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PRESS DRYING/CURING--The ABCs of Press Drying

March 2001
BY SCOTT POLK


For printers looking for a cure to their press drying woes, it would be wise to brush up on your alphabet skills. That's because the current solutions have names like UV, IR, WIR, EB and TDS. And if that sounds like a bunch of hot air, well, that's another option, too.

Though this multitude of choices can be staggering to someone not versed in the world of sheetfed and web press drying systems, it is also a blessing since the different options have pluses and minuses that benefit a variety of applications.

Ultraviolet (UV) curing is a favorite among printers because of its instant curing properties, the elimination of spray powder and the ability to achieve high gloss. Baldwin Technology offers two UV systems, filtered and unfiltered, depending on the customer's requirement, relates John Chapman, director of drying and ink systems.

The filtered system consists of a medium-pressure mercury vapor UV lamp that produces approximately 25 percent UV output, 25 percent white light and 50 percent infra-red (IR). In some UV curing processes, such as plastic, foil or lightweight substrates, the heat of IR causes problems. To alleviate this, Baldwin Technology places quartz filter tubes in front of the UV lamp. De-ionized water is pumped through these tubes, allowing pure UV to emit while filtering out 90 percent of the IR, resulting in a cool substrate. There is no need for shutters in this system.

In heavyweight and nonheat-sensitive substrates, unfiltered UV offers the ultimate curing process. Utilizing the same lamp as the filtered system, a perfect cure for inks and coatings can be achieved. To protect the press and operators, the system is both water- and air-cooled, and includes water-cooled shutters to allow the lamps to stay on when the press is not in motion.

"Generally a printer will put in the system best suited to his production," Chapman remarks. "Points that should be considered whether to go IR or UV will depend on end-result requirements."

Another vendor that praises the benefits of UV curing is Prime UV. The company was founded 14 years ago when UV curing was primarily used on sheetfed and label presses. To make the transition to today's web offset presses, Prime UV had to develop a high-intensity, finely focused UV dryer that could be installed on commercial web and high-speed direct mail presses running 2,000 fpm, as well as folding carton and flexo packaging presses running at 1,500 fpm. Because of this development, the UV printing process has become the drying system of choice for all direct mail, security printing, sheetfed offset printing on plastic substrates and folding carton web printing.
 

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