Parameters Affecting Needle Thread Tension during Lockstitch Process

Role of check spring and parameters, like fabric compressibility, feed rate, breaking elongation percentage of thread and needle thread pre-tension, on the thread tension profile and peak tension values of needle thread has been studied during the stitching cycle. Needle thread tension is measured at two different locations, viz Zone 1 and Zone 2. Zone 1 lies between guide element 1 and guide element 2, while Zone 2 lies between guide element 3 and needle bar. It is observed that the values of thread tension peaks developed in Zone 1 is higher than those developed in Zone 2. It is also observed that in a full cycle of a stitch forming process, tension profile of needle thread has four peaks, out of which tension peaks 1 and 3 occur due to the action of check spring and these two peaks almost vanishes on removal of check spring. The effect of different parameters on needle thread tension profile and its peak values are studied in Zone 1. It is found that the major tension peak values of needle thread reduces with the increase in fabric compressibility and thread extensibility but increases with the increase in feed rate and needle thread pre-tension.