Abstract
The rubber surface of a size press roll of a paper making machine is deformed into a certain convex polygon at a high nip force and at an operating speed of the rolls rotating in contact with each other viscoelastically. In the size press part, the surface of the paper is coated with starch between the rubber rolls. This polygonal deformation is called pattern formation phenomena, and occurs gradually, which leads to strong vibration of the machine. This problem is similar to other pattern formation phenomena, for instance, polygonal deformations of the smoother roll in paper making machine, regenerative chatters in cutting, and the polygonal deformation of the work roll in a hot leveler. This paper describes the countermeasures to avoid the pattern formation by changing the diameter ratio of the top roll to the bottom roll. It is found from the numerical analysis and experiment that the optimum ratio exists to decrease the instability effectively.
