Investigation of stitch length change under the conditions of sewing garment inertia motion

One of the qualitative indicators of joining with threads involves stable stitch length within individual seam sections. The key factor of the sewing garment, influencing the instability of stitch length along the seam, is the uneven shift of the sewing garment in the process of sewing. The paper deals with the possibilities of stabilising stitch length using two-sided loads of the sewing garment. This offers the reduction of stitch length, increased due to higher sewing speeds. In the investigation, 100% PES fabrics of plain and twill weave were analysed. Rotational frequency of the sewing machine main shaft was changed from 200 and 2100 min(-1) range, whereas the two-sided loads of the sewing garment were changed within the range of 0.39 to 5.8 N. A specific technique for measuring stitch length was provided. Dependencies of stitch length upon sewing speed and load were obtained. It was established that, irrespective of the rotational frequency of the main shaft or fabric direction, stitch length decreased by up to 0.5 nun as the load grew. It was demonstrated that, after changing rotational frequency of the main shaft, it was necessary to change the load of the sewing garment as well. The experimental data for 10 plain weave fabrics are presented. It can be seen that, in order to maintain constant stitch length when rotational frequency of the main shaft varies from 200 to 2100 min(-1), it is necessary to apply the load of 1.96 N to the sewing garment at the sewing speed of 2 100 min(-1). Stitch length remains more stable at higher loads. Dependencies of stitch length variation under the action of the load are presented.