Investigation into Five Hypotheses to Increase Bottom Thread Run–Out Time on Lock Stitch Sewing Machine

Superior durability against different stresses and strains on laundering and wear has given prominence to lock stitch in making up. This serviceability arises from the interlacement of participating threads that bed well within fabric structure and not directly exposed to the wearing medium. However, the complexity of the bottom thread supply system restricts bobbin size which implies frequent stoppages for bobbin thread winding and resulting into lower sewing efficiency. An unpicking of top stitch and working with limited numbers of needle thread are added defects channelized via the same draw back. Thereby, present study has been designed to work out feasibility of employing bigger package for bottom thread without affecting quality of the stitch and operative hitch. Five hypotheses have been investigated to resolve or minimize problem of bobbin thread run out time. The main challenges behind these drafts are making use of bigger bottom thread package and retaining consistent thread tension throughout feed passage along with a controlled sewing geometry. Accordingly, domestic lock stitch set up was restructured to accommodate reel or cone instead of bobbin and tension regulation with gate tensioner or disc tensioner or air nozzle in place of spring tensioner. Apart from this, trial was also made with a continuous but positive bobbin thread feed by modifying existing bobbin case design. Nevertheless, appropriate strength tension relationship maintenance was indeed difficult for many factors centered around bottom thread passage and has limited success to all the trials made. However, continuing studies on the floated hypotheses can explore a new horizon for long lasting prototype bottom thread supply system and can be successfully implemented at the shop floor.