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FLEXO Magazine : June 2008
TECHNOLOGIES & TECHNIQUES FIGURE 7. Image courtesy Cordes Porcher. FIGURE 8. determine tonal range, dot gain and print contrast. Ultimately, the tone scale is one of the best monitors of ink film thickness and will act as an early warning indicator of such things as changes in viscosity, pH, and metering system. Solid ink density (SID)jtrap targets pro- vide information on how each color traps or sticks to the other when printed (see Figure 7). This information is useful when learning about the characteristics of the ink being used. They are also used to set impression of each color of ink. Pressmen can also read the solid ink density blocks to determine how well their ink configura- tions match predetermined standards. FIGURE 9. Images courtesy Cordes Porcher. A simple gray scale (see Figure 8), which can be reproduced with the three process colors, will imme- diately inform the press- man if his ink and anlilox configuration are allowing him to maintain a gray balance, which is essential to excellent color reproduction. By adding this quality control tool, your pressman will be better prepared to reach and maintain high qual- ity color reproduction. 3. Avoid moiré! Proper screen angle is critical to the success of any multi-colored print job, but with flexographic printing it is also necessary to consider the angle of the anilox roll cell pattern as well. As Figure 9 shows, inattention to screen angles can cause horrible results. 4. Designfor process variables! Designers have to remember that the corrugated substrate was created as a tough packaging material to protect product; it was not nec- essarily designed for print. However, we have developed techniques to print beauti- ful process color graphics on corrugated. With that said, it still isn't the same printing surface as a luster-finished, clay- coated offset lithography sheet. Designers must realize the difference and create designs that match the abilities of the print- ing process. For example, chang- ing anilox rolls on many corrugated presses is a long and arduous task. Changing anilox rolls may not even be an op- tion. Therefore, your FIGURE 10. Images courtesy Cordes Porcher. design should be suitable for print by the intended press configuration. Figure 10 shows the results of a graphic printed with a press with too much ink volume. It also shows the same graphic printed with proper volume. This is but one example of many pro- cess variables, but good communication between the designer and the printerj converter goes a long way to prevent this type of problem. The best designers have the technical knowledge of the print pro- cess to effectively communicate with the converter and to make appropriate design changes to avoid disaster. While I'm sure you can think of dozens of other hints to ensure great design for corrugated pack- aging, I trust the above suggestions will help eliminate those "But it looked great on screen" moments. . ABOUT THE AUTHOR: Dr. E. Dean Gilbert is an assistant professor and coor- dinator of Printing and Publishing in the Department of Graphic Communication Systems and Technological Studies at North Carolina A8[T State University. He has nearly 30 years of teaching experience at the college level. Gilbert has expertise in a wide range of graphic communication subjects, though his research and publishing interest are in packaging,flexography, and variable data printing. He holds a Bachelor's and Master's degree from Appalachian State University and the Ed.D. degree from Clemson University. IT'S A QUANTUNI LE -=- IN FLEXQ "Professor" Ned Wier has done it again. First, he brought you our patented ExSpect™ sheet photopolymer plates for exceptional print quality with analog plates. Now, DIGITAL EXSPECTTM PLATES, available exclusively from PRPflexo, offer you FLAT-TOPPED DOTS, 30% more relief depth, and greater tolerance for overimpression. Have you ever seen a more beautiful halftone dot? Virtually NO fluting on corrugated. Fully digital workflow, using any digital material in the caliper, configuration, and size you need. No lamination, and no bump curves. The plate replicates the ablat . This is, quite simply, the BEST PLATE you can buy. We want to prove it on your press with a fingerprint trial at no obligation. <j] D:!tJï:0 (317) 783-3226 www.prpflexo.com ----I J ----I J---l.....l J Eêí: