A Study on Easing by the Bottom and Variable Top Feed Sewing Machine. Influence of Sewing Condition and Fabric Properties on Easing.

The aim of this study is to clarify effects of the sewing condition, fabric properties on easing using the bottom and variable top feed sewing machine. The results obtained were as follows: (1) The seam shrinkage tended to increase with the ratio of differential feed. The relation between the seam shrinkage and the angle between weft and sewing directions was equated with the sine curve by using the experimental values of seam shrinkage obtained from 4-directional sewing(45°, 90°, 135° and 180°). (2) The apparent slippage of fabric on the main feed dog(LB') was predicted using the seam shrinkage and stitch length. LB' tended to increase with the ratio of differential feed. The relationship between LB' and the angle between weft and sewing directions was approximated with the cosine curve by using the calculated values of LB' obtained from 4-directional sewing(45°, 90°, 135° and 180°). (3) The relation between the seam shrinkage and fabric properties was considered by means of the multiple regression analysis. The important factors which influence easing were the product of two tensile strains EM1 × EM2, bending rigidity B and fabric thickness d, where EM1 and B were obtained from the KES-System along the sewing direction and EM2 was obtained from the direction perpendicular to the seam line. (4) The relationship between EM1 × EM2 and the angle between weft and sewing directions was approximated with the sine curve by using 4-directional measured values of fabric using KES-System. The relationship between B and the angle between weft and sewing directions was also approximated using same way as mentioned above. (5) It was shown that the seam shrinkage under the desired condition could be predicted quite well using the two methods shown in this study.