Assessing wound roll quality using a measured stiffness/model method

Abstract

For those concerned with roll quality it is difficult to suppress the urge to compress the outer surface of a wound roll with your thumb to sense how tightly the roll was wound and how large the internal pressures might be. If several rolls of a given web are wound at unique tensions a human could often arrange these rolls in order of ascending winding tension using their thumb test. The thumb senses the relative conforming deformation of the roll surface. A soft roll would deform more and have greater contact area with our thumb than a hard roll for a given load. The thumb test is most useful on softer rolls wound from nonwovens, tissues, some grades of paper and polymer films but less so on metal coils that deform little in comparison to our thumb. The physics define stiffness as the extent to which an object resists deformation in response to an applied force. This publication reports the results of research where the stiffness of the outer surface of a wound roll is used to characterize the internal residual stresses throughout the roll due to winding. Measurements of stiffness of the outer surface of wound rolls will be demonstrated using commercially available devices along with a proposed handheld device all having greater resolution than the thumb. These measurements will be coupled with models to allow the exploration of internal residual stresses in the wound roll that can be used to investigate winding defects and roll quality.