Study on Dynamic Needle Thread Tensions in a Single Needle Lock Stitch (SNLS) Sewing Machine. I. Effect of Stitch Length, Check Spring Tension, Fabric Feed Timing and Needle Thread In-take Length

This paper, the first of a two-part series aims to find the effect of stitch length, check spring tension, fabric feed timing and needle thread in-take length on tension peaks occurring on a spun polyester needle thread-during a sewing cycle of a SNLS sewing machine. The pre-tensions on the bobbin and needle threads and sewing speed were kept constant. A PC Four prominent tension peaks were detected. Longer stitch length causes higher tension peaks and shorter length stitch requires higher pre-tension to obtain a balanced stitch. The check spring tension has no effect on tightening tension. Incorrect of needle thread at critical guides which determines the length of thread to be released through tensioner, release of longer length of thread results in lower tension peaks (1, 2 and 4) and vice versa.