Digital at the Finish Line

Digital print's short-run suitability presents a sizeable learning curve to converters' in-line finishing.

by Jessica Millward, Associate Editor

THOUGH COMMON WISDOM claims otherwise, sometimes you can have things both ways. That need has been, and will continue to be, the mother of invention regarding digital print finishing. The paradox: How do you pair in-line converting with a print process engineered for short-run jobs? The stops and starts of in-line have thus far greatly restricted much integration with on-demand techniques, but press manufacturers' discovery process has only just begun.

Cost concerns

Thoro Packaging's hesitation to embrace digital technology in its folding carton facility is typical for printers. As Plant Manager Steve Jokela enumerates, one of the chief reservations his firm has in investing in digital is its ability to handle the in-line application of aqueous coatings, which are so common with its traditional offset jobs.

"The driving force is economics," Raymond Dickinson, marketing manager at Indigo America, summarizes concerning the choice of finishing system for the digital print process. And while suppliers differ on precisely where the digital print/in-line converting combo becomes infeasible, they all seem to agree on the priority of bang for printers' buck.

Dickinson relates digital press speed is the gating factor governing throughput in any in-line digital printing/converting configuration. Financial analysis leads most converters to conclude it makes little sense to allow the comparatively slow digital press to shut down for even one second of the time required for the converting set-up.

Nilpeter President John Little sees time/money loss in the die configuration of many digital presses. "The real problem is: How do you change a die with short-run work? If you're running 1,000 small, ten-up labels, it takes you longer to change the die than to run the material."

Unfortunately, the cost issue can run deep even with add-on, off-line converting machinery. Ken Daming, director of product management for Mark Andy, insists the major challenge to converting with existing equipment is its add-on nature. Because the press has its own web tension system, and the printer material must conform to another tension system for finishing, the need for a zero-tension loop in the web in between the two systems arises. The finishing line must then be capable of sensing an eye-mark on the pre-printed web to re-register.

Daming maintains, "This ability means that the finishing line usually needs to be servo-controlled, and has to be very sophisticated—and expensive."

Dickinson believes there are no insurmountable hurdles unique to digital finishing, but mentions three major factors to consider: 1) maximum utilization of the press; 2) protection of the printed image; and 3) for dry toner printing, cracking and stretching.

As it stands, most digital converters have not yet experimented with in-line technology, primarily because it is, for the most part, in development stages.

Xeikon's VP/GM, Packaging Products, Don Bence affirms, "With the exception of only a few cases, most finishing is performed as an after-print, off-line operation, on either existing flexo presses, or on new, roll-to-roll modules that are capable of laminating, coating, diecutting, and rewinding."

Daming concurs. He states most label printers today will print the product, rewind it, then run it back through a finishing solution off-line. "Naturally, the less the converter has to move the printed materials around, the better."

Press manufacturers list a host of issues to be considered in formulating digital print finishing solutions. Indigo's Dickinson recapitulates the need for converters to topcoat to protect digitally printed images and ensure durability against the abrasion and wear labeled products normally encounter in packing, shipping, and consumer use. The company does offer a simple nip module to maintain web tension, which allows the press to be configured with almost any converting equipment.

Of course, Dickinson comments, "Adjustments are usually required to develop compatibility and performance, e.g., adding UV initiator to top coating to boost adhesion to ink."

Interestingly, Bence cites a converting bonus unique to digital print. As he notes, "With Xeikon digital printing, the imaging polymer exits the press completely fused and dry, without worry of bleeding or smearing during the coating or laminating process."

Help is on the way

Nilpeter has been working on its custom-built digital system, the DL-3300, for approximately five years. As Little admits, "The first year or two was very hard - just in trying to figure out what people wanted." Currently, the press can be configured with equipment on either or both sides of the Xeikon digital engine.

To combat the difficulties in changing dies for digital work, Nilpeter devised a magnetic die system, in which the die switches to the other side of the accumulator while the press is still running.

Nilpeter has had substantial success with the DL-3300, especially in Europe. Little accounts for the increased number of European installations with two reasons: "First, because Europeans are much more likely to try something new; and second, because there is a greater quantity of short-run work there."

The Digital Label Alliance (DLA) premier of the Argio 75 SC digital press in Chromas Technologies' booth at last year's Labelexpo expounded on a new UV ink jet method of variable printing. The Argio digital system, still in beta testing, is engineered for single or multi-color applications in a variety of industries, and can be retrofitted onto a conventional press.

Also wowing Labelexpo onlookers was Mark Andy's partnership with BARCO in the production of an inkjet system designed to fit into a normal Mark Andy 2200 press. The joint technology, known as SPICE (Single Pass Inkjet Color Engine) architecture, prints six colors at 360 dpi on pressure-sensitive stocks, laminate substrates, films, foils, and tag stocks.

Daming says the same tension system used to pull the web through the press will also pull it through the ink jet printer, thereby eliminating the need for complex re-registry controls. He also points out the press will not require special temperature and humidity conditions, and can diecut, strip waste, hot foil stamp, laminate, sheet, rewind, etc., all in one pass. Production on the press is scheduled to begin in the second quarter of 2002.