Simulation of Bending Vibrations of a Roller System

To improve the efficiency of printing or coating processes for paper products the velocity of the web and the roller width can be increased. However, these measures cause deformations of the rollers, heating effects and streak print defects due to undesirable oscillations. The vibration characteristic is significant for the quality and efficiency of the printing or coating processes. Approved methods like balancing of the rollers and maximizing the bending stiffness have come to technical limits. This paper describes a new promising technology for further optimization of printing and coating machines. Piezoelectric actuators are integrated in the bearings of a roller of a flexographic printing machine and generate counterforces to compensate undesired bending vibrations. Strain gauges applied on the roller measure the vibrations. A simulation model of the mechatronic overall-system has been developed to design the control strategy. The oscillations of roller systems in printing machines and other industrial applications are mainly stimulated by disturbances that occur periodically with each rotation. A feedback control strategy combined with a feed forward compensation of predictable disturbances has shown promising results in simulation and experiments. Due to the fact that the excitations of the oscillations are periodically with the rotation of rollers, another approach for vibration reduction has been developed. The forces for vibration reduction are not generated by an active mechatronic system but by passive profile rings.