Predicting the web length and layers in a wound roll

Abstract

The length of web in a wound roll is one mark of roll quality. The available web length in a roll is a concern for many who process webs and those who convert webs. There are algorithms that estimate the length of web and layers in a wound roll based on simple geometry and inputs of inside and outside radius and web thickness. If webs were infinitely stiff in the machine and out-of-plane directions such calculations could be accurate but this is not the case. Webs deform as the result of winder operating conditions such as winding tension and the contact pressures and stresses due to winding. Length calculations based on geometry will err as a result of web deformation in the length and radial directions. Webs are generally subject to tension during transport through process machines, the apparent deformed web length will vary with transport tension. The mission of this paper is to describe means by which the available deformed web length and the number of layers in a wound roll can be accurately predicted. The accuracy of the predictions will be verified by winding trials in the laboratory. The winding trials will demonstrate the levels of accuracy that can be realized on laboratory and production machines.