The Displacement of the Twists in the Needle Threads during a Sewing Process

Abstract

This paper has investigated the displacement of the needle threads twists of the stitches which were made by one-needle lockstitch machine (forward or backward stitching), two-needle lockstitch machine and zigzag seamer. In order to determine easily the number of twists in sewed threads, a three piled thread consisting of three single yarns dyed in diffe rent colors were used as needle threads. The results obtained were as follows : (1) Remarkable increases of sewed thread twists on reverse sewing by one-needle lockstitch machine and on the left needle of two-needle lockstitch machine and the change of the twist in the zigzag seam are caused by the effect of the edge of the needle eye.(2) The needle thread breakage and irregular stitches occur owing to the remarkable decrease of the twists in the threads under the sewing operation on reverse sewing of one-needle lockstitch machine and on the left of two-needle lockstitch machine by the edge effect of the needle eye.(3) The displacement of the thread twists by the edge effect of the needle eye in the zigzag seam is largely dependent on the angle (θ) between needle eye direction and the needle thread, and it is also influenced by the thread tension.