抄録
We investigated the thread tension of sewing machines in practical conditions by interviewing several sewing engineering experts. Of those interviewed, 80% replied that they rely on their experience and intuition, when they adjust the needle and bobbin thread tension of a sewing machine in order to obtain a well balanced stitch. Bobbin thread tension changes during a pulley rotation and also reeling amount of bobbin thread, even if the other condition is the same. In this study, we tried to clarify the effect of needle and bobbin thread tension on stitch balance and seam puckering. The seamed samples were prepared using the fabrics and sewing machine threads having different mechanical properties. We postulate the following the criteria that when the length of the needle and bobbin thread per unit fabric length are the same, a stitch is well balanced. Needle thread tension should increase if bobbin thread tension raises to obtain a balanced stitch. To achieve a pucker free seam, the thread tension must be maintained as low as possidle. In the above conditions, a large amount of thread is necessary to obtain a good seam. We established the relationship among needle and bobbin thread tension, stitch balance and seam puckering. The effect of physical properties of fabric and sewing thread on the above relationship was also studied.
