Dependence of Stitch Length along the Seam on External Friction Force Theoretical Analysis

Abstract

At joining of clothing details different defects may be observed. One of the most obvious defects is stitch length unevenness along the seam. The maximum stitch length unevenness along the seam is known to be obtained by sewing at different speed. This paper concerns with the theoretical research of fabric load and external friction forces that have influence on change in stitch length along the seam. It was demonstrated that the inertial motion path, after its detachment from the toothed plate, of the fabric is determined by sewing speed, mass of the fabric and load, and friction conditions. The carried out calculations illustrate that at a low ratio between the fabric mass and load mass, influence of the ratio between the friction coefficients of the sewing garment and load on change in length is different: when the ratio between friction coefficients is below 1, increase of the mass ratio leads to higher change in stitch length; when the ratio of friction coefficients is above 1, increase of the mass ratio leads to lower change in stitch length; when the mass ratio fluctuates within greater limits, a tendency of stitch length change variation is not subject to the friction ratio, and change increases in all cases. It was established that greater influence on stitch length change in made by friction conditions. With the increasing ratio of the aforementioned friction coefficients, the stitch length may decrease down by 80 %.