper web.
At the heart of the anilox inking system are the anilox roller and the doctor system. The doctor system, has three fundamental tasks:
- To fill all the anilox rofler cells evenly with ink
- To wipe excessive ink from the anttox roller surface
- To wipe smooth the profile created on the surface of the anilox roller through contact with the forma rofler and the printing form, and to direct the ink back into circulation. Now-a-days doctor blades have a life-expectancy appropriate to the demands of everyday practice.
Half width and quarter-width doctor systems can be used in the inking units. This is to satisfy the demand for increased colour in newspaper. Because of quick-lock mechanisms, valve mechanisms, system orientated auxiliary devices and an accessible layout at all operating levels, replacement of the doctors and inking systems anilox and forme roller is now quite a simple matter.
A slight surplus of printing ink is directed continually into the doctor blade chamber by ink pumps; excess ink and that wiped from the anilox roller is returned into circulation The individual ink troughs are filled by means of ink-feed systems. This can be done manually on small presses and fully automatically on large ones.
Because of the hydrophilic quality of chrome only ceramic coated, laser-engraved anilox rollers are used in ANILOX OFRSET. These have an additional advantage over chromium -plated rollers in that their life-expectancy is very much longer. Thus the ceramic rollers used show no recongnisable signs of abrasion even after a year in daily production. In order to achieve a good ink transfer the cells on the ceramic roller are coated with a this layer of copper.
The depth, angling and geometry of the cells, the cell wall ratio the number of cells per line, the surface temperature of the anilox roller during running -on the viscosity and pigmentation of the ink-these and many other factors all determine the ink laydown behavious on the anilox roller.
Because of the shortness of the inking device in ANILOX OFFSET the range between tonning and emulsifying is narrower than in the conventional inking unit. Aprecise dampening unit is therefore a top priority for an optional ink /water balance.
An instant response to alterations in the dampening procedure and a rapid run clean of the plates at the start of production are guaranteed with this contact free system. The dampening-duct roller drive enables finely controlled metering at all machine speeds.
In addition a page-wide adjustment of the dampening application is also possible according to subject and dampening liquid requirements.
This shutters are available in a variety of levels ranging from manual setting, to mechanical setting on the outer press surface , to motor-operated setting controlled from the console and complete with display. The double-walled dampening water trough insulated with polyurethane foam ensures an even dampening -water temperature from production start-up right through to the final printout.
Due to this contact-free system of operation contamination of the dampening liquid, recycling of paper dust and ink back into the dampening-water preparation and circulation system and the resultant alteration in the chemical composition of the dampening liquid (e.g. pH valve) arc almost completely eliminated,
Compact press configurations with high production and colour-flexibility are in ever greater demand in the newspaper industry. The ergonomics of the press itself, i.e. case of access to the inking and dampening units as well as to the plate and blanket cylinders, also plays an important role.
All mechanical, pneumatic and electrical operating elements should be arranged in such a way as to enable work to be carried out on the printing unit safely, flawlessly, rapidly and precisely.
Against this back ground there is now also an increasing demand in Europe for the 5 to 8 couple tower configurations which originated in the USA for the blanket to blanket printing process. These offer a technically less complex and more printer friendly alternative to the satellite units which have so far dominated. One of the merits of the tower concept, quite apart from its economic efficiency and ergonomics, is the simplified web-lead.
The basic configuration is the so-called archtype printing unit for 1:1 printing, which can be supplemented with a colour hump to form a Y-forination for verso printing (2:1 printing). Thus by stacking arch -type or Y-units it is relatively simple matter to extend the unit to form anything upto and including an 8-couple tower (4:4 printing) in order to suit specific production needs. The range, of possible configurations is shown in the accompanying illustration.
Now-a-days all the newspaper offset presses manufactured by KBA can be equipped with the anilox inking system.
With regard to initial colour-register waste appreciable reductions in make ready times and start-up waste are achieved using the anilox inking system. This ensures good, consistent quality across the whole width of the press and throughout the whole course of production from start-up to print-oul
KBA can supply two or three armed reel stands, both equipped for fully-automatic pasting once the given rel end diameter has been reached and designed for web speeds up to 12.5 m/sec. The reel diameter can measure up to 1270 mm. This is designed for automatic or manual paper-reel feeding and loading.
KBA folders in the 2:3:2 system, 2:3:3 system and 2:5:5 system are available in the following versions:-
- With adjustment of the over-fold or underfold during operation by means of an external hand wheel and calibrated display.
- With press-button conversion from single to double production.
- With automatic conversion from single to double production.
- With collecting-andjaw-cylinder diameters adjustable during operation.
For large numbers of pages gear folders are also available. There are following advantages of the KBA offset technology:
- less start-up waste,
- even ink transfer during production,
- sven ink thickness across the whole width of the machine,
- negligible ink-misting,
- simple operation,
- optional accessibility due to economically constructed, identical printing units,
- reduction in maintenance costs,
- production with customary ink adapted for anilox inking units,
- production with customary colour separations,
- production with customary paper types.
The printing quality is no different from that of good conventional offset. Dot gain and printing contrast are also comparable.
WATERLESS OFFSETS PRINTING FOR SHEET FED & WEB FED
The offset process still contains the potential of increasing quality and technological improvment; particular attention. Reducing the amount of alcohol in the dampening fluid has become an important goal, desirable because it affects the protection of workers and the environment, and it also influences costs. In this context, waterless offset is fast emerging as an alternative. The process had been known for almost as long as wet offset, but up to around 10 years ago, there were no practical printing plates. Waterless offset is, however, accepted by an increasing number of users since Marks-3zet introduced Toray industries waterless plate from Japan to Germany in 1982.
Silicone Instead Of Aluminium
In the waterless process, a sillicone coating replaces aluminium as the hydrophilic surface to keep non-image areas free of ink. Special inks are required to make possible, in cooperation with the sillicone coating, the separation of printing (text and pictures) and non-printing areas.
For many years, MAN Roland has been gaining extensive experience with waterless offset. This enabled the company to put Toray plates on sheetfed presses and recently also webfed, presses since have been constantly improved, including their use for water less offset printing.
Best Results With Temperature Control
Practice has shown that constant temperature is required to stabilise the waterless offset process. The silicone coating of the Toray plate starts to-pick up ink, that is, to scum, when the temperature of the plate surface exceeds a certain lin-dt. Too low temperatures have a detrimental effect, particularly in solids. This is due to a developing picking tendency. Equipping the press with effective temperature control of the inking units keeps the process within the required temperature range.
The users may switch to wet offset without problems even when the presses are equipped for water less offset.
An efficient temperature control for plate cylinders has been developed. The unit blows cooled air from the outside onto the plate surface. Fens suck off the surrounding air and conduct it through heat exchangers. These adjust the air temperature to the value which is ideal for waterless offset and the energy used is optimised by circulating the cooling air through the cooling beam. The fan speed can be controlled individually if desired. This permits to compensate very quickly for temperature variations over the plate width. A combined cooling unit with two separate water circulating systems supplies as required, either cooled dampening fluid for wet offset or cooled water for the hea; exchanger in the cooling beam.
Temperature Control Of The Inking Units
The temperature of Roland 700 units is controlled via the inking units, a plant-proven method. Temperature -controlled water is conductedthrough the ductor and two distributors which are located in the immediate vicinity of the four plate inking rollers. An infrared sensor constantly monitors the temperature of the plate surface; water is automatically heated or cooled if the temperature deviates from the pre-set value.
There are two variants of temperature control of the inking units.
- Uniform temperature control for all printing units; All the units are supplied with water of identical temperature this method is sufficient for most applications.
- Individual temperature control of each painting unit; This variety is recommended where special inks, or inks with differing temperature stabilities, are used. Separate water circulations make it possible to eliminate eventual scumming in a printing unit by feeding only the affected unit with water of proportionally lower temperature.
In addition, two options are offered for temperature-controlled distributor roller surfaces; Rislsan or copper coating. Copper has a more favourable effect than Rilsan because of its superior temperature conductivity. It is therefore recommended where mainly waterless offset is to be used.
Another option recommended for waterless offset is a sucking system in the sheet feeder area which helps to prevent the formation of hick-eys.
Addition allym, dirt particles on the printing plate can be removed during the run with hickney catchers, yet another option.
Start-up Waste In Web Offset Reduced
An additional advantage of waterless offset is the fact that the process quickly reaches a stable system condition, a marked reduction of sta-t-up waste is possible on web presses because there is no need to reach an ink-water balance that is a major economical plus point.
Thee success already achieved with waterless offset on sheetfed presses, encoura the new technology for webfed presses, too. An important aspect is the fact that Toray, meanwhile, made available printing plates for longer runs which, in addition, are less sensitive with regard to handling than the plates of earlier generations. These new plates, therefore, can be used for longer web offset runs.
Waterless Technology For Heat-set Presses
All modem web presses are equipped with temperature control via the inking units. The temperatures achieved in the inking units are, however, too high for waterless offset This is due to the miling work of the rollers and to mechanical heat increase.
Systematic development has shown that, generally, waterless offset will work only if appropriate measures are taken in the printing unit to reach constant surface temperatures on plates through-out the run.
The dampening fluid which is transferred to the plate when printing wet offset and the evaporation of isopropanol alcohol provide for constant cooling of the plate surface. This cooling effect does not, of course, exist with waterless offset. Therefore, manufacturers developed a cooling air fan system which is mounted in place of the dampening units, these are replaced by inserting a cooling air beam, the press is equipped with an operating console for air cooling and temperature monitoring. Additionally, a cooling system of sufficient capacity is required.
Active Air Cooling
Active air cooling for blanket and plate cylinders is used in addition to temperature control via the inking units to keep the surface temperatures of plates and blankets constant within a closely defined range. This system consists mainly of several radial ventilators arranged in a row and a water-cooled heat exchanger. It enables the operator to adjust the amount of cooling air and therefore, temperature across the width of the plate. An infra-red sensor constantly monitors the plate temperature, another sensor picks up the surface temperature of a distributor roller. The water temperature for cooling the inking unit is calculated by a comparison between the distributor and plate temperatures. Inks are comparatively viscous. It is therefore important to create constant temperature conditions in the ink duct/duct roller area. The water-cooled duct rollers are supplied by a separate water circulating system. Temperature control valves take care of keeping the duct roller temperature at a constant value of around 25 degree C.
Making plates for the waterless process does not require any major changes. The plates are exposed in conventional vacuum frames and the use of control elements makes it possible to establish the correct exposure time with a stepped exposure the use of diffused light has no determental effects.
The plates are processed in an automatic processor, using appropriate chemistry. The equipment does, of course, require the investments of capital. The chemicals are not subject to labelling requirements. They may be disposed of in the normal way, and this applies to the Toray plates as well, plates may be corrected after development. Once ready for printing, the plates require slightly more careful handling because they are more prone to scratches than non-nal offset plates-care, therefore, -has to be taken when bending the plates and mounting them on cylinders.
THE SECRET OF THE WATERLESS PROCESS
The special feature of the Toray plate-the secret of the waterless process is the silicone coating it carries. It repels the ink, thus replacing the dampening fluid. The coating lies on top of the light-sensitive photopoly-mer layer which is coated onto an aluminum plate serving as carrier. The sillicone coating is protected by a transparent plastic film. The plate isexposed with ultraviolet lamps through the protective film. The light hardens the polymer coating, creating a firm bond with the silicone rubber coating, the protective film is removed after the exposure.
Subsequently, the developer (a swelling fluid) is applied. The swollen areas are rubbed off while the photopolymer coating remains as the ink carrier in the image areas.
The areas exposed to light develop a hardened silicone coating which serves to repel the ink in non-image areas.
In the waterless offset process, the halftone dots are on a slightly lower level than the surrounding silicone coating. This permits the transfer of large amounts of ink, increasing the print density. The smooth plate surface makes it possible to transfer the halftone dots on film to the plate, perfectly and with sharp edges. Waterless offset, therefore, is particularly suited for fine halftone work and for stochastic screens.
Printing plates for waterless offset cost about twice as much as conventional plates. Otherwise, the process offers many advantages. The print quality increases, the waste rate decreases, and the process is a perfect answer to environmental concerns.
The processing of the Toray plate is rather similar to the processing of plates for wet offset but the quantity of chemicals required is much lower. Waterless offset permits lengths of runs of around 300,000 sheets. The further extension of this length is currently under development.
Cylinder Machines: Hand and auto-fed cylinders are both made by several reputed manufacturers. While users are generally satisfied with both the price level and the quality of the machines, there are reservations about the lower output of the indigenous machines as compared to the older models of imported machines. Users also complain about the obsolete design and the engineering aspects of the machines which, in certain cases, have resulted in an unacceptable level of down time. There is therefore, an immediate need for Research & Development and quality control machines in order to upgrade the quality of these machines. Manufacturers of autofed platens is being phased out owing to failing demand.
India is a significant importer of printing machinery. Imports have grown at an Annual compound Growth Rate of 30 pe cent from Rs. 7 crores in 1980-81 to Rs. 42 crores in 1987-88. The largest share of imported printing machinery is accounted for by offset presses, Details are provided in Table 2.11.
Imports of Printing Presses: 1980-81 To 1987
(Qty. in Nos.; Value in Rs. Mns.)
DGCIS Monthly statistics of Foreign Trade of India.
- Includes sheetfed offset machines also.
- No letterpress rotaries are being imported.
- Includes sheet-fed, office type machines (sheet.size not exceeding 22 Ã— 36 cm).
Population of Sheetfed Offset Machiness by Various Sizes: 1990 to 1994
The number of web offset machines are expected to increase from the present 365 to 500 nos. by 1994.
Since many medium sized newspaper presses are in the process of switching over to offset technology, it is expected that the share of single plate cylinder (large sized) machine will increase from the present 26 per cent to about 30 per cent by 1994. Table 7.18 gives the population of web offset machines by type and sizes in the future.
Population of Web Offset Machines by Type & Size
Thus the total numbers of offset machines will increase from 17,560 in 1989 to over 21,300 by 1994 i.e. at an annual compound growth rate of 4 percent.
Demand for Plates
Based on the assumption that the norms of consumption of plates per machine will remain the same as of today, the demand for offset plates will increase from the present 27 lakh square metres to 33 lakh square metres by 1994 i.e. at an annual compound growth rate of 4 percent.
Imports play a particularly important role in the availability of photo-typesetters, offset machines, etc. In the case of equipment like four-colour sheet-fed offset machines, highspeed web-offset, film processors and colour scanners, automatic binding machines etc., the dependence on imports is total.
Details of product range and names of the large overseas suppliers in the Indian market are given in Annexure 4.
The exports of printing machinery have fluctuated over the years. They increased from Rs. 245 lakhs in 1980-81 to about Rs. 280 lakhs in 1989-90. Details of exports are given in Table 2.12.
Export of printing Machinery: 1980-81 to 1986-87
(Qty. in Non.: Value in Rs. Lakhs)
Source: DGCIS Monthly Statistics of Foreigen Trade of India-Exports.
Note: Includes booksewing Q. = Qunality, v = Value
The present (1989) market Size Of various items of printing & graphic arts equipment is estimated to be as under:
Produce a complete newspaper by computer software
Software to paginate a broadsheet newspaper page works in conjunction with the Editorial System Software. Pagination software, works on a standard platform IMB-PC compatible system. Both the Editorial and Pagination software operate simultaneously on the same system.
The body copy of the story can be generated in the Editorial system, either by key entry-or import of the story from a wire service or the word processor. The composition of the body copy is done automatically by the system, without the need to enter any conunand. The status column of the Editor gives information on the depths of the story in newspaper lines and in other units of measurement. The status is also given on the active font, point size, leading, X and Y position of the cursor on the printed page, line length occupied and remaining. The information can be used to detem-dne the size of the storyhole on the page grid.
As a one time effort, the basic constant elements on a page such as masthead, page slugs, etc., are created as page from files. These page form files get utilised by the system automatically while preview or print of any particular page.
Page grid is a screen representation of the news-paper page. It represents graphically, on the screen the number of columns and lines. Every vertical lifie denotes a column and a horizontal line repeated at a frequency of 5 newspaper lines. The accurate position of the cursor is depicted in the right hand of the screen, which shows the column and the line on which the cursor is currently located. The screen also gives the default typesetting parameters of line length, gutter space and leading. A menu of available functions/ commands also appears on the right hand bottom of the screen.
Creating a story-hole on-the page grid
Story hole is a rectangular space reserved on the page grid, to accommodate the story which is active on the terminal. The story being edited on the terminal is the active story. Page gird can be accessed by pressing â€œEâ€ in the Command mode.
If the body copy and basic elements (Headline etc.) are ready, the story can be registered automatically on the page gird by a single key command, â€œAâ€. This command will calculate the space required by the story and generate an appropriate story hole. The story hole can be placed at a required position on the grid.
To commence â€˜Registrationâ€™ of the storyhole, a user has to press â€œFtâ€ on the page grid, after moving the cursor to the top-left comer of the story hole. Using normal cursor keys, the â€œStory-holeâ€ is drawn. Registration is completed by pressing â€œRâ€ again. During the process of drawing the â€˜story-holeâ€™, system gives the user information on the number of columns and newspaper lines spanned by the story hole on the page grid. Columns with unequal depths can be defined visually on the page grid, after the story-hole is generated.
The geometry of the story hole, including number of columns and newspaper lines is transferred to the active story in the Pagination System and the story is now automatically composed with this geometry.
After the story elements like Headline, Intro, Slugline etc., are composed, the system will automatically feedback the user on the over/under setting of the complete story.
All the story-elements can be composed from the menu in an easy way. The â€˜Menuâ€™ is accessed by pressing â€˜Shift+?â€™ from the Command Mode.
To compose Headline, for example, press â€˜Hâ€™ from menu. The screen is horizontally divided in two parts. The upper half denotes the default typesetting parameters which Will be used by the â€˜Headlineâ€™. Any of these default parameters can be altered.
The Headline matter is keyed-in in the lower half. The status column on the right, besides giving information on typesetting parameters is also used to determine the head fine fit, since information is available on the space already occupied by the text and the space balance.
For any story element, it is possible to define the font, point-size, leading, justification and over/under line. It can also be specified to span a given number of columns, for a specified number of lines, to begin from a given column and also the ability to place it vertically at Top, Middle or Bottom, or at a specified line number within the story.
Composing the Complete Story
With body copy and all story elements in place, if the story is composed, it will automatically acquire the layout from the geometry of the â€˜Story-holeâ€™ to fit the story. The story can also be previewed on the screen, with facility for zooming.
A story can be automatically encapsulated in a box. The rule thickness of the box is derived from the default settings. The story will be boxed; if the option of Boxed text in the â€˜compose Setup Menuâ€™ or in Story Elements Menu is turned ON. The system will automatically alter the column width of the body copy to accommodate the box.
Rules between stories and Over Underline for Story Elements
Rules of defined weight will be drawn automatically between individual stories. These can be both horizontal and vertical. Also, for story elements like by-line, the rules above & below are drawn automatically. Horizontal and Vertical space between rules and the text is also handled automatically.
This is very useful facility available with the software for last minute changes on a page. The page as a whole can be accessed without opening any particular story. This is simply done by asking for a specific page grid identified by publication date and page number. The full page grid is displayed on the screen. Any story in the page can be selected for functions like sizing, edition, deregistering or processing in any other permissible way.
The Classified Advertisement Management & Processing System (CAMPS) allows you to book an advertisement, modify, inquire and cancel an ad, schedule the advertisements, generate page layout and screen or printer output as required. Apart from this, a history of transaction data is maintained and updated at specific intervals. CAMPS also provides several vital reports, which can greatly influence marketing decisions. Since there is an exact calculation of the number of word, line and size of the ad, the charges calculated by the system will be exact reducing the loss of revenue caused due to miscalculation. Moreover, the time spent in manual sorting of ads and page layout will be reduced due to automatic scheduling and layout, this greatly improves efficiency, saving a lot of money and time.
The uniqueness of the system lies in the fact that a user can configure the entire system as per his specific requirements. The system provides tools for designing pages and the elements of the pages. The user can configure the details of each publication, category, sub-category, appearance of different types of ads, rates and the discounts.
Yellow page software
Abacus Computer Limited with their expertise in the pre-press technology, have developed just the right solution for the Yellow pages directory publishers. The software, a combination of commercial data entry/ analysis module and an automated typesetting module has proven to be a very successful Yellow Page pagination software.
The concept applied to develop this product is Database Publishing.
The front-end module of Yellow Page software is dedicated to data capture, validation, archival and sorting. Various information analysis can be performed using this module, such as salesman wise statistics, business category wise statistics, etc. The data thus captured is stored in a Data base formal. Data entry is an integral part of the Yellow Page Software. Depending on the type of listing/ladvertisement, the data entry formats are provided.
For boxed type ads (NB ads), the text is taken at the time of data and is formatted automatically.
The back-end module essentially is an interface to the typesetting software, Abacus SCRIPT. This module will take in the validated and sorted data from the frontend module and embed pre specified page pararheters on the entire job and will also attach typesetting parameters to each of the database fields, depending upon the definition of the type of the entry (fee listing/bold listingfboxed listing, etc.) The system will also caterto the display advertisements by providing space asked for on the page. Dynamically, the depth remaining on the page will be calculated and page will be planned accordingly, automatically.
The software is totally menu driven. Described below are the menu options, which will give an insight to the software capabilities and operations:
Parameter File Maintenance
Here, you can define Page Parameters. For example, as Paper Length, Paper Width, Number of Columns, Column width and Gutter Space according to your specifications. In the same way, index page parameters like number of columns, column width, gutter space, can be defined. Identification code, product code, reference code, page number, heading text, point size, line space and font to be used, can be defined.
Text parameter particulars like page header and product category point size and line space can be set. The input product may or may not be placed in a box. For different types of ads like free listing, normal listing, bold listing and NB ads typesetting parameters like point size, font type canbe defined individually.
The software also allocates free space for dummy information. For example, on which page the dummy information is to be placed, number of columns and size of the advertisement. The chooser has three options (as example, the dummy ad should be on every 2nd page, or every 6th page, or every 10th page).
Advertisement Size File Maintenance
The option allows to enter the type of advertisement (normal or display), advertisement type in codes, number of columns and size of the advertisement. The advertisement types can be modified/deleted and a list of records present can be printed and displayed.
Area Master File Maintenance
Records can be added by giving an area code and area name. The enties can be modified, deleted, displayed and printed.
Category Master File Maintenance
Records can be added by giving category code and the category name. Also, a across reference code can be given. An indication can be set to show, whether an area wise sorting is required or not for this product category. The entry in the file can be modified, deleted or printed.
Salesman Master File Maintenance
This file maintains information regarding sales persons involved in sales of advertisement space. This information is further used to process the database towards analytical reports.
All file maintenance options are design definitions for the Yellow Page directory and as.such, are one-time efforts.
After the data is entered, the page formating option flows the data into pages and generates SCRIPT files using The page parameters already specified. Similarly, the index (with cross reference) will be generated with headings, automatically. Abacus Computers Limited has its origin in the fascinating world of computers in India in September 1983, with intention to impart technical consultancy services to the industry.
From the formative years, Abacus has shown abilities to be innovative. Abacus pioneered the Desk Top Publishing revolution in India. It has to its credit more than 150 newspaper installations and thousands and odd DIP customers in India. The impressive client list is exhaustive and evergrowing. The Pioneer (Delhi and Lucknow), Independent (Bombay), Economic times (Ahmedabad), Economic Times (Calcutta), Navbharat Times (Bombay and, Lucknow, The Afternoon (Bombay), offer eloquent testimonies to the cost-effective and most productive techniques developed indigenously by Abacus.
The history of gravure printing begins with the work of creative artists during the Italian Renaissance in the 1300s. Fine engravings and etchings were cut by hand into soft copper. The designs were cut away, leaving a channel, or sunken area, to hold the ink during printing. The term intaglio, which we use today to describe a class of printing, is an Italian word meaning to print with a sunken pattern or design. Gravure is a type of industrial intaglio printing that is used for extremely long press runs.
Intaglio quickly gained widespread recognition as a rapid, high-quality printing process that could be put to many different Uses. The French artist Jacques Callot developed his reputation by sketching the fighting on battlefields and then rushing back to his studio to print etchings of the scenes. He would sell the etchings only a few days after the battle. Callot is sometimes called the first photojournalist because of the speed with which he distributed copies of his sketches.
An early paternt design for a French rotogravure press.
The first photographic intaglio prints were made by Joseph Nicephore Nidpce in about 1814. Nidpce, who called his process heliog-raphy, printed his products on a copperplate Press. Fox Talbot refined Ni6pceâ€™s work and developed the first film negative in addition to working on heliography printed his products on a copperplate press. Fox Talbot refined Nicpceâ€™s work and developed the first film negative in addition to working on heliography.
The person who is recognized as the inventor of modem gravure printing, however, is Kari Klif (born Klitsch). Klif began experimenting with photographic copper etching in 1875. By about 1879 he had refined the process and formally announced his â€œheliogravureâ€ process to the Vienna Photographic Society. Klif produced very high-quality reproduction for art collectors but gained little recognition outside Vienna because he wanted to keep his techniques secret. Klif eventually sold his â€œsecret,â€ but continued to refine the process until his death in 1926. He made the revolutionary move from flat printing plates to printing from cylinders. He developed the first doctor blade, or squeegee, and even designed a method of printing color on a web press. Klif originated the term rotogravure for printing from a cylinder.
After Klif shared his secrets, others became interested in rotogravure and began designing and building equipment for the process. By the beginning of this century, rotogravure had developed a relatively widespread reputation for fine reproductions. By 1920 huge presses with four or five color units were being used for gravure Postcards, calendars, book illustrations, and even magazines were being printed in full color.
One of the major uses of gravure that began in the 1920s was the printing of the supplement section of the Sunday newspaper. The section carried human-interest stories, many advertisements, and lots of color photographs. The supplement section was, and continues to be, a favorite item that readers look forward to each week.
The supplement section and rotogravure printing gained such widespread public recognition that living Berlin wrote a Broadway play that used the two as a theme. Although Berlin was one of Americaâ€™s most famous songwriters, few remember that 1934 play called As Thousands Cheer. However, almost everyone remembers the playâ€™s opening song, called â€œEaster Parade,â€ The most famous lines of the song mention both rotogravure printing and the Sunday supplement because the two terms had come to mean the same in the publicâ€™s eye.
Figure 1 Five or the printing processes. Relief printing (a), Intaglio printing (b), Screen printing (c) lithographic printing (d), and electrostatic printing (e)
On the Avenue, Fifth Avenue, the photographers will snap us, and youâ€™ll find that youâ€™re in the rotogravure.
Recall from chapter I that intaglio is one of the five major printing processes.
- Relief forms an image from a raised surface.
- Screen passes ink through openings in a stencil.
- Lithography prints photochemically from a flat surface.
- Electrostatic prints electromagnetically.
- Intaglio transfers ink from a sunken surface.
Students new to the printing industry some- times have difficulty visualizing how it is possible to print from a sunken or negative surface. As you will see in this chapter, preparing industrial intaglio plates is perhaps the most sophisticated and technically demanding of all current methods, yet they are the simplest to print on a high-speed press. The intaglio process also delivers the most significant v consistent, high-quality results.
Terms associated with intaglio include etching, engraving, drypoint, and collagraphy. Artists use these terms to describe images printed from lines cut into the surface of metal or plastic.
Industrial intaglio is called gravure printing, or rotogravure. Roto means â€œround.â€ Therefore, rotogravure is printing from a cylinder. All industrial intaglio transfers an image from sunken areas cut into the surface of a cylinder. Except for small proof presses, most industrial gravure presses are web fed. As the plate cylinder turns, a continuous roll of paper, foil, or plastic passes through the press to receive the image. After printing, the roll is either re wound for shipment to the customer or cut into sheets at the end of the press by a device called a slitter.
Figure 2. A gravure press Cylinder. Rotogravure means printing from a cylinder
Figure 3. A web-fed gravure press. Almost all Production gravure presses are web fed
The Gravure Industry
Gravure is a major printing process. Over 18 percent of all printing in this country is done by gravure. The gravure industry has enjoyed a relatively steady growth rate and, with recent technical advances, will continue to gain a larger share of the printing market. Several important characteristics make gravure an ideal process for jobs requiring high quality and extremely long press runs.
- Gravure is the simplest of all printing systems, with the fastest press start-up and the. most direct press controls.
- Gravureâ€™s easy press control results in very little paper waste. Gravure has less tha half the paper spoilage rate of lithography.
- Gravure press speeds are extremely high. The largest gravure presses can operate as rapidly as 45,000 impressions an hour.
- Gravure cylinders are especially hardy. Several million impressions from the same cylinder are common. Some printers report press runs as long as 20 million copies without the cylinder wearing out.
- Gravure gives the highest-quality image of the five major printing processes. It has a reputation for delivering excellent color and inkdensity, even on low-quality printing papers.
Traditionally, the most significant disadvantage of gravure was the length of time required to prepare the cylinder. New tehnology has automated much of the process, but this has not changed the fact that gravure cylinders are enormously heavy and require special equipment to maneuver them and significant plant space to store them, Gravure presses are also massive, expensive, and out of the reach of smaller shops. Traditionally, gravure has only been used for jobs of 60,000 or more, but this is changing as automation improves and turnaround time decreases.
Gravure printing is divided into three broad product areas, each with its own special problems and solutions. The first area is packaging printing. This includes producing folding cartons, bags, boxes, gift wrappers, labels and I flexible materials that eventually form containers.
The second area is publication printing. Publication printing includes producing newspaper supplements, magazines, catalogs, and mass mailing advertisements. Gravure is ideally suited for the long press runs required for the Sunday newspaper supplement sections that are distributed on a national basis.
The third area of gravure printing is specialty printing. In this area, gravure is used to print such materials as wallpaper, vinyl, floor coverings, and even textiles for both decoration and clothing fabrication.
Companies have found that they become more efficient and cost effective by limiting the jobs they accept to a specific product, area.
The Gravure Association of Amrlca
One reason for the steady growth of gravure printing in the United States has been the cooperative efforts of gravure printers, suppliers, and manufacturers who focus through the Gravure Association of America (GAA). GAA provides consultative assistance, publishes a wide range of technical materials related to all phases of gravure production, has worked to establish industry standards, supphes technical aids, and has a tradition of collegial efforts to educate printers and to disseminate information on gravure printing. Much of the information contained in this chapter was compiled through the courtesy and cooperation of the GAA. Individuals interested in using GAAâ€™s services or in becoming affiliated with the organization should write to the Gravure Association of America, 1200A Scottsville Road, Rochester, New York 14624.
Basic Gravure Concepts
Gravure is so radically different in both concept and technique from other printing processes that it is important to first review a number of key ideas. With these concepts in place we can move to descriptions of cylinder preparation and presswork.
Methods of Cylinder Preparation
There are four basic methods of gravure cylinder preparation:
- Diffusion etch
- Direct transfer
- Electromechanical process
- Laser cutting
In the diffusion-etch process a special mask is prepared by first exposing it through a special gravure screen and then through a film positive of the printing image onto a light-sensitive base. The mask is then applied to a copper gravure cylinder and is developed on the cylinder. After development, the mask is thick in the nonimage areas of the cylinder and very thin where the image will carry ink. The cylinder and mask are then placed in an acid bath. The acid bath penetrates the thin areas of the mask and eats or etches away the copper of the cylinder. The final step of diffusion etch is to remove the mask and apply a thin layer of chroriie over the entire cylinder by an electroplating process. (See the Copper Plating - and Polishing section of this chapter). The purpose of the chrome is to extend the life of the surface areas. Direct-Transfer Process
The second method of cylinder preparation is called direct transfer. The main difference between diffusion etch and direct transfer is the way in which the cylinder mask is exposed. In direct transfer, a light-sensitive mask is sprayed or applied over the cylinder surface. The mask is exposed by directing light through a halftone positive as, it moves past the cylinder, which turns at the same rate that the positive moves. The final steps of developing, etching, and chrome electroplating are the same as in the diffusion-etch technique.
Figure 5 : Cylinder preparation : Direct transfer. In the direct-transfer process, the lightsensitive mask is exposed by passing light through a halftone positive as it moves in contact with the rotating cylinder.
cylinder preparation Diffusion etch.
The Three main Step in the conventional gravure process are mask exposure (a) attaching the mask to the cylinder (b) and etching (c)
This direct digital process has essentially replaced chemical engraving as the most prevalent method of cylinder engraving. In this electromechanical process, a clean copper cylinder is mounted in a special engraving machine. The mask and copy to be engraved are scanned by an optical device that uses photodiodes to receive the image, which is then transformed into digital data. This digitized information is translated to the motion of an engraving head, typically a diamond stylus that cuts into the surface of the cylinder as it rotates. A diamond stylus can vibrate at approximately 5,000 cells per second. After cutting, the cylinder is chrome electroplates and made ready for the press.
Figure 6. Diagram of the electromechanical process. The cylinder is etched by using a diamond stylus in the elctromechanical process.
One computer-driven approach to engraving large-format cylinders has been the Helioklischograph, developed by Hell Gravure Systems. This electromechanical engraving machine can be driven from film mounted on a scanner or directly from computer files. Hell has continued to improve the capabilities of its HelioKlischographs, with current machines capable of working as part of a fully automated workflow with up to 16 simultaneous engraving channels.
The fourth technique of gravure cylinder preparation is called laser cutting. In this process, a series of small holes, or wells, is etched chemically over the entire surface of a clean copper cylinder. The wells are then filled with a plastic material until the cylinder again has a smooth, uniform surface. Like the electromechanical method, the original copy is scanned by a beam of light. The laser cutting process, however, uses the narrow beam of a laser to blast away or remove parts of the plastic from individual wells rather than a diamond tool to cut way metal. In the final step of laser cutting, the cylinder, can then be sprayed with a special electrolyte and electroplates with chrome.
Direct laser engraving is not that widely used yet, but is gaining attention. Advancements such as a copper alloy developed by the Daetwyler Corporation has proved much more successful at being digitally engraved by laser than ordinary copper cylinders. The LaserStar, by Daetwyler, engraves data processes in an open TIFF format and has dual engraving heads that allow for speeds of up to 140,000 cells per second As laser engraving does not involve parts to be worn down such as the diamond stylus used in electromechanical engraving, it eliminates certain multichannel ribbon variances that could occur.
Figure 7. A High-speed laser engraver.
Of the four cylinder preparation processes, diffusion etch is the old-est and now, along with the direct-transfer process, the least used in the industry. Recent advances with the laser process point to changes in the future that may revolutionize gravure cylinder preparation. Currently, direct digital electromechanical engraving accounts for the vast majority of cylinder-making in the United States). It is a proven cost-effective way to engrave cylinders and, coupled with a fully automatic workflow, is making gravure competitive with other shorter-run processes.
An Electromechanical publication engraver with extensive automatic controls.
Figure 9. Diagram of the Gravure Printing process. Etched wells in the printing cylinder pick up in from the fountain. The excess ink is wiped from, the surface of the cylinder by the doctor blade the ink is applied to the press sheet.
Gravure transfers ink from the small wells that are etched or cut into the surface of the cylinder On the press, the cylinder rotates through a fountain of ink. The ink is wiped from the surface of the cylinder by a doctor blade. The cuplike shape of each Well holds ink in place as the cylinder turns past the doctor blade. The formation of perfect weds is the main goal of the gravure engraver. There are several important ideas to understand about gravure wells.
Every gravure well has four variables (figure 14.10):
The depth of the well is measured from the bottom of the well to the top surface of the cylinder. The opening is the distance across the well. The bridge is the surface of the cylinder between wells. The doctor blade rises against well bridges as it scrapes ink from the cylinder.
Within the diffusion-etch technique are two basic types of well design:
- Conventional gravure
- Lateral hard-dot process
In the conventional grevure design, every well on a cylinder has exactly the same opening size. The amount of ink to be transferred to the paper is controlled only by the depth of the well, When reproducing photographic material, a continuous-tone film positive, rather than a high-contrast halftone, is used to expose the mask.
The second major type of well design with diffusion etch is called the lateral hardtone process (sometimes called halftone gravure design). Two separate film positives are used to expose the mask with the lateral hard-dot process. The first is a continuous tone film positive, as with conventional gravure. A second exposure is then made with a halftone film positive that falls in the same position on the mask as that of the first exposure. The result is wells that, vary in both opening size and depth.
Figure 10. Diagram of gravure cylinder wells. A gravure well has four varialbles: depth bottom, opening, and bridge
The direct-transfer method of cylinder preparation produces yet another well design. A single halftone positive is used to expose the mask in this process. The dot formation in the halftone defines the opening size of each well. The depth of each well is the same, however.
Electromechanical well formation is a bit different from diffusion etch or direct transfer.
In the electromechanical process, each gravure well is created by the action of a diamond stylus as it pushes into the soft copper surface of the cylinder. A direct relationship exists between the depth of the cut and the well opening size. As the stylus pushes deeper into the cylinder, increases the opening of the well. This action influences the Volume of ink that the well can carry. In photographs, shadow area wells are much deeper than highlight wells.
Figure 11 Three Examples of gavure well, (a) Conventional gravure wells (a) very in depth, but all have the same opening size, (b) Lateral hard-dot wells vary in both depth and opening, (c) Direct-contect wells depth vary in opening size, but all have the same depth.
Figure 12. Cutting a cylinder surface. In the electromechanical engraving wells are cut in the cylinder as a diamond stylus moves into and out of the copper.
Most art work is delivered to the gravure engraver in the form of film positives. The characteristics of film images used by gravure are somewhat different from those used in other printing methods, however. The main difference is the image density range (see chapter 4 for a review of densitometfy). Wells are etched or cut in proportion to the density of the corresponding area on the film positive.
There is a minimum well depth that holds ink during the gravure printing process. If the well is too shallow, the actions of the doctor blade and the rapidly spinning cylinder can actually pull ink from the well. Film positives must therefore be prepared with a minimum density so that each well is deep enough to hold ink.
For continuous-tone images, the GAA recommends a density range of 0.30 to 1.65. This means that the highlight areas of the positive should have a transmission density of 0.30 and a shadow reading of 1.65. The difference between the two measurements produces a BOR of 1.35, which is acceptable to commercial photographers yet still exceeds the range o most halftone negatives used in lithography.
Line images, such as type, ink, or line borders, are also supplied ir film positive form. Line image density should be near the 1.65 shadow area density of continuous-tone images. Film positives are often sup plied to the engraver with both continuous-tone and line images on the same piece of film. The most common approach is to first prepare each type of image separately in negative form, and then to make several contact exposures on a new sheet of film to create one film positive.
Cylinder Construction and Preparation
The quality of the final gravure image depends first on the construction of the cylinder. Almost all cylinder cores are made from steeltubing. Some packaging printers prefer extruded, or shaped, aluminum cores because they are much lighter, less expensive, and easier to ship thin steel. A few companies use solid copper cylinders, but steel remains the most popular core material.
A steel cylinder is used when printing with adhesives or other corrosive materials. In most gravure printing, however, a thin coating of copper is plated over the steel core of the cylinder to carry the image. Copper is easier to etch than steel and can be replaced easily when the job is finished.
There are five important parts to identify on gravure cylinder 3).
Figure 13 Parts of a gravure cylinder. The most commonly identified parts of a gravure cylinder are axis, shaft, diameter, circumference, and face length.
- Face length
The axis is the invisible line that passes through the center of the length of the cylinder. The cylinder shaft is the bearing surface as the cylinder rotates in the press. If you look at the end view of a cylinder, the shaft appears as a circle. The diameter is the distance across the circle, through the center of the shaft. The circumference is the distance around the edge of the end view. The face length is the distance from one end of the cylinder to the other, along the length of the cylinder.
The face length of the cylinder limits the width of paper to be printed. The circumference limits the size of the image. C one rotation of the cylinder around its circumference is called one impression. Continuous images can be etched on a cylinder without a seam so the design is repeated without a break. Wallpaper designs are commonly printed by gravure.
Figure 14. Two forms of gravure cylinders.
There are two basic form of cylinder construction: mandrel (a) and intergral shaft (b)
Gravure cylinders are built using many different sizes. The face length is always the same for each press to match the press sheet size but varies in diameter and circumference to closely match the cut-off size of the specific job. There are two basic cylinder designs.
- Integral shaft
A mandrel cylinder (sometimes called a sleeve or cone cylinder) is designed with a removable shaft. Most holes are tapered so that the shaft can be pressed into place and then removed easily.
In the integral shaft design, the shaft is mounted permanently on the cylinder. The cylinder is formed first, and then the shaft is either pressed or shrunk into place. The shaft is attached permanently by welding and remains in place for the life of the cylinder.
Integral shaft cylinders are more expensive than mandrel cylinders but are generally considered to produce high-quality images. This is because they produce greater support -across the length of the cylinder during press runs than hollow mandrel cylinders.
Balancing the Cylinder
When a cylinder (or any round object) rotates at extremely high speeds, vibration can be a problem. That is why automobile tires must be carefully balanced before use to prevent undue wear or poor steering control. A major concern with gravure printing, is vibration caused by an unbalanced cylinder. A great deal of fibration can bounce the cylinder against the doctor blade and result in a poor image Vibration can also damage the press. There are two types of cylinder imbalance: static and dynamic.
Static imbalance occurs when the cylinder is not perfectly round or has different densities within a cross section Static imbalance can result from such defects as air holes, impurities in the steel core, or improper copper plating and polishing (see following section).
Figure 15 Example of cylinder imbalance.
Dynamic imbalance occurs when the cylinder differs in density or balance from one end to the other Dynamic imbalance is the greatest cause of cylinder vibration at high press speeds. Both static and dynamic imbalance can be corrected by either reducing or adding weight to each end of the cylinder.
Copper Plating and Polishing
Electroplating is the process of transferring and bonding very small bits (called ions) of one type of metal to another type of metal. This process takes place in a special liquid plating bath. The ions are transferred as an electrical current passes through the bath. The longer the current flows, the more new metal that is plated to the cylinder.
The first step in the gravure electroplating process is to clean the surface of the cylinder thoroughly. The cylinder is cleaned by brushing or rubbing it with special cleaning compounds and then rinsing it with a powerful stream of hot water. Some plants use special cleaning machines for this purpose. The goal is to remove all spots of grease, rust, or dirt so that a perfect coating of copper can be applied over the entire cylinder surface. Cylinder areas that will not be plated, such as the ends, can be coated with asphaltum or other staging materials, which covers and. protects its clean surface.
To electroplate a cylinder, the cylinder is suspended in a curved tank and rotated through the plating bath. The electrical current is allowed to flow from the copper anode (the plating metal) through the bath to the cylinder (base metal). Zinc sulfate, copper sulfate, or cyanide solutions are common plating-bath liquids. Six-thousandths of an inch (0,006 inch) to thirty-thousandths of an inch (0.030 inch) is the common thickness range for the copper layer on a gravure cylinder.
Figure 16. Cleaning the cylinder surface. It is important to remove all spots of grease, rust, or dirt so that a perfect layer of copper can be applied to the cylinder surface.
A newage gauge is a device used to test the hardness of copper. Copper hardness is measured by pushing a diamond point into the copper surface. The diagonal length of the opening created by the diamond point is measured and then compared with the amount of force required to push the diamond into the copper. The result is expressed in diamond point hardness (DPH). Most printers look for a DPH between 93 and 122.
Figure 17. Diagram of the electroplating process. An electrical current passes
from the copper anode through the plating solution to be the steel of aluminum cylindjer until the desired thickness of copper is plated on the cylinder.
Figure 18. Diagram of a doctor blade against an uneven cylinder. If the cylinder is not uniform, the doctor blade will not be able to remove excess ink from the nonprinting surface.
The last step in constructing a gravure cylinder is to bring the diameter (and circumference) of the cylinder to the desired size and at the same time create a perfect printing surface. The cylinder must not only be round and balanced perfectly, it must also be perfect smooth and uniform across its length. If the cylinder is not uniform, the doctor blade will not be able to remove excess ink from the non-printing surface.
The newly plated cylinder is mounted in a lathe and prepared for final turning, Some plants use a diamond cutting tool to bring the cylinder into rough dimensions; they then use separate grinding stones to polish the cylinderâ€™s surface. Other plants use specially designed precision machines that both cut and polish the cylinder at the same time. With these machines, cylinders can be cut within one ten-thousandth of an inch (0.0001 inch) of the desired size and surface. After the final turning, the cylinder is ready for image etching.
Gravure cylinders can be reused many times. One way to reuse a cylinder is to cut away the old image on a lathe. This involves removing only two-thousandths to three-thousandths of an inch of cylinder surface. The cylinder is then replated with copper and recut or reground to its original diameter.
Figure. 19 Final turning of a plated Cylinder, (a) The cylinder is first cut to rough dimensions, (b) Then it is ground of polished to final Size.
Another way to reuse a cylinder is to simply dissolve the cylinderâ€™s chrome coating (added as the final step in cylinder preparation to protect the soft copper on the press) and to then plate over the old image with new copper. The replating process fills the image areas above the original cylinder surface. Excess copper is then cut or ground away, and the cylinder is returned to the desired diameter size.
Ballard Shell Cylinders
The ballard shell process is a special technique used by some publication printers that allows easy removal of a copper layer after the cylinder has been printed. The cylinder is prepared in the usual manner, including copper plating, except that it is cut twelvet housandths to fifteen-thousandths of an inch undersize in diameter. The undersized cylinder is coated with a special nickel separator solution and is returned to the copper plating bath. A second layer of copper is then plated onto the cylinder over the first layer. The cylinder is then cut or ground to the desired size, given an image etch, and, printed.
The difference between most gravure cylinders and ballard shell cylinders is seen when the cylinder has been printed and is ready to receive another image. The second copper layer can be simply ripped off the ballard shell cylinder base. A knife is used to cut through the copper to the nickel separator layer, which allows the shell to be lifted away. The cylinder can then be cleaned, a new nickel separator solution can be applied, and another shell can be plated to receive the image,
Almost all gravure printing is done on web-fed presses . Paper or some other material (called a substrate) feeds from large rolls to the printing unit through an intricate system of tension and registration controls -The paper then passes between the image cylinder and an impression cylinder. Some companies use offset gravure, but most transfer the image directly from the cylinder. After the paper leaves the printing unit, it might pass through a set of driers to set the ink, or it might follow an intricate set of rollers to dry by aerial oxidation and absorption. When the paper enters the delivery unit of the press, it might be slit cut into sheets and folded or re-wound onto a roll for shipment to the customer.
Figure 20 A printing unit of a web-fed press
Many of the common concerns of gravure web-press operation are similar to others dealing with basic press design and operation. Special concerns of gravure inks are discussed in chapter 16. Some concerns, however, are unique to gravure press operation. The two main concerns of cylinder and doctor blade adjustment and impression rollers ire examined here to complement the information presented in other chapters.
Figure 21. Sitting the printed paper. Some jobs require that the web slit into smaller rolls at the delivery end of the press.
Figure 22. Folding unit of web press. Some jobs are cut into sheets and folded in line on the press.
Figure 23 Rewinding printed paper. Some jobs are rewound onto a roll after printing.
Figure 24. Diagram Showing the counter.
The counter is the angle between the doctor blade and the cylinder surface.
Cylinder and Doctor Blade Considerations
The function of the doctor blade is to wipe ink from the surface of the plate cylinder-, leaving ink in only the recessed wells. A great deal of research has been done on materials, angles, and designs for doctor blades.
Several different materials are used for blades. The goal is to minimize blade wear and reduce heat generated by the rubbing of the blade against the turning cylinder. Plastic, stainless steel, bronze, and several other metals have been used with success. The most common blade material, however, is Swedish blue spring steel. Blades are usually between 0.006 inch and 0.007 inch thick. The blades must be relatively thin to reduce wear on the cylinder, but strong enough to wipe away ink.
Blade angle is another important consideration. The angle between the blade and the cylinder is called the counter. There is much debate about the proper counter for the best image quality. The best counter depends on the method used to prepare the cylinder. For example, with electromechanically engraved cylinders, image quality decreases as the counter increases. Most angles are set initially between 18 degrees and 20 degrees. After the blade is placed against the cylinder and production begins, however, the counter generally increases to around 45 degrees.
One way to set the blade angle is by using the reverse doctor principle. With this approach the doctor blade is set at a large enough angle to push the ink from the surface.
Several different doctor blade designs are used by gravure printers. The most popular are conventional and MDC/ Ringier. Care must be taken to keep the conventional design sharp and uniform. Most printers hone the blade by hand with a special stone and then polish it with a rouge or emergy paper to get a flawless edge while the MDC/Ringier design tends to self-sharpen. The MDC/Ringier design has a longer working life then the conventional form design and requires less press downtime for blade cleaning and repair.
Figure. 25 Diagram showing a reverse doctor blade. A reverse doctor blade pushes ink from the cylinder surface.
Figure 26 Example of different ductor blade designs
The action of the doctor blade against the cylinder is of special concern. The blade rides against the cylinder with pressure. Pressure is necessary so that the ink does not creep under the blade as the cylinder turns. The most common method of holding the blade against the surface is by air pressure. The blade fits into a holder, which is mounted in turn in a special pneumatic mechanism. Most printers use pressure of one and a quarter Pounds per in across the cylinder length.
Most doctor blades are not stations however. As the cylinder rotates, the blade oscillates, or moves back and forth, parallel the cylinder. This oscillating action works remove pieces of lint or dirt that might other wise be trapped between the cylinder and ti blade. Dirt can nick the blade. Nicks allow narrow bead of ink to pass to the cylinder su face. Nicks are major defects that can ruin the image or scratch the surface of the cylinder.
Figure. 27 Diagram of a gravure cylinder showing prewipe and ductor blades. Most presses use prewipe blades to skim most of the ink from the cylinder before the cylinder reaches the doctor blade.
Figure 28. Diagram showing the nib width
The nib width is the area of the cylinder where the paper contacts the cylinder by the pressure of the impression roller.
A prewipe blade is commonly used high-speed presses to skim excess ink from cylinder ( 7). This device prevents large quantity of ink from reaching the doctor blade and ensures that the thin metal blade wipes the cylinder surface perfectly clean.
Figure 29. Diagram showing inking on defective paper. If defects in the paper prevnt contect with the gravure cylinder, ink, will not transfer.
Use of an impression roller is the second main difference between gravure presses and other web-fed machines. The purpose of the impression roller is to push the paper against the gravure cylinder to transfer ink from the image well. The major considerations for impression rollers are coating and hardness, pressure, and electrostatic assist.
Coating and Hardness
Most impression rollers are formed from a steel core coated with rubber or a synthetic material, such as Du Pontâ€™s Neoprene. Rubber hardness is measured by a Shore durometer. Values are given in Shore A readings. Hardness increases as Shore A numbers get larger. Different types of paper or substrates require different degrees of hardness for the impression roller. Material such as cellophane might require 60 Shore A, but kraft paper or chipboard might need 90 Shore A.
Ink transfers to the web by pressure of the impression roller. Pressure might vary from 50 pounds per linear inch (pli) to 200 pli. More pressure does not always give better image quality, however, The amount of pressure the operator sets is determined by previous tests for the kind of paper being printed. Whatever setting is selected, it is critical that uniform pressure is applied over the entire length of the cylinder.
The area of contact between the impression roller and the cylinder is called the nib width, or flat The amount of nib width is determind by the hardness of the impression roller and the amount of pressure. The nib width is important because it is the area of image transfer to the paper or plastic web. The nib width is adjusted to give the bestquality imago on the web stock.
A great advantage of the gravure process is that it allows high-quality images to be printed on low-grade papers. Problems do occur when the paper surface is coarse and imperfect, however, ink transfers by direct contact. If a defect in the paper prevents that contact, then no image will transfer The Gravure Research Association (now part of the Gravure Association of America) designed and licensed a special device, called an electrostatic assist, to solve this problem and improve image transfer. With electrostatic assist printing, a power source is connected Electrostatic assist printing charges the impression roller and the gravure cylinder so that the ink lifts electrostatically from the cylinder to the paperbetween the cylinder and the impression roll. A conductive covering must be added to the impression roller, but the cover causes no special problems. An electric charge is created behind the web, which forms an electrostatic field at the nib width. The charge pulls the ink around the edges of each well, which causes the ink to rise and transfer to the paper. Most presses are now equipped with electrostatic assist devices.
Figure 30. Diagram of electrostic assist printing.
Trends in Gravure
Gravure printing presses are sophisticated devices that have a wide range of controls to ensure high image quality. Technology has created rapid advances in press design and workflow. In 1997 the worldâ€™s first 3.6-meter (11ft 9 in.) wide gravure press was installed in Hamburg, Germany. According to Koenig and Bauer-Albert, a leading manufacturer of rotogravure presses: The maximum speed achievable today with four pages around the cylinder circumference is 60,000 cylinder revolutions per hour. This is equivalent to a web speed of almost 3000 fpm. So, in a single second the press can print 615 sq ft of paper with four colors on both sides.â€
Figure 31. Print units of a 3.6 meter gravure press, operator side
Figure 32. High-Speed web
Figure 33. Lightweigh gravure cylinder sleeve. Sleeve is on a cylinder mounting syste.
New cylinder technology is being developed to make the cylinders fighter and smaller. Different materials, including lightweight polymers, are being looked at to reduce the weight and difficulty of handling. Armoteck Corporation has developed a product called Fiberlyte that it claims reduces the weight of a cylinder by up to 80 percent, depending on size. Armotech has combined this with a new technology that uses lightweight disposable sleeves, which are then mounted on the cylinder. The sleeves can be engraved remotely and then shipped at low cost to the printing or embossing plant.
The technological advances of the past decade, coupled with the fact that the gravure process offers high quality with a relatively simple printing process, will continue to make gralure printing one of the major printing processes in this country.