Flexographic Printing Redesign

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Date
2013-12-02
Authors
Phill, Justin
Houssin, Aron
Moncek, Jordan
Chan, Cher Yeng
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Abstract
Winpak Limited is an international company which manufactures and distributes high quality packaging material and related packaging machines. Food, beverage, and health care packaging are some of many products Winpak has to offer. The design for the packaging is created through a flexographic printing process. The machines used in the flexographic printing process are capable of producing packaging up to a rate of 500 metres per minute. The machines are currently running at 100 metres per minute or less due to a phenomenon called "bounce." Bounce is recognized by print variability, specifically in the formation of horizontal bands where the ink transfer is noticeably diminished or increased. The phenomenon does not appear at low printing speeds, but begins to occur when print speeds approach 100 metres per minute. Bounce is currently limiting the amount of packaging Winpak can produce. The team was tasked with the goal of finding what could be causing bounce in the printing process and to recommend possible solutions to the problem. Resonance and rotational imbalance of the rollers, the doctor blade used to remove excess ink from the printing material, and the sticky back tape used to hold the print template to the roller were all are as the team investigated. A modal analysis of one of the print cylinders was created in ANSYS. The first vibration mode occurs within the operating speed of the printing press. This means bounce could occur at a print speed of 270 meters per minute. However, the finite element model does not take into account environmental effects, or vibrations occurring in other components of the printing press, which can change the speed which bounce would occur at. This mode shape would cause the material at either end of the print cylinder to print more faint than the material in the middle. The recommended course of action is to install a new doctor blade and try a different brand of sticky back to increase the amount of damping on the print rollers. Increasing the amount of damping should reduce the amount of vibration, and bounce as well. A doctor blade […]
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