Thesis Details

Thesis Title: Using variance length curve analysis to determine the impact of medium term yarn variations on fabric appearance
Thesis Author: Matthew Moyer
Abstract: Evenness is a critical yarn quality parameter because it influences many other properties of the yarn and the aesthetic properties of the fabric made from the yarn. Evenness is normally either categorized by testing instruments which measure mass uniformity among eight millimeter lengths within a yarn, or by the variation in weight of 120 yard skeins from at least twenty different packages. However, fabric defects such as "chatter" or "window paning" are often caused by variations in yarn mass between eight millimeters and 120 yards. Modern evenness testers have the capability of calculating and displaying a variance length curve which represents mass variability for different cut-lengths of yarn. This variance length curve could be the key to discovering the cause of some fabric defects as well as being a process control tool. Ring spun yarn was made with nonstandard conditions deliberately set throughout processing to ensure there would be a wide range of variation at several different cutlengths. Yarns were knitted in order to determine which cut-lengths had the most influence on fabric appearance. It was discovered through fabric appearance tests that the one yard cut-length had the most influence on fabric appearance. It was also found that the variance length curve of the yarn could be used to determine from which process the origin nonstandard conditions are located (i.e. spinning, roving, or drawing).