American Printer's mission is to be the most reliable and authoritative source of information on integrating tomorrow's technology with today's management.

In Control: Advanced Press Controls for Web Printing Operations

May 1, 1998 12:00 AM


         Subscribe in NewsGator Online   Subscribe in Bloglines

Color-to-color register, cut-to-print register, web guides, color management systems. Alone, these items may not have earth-shattering effects on the web printing process. When banded together, however, web press controls maintain print quality on-press, reduce paper and ink waste, slash makeready times, and allow operations to use fewer and, perhaps, less-skilled operators.

This equipment has evolved with press technology and industry trends, increasing in sophistication to keep pace with today's 2,000 to 3,000 fpm presses, shorter press runs and the advent of wide webs.

Color management devices may be the hottest area, featuring closed-loop systems and stirring up debates about densitometry vs. spectrophotometry and the benefits of on-line vs. off-line systems. Other control devices, including register controls and web guides, are relatively staid technologies, though they have inched forward with small refinements.

One exciting trend relates not to individual web press controls but to the ability to tie these controls to other printshop operations--prepress, press and postpress. CIP3 Print Production Format (PPF), an attempt to link islands of automation in all print production areas, holds the promise of a completely computer-integrated manufacturing (CIM) process for print. The work is proceeding under the auspices of the International Cooperation for the Integration of Prepress, Press and Postpress.

Collectively, all these advancements add to the benefits web press controls confer on printers. For instance, on-line color management devices take measurements quickly, bringing the press up to color quickly, thus reducing makeready times and slicing paper and ink waste, relates Ron Bartell, product manager at Heidelberg Web.

Web press controls also sense out-of-tolerance changes in a run--changes that can be immediately corrected (at least with closed-loop systems). This ability boosts quality and reduces rework. "If press operators can rely on these systems to hold the run stable, they can pay more attention to other tasks, such as judging color," observes Joe Abbott of MAN Roland.

"One of the greatest feats of modern web controls? They make it easier to run the press with less skilled operators," continues the exec. "The ability to utilize less-skilled workers, in turn, deepens the graphic arts labor pool."

"Operators aren't necessarily less skilled, but have different skills," argues Bruce Quilliam, vice president of sales and marketing for Perretta Graphics. "Operators on today's high-speed web presses are more technicians than craftspeople. Someday these high-speed webs may be run by one engineer, with some assistance."

Such advantages are likely to multiply if CIP3 becomes a reality. According to Tom Quadracci of Quad/Tech, Inc. (Sussex, WI), "CIP3 is a protocol for interfacing all parts of the printing process so information can flow back and forth from one process to another. It's primarily a design specification for equipment vendors.

"For instance, we wouldn't have a problem interfacing a color management system to a press manufacturer's color desk if that manufacturer designed the desk using CIP3 because the protocol has been standardized."

The concept applies to all web press controls. Color measurement devices offer an example of a prepress-to-press link. Shops can take digital presetting information for a plate directly from a computer file in prepress, input that information into a color measurement system, which then controls the ink keys on press, explains Patricia Johnson, manager of marketing, communications and sales administration for Graphics Microsystems (Sunnyvale, CA).

"When you begin the press run, you already have good preset data," says Johnson. "Instead of going to 3,000 sheets to get the best color, perhaps you'll run only 1,000 or 800 using CIP3," she adds. Advantages include greater accuracy than using a plate scanner, reductions in waste and cost, as well as a shorter production production time cycle, claims the marketing exec.

Quad/Tech is involved in a similar project. The firm is working with direct-to-plate equipment manufacturers to preset the press for the color management system with the same image data used to image the plates, Quadracci explains. "We're also working on a bi-directional link to understand how the press is printing on any particular day and convey this information to prepress.

"For instance, the color management system on-press can determine dot gain, trapping and the press' printing characteristics. We feed that data back to the prepress system. Suppose the press is printing full in the midtones that day. Data used to image the plates can be adjusted for that press characteristic," concludes Quadracci.

CIP3 has applications for other web controls as well. "Data in the CIP3 format can be used to set up web guides," relates Quadracci. "If we knew the paper width for a certain job, as well as the location of the folds, we could determine where the web guides would place the web in the press. Further, we could use CIP3 data to set up cutting knives in the rotary cutter--it would tell the print-to-cut register system where to place the printing in relationship to the rotary cutter."

The ultimate vision? To link all print operations. While the vision requires creativity, the reality requires, among other things, an all-digital operation. Today printers may have linked only portions of their process digitally.

Indeed, trends are moving toward more integration. Nearly all text and graphics are created initially on computers. Conventional prepress has metamorphosed into digital prepress. The number of filmless and plateless digital presses in operation continues to increase. Digital bindery, finishing and distribution equipment increasingly incorporate digital control technologies.

Advancements not only re-sculpt the big picture, they occur on a smaller scale as well. After all, individual web press control devices are intimately connected to the printing press and graphic arts industry they serve. If press speeds skyrocket or short runs become commonplace, press controls must adapt.

And adapt they have. In many web shops, press speeds reach 2,500 to 3,000 fpm, according to MAN Roland's Abbott. The result? Press controls must become more sophisticated, according to Mike Gregory, product manager for Baldwin Graphic Systems, which produces print-to-cut register systems, web guides and more. Indeed, knowing press speeds would rise, the firm designed several of its products to function with 3,000 fpm presses.

"The reading and response times must change," adds Perretta's Quilliam. "At top speeds, you have to scan, process data and make corrective actions in less than a minute. Otherwise, at these speeds, you waste tremendous amounts of ink and paper."

"In order to keep up with faster press speeds, we've had to go to faster processors and maximize the speed at which the software executes," adds one expert.

"Web press controls have become more sophisticated, but I'd tie this trend to shorter runs rather than high speeds," relates Bartell. "For instance, reading a color bar at 3,000 fpm is difficult, but probably not much more difficult than reading it at 2,000 fpm. You'll need a sophisticated device to read it at any speed. But when you want to make ready in 2,000 impressions instead of 8,000, you need real sophistication in the controls."

Indeed, the need to speed makereadies is booming since today's shorter runs spell more makereadies. Short runs, in turn, are spurred by demographic splits and regionalization, according to Quadracci.

How short is short? Bartell adds that one full-size Heidelberg web operates in a shop in which run lengths are as low as 2,500 pieces and average 7,000 pieces.

Another change in today's presses? The advent of wide webs. "Wide webs mean more ribbons," which can spell more control problems, says Bartell. "The trend is to use ribbon control systems to guide the web or ribbon laterally and control registration" versus using a main compensator control and web guide. Indeed, he adds that the Sunday press can be equipped with such a control system.

Finally, web press controls, such as tension controls, became more sophisticated with the advent of shaftless controls on press, explains Gary Owen, director of marketing and newspaper sales for KBA-Motter (York, PA). They'd need higher speed communication capabilities, he adds.

For instance, control devices must communicate with various systems within the press--tension controls must communicate with "the unit infeed system, drag rollers and folder controls to work as a complete system," says Owen.

While press and industry advancements have mandated changes in all web press controls, color management devices have snared the limelight. While all these devices find and read press bars or patches, take measurements, display data to a press operator and (closed-loop models) automatically adjust ink keys on press, they employ different technology to do so.

Graphic Microsystems recently introduced ColorQuick, an on-line closed-loop color measurement system. "We have two sensors--a video to locate the color bar, then a dual-beam spectrophotometer to measure the color," relates Fred Barnes, vice president of sales and marketing. "We calculate density from the spectral measurement of the color."

Dynascan, another on-press closed loop color management system, features a densitometer using an area array of CCD sensors to scan color bars, relates Perretta's Quilliam.

The Quad/Tech on-line, closed-loop model uses a video camera system, says Quadracci. "We capture a much larger field of view (approximately one inch) than possible with a spectrophotometer or densitometer (approximately 1/8 inch)."

Tobias Associate's SDT, an off-press, closed-loop scanning densitometer, locates and reads color bars as small as 1/16 inch, according to president Phil Tobias. The system reportedly locates the color bar and follows it, even if the paper is bowed and the bar isn't perfectly straight.

All of these closed-loop systems sense when corrections are needed and automatically make them on-press. Closed-loop devices are the wave of the future, though they're not yet common, according to Bartell, who says only two Heidelberg web presses operate with closed-loop control.

The differences among color measurement systems on the market are points of controversy. Are spectrophotometer- or densitometer-based systems optimum? Are on- or off-press systems superior?

"We believe spectrophotometers are the only way to go because these systems need to identify what color patch they're reading. If they measure only density, operators don't know if they're measuring a magenta patch, cyan patch, etc.," claims Bartell.

Dave Hazlett, product manager for X-Rite (Grandville, MI), agrees. "Potential problems exist in controlling color on-press that can't be caught using only density values; spectrophotometers are vital."

"Spectrophotometry is theoretically better; it gives a more precise reading," says Abbott. "But that information may or may not be necessary. For most work, knowing the density gets the job done. Besides, densitometers are more stable than spectrophotometers. The latter frequently require recalibration."

In the on- versus off-press debate, "the former systems will dominate since they typically can read a smaller color bar than off-press systems," remarks one expert. This is an important quality since in web publication work, the smaller the color bar, the better. These operations tend to use a small 1/16-inch color bar, according to Hazlett.

Further, on-press systems don't require operator intervention, offering the chance to reduce press manning. "These systems function automatically as the press is running. If operators trust the system, they can tackle other tasks, such as monitoring quality," claims one expert.

More speed and less waste also tip the scales toward on-press systems. These devices make many measurements quickly, whereas off-line reading is a slower process. Then, too, on-line systems reportedly easily handle SPC data collection and reporting, which quality conscious customers demand more and more frequently. While data collection can be done off-line, it involves more work.

Advancements to web press controls have been categorized as "small improvements" and "better versions" that are "easier to set up" and "faster." There aren't any revolutionary changes, according to Baldwin Graphic Systems' Gregory. "In terms of small changes, even tolerances probably can't get much tighter than they are now on register systems."

Yet, little in the graphic arts industry remains static for long. In fact, "we're using an air stand to move the scanning for register closer to the printing units. That way we can scan as soon as the web is printed rather than looking for register after the printing goes through the dryer and chill, etc.," says Quadracci. "We're taking a reading hundreds of signatures sooner." "In addition," he continues, "early next year Quad/Tech plans to use fuzzy logic in its color-to-color register control, allowing the system to anticipate changes in register and adjust for these changes before they occur."

Press manufacturers also have jumped into the fray with their own contributions to the press control arena. For instance, Komori boasts its KMS (Komori Monitoring System), which "monitors and displays essential status and operating data from the press and peripheral devices," according to Mary Lisi, director of marketing communications. The KMS also affords a closed-loop registration system, directs the remote ink key profile and more, continues the marketing exec.

The fact that Komori considers press controls vital to the health of web presses is evident in the firm's plans to incorporate KMS into its cutting-edge System 20 press. "The press will have the Komori Monitoring System; it's just not up and running yet," says John Dorshimer, pressroom manager for Dolan Wohlers Terwilliger, a New Jersey shopthat has operated the long-grain, half-size web press since December 1997. "The monitor is there, the computer is there, but the software has to be written."

Currently, System 20 boasts the Komori color console, which controls the ink fountain keys, ink and water balance, main press functions, etc., explains the pressroom manager. Although System 20 has been in the European and Asian markets for years, it only recently was brought to North America with a 23-inch North American cutoff, says Lisi.

Less ink and paper waste. Higher quality. More productivity. The advantages of web press controls are easy to see. However, there must always be at least one press operator per web, contends Abbott. "The controls make it easier for the operators to be more efficient, but an operator always must be there" to monitor quality and color.