03.15.10
Offset Printing
Setting up the Gallus RCS offset press.
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A time-testedand challenging print process,offset has loyal followersamong high-endlabel converters and their customers.
By Jack Kenny
Offset printing is also called lithography, a word created from the Greek lithos (stone) and graphos (to write). The process is said to have been invented in Bavaria in 1796 by Alois Senefelder as a low-cost way of publishing theatrical works. The original process involved creating an image in wax on a stone. Direct printing would require a reverse image, of course, but in time a positive image was etched on the surface and offset to a flexible plate, which then came into contact with the substrate to be printed.
Offset has a reputation as a high quality printing process, and also as a challenging process. Offset printing plates, made of aluminum, polymers or other materials, are quite inexpensive to produce and do not have raised images, as do flexographic plates; dot gain, therefore, is virtually nonexistent. Where offset gets complicated is in the ink train, a series of rollers whose function is to spread the paste ink evenly over their surfaces before it is transferred to the offset blanket.
Letterpress printing, another process that makes use of an ink train, is decreasing in use throughout the narrow web industry. To be sure, letterpress machines are still running and will be engaged for years to come, but production of new equipment has slackened or stalled. Flexography, of course, dominates the label printing industry worldwide, but it does not own the marketplace. Today we have a strong challenge from digital printing processes of various kinds, including the strong digital offset of HP Indigo.
But not to be overlooked is narrow web rotary or semi-rotary offset. It has its devotees, most or all of whom command market share among high end consumer products labels. Just how widespread is narrow web offset today? And what type of label printer makes use of this process?
“The current estimate is 18 to 20 percent penetration,” says Jakob Landberg, vice president of sales and marketing for Nilpeter, Slagelse, Denmark. “Many labels are still done on small ‘stop-and-go’ offset machines, but the volume comes from highly industrialized and professional players, going to the high-end brand owners. Offset combination quality is still a way to differentiate from your competition. Offset label printing among EU countries is still over the rest of the world, but with globalization of brands this will even out in the future. I estimate the growth in offset to be second only to digital.” Nilpeter manufactures offset presses and combination presses, such as the MO-4, that can utilize offset, UV flexo and a variety of print processes.
Codimag’s Aniflo waterless offset process eliminates the many rollers of the ink train and makes use of an anilox roll to transfer the ink. |
“The first market to be receptive to offset has been the wine and liquor market,” Panel says. “It has always been served by offset, first with glue-applied labels, now with self-adhesive. Then comes the health and beauty market, with designs that require high quality printing, with fine vignettes, nice baby smile faces, smooth skin reproduction… High-end food and industrial labels are also turning to offset for high quality work.”
“The worldwide offset press population is not mainly focused in geographical regions, but rather it is more focused on the applications,” says David Baumann, product manager for Gallus, St. Gallen, Switzerland. “Traditionally the wine and spirits market is dominated by offset technology, so we see a high penetration of offset presses in the typical wine producing (or consuming) regions.” Baumann says that 90 percent of Gallus TCS 250 presses are located in wine regions around the world.
“The second important segment is the cosmetics segment, where the production is based mainly in adult markets or in local hubs,” Baumann adds. “Thanks to the excellent quality, the high degree of standardization and the low plate costs, offset printing is in greater demand also for relatively simple labels.”
Eric Hoendervangers, managing director of MPS, Didam, The Netherlands, says that his company had seen a steady and stable growth of offset in the narrow web industry until the start of the recession. “As these machines are much more expensive, these investments came to a stall,” he says.
Offset machines, he adds, are utilized “mainly by those converters who supply labels to the bigger global brand owners. Normally these converters are a little bigger, too, and unafraid not only to invest in an offset technology but also to learn the technology.” MPS works with Goebel GmbH on development of offset technology for its label presses.
Omet is another European manufacturer of offset presses, along with flexographic machines. Steve Leibin, of Matik Inc., is Omet’s sales manager for North America: “Traditionally, offset has delivered better quality printing than flexo, and a wider color gamut and better color consistency could be attained from four-color offset process than from flexo. This is due to the offset ink train, which offers better ink controls. So typically the converter that is focused on high quality labels and wants better consistency and better process controls would choose offset over flexo.” Flexo, he hastens to add, “has made great improvements in prepress, anilox, plates, and presses, and that narrows the gap with offset.”
Edelmann Graphics is a German company that manufactures web offset presses in widths from 15" to 30". Chris Davis, also of Matik, represents Edelmann in North America. He says, “The European market seems to have led the offset application in this market due to quality demands, fragmented regionalization and standardized reproduction requirements from global retail suppliers. The North American market has started to adopt some of the technologies and techniques to tackle this growing requirement.
“With marketing changing emphasis in retail skin tone, refined graphics, FM screening and so on, this has led some converters to access the potential of offset and what the cost implications are to move in this direction. We are seeing an increasing number of converters who are looking at hybrid and open platform presses, which can run typically flexo and offset and occasionally gravure, as the printers become more educated on how these multi-task platforms can add value.”
Matching the press to the label
Why would a label printer choose to acquire an offset press? Is there a type of label that is best suited for such a machine?
“Everywhere we need excellent quality, offset is the first choice,” says Baumann of Gallus. “Thanks to modern servo machines, and low plate costs, and a beneficial cost per label, offset is used more and more. A modern servo machine is able to reduce setup times and waste significantly. In the last few years these improvements have been so significant that often offset is now able to compete with flexo printing.
“Additionally,” he adds, “substrates are influencing the choice of the main printing process as well. In particular, textured substrates in the wine industry are restricting flexo. Because of the low ink laydown, offset is preferred for all wrap and shrink applications too.”
“Offset is extremely good in CMYK and vignette printing,” says Hoendervangers of MPS. “The technology gives outstanding results in the light and dark areas. Offset has low dot gains, like the new advanced flexo presses, but the size of the minimal dot in offset can be virtually zero. Offset is second best in solids; for that reason 95 percent of all offset presses are combination machines with offset and flexo. Also, offset has relatively large setup wastes and times (it’s a more complicated process), and for that reason offset is used for relatively big order sizes.”
According to Davis of Matik, offset has always been ideal for four-color process, “which has now broadened out to the extended gamut printing of Hexachrome and Opaltone. In essence, because offset is capable of printing 1 percent and 99 percent dots on the same plate without any special technologies, this has allowed the process to dominate the need for a ‘pretty picture’, but lacks the capability of laying down heavy ink for deep solids. Primary labels in wine, beer and spirits are good candidates for offset, as are health and beauty as well as personal care.”
“There are two segments for typical offset labels,” says Nilpeter’s Landberg. “First, non-combination labels in long runs: detergent, under-the-sink products, some high-end food. Second, combination requesting products: H&B, cosmetics, wine. My interest is in the second one. Here the offset is used for very fine process combined with flexo, screen, gravure and foiling for adding value to the design and shelf appearance. Good examples are wines from the New World plus Italy, Pantene, Dove, Fructies, and Herbal Essence.”
Smart operators wanted
The operation of an offset press can be a challenge on several fronts, which is why experience is necessary for effective production.
“Yes, offset does require specialized knowledge,” says Steve Leibin of Matik. “Whether it is wet or waterless offset, there are operating nuances that come only with experience.
“For the wet offset process, there is a water/ink balance and ink keys that must be maintained, as well as ink roller adjustments that can vary based on the substrate. Traditionally, the offset ink train has numerous rollers that can create maintenance and adjustment issues which, if not handled properly, can lead to print quality issues.
“The traditional waterless offset press eliminated the hassles of the ink/water balance and provided the offset ink key control and offset print quality. The disadvantages of waterless are that it required a sophisticated heat management system, special waterless inks and a long ink train (similar to wet offset) that required maintenance. Waterless offset is also prone to tinting issues if the ink is not matched to the substrate or due to other maintenance issues.
“Semi-rotary waterless offset presses are ideal for short runs because there are no cylinders to change for size changes, the plate costs are very low ($5), the offset four-color process could build a wide color gamut requiring few color changes, and the startup waste is low. By eliminating the ink/water balance issue of wet offset, the waterless offset process produces a crisper dot and more brilliant colors.”
Pierre Panel of Codimag says that the printer has two parameters that need to be taken into account for offset printing: “The first one is ink key control – to be able to set efficiently all keys to bring the right amount of ink in the different areas. The second one is ink/water balance – to be able to bring enough water to repel the ink in the non-image area, but not too much to make sure that the image area is not invaded by water.
“This second process can be avoided by the use of waterless offset, in which a dedicated plate uses a silicon layer to repel the ink without use of water.”
The first parameter, Panel observes, is eliminated when using anilox offset. Codimag manufactures the Aniflo Viva 420 press, a waterless offset machine that utilizes an anilox roll to apply the ink instead of a multi-roller ink train. The anilox transfers ink to a rubber roller, which then delivers the ink to the printing plate and from the plate to the offset blanket.
A close look at an MPS offset press
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“Now with offset, you have an ink pan, ink keys, a ductor roller, several ink transfer rollers, water balance and application rollers, form rollers (those that finally ink the plate), a plate roller, and a blanket roller. It is obvious that the operator has to control many more parameters compared with flexo. Again, if the print result is too pale, what should the operator check? Yes, indeed, all eight parameters, which influence each other tremendously. In this case especially the ductor roller, the ink keys, the water balance, pressure from rollers, pressure from plate to blanket, pressure from blanket to substrate and the type of rubber on the blanket!
“Here are the facts: much more operator skill, more setup time, more setup waste material,” says Hoendervangers.
David Baumann of Gallus says, “Flexo is more easy on the press, but more complicated in prepress. Offset is the other way around. Therefore all offset press manufacturers are concentrating on the ease of use. Thanks to the servo technology and computer supported machine controls, a modern narrow web offset press does offer a lot of support, in such areas as ink/damping presetting, automated substrate adaption, recallable machine setting thanks to job storage, waste saving startup sequences, and so forth.”
Inks, speed, makeready
Landberg notes that with makeready, speed and cleanup on an offset press “we have to distinguish between non-combination and combination. Non-combination printing is mainly for long runs, so the production speeds are higher, and so is the setup speed and consequently the setup waste. With combination printing, the complexity of the job determines 100 percent of the makeready, speed and cleanup.”
“Offset inks are thicker than flexo inks,” says Leibin. “The offset ink train uses many rollers that ‘mash’ the ink. The nip pressure and heat generated in the process reduce the viscosity of the ink to achieve a more printable ink. This is one of the characteristics that an operator needs to maintain in the offset process and requires offset experience knowledge of how to manage this with different inks and substrates.
An Edelmann Graphics offset unit
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“Closed loop color calibration is available with direct reading of printed jobs during the press setup. This eliminates manual color settings and provides more accurate, consistent color – better color control than flexo.”
Leibin notes that while wider wet offset presses can run at speeds up to 1,500 fpm, narrow web waterless offset is usually in the 100 fpm range.
“Most often, speed is restricted not from the main printing process, but from the refinement processes like screen or hot foil,” says Baumann. “If we compare pure offset with pure flexo, offset is able to achieve slightly higher production speed. The impact of the offset plate (no high builds) onto the web is lower than the impact of a flexo plate.”
Making changes
Like everything else, offset improves with time. Most recently, the improvements have included “servo technology, integration; inline automatic press controls, including ink densities; utilizing other print processes; broadening the inline converting options; and marrying to packaging equipment behind the press,” notes Chris Davis.
“The full focus has been to bring down setup and running waste – to bring more leanness to offset presses as well as to flexo presses. In offset this has been accomplished via enhancing the tooling towards light sleeves compared with the more old-fashioned and cumbersome cassette systems, and to focus on enhancing the control systems: programmable water balance, ink balance, pre-register systems, job-storage, etc.”
An Omet Varyflex offset unit |
Codimag believes that its Aniflo represents the most significant change. “Anilox offset is probably the biggest new thing in the offset world,” says Pierre Panel. “It allows printers to print offset quality without having the need to master ink key control, to check inking rollers, and to fight against ghost images. It give the highest grade of predictability and repeatability as the ink feeding system relies on an anilox.
“This change has already been implemented in the short run sheetfed business with KBA and Heidelberg offering anilox offset on their small size presses.”
Offset’s future
Offset equipment manufacturers – most of which also make flexo presses – have mixed opinions about the growth of offset printing in the narrow web label business. Here’s Pierre Panel:
“Offset quality has never been questioned. Getting offset quality results in flexo is a challenge and an expensive one, but the future of offset technology in the label world will be growing faster once solutions are easier to implement.
“Today, the biggest resistance to offset in the label world is a fear of press complexity and the fear of not finding the right people to handle the press efficiently. This is why Codimag came to the idea of implementing anilox offset technology into the label industry. It makes offset very simple and puts offset quality within reach of everyone. Now, offset can be used even for simple, unsophisticated work, at a very reasonable production cost.”
Steve Leibin has a different view: “I think offset is a niche player in the high-end label market. Flexo print quality and consistency have made great strides in recent years and can rival offset.”
Eric Hoendervangers: “When press designers are not able to simplify the offset technology, then the share of offset presses will stay much lower then the number of flexo presses installed.”
Jakob Landberg: “I expect that the highest growth in the label industry will come from combination digital printing, and second will be combination offset. Flexo will lose to digital presses as the speeds in inkjet printing will increase.”
Chris Davis: “The future is strong, because offset is tackling the traditional flexo areas of packaging, both flexpack and board, with P&G, J&J, etc., looking for color simplification globally and color standards being reproduced according to the master in Ohio.
“The trend is for combination presses to combine big color hits from flexo with offset putting down to Opaltone gamuts, and gravure adding pearlescent and metallic decoration … as an example. Printers are becoming more educated, and press manufacturers have evolved to provide solutions to the multi-process questions.”
David Baumann: “We see a growing demand for narrow web offset presses, for two reasons. First, enhanced productivity, flexibility and quality are boosting the trend towards offset. Today we have no more restrictions in offset combination printing, and costs per label are extremely attractive. At least the industrialized label printers have accepted this technology very well and implemented it into their strategies.
“The second reason is the battle for shelf space. The high level of standardization offered by offset printing is a crucial factor when deciding on which main printing process to use. Requirements relating to logistics (e.g., multi-sourcing) and brand image (continuity of product lines, uniformity of packaging and labels) call for standardization and, therefore, for offset printing.”
