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FLEXO Magazine : July 2014
“It is much easier to have a customer approve a job that’s over impressed with too much gain than it is to have a customer approve a job that is missing graphics because it was under impressed. ” Pucker Up A Kiss Impression Is Key in Preparing And Executing an Ideal Pressrun A s the industry introduces new presses, inks and substrates, it is important to remember that it is often simple best practices that determine the success of a printrun. Methods for consistent impression are some of the most important best practices a printer can establish and the “kiss” impression is one of the most essential. What is a kiss impression? Simply put, on an ideal printrun, the printing sleeve or plate should just "kiss" the substrate. Technically, a kiss impression is the minimum impression needed to transfer all text, solids and halftones to the substrate. The advantages to a kiss impres- sion are numerous. The kiss allows pressmen to hold a fine dot while increasing graphic fidelity. It allows for printing at faster speeds, with less wear, and will protect the most fragile dot: the highlight. But a kiss impression is an ideal. In most “real world” environments, it is difficult to achieve. Lots of things in a print environment can ruin the perfect impression, so every printer has to look at the printing process from the center of the press outward and ask questions like these: • Is the substrate a perfect thickness on the roll and on every different roll? • Are the mandrels perfect in total indicated runout (TIR) without tapering? • Does the bridge mandrel have low spots? • Is there any “play” or movement in the mandrels from one unit to the next? • Do you trust that the plates are mounted to the cushion tape without waves? • Is the printing sleeve perfect in TIR and without tapering? • Have you ensured proper and consistent ink acetate levels and viscosity? • Have you ensured consistent surface tension that is within the substrate’s specifications? • Is the corona treatment of the substrate working correctly? Print managers have to be risk managers. Most pressmen and print managers will err on the side of over impressing a printrun to compensate for those real world problems. It is much easier to have a customer approve a job that’s over impressed with too much gain, than it is to have a customer approve a job that is missing graphics because it was under impressed. And the difference between a perfect impression and an under impression may be as small as 0.001-in. 22 FLEXO | JULY 2014 PLANTS & PROCESSES