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CLOSED-LOOP COLOR CONTROL — SMALL CHALLENGES, BIG REWARDS

May 2006 BY ERIK CAGLE
Senior Editor
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THE WORLD of closed-loop color control (CLC) somewhat resembles a PGA-caliber golf course. In both cases, the rewards for mastering it are high, but hazards along the way can certainly leave you in a tough spot.

What some web offset printers agree upon is this: closed-loop color control is a tool, not a turnkey panacea that will solve all color reproduction issues. Perfect, it is not.

Generally speaking, CLC is a process where the control system analyzes printed color bars at full web press speeds and makes on-the-fly adjustments to maintain accurate color control.

“The biggest challenge is getting our internal and external sales teams on board with the fact that closed-loop color control systems are a tool, not a cure-all,” notes Russ Welch, pressroom manager for Ripon Printers of Ripon, WI. “Just because you have these systems does not mean you have perfect color on every job with any type of color or format. It helps you to get to pleasing color much faster, which gets product on the skid faster.”

According to Welch, Ripon Printers runs 99 percent of the time controlling color to gray balance with QuadTech Classic, running to density only when necessary. With an average makeready of about 1,600 impressions and a varied run mix ranging from an eight-page signature on SCA stock to a 32-page form on 70-lb. paper, Classic has helped to enable that versatility for Ripon.

What has allowed Ripon to be competitive in this regard is the reduced makeready waste savings. Staffing issues are also improved; with a two-web stack and a small footprint, Ripon has been able to reduce manning from four operators to three. Eliminating subjective color judgment frees press operators to do other things.

Running to dot gain can be challenging, according to Welch. He notes that the CLC system needed some tweaks in the manner in which it was reading dot gain versus solid density. While running in dot gain control, variables in the press run can provide challenges—substrate issues, blanket piling or water levels, to name a few.

“The beauty of these new tools is the ability to see these variables change and correct them in real time,” Welch says. “Without this type of system, print defects go unnoticed for longer periods of time.

“We do a pretty good job of matching our digital proofs, given the technology of proofing available today,” he adds. “To do this by hand on-press would cost much more in press time and waste. If we change inks or some other products, we are just a press run away from updating the prepress profiles for proofing.”
 
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