Web bagginess: Making, measurement and mitigation thereof

Abstract

Web bagginess is a defect so tenacious that few machines will totally escape its grip. It is so pervasive that it can be found on materials as diverse as tissue, writing paper, carpet, nonwovens, plastic film and steel. It is so chameleon-like in its appearance that it is given many aliases such as baggy lanes, camber, layflat, puckers and many more. Yet as common as this ailment is, objective measurements are tedious or fraught with uncertainty or both. This means that culling and rejection is typically done by subjective visual appearance. As common as this ailment is, few can take a specific baggy lane and point to the machine element that made it, much less how it was made.

This paper begins by defining bagginess in three entirely equivalent ways based on variations of flatness, stress and strain. It then develops a taxonomy of bagginess by classifying the general case into major groups depending on how the stress variations are distributed. Next, it discusses all of the common and most of the arcane means of measurement. Each is described by principle of operation, application and practical difficulties. Next, the more common sources of bagginess, such as nonuniform formation and yielding during handling are described. Finally, a methodology is developed for troubleshooting bagginess whose source is not certain.