The increasing demands on sewing and seam performance have made sewing-thread manufacturers constantly modify the technological properties of the thread to suit the performance requirements under varied conditions. The number of problems related to sewability increased as higher sewing speeds were needed to join newer textile materials. Changes to finer-gauge knitted fabrics', the popularity of microfibre fabrics, and fabrics finished with different dyes and finishes, together with the widespread acceptance of synthetic fibres in both fabric and sewing threads, have created new sewability problems. However, the maximum machine speeds have increased but little in the last decade, the main reasons being that, with the present sewing-machine design, speeds have reached an optimum level, above which thread and fabric control deteriorates. Again, from techno-economic considerations, spun-polyester-fibre thread is dominating all other sewing threads in the apparel industry that are facing a challenge towards high-speed sewing operations. During sewing, the sewing thread is subjected to various stresses, most of which are cyclic in nature. These stresses are converted into thread tension, which ultimately affects sewability. It is therefore important to optimise and control thread tension so as to achieve higher productivity and good quality.
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