Simulation of Needle-Fabric Interactions in Sewing Operations

The nature of the forces involved when a sewing needle penetrates a fabric have been studied on an Instron in an attempt to identify some of the factors which influence the needle-fabric interaction leading to heat generation. The measurements were made at velocities three to four orders of magnitude lower than actual sewing velocities. Four major variables considered were needle velocity, needle diameter, needle surface finish, and number of fabric layers. The influence of these factors on the maximum penetration force and on the energy required to drive the needle into and out of fabric has been studied. All these factors and their interactions (except needle velocity in some cases) affect the maxi mum penetration force of the needle and the energy of penetration. The effect of needle velocity over the range covered, even when significant, was minor (of the order of about 10%). The needle diameter affects the maximum penetration force and energy of penetration to a much greater extent. They are found to increase at a greater than linear rate with in creasing needle diameter. In one fabric, these parameters increased with the third or fourth power of the diameter. Whereas certain special high-emissivity needle-surface finishes have been found to reduce temperatures of needles during sewing, more energy is expended when these needles pass through fabrics than is expended with regular-finished needles. In a series of exploratory experiments, no differences in behavior were observed for a variety of needle-point shapes (twist point, diamond point, and standard ball point) or for tests using sewing threads compared with tests made without sewing threads. The bulged eye needle was effective in reducing energy buildup, compared with ball-point needles. The maximum penetration force and energy of penetration were found to increase linearly with increasing numbers of fabric layers. Wherever feasible, attempts are made to relate observed penetration energy measurements with expected needle heating characteristics and with results reported in the literature.