Calculation of film tension from film position and roller position

Abstract

The web tension as a crucial parameter for a web line is normally manually influenced by the speed of the motors driving the rollers. This paper shows that is better and easier to use the roller position derived from the motor position. For each roller there is a point where the web has the same speed as the roller surface. For each time step we read from the increase of the roller position during this time step (length of roller surface passed during that time step) the amount of material transported during over one roller. Looking at one web span, we know how much material has entered in that span over the roller in front of that span and how much material has left over the roller behind that span. This leads to the elongation of the material in that span. From the know Young's modulus we can calculate the web. The benefit is, that this calculation is independent of line speed and also works at stand still of the line. This type of calculations is very simple and useful for stationary effects (long-term effects) and also dynamic effects (instant changes in speed).