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FLEXO Magazine : July 2013
Testing the Plate 1. Mount plate onto impression cylinder and attach into first unit of Comco Cadet 7-in. press 2. Load press with cyan ink 3. Adjust impression pressure until optimal image quality is achieved 4. Adjust press speed until optimal image quality is achieved Clockwise from top left: Examining plate; mounting plate on impression cylinder; output on press; cylinder mounted on press; adjusting press. (pictured, Hannah Plavnick) and dot forming. RFID shape appears to have no effect on dot forming. There are no discernable differences in the plate face due to the presence of the RFID tags. Results from the pressrun were much less successful. There was a noticeable difference in dot gain for the image area where RFID tags were embedded in the plate. There were no pressure settings or press speeds that could elimi- nate this problem. Several factors could have compounded the problem: • Plate Caliper: Liquid photopolymer platemaking has lower image quality and is usually reserved for printing lower quality jobs. RockTenn’s Merigraph machine is de- signed to create thick polymer plates used for corrugated boxes. The Comco Cadet press is not equipped to run plates of this thickness. The gear teeth on the impression cylinder were shorter than the plate itself, and the entire run was friction driven by the impression cylinder. This is not an ideal way to run the press, and in fact, created a thicker band along the “D” row that could not be ex- plained by RFID placement • RFID Tag positioning: The RFID tags may be providing slight resistance to bending. Aligning the tags along the circumferential direction may have had an affect on the ability for the plate to wrap around the impression cylinder • Too many RFID tags: The wide spread area of dot gain in the general area of the RFID tags makes it hard to determine exactly which tag is causing the problem. In fact, the sheer amount of RFID tags within one plate may have compounded the dot gain • Taping RFID tags to the backing sheet: The added thick- ness of the clear tape we used to attach the RFID tags to the backing sheet creates added thickness underneath the photopolymer Due to the amount of variables involved with this procedure, a new test is required to determine the viability of embedding RFID tags within a liquid photopolymer plate. Here are a few changes I would suggest: • Conduct pressrun on a press designed for this plate thickness • Create two plates per RFID tag design, one with the RFID tag placed along the circumferential direction, and the other with the RFID placed in the width direction • Embed only one RFID tag within each plate • Glue the RFID tags to the backing sheet instead of taping • Conduct a test on placing the RFID tag outside of an image area. Theoretically, this should have no effect on image quality Due to the variability of the testing procedure, it is difficult to make any conclusive statements about whether embed- ding a RFID tag within a flexographic photopolymer plate 28 FLEXO July 2013 www.flexography.org