Evaluating the pressure pulse in a flexographic printing press : Linking process parameters to specific pulse shapes

Abstract: In the printing industry quality is key, this is because a product is printed for a better appearance or to convey information. If the packaging for a product looks bad customers will get a bad first impression of the product. The quality of the print can be affected by many different factors. The material properties of the paperboard such as stiffness, surface roughness, and thickness. It could also be affected by the coating of the paperboard, the properties of the ink, the material properties of the printing form, etc.  In this thesis, the effect of the contact time and the maximum pressure in the nip of a flexographic printing press was studied. To separate these variables six different desirable pressure pulses were decided upon. Three of them where the contact time remains constant while the maximum pressure changes, and three other pulses where the maximum pressure is constant while the contact time changes. The printing was done in an IGT F1 laboratory printing press. The different pressure pulses were achieved by using three different printing forms and varying the force settings in the printing press. The mottle results from the mottle analysis do not show a clear reliance on the contact time or maximum pressure. Instead, the stiffness of the printing forms influences the results to such an extent that it overshadows any effect that the contact time or maximum pressure has. In the case of dot gain, it can be determined that a larger impression leads to more dot gain. However here the stiffness of the printing plays a large role, and no clear conclusions can be drawn when strictly comparing contact time or maximum pressure.