Darja Zˇunicˇ‐Lojen and Jelka Gersˇak
The quality of sewing threads, as defined by their mechanical and physical properties, is connected with seam quality and seam strength. Seam quality and seam appearance depend…
Abstract
The quality of sewing threads, as defined by their mechanical and physical properties, is connected with seam quality and seam strength. Seam quality and seam appearance depend mainly on the following sewing thread properties: bending properties, dimensional stability, thread twist and twist direction, fineness, regularity and surface properties on used fibres. The friction on the guide elements of the sewing machine depends on the surface treatment of the thread and affects the tensile force during the stitch formation process. It is important therefore, to know the friction coefficient when choosing the appropriate sewing thread. This contribution presents the influence of the sewing thread movement velocity over the guide element, the influence of the contact angle between the thread and guide element and the influence of the guide element material on the friction coefficient. The results of the research show that on increasing the thread velocity over the guide element, the friction coefficient slightly increases, whilst with the increase of the contact angle between the thread and guide element, the friction force exceedingly decreases. Furthermore, the results show that the friction coefficients using the steel guide are lower when compared with the ceramic guide. The behaviour of the sewing thread during the sewing process, can be concluded, based on these statements.
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Considers the complexity of a problem of thread’s rheological properties evaluation, and evaluates the visco‐elastic properties of a thread on the basis of static tests using…
Abstract
Considers the complexity of a problem of thread’s rheological properties evaluation, and evaluates the visco‐elastic properties of a thread on the basis of static tests using numerical methods. Describes a new software package VILKUS which was designed and programmed for this purpose. This program calculates parameters needed for the evaluation of visco‐elastic properties on the basis of numerical values of a stress‐deformation σ(ε) curve. The stress‐deformation σ(ε) curve served as a starting‐point for evaluation of visco‐elastic properties of threads. The B‐spline approximation using the least squares method was chosen as an appropriate and suitably smooth curve for construction of the average σ(ε) curve.