UV WEB OFFSET PRESSES -- Finding the Cure
Because UV inks are sensitive to press-generated heat, temperature fluctuations make them break down, which affects printability. But, new press technology has taken care of that problem. The new generation of presses feature full cooling of ink trains and the web itself—so everything is kept at the optimum temperature. Maintaining the temperature in the proper zone has also helped eliminate ink breakdown and all the problems associated with it.
Since the UV process has gotten easier to use, and the new generation of presses offer the same advancements that are reducing make-readies and increasing the speed of conventional heatset web configurations, UV presses are now easier to run and much more productive to operate.
The primary benefit of UV over heatset printing is the flexibility gained in running in-line presses versus blanket-to-blanket presses, reports Pitel. “With in-line equipment the customer gains in his color combinations. For example, on an eight-color heatset web press the printer must run the color placement that the dryer layout dictates. With UV, the customer can run five-over-three colors, six-over-two, etc.,” he states. “The UV process holds an inherent advantage when teamed with its most common partner—the hard cylinder (blanket to impression cylinder) webs.
“Through interstation drying (i.e., drying the ink after each print unit), a wider variety of color combinations can be achieved by simply inverting or perfecting the web where required,” Pitel adds. “For instance, while a five-unit (10-color) heatset perfector is capable of no more than five colors per side, a UV equipped 10-color in-line hard cylinder web can print five-over-five, seven-over-three, or even 10-over-0,” he reveals.
Another UV advantage becomes most evident in direct mail applications, where post-processing is a critical component. First, UV inks are instantly dried to allow for immediate personalization via laser printers. Second, UV eliminates web shrinkage caused by the intense heat found in the typical heatset drying process, the result of which can affect fit between the printed material and the personalized message. Finally, because the UV process does not remove much of the web’s moisture, cracking in an off-line folding process becomes much less of an issue than with heatset work.