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High-flying flexo

Jan 1, 1996 12:00 AM


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Flexography, dramatically improve printing process, but will it ever win in the commercial printing market?

Flexography, characterized by its advocates as a process showing dynamic technical change, is the process of choice for the majority of package printers. It also runs a close second to offset in the related areas of tags and labels.

When newspaper publishers decide to purchase a new press, flexography almost always is considered, but offset still wins most of the time. In the production of freestanding inserts (FSI), flexography is a strong contender, but, nevertheless, holds a small minority share. Sunday comics, pocket books, telephone directories and a range of other niche market products, however, are printed using flexo.

To mainline commercial, magazine and catalog printers, as well as thousands of small and quick printers and in-plants, flexography is a process virtually unknown and never considered a production alternative. However, sheet-fed commercial printers now are being introduced to flexo coating technology.

Flexography is a simple and versatile process encompassing a variety of press configurations with sizes ranging from an inch or two to 90 inches or wider. Flexo prints from either rubber or photopolymer plates using solvent-, UV- or water-based inks. Products printed range from pizza boxes to very high quality packaging on paper, film and board to colorful newsprint and similar groundwood products.

Over the past decade, the flexo process has shown dramatic improvements. The advent of water-based inks has catapulted flexo into the leading position as the "environmentally friendly printing process." These inks now are used in most flexo applications, except when printing on film or other non-absorbent materials.

Water-soluble flexo inks are reader friendly because they eliminate rub-off, a common source of complaint associated with newspapers and non-heat-set offset produced products.

The vibrant colors made possible by flexo's water-based inks produce sharp, clean colors that "pop-off" the page and give the process an advantage over other printing methods. The results are ideal for FSIs, direct mail and newspapers.

There are several characteristics of water-based inks that provide flexo with an advantage. The water vehicle carrying the flexo pigments provides a purity of hue. The ink pigments are carried by the water onto the sheet being printed and are deposited on top of the sheet; in the drying process, they bond to surface fibers. Because the inks are not defused into the sheet, an image with edge sharpness is created.

Solvent-based inks used by offset and other processes wick into the paper, diffusing the edge of the image and distributing solvent throughout the sheet. This can muddy the natural whiteness of the paper. With solvent eliminated, flexoprinted materials appear to be on paper that looks whiter and brighter, with a clean look that enhances the appearance of halftones and color work.

The fact that the waterbased flexo inks sit on top of the sheet and do not wick into the paper fibers reduces the amount of show-through. This makes it possible to reduce paper weights and, therefore, postage and distribution costs--all without sacrificing image quality due to show-through.

While water-based flexo inks are important, packaging flexo's current hot button is UV printing. UV flexo gets high marks for its ability to print crisp round halftone dots, which flexo enthusiasts say are superior to the non-uniform asymmetrical offset dots. It also is renowned for its excellent rub resistance, exact ink metering, minimal running adjustments and instant curing, which makes it possible to handle, finish, box and ship products as they come off the press.

Traditionally focused on specialty colors, flexo printers, particularly label manufacturers, are increasing their use of process colors to create the wide range of special colors required in packaging and to improve the process color print quality of food and other packaged merchandise.

As flexo packaging printers produce more process color work with V flexo, sheet-fed offset packaging printers can expect to see more competition from their flexo counterparts, forecasts consultant Dennis Mason. This, in turn, he says, will lead flexo press manufacturers to incorporate UV curing systems directly into their presses rather than hanging them on as accessories.

The nature of the flexographic printing process, its inks and press designs are such that it is a less abusive process to paper than either offset or gravure. Because the presses run with less tension and temperature extremes, paper with less strength can be used without increasing the frequency of web breaks. Since paper usually weakens as weight is reduced, this process advantage is translated into the ability to cost-effectively use lighter weight papers.

Similar to letterpress, a characteristic of the rotary flexo process is its ability to come up to color virtually instantly and to produce commercially saleable product with the first or second revolution of the press. This equates to almost no makeready paper waste, low makeready labor charges and short makeready time cycles.

Maintaining color consistency throughout the press run in a manner similar to letterpress and without the color variations inherent in the water balance requirements of offset is another flexo process advantage cited by advocates. This characteristic makes flexo presses easy to run and tends to reduce press manning requirements.

An important characteristic of flexo is the process' ability to print on a wide variety of materials, including rough or smooth, coated or uncoated paper or board, as well as film, other plastics and metal.

Flexographic technology is newer than offset or gravure and is developing and changing faster than these more mature processes. Improvements in flexo color separations, inks, plates, presses and auxiliaries, such as register systems, all have contributed to the development of the process.

Just a few years ago it was not possible to print the full range of halftone dots with flexo, but now the process approaches offset--although in this regard it generally is acknowledged that flexo does have some limitations when compared to offset. The extent of this limitation and its impact on print quality is somewhat controversial and depends on the nature of the specific product produced, as well as the experience and prejudices of the process evaluator.

Nevertheless, it is the improvements that have been made in flexography, combined with the inherent nature of the process, that have pushed flexo into the dominant position in packaging and attracted the attention of newspaper publishers and insert merchandisers.

More than 50 newspaper titles are printed worldwide using flexography. About 75 percent of these installations are in the United States.

Cerutti dominates an active Italian market with 18 newspapers using about 200 printing couples. The largest installation, however, is at the Daily Mail in London, which operates 144 Koenig & Bauer-Albert couples.

U.S. newspaper titles printed using flexo include: the San Francisco Chronicle and Examiner, the Raleigh (NC) News and Observer, the Charlotte (NC) Observer, Louisville (KY) Courier Journal, the Fresno (CA) Bee and the Providence (RI) Journal.

Worldwide, there are about 2,000 newspaper flexo printing couples in operation. KBA, including KBA-Motter, is the leading supplier with about half of the market, followed by MAN with almost 30 percent. Rockwell-Goss and Cerutti each hover around a 10 percent market share.

In the commercial printing world, where offset dominates and gravure still snags a significant volume, letterpress is an anachronism. In worldwide newspaper printing, however, letterpress is a declining but still significant production process. Many of these older single-color letterpress lines have been given a temporary new lease on life with the addition of flexo full-color units. Known as "sprinkle units" because of the way in which they can be added or "sprinkled in" to existing lines, this application of newspaper flexography has helped publishers extend the life of press investments while meeting reader and advertiser demands for color.

One of the most successful sprinkle units is KBA-Motter's Colormax, which is a common-impression cylinder (CIC) design. The CIC approach is used to produce a compact unit with accurate registration and fast start-up. To date, more than 200 double-width newspaper units have been sold, according to Gary Owen KBA's director of marketing and newspaper sales.

A single-width Colormax unit recently was introduced for the non-heatset commercial market, as well as for smaller newspaper applications.

Although flexography once was considered to have potential as the growth process for telephone directory printing, it has faltered in this application despite the success of World Color Press' Merced, CA operation. World Color has two Cerutti flexographic directory presses, each consisting of two reels, two towers with eight printing couples providing 4/4 color on each web, and an upper and lower folder to produce signatures for Pacific Bell Yellow and White Page Directories.

With each revolution of the press, the Cerutti at World Color delivers 64 nominal size 9.6 x 11.4-inch page signatures on 22.5-lb. telephone directory stock. Flexo's environmentally friendly characteristics play a major role in World Color's decision to "go flexo" in California.

At DRUPA, Cerutti sold a telephone directory flexo press to the giant Latin American printer Carvajal, which is located in Cali, Columbia. This press will consist of one reel, one tower of three printing units and an upper and lower folder. It will produce 32-page signatures, two-off, with 3/3 color.

Newspaper comics, freestanding inserts and flyers are newspaper-like products printed on newsprint, uncoated groundwood or perhaps a supercalendered sheet. These products often are printed on newspaper-style flexographic presses. Flexo's brilliant colors and clean, crisp appearance on groundwood are major attractions for FSI advertisers and newspaper publishers that want to give their Sunday comic section extra punch. This market niche is about as close to general commercial printing as flexo currently gets.

If flexo is a dynamically improving process with a stableful of attributes, what has limited the penetration of flexo into magazines, catalogs and commercial printing? Our research for AMERICAN PRINTER indicates that flexo is an overlooked process, at least in part, because it lacks a champion. Some suggest that a flexo publication or general commercial press never has been built. Adaptations of newspaper and packaging equipment simply won't do, goes the claim.

While flexo presses are continuously being improved with onboard computers that provide for greater accuracy in process color work and better control in trapping lighter colors beneath darker ones, the process is not targeted at the publications market. Flexo presses, too, have seen major improvements in terms of mechanical enhancements and the addition of peripherals such as self-compensating ink fountains. The fact remains, however, that flexo is at a considerable speed disadvantage when compared to lithography and gravure.

Joel J. Shulman, president of Jelmar Publishing Co. and long-time Flexographic Technical Assn. guru, comments that flexo often is overlooked as a printing process because most non-packaging printers are not geographically located near plants where they can see and understand the potential of the process. Process color work and 150-line screens can be printed consistently on standard offset papers, he claims.

Flexo excels in its ability to reduce waste, print on lightweight papers and produce consistent high-quality work. As a production process, it is less demanding and, therefore, press operators can be trained easier and faster, Shulman says.

Joseph R. Abbott, MAN-Roland director of technical support, notes that while flexo may excel in some applications, the process nevertheless does have a number of drawbacks when it comes to competing in the heatset commercial printing world. The tonal range of the process is limited, Abbott asserts. "It's difficult to hold dots below 10 percent and dot gain often is out of control," he explains.

Plate manufacturers claim that solid-sheet photopolymer plates have undergone major improvements. Today's plates are more wear resistant and provide for better dot control and image clarity. Most flexographers, however, believe that improvements in this area still are needed.

Plate plugging, a longstanding flexo limitation when printing on groundwood, has been improved but continues to surface as a quality issue. The problem appears to be a combination of contamination by particles of paper, particularly from groundwood and recycled sheets, and ink drying characteristics. Plugging is not a problem when higher quality paper is used, such as is common in packaging and labeling applications. The prognosis when lower quality papers are used is for continued improvement, but the outlook is doubtful when it comes to a complete cure.

In other developments, the "thin plate" has enable flexo to make inroads into the production of quality graphics on corrugated boxes. High-quality graphics on corrugated-traditionally have been produced by preprinting a liner or outer shell material by lithography and then combining it with the corrugated medium to make a box. The new thin plates incorporate a compressible backing that overcomes the problem of poor image quality caused by press and plate variations. This tendency is magnified by fluted substrates with significant thickness variations and low crush strengths.

While the commercial printing world may not be aware of the process advantages that have attracted packaging and newspaper producers to flexo, they are beginning to be introduced to the process through the addition of anilox or flexo coating technology to commercial presses.

The use of flexographic inline double coalers on sheetfed presses is an emerging commercial printing coating capability. It is designed to provide an environmentally friendly and cost-effective means for improving product quality by putting down an ultraviolet curable coating over an aqueous primer, which creates a gloss that enhances color and resists abrasions. This approach also is effective for the sheet-fed in-line application of metallic inks.

In touting the advantages of anilox or flexo double coating, MAN-Roland's Tony Kenney, senior product manager for sheet-fed presses, notes that the approach provides commercial printers with a marketing differentiation. If printers go to anilox double coating, they can cost-effectively offer print buyers product enhancements such as UV coating, spot gloss, combinations of various coatings (such as spot matte with spot gloss) and, of course, the increasingly popular metallic effects.

At Graph Expo, the MAN anilox center explaining the flexographic approach to coating was a popular attraction, Kenney points out, and an eye-opener to commercial printers, who generally do not understand flexography.

On coating equipment, press operators typically make frequent adjustments of the metering in order to get and maintain the right film thickness. Considerable variation may exist in film thickness if applied by different operators. The nature of flexography, with anilox coating rollers, changes this to a repeatable constant. Flexographic coating also eliminates beading and foaming problems and drastically reduces variations in coating film thickness due to changes in press speeds.

Flexography technology has come a long way in the past two to four years, Kenney observes, predicting that this approach will become the dominant commercial printing coatings application technique.

Unlike offset or gravure, critics note, flexo has not embraced digital production techniques. Flexo advocates, on the other hand, point out that a high percentage of packaging and label flexo products are prepared digitally. FM (stochastic) screening is being tried and computer direct-to-flexo-cylinder technology is in the wings.

While the scorecard is still out, the value of FM screening for packaging flexography may be questionable. Experiments suggest that there are no press productivity gains with the use of FM screening. From a print quality perspective, the difference between FM and conventionally screened packaging samples is a matter of opinion.

Previewed at DRUPA and the CMM show in Chicago, Du Pont's Cyrel Digital Imaging System (CDI) provides a look at the computer-to-flexo-plate system of the future. The Du