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FLEXO Magazine : January 2013
Vijay Ramachandran of DuPont re- cently attributed the rise in flexography to three factors: 1. Economics of consumer demand for shorter printruns 2. Shifting marketplace brought on by industry globalization (driving growth in the Asia-Pacific markets) 3. Demand for sustainable workflow solutions QUALITY & BEYOND With print quality reaching the level of gravure and therefore no longer determining the method of printing, factors like faster turnaround times, combination printing possibilities, easier transportation and storage of print me- dia, and more environmentally friendly media production all make flexography the more attractive option. With that said, converting a job from flexography to gravure while still main- taining the same quality can challenge even the most learned prepress and printing experts. Compensating for dot gain is one of the more challenging aspects of separating for flexography. The best minimum dot might print near a 15 percent dot on film, and as the number of impressions increases and the plate begins to wear, that dot size can continue to climb. For example, an image of a skier on a snowy slope might contain a majority of highlight dots. With gravure, the separator may be able to keep all four process channels in the snow to give it shape and definition. Flexographic separators, however, have to be cognizant of higher dot gains and might best serve the printer by limiting the snow to only one or two channels, perhaps cyan and black only. This restraint might make the image slightly flatter, but it keeps the snow from turning a dirty gray as the dot gain increases over the course of the printrun. Gravure is capable of printing a nice solid and an open screen on the same print station; flexographic printers do not have that luxury. In order to maintain an open screen but still lay down ink well in the solids, two different anilox rolls are needed which means that two different printing stations will be required. An eight-color job in gravure could easily become nine or 10 colors, so printers and separators need to be mindful when taking a gravure job to flexo. ESSENTIAL TOOLSET Flexo separators have to be aware of shadows or any ele- ments that fade to nothing (or even a single separation that fades to nothing, such as a magenta glow around an element over a gray background with no magenta minimum dots present outside the glow). Because of flexographic dot gain, this fade will create an artificial, “puddled” edge around the object. To have the desired effect, a separator would need to carry minimum dots of the faded color in the background or use some sort of transitional, hybrid screen to limit the effect. Most of the major plate suppliers and vendors have devel- oped some method for creating flat top dots on plates which, when paired with the correct screening or surface roughen- ing, can improve solid ink laydown and consistency in the highlights. MacDermid’s LUX process, DuPont’s DigiFlow process, Flint Group’s NExT process, Kodak’s NX process and Esko’s InLine UV2 all deprive the plate of oxygen during exposure (or expose the plate with such intensity that oxygen doesn’t have time to interact during the crosslinking of the polymers), producing more consistent and predictable dot shapes on the plate. These advancements have helped to give printers an additional toolset to match gravure quality in a flexographically printed package. There’s no substitute for paying attention, and any prepress separator and printer must understand that changeovers from gravure to flexo, as opposed to new jobs designed specifically for the flexo process, can prove some of the most challenging. Files have to be dissected and adjusted, press considerations must be made, and customers need to under- stand the challenges and reasons for modifications. If printers and separators can accomplish this, then the path to a suc- cessful gravure conversion project can pass on the benefits of flexography to customers without detractions elsewhere. n About the Author: Tyler Mills works as special projects man- ager for Cyber Graphics in Memphis, TN. He graduated from Clemson University in 2006 with a degree in Graphic Communications. He’s led a number of internal projects around quality manage- ment, workflow optimization, scheduling and color profiling, and he currently manages the organization’s sustainability objectives. An image of a skier on a snowy slope might contain a majority of highlight dots. Flexographic separators might best serve the printer by limiting the snow to only one or two channels — perhaps cyan and black. www.flexography.org jAnuAry 2013 FLEXO 53