Impact of Positive Thread Feeding for High-Speed Industrial Lockstitch Sewing Machines: Part II Response with Cotton and Spun Polyester Needle Threads

Abstract

During high-speed industrial lockstitch sewing, the dynamic, thermal, bending and abrasive loading of the thread has a negative influence on the tensile properties of sewing threads. For maximum strength retention of needle thread, a positive thread feeding device is developed which lowers the stitch tightening tension (or peak tensions). Two types of threads, viz. mercerised cotton and spun polyester threads of linear density 40 tex and 60 tex, are taken for investigation. During conventional sewing, there is a significant loss in breaking force and elongation for cotton and spun polyester threads. It is observed that loss in breaking force is significantly lower with positive thread feeding device as compared to conventional sewing, whereas loss in breaking elongation is significantly lower in most of the cases for both cotton and spun polyester threads. The peak tensions observed during sewing with positive thread feeding device are much lower than the conventional sewing. The loss in breaking force and elongation for the cotton threads during sewing is higher than that of spun polyester threads in the case of both conventional sewing and sewing with positive thread feeding device. In both the cases, coarser threads show higher loss in breaking force and breaking elongation during sewing as compared to finer threads. During conventional sewing, the initial modulus of cotton threads decreases significantly, while there is a significant gain in initial modulus of spun polyester threads. With positive thread feeding device, there is a significant improvement in initial modulus for cotton and spun polyester threads.