A New Perspective on Yarn Unevenness: Components and Determinants of General Unevenness

Abstract

A simple analysis of the local linear density of a yarn yields an equation of its overall variance, which has three components: variance of the number of fibers per cross section, variance of the mean local fiber fineness, and that of the mean parameter of fiber inclination relative to yam axis. Further mathematical analysis of the component variances reveals a set of determining factors: the sequence of the fiber ends along the yam, the distribution of the fiber length, fiber fineness and its irregularity, the irregularity of the fiber configuration relative to the yam axis, and the blend uniformity along the yarn. To help in this analysis, a representation of the yarn, free of any structural hypothesis, is derived from the way the yam emerges from a ring spinning process: a superposition of elementary strips, each resulting from an initial sliver. This represen tation demonstrates that inverse proportionality between the squared CV of the yarn and its mean number of fibers in cross section holds for any yarn, including those idealized by Poissonian or other similar models.