Effect of Process and Machine Parameters on Changes in Tensile Properties of Threads during High-speed Industrial Sewing

The dynamic, thermal, bending and abrasive loading of thread during sewing process has a negative influence on the properties of sewing threads. In this study, the individual and interactive effect of the number of fabric layers, stitch density and needle size on the loss in tenacity, breaking elongation and initial modulus of four types of thread has been studied using Box-Behnken design. Response surface regression equations of loss in tensile properties on the above parameters were developed. The predicted equations agreed well with the experimental data. Contrary to the general expectation, the loss in tenacity and breaking elongation was found to decrease initially or remain unchanged as the number of fabric layers increased. Initial modulus loss decreased with the increase in number of fabric layers for all threads. Except for cotton thread, stitch density did not show any significant influence on tenacity and breaking elongation loss. As the needle size increased, the loss in tenacity and breaking elongation increased for all polyester threads, whereas these properties remained unchanged for cotton thread. Analysis of variance was carried out to find out the contribution of parameters in loss in tensile properties. The number of fabric layers was found to have the highest contribution on tenacity and breaking elongation loss of cotton threads, whereas needle size contributed substantially to the loss in these properties of polyester threads.