Abstract:

Needle movement in a standard lockstitch sewing machine is produced by a slider-crank mechanism. The needle moves in a vertical plane and penetrates the fabric on its way down. Friction between the needle and the fabric generates heat during the penetration phase. The heat causes severe problems during the sewing process, such as thread & fabric melting as well as residues around the needle’s eye. These cause thread or fabric damage and may interrupt the sewing process. One possibility of reducing heat generation is to reduce the needle penetration velocity. This is a function of the geometry of the sewing machine’s driving mechanism and the angular velocity of the main shaft. Since friction is a function of needle penetration velocity, the heat generated is directly dependent on the configuration of the driving mechanism, as well as the sewing speed. The aim of this work is to introduce the possibility of replacing the slider-crank mechanism, which is typically used in sewing machines, with a link drive mechanism. With this type of mechanism we may be able to reduce the penetration velocity of the needle without any loss of sewing speed. The optimal geometry of the link drive is achieved using a non-linear optimisation procedure.