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FLEXO Magazine : July 2007
3 0 F L E X O J U LY 2 0 0 7 w w w . f l e x o g r a p h y . o r g nEwspapErs Homemade Solution To begin the project, all possible targets had to be researched to determine the benefits of adding them to the new test plate. There were many to choose from, but we were able to narrow them down and arrange them in the way we felt they would be most beneficial. The objective of the new plate was to have many different targets that would allow the user to challenge his or her plate’s abilities to perform to the specifications required. We wanted to include any and every target that would help us to spot a problem long before the wheels on the press were set into motion. Finally, a plate was developed that we believed would be the perfect test for any flexo plate on any flexo newspaper in any printing situation. Knowing that one of the most important things that you must test for in a printing plate is the minimum highlight dot percent- age, a new target was created that contained four boxes with each holding a separate dot percentage from 2 percent to 5 percent. A flexographic newspaper plate is capable of holding a solid 4 per- cent dot with the 3 percent dot breaking off. These targets were evenly distributed across the page to make the minimum dot easy to determine. Another important factor is the ability for the plate to hold all highlight dots evenly across the face of the plate. A significant difference with the processing of flexo plates for newspaper is our speedy 3-minute plate wash-out. In this water wash system, the plate passes under a row of spray nozzles that blast away the unhardened polymer. This can cause a variation of the amount of polymer elimination across the plate, depending on the water pressure at each spray head. Tint scales are added to the four outer edges of the plate and down the middle of the plate to test for uniform hold-out from side to side and top to bottom. The tint scales can also be used to determine the darkest shadow dot held and where your 50-per- cent dot shows up on your plate. Minimum type and minimum line targets were added to test for this in both positive and reverse print. When checking these targets on the plate, you can thoroughly examine the shoulder that is created under your type and also the depth and width of the valleys created in the reverse type. Resolution targets were also included to compare your positive and reverse lines, showing your dot gain status. The lines created on this target travel in a box shape from positive to re- verse, letting you determine the extent of your dot gain. look WHat i Found Recently we used the new plate test im- age to discover a light exposure problem that we have been having in our plate- burning machine. In the minimum dot targets we noticed that the targets at the top of the plate held their dots well. The 4- percent dots were held solidly while the 3- percent dots were slightly breaking away. However, when checking identical targets in the middle of the plate, the 3-percent dots were almost totally gone and, by the bot- tom of the plate, had completely disappeared. We were even los- ing some of our 4-percent dots. This was a clear indicator that the light intensity in our plate-burning machine is uneven across the plate, causing much more light exposure to the top of the plate compared to the bottom. This makes it impossible to hold the dots to our specification across the entire plate. We have contacted our plate rep and are having our machine serviced as soon as possible. Without the new plate test target page we may have never spotted this inconsistency. SHaring inFormation We then went one step further to help the operator understand what he or she can examine on his/her test plate. We created an informational poster of the test plate with short explanations of what to look for with each target. If hung in the plate room it can be used as a tutorial for new platemakers, a refresher for old platemakers, and a constant reminder of the defects that can be spotted by examining the targets on the plate. After completing the new test plate and poster, we felt that it would be a useful tool for all of the flexo community, printers and suppliers. If all flexo newspapers utilized identical test nega- tives with matching targets, we could treat it as a corresponding form which we could compare, allowing us to more easily share information about any problems we may be having with plate exposures, processing, and quality. Conversely, we could share in each other’s new ideas and successes. We would all be speaking the same language, creating a higher understanding and greater unification between us. Sharing information is what makes us, as a printing commu- nity, better at what we do.? ABOUT THE AUTHOR: Lindsay Limbaugh is quality con- trol manager at Chattanooga Times Free Press, Chattanooga, TN. Limbaugh is a 2005 graduate of Clemson University with a degree in Graphic Communications. She moved to Chattanooga, TN in October of 2005 to begin her current position. The objective of the new plate was to have many different targets that would allow the user to challenge his or her plate’s abilities to perform to the spec-
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