Dynamic Model for Estimating Friction Effect on to the Sewing Regularity

When the slippery fabric is sewn at high rates, the transport becomes critical because the motion of the fabric can escape control. The process parameters (foot presser force, sewing speed) require the proper adjustment within given limitations. A dynamic model of the fabric motion, driven by the feed mechanism of a sewing machine, is proposed as a means of an approximate evaluation of the level of process parameters at which the formation of the sewing seam will be regular. Vertical and horizontal component of motion are analysed separately. In both models the driving motion of the support (feed device of the sewing machine) is approximated as typical sequences of transport motion. In vertical motion the system spring - mass of the foot presser - fabric (non-linear elasticity and damping) is considered, and the horizontal component of motion is described by a 2 DOF system with friction. Velocities and displacements are computed by the numerical explicit time integration of the equations of motion. The computer programme automatically produces the time - displacement diagrams for two layers of fabric, indicating the effect of friction and process parameters to possible deviations from the motion required for the regular sewing.