’Round, ’Round, Get Around …

What hath computer-to-plate (CTP) wrought? Consider “in-the-round” imaging or ITR. The term refers to digitally imaged, continuous polymer printing sleeves that arguably are the future of flexography, and that already are opening up a number of attractive opportunities to printers and end users. Flexo sleeves not only work well with less expensive substrates, such as tissue, napkins, and paper towels, but provide excellent lay-down of solid and metallic inks. Advances in flexo sleeve technology are yielding similar opportunities in markets traditionally dominated by other processes—paper or foil gift-wrap (rubber flexo or gravure), folding cartons (offset or gravure), and shrink sleeves (gravure).

In compiling the following overview of flexo sleeve technology, packagePRINTING gratefully acknowledges input from Ray Bodwell, marketing manager, DuPont Packaging Graphics; Ian Hole, Vice President, market development, Esko-Graphics; Gene Profitt, general manager, Stork Prints; and Mike Smoot, business manager for Xymid Print Sleeves, Xymid, LLC.

A primer on ITR

ITR actually refers to two forms of imaging: laser ablation mask (LAM) imaging and direct laser engraving (DLE). The digital ITR process most printers are familiar with today involves imaging by means of laser ablation of a carbon layer “mask” that covers the photopolymer plate or sleeve, followed by conventional UV exposure, removal of uncured photopolymer, solvent washing, and drying. The photopolymer sleeve itself comes in two formats. The first is a continuous pre-manufactured sleeve with a seamless layer of photopolymer topped by a LAM coating, ready for imaging, exposure, and processing. The alternative involves mounting individual pieces of photopolymer on a base sleeve with stickyback tape, then imaging, exposing, and processing it as described above.

Sleeves are made from various materials, including thermoplastic composites, thermoset composites, and nickel, and may or may not be reinforced with fiber. So-called “thin” sleeves without foam or cushioning were developed to be thrown away after use to keep costs down. Long-run, reusable sleeves with a foam or cushion base are used for very high-quality printing. Most are currently processed in solvent chemistry processors. However, predicts Esko-Graphics’ Hole, “By the time drupa 2008 opens next year, you can expect to see a number of sleeves that are processed with thermal systems.”

A few new tricks

There are some things a printer needs to do to run sleeves. Here are a few things to keep in mind:

Retrofittability—It is important that the press be compatible with sleeve technology. For printers with older equipment, the cost to retrofit cylinders can be somewhat discouraging; however, nearly any existing print cylinder can be modified for sleeve mounting. “The return on the relatively low investment increases as the frequency of print changes increases,” Stork’s Profitt says. “Given the market trend toward shorter runs, the investment payback is becoming more attractive every day.”

Handling—Different sleeves have different damage tolerance capability. Some sleeves crack and chip more easily than others, while some sleeves have greater cut resistance than others. The thinner the base sleeves, the more careful the handling needs to be. However, says Xymid’s Smoot, “The life of any sleeve will be extended and the printer will obtain greater value for his investment by exercising sufficient care in handling.”

Storage—For high-quality repeat work, it may be necessary to install a sleeve mounting stand, in which case space may be a challenge. “Printers have developed some clever ways to address this problem, including nesting sleeves inside one another, storing in large arrays of locker type bins, and storing in elevated mezzanine-type areas that are unusable space for the rest of their operation,” Smoot says. “Whatever approach is used, sleeve storage, identification, cataloging, and timely acquisition can be challenging.”

Cost—Sleeves typically cost more per square inch than their flat-plate equivalents, and in today’s environment it can be difficult for the printer to recoup those costs. “In most cases there will be savings associated with the elimination of mounting, higher press speeds, and greater run length,” says DuPont’s Bodwell, “but these are sometimes viewed as ‘soft’ savings and may be difficult for the printer to quantify.”

Time—ITR image carriers are manufactured one at a time, and all are built on top of sleeves, which can take days or weeks to obtain. As Bodwell reports, however, “These lead times are starting to improve as capacity increases.”

In addition, some changes in software may be necessary to take full advantage of available sleeve technology. For example, says Esko’s Hole, “You want to create your step-and-repeat design to take care of seamless artwork.”

Caveats aside, the financial benefits of using sleeves far outweigh the inherent costs and logistical headaches, Smoot says. “Printers who employ sleeves in their operation will have, on average, the lowest cost and fastest cycle time.”

DuPont’s Bodwell concurs. “We’re told that sleeves are easy to print with, will run at higher speeds, and will run significantly longer than flat plates. They are easy to re-run and will re-run many times before they wear out. Many sleeves are designed to be disposable, so that at the end of their useful life they do not have to be returned for recoating.”

Direct laser engraving

DLE denotes the engraving of the printing form material itself. For relief printing processes like flexo, dry offset, and letterpress, DLE is used to engrave plates that are mounted on the drum or on the sleeve, which is then used on the press. In this workflow, the sleeve is coated with an elastomeric material—typically rubber, polymer, or hybrid composite—and a high-powered laser is used to burn away the non-image area of the sleeve, leaving the image carrier surface intact. Says Profitt, “DLE is a simpler workflow requiring fewer steps, less machinery and machinery maintenance, incurring lower consumable costs, and yielding fewer variations. It is regarded as the purest form of computer-to-plate available.”

Not everyone agrees. According to DuPont’s Bodwell, “Engraving technology is somewhat limited by the power and spot size of the lasers used, and does not generally achieve either the quality or productivity levels of laser imaging. It is essentially a one-step process, which means access to the first sleeve may be quicker with engraving, but it will not be able to keep up with laser imaging once you’re into a pipeline production mode.”

Dynamic duo

The twin drivers of ITR imaging and engraving technology are productivity and quality. In the prepress area, productivity gains come from predictability and repeatability. Considerable time is saved by eliminating plate mounting for job reruns, as well as rework caused by the distortion inherent in the plate mounting process. Images can be stored in register, on sleeves for reuse on subsequent print runs, with no plate mounting required.

Accuracy also improves with digital ITR imaging. Reduced makeready times brought about by using ITR and sleeves make possible shorter package production runs and more frequent design changes. Distortions associated with imaging and mounting flat plates are eliminated. Even greater accuracy can be derived from imaging sleeves with blank plates pre-mounted, or with seamless sleeves, since there are no gaps or bleeds between separate images on the sleeves. “As a result, the narrow-web printer’s preference for sleeve and ITR imaging solutions is increasing,” Profitt reports. “The precision of thin sleeves and plates, using thin composite or nickel base sleeves, supports the high resolutions and quality that many narrow-web printers demand. In addition, ITR print sleeves are characterized by reliability and durability. Longer print life has been demonstrated by seamless sleeves.”

Given all these advantages, the adoption rate for digital ITR imaging should be climbing skyward, right? Not exactly, says Ian Hole, and for the following reasons:

“The issue with digital ITR imaging has always been the cost of the blank sleeves,” he says. “Despite the fact that suppliers are ready with sleeve products, pricing per square inch of material is considered too expensive to most converters and trade shops, limiting adoption.”

Also daunting can be the upfront investment, which includes an ITR processor, ITR digital imager, and software to make seamless sleeves work. In the United States, says Hole, Esko-Graphics’ market research reveals that more than half of sleeves that are mounted on press are created from raw blank sleeves made by the printer/trade shop themselves. In other words, a large percentage of the sleeves in use in the U.S. were not supplied by vendors as sleeves, but created in the plant from plate material.

Although there is a finite group of converters and trade shops that are increasing their ITR business, Hole doesn’t see many new companies experimenting with ITR. What this means, says Hole, is that for the time being, “People are living with plates. Those who are accustomed to sleeve pricing will continue to use it. Until demand or costs adjust, others will not. Clearly, there is also not enough demand in North America to drive this, or we’d see a faster adoption rate.” pP

In-the-round imaging equipment

DuPont Cyrel® round Classic and Cyrel® round Thin are newly developed photopolymer sleeves said to be ideal for very high-quality printing. Cyrel® round Classic performs particularly well on critical materials and is useful for halftone printing. Combined with a compressible adapter sleeve, Cyrel® round Thin creates the perfect compromise between low dot gain and solid coverage.

Esko-Graphics offers the CDI Advance 5080, which is capable of imaging sleeves up to a length of 83.1˝ for the highest quality flexo applications. The CDI Compact 4835 images sleeves up to 51˝ and serves the middle-format highest quality flexo markets, including flexible packaging and folding carton printing.

Stork Prints offers a complete range of direct laser-engraving systems including the Helios 6010, which digitally engraves flexographic, dry-offset, and letterpress plates and sleeves. The Helios 6010 offers label printers enhanced quality and a shorter, much simplified workflow. Special software enables three-dimensional engraving at a wider range of angles than is possible with LAM. The company’s 2006 acquisition of AKL Flexo Technik enables Stork Prints to offer a complete line of flexo engraving products, including hard composite, nickel, and compressible sleeves for plate mounting; sleeves with seamless polymers for engraving; adaptors (repeat builders and bridge mandrels) that cover many repeat steps; and thin photopolymer sleeves for use on cushion adaptors.

Xymid polyester sleeves are available in thicknesses from 0.010˝ - 0.320˝ and unlimited widths. They can be manufactured and shipped in five working days, provided the mandrel is in stock. The composite construction of Xymid sleeves resists cracking and splitting. Sleeves can be used on existing print cylinders with only minor modification of the existing cylinder.