Study on Gate Location and Gate Number for Manufacturability of Polymer Gears

In recent years, the utility of polymer gear increased tremendously due to their substitutability over the conventional metallic gear for light load applications. The gear is subjected to complex working conditions during the meshing; therefore, manufacturing technique may play a crucial role to produce the gear with high material characteristics and dimensional accuracy. The injection molding process is one of the most useful techniques for mass manufacturing of the plastic parts and gear as well because this process offers lower production cost and superior profile accuracy. However, the injection molding product may contain some common defects, namely weld line, shrinkage, residual stress, deflection, etc. This study emphasized to find out the best gate location and gate number for the spur gear made of KEPITAL®F20-03 material. A set of designs and locations of the gate have been studied using molding software with the aim to minimize molding defects. The result shows that the polymer gear with four-gate central injection system (CIS) possessed better weld line location, the maximum value of minimum weld line meeting angle of 13.292°, the minimum value of maximum von Mises residual stress of 118.352 MPa and maximum weight of 11.57 g. However, the polymer gear with two-gate CIS possessed minimum value of maximum volumetric shrinkage of 14.454% and deflection of 0.26 mm.