Top Web : Slip and Wrinkles Slip, Alignment and Wrinkles Do you get scratching, do you have baggy webs, do you have wrinkles that you can't get rid of? This TopWeb module will let you find out how to fix those problems. When you wrap a web round a roller, the effect of the roller on the web (e.g. scratching) or the web on the roller (e.g. deflection force) depends on the Wrap angle, the Friction coefficient, the Radius of the roller, the Web roughness and Roller roughness and, of course, on the Tension of the film. From these inputs, the program calculates the theoretical Air gap based on lubrication theory. If this is greater than the roughness of the web and roller then the web will slip and a Warning: will appear. It also calculates the Tension force and Friction force exerted by the web onto the roller. These are affected by torque on the roller. If the roller exerts a Torque (either intentionally in a driven roller or unintentionally because of a poor bearing – you can select whether it’s working in Brake or Drive mode) then there will be a tension difference which can cause scratching if the web slips. To avoid scratching you must increase wrap, tension or friction coefficient, or decrease the torque on the roller (e.g. by greasing the bearing). The tension of the web exiting the roller is bigger or smaller (depending on Brake or Drive mode) and is shown as a % of the original tension in the diagram of the wrap. The stretching of the web under tension causes a shrinkage in the transverse direction. The ratio of the two is called the Poisson ratio, and the Poisson shrinkage is calculate from the Poisson ratio, tension, modulus and web thickness. This shrinkage is normally negligible, but for thin webs and/or low modulus webs, this ‘necking’ can become significant. | 
