Effect of injection molding cycle time on shrinkage and weight of manufactured polymer gear

Abstract

In the present study, effect of cycle time on diametric shrinkage and weight of polymer gear was analyzed experimentally and numerically. The experimental investigation was carried out using two plate single cavity gear specimen mold and numerical validation of same was done using the “Fill-Pack-Cool-Warp” analysis sequence. Cycle time mainly consists of injection time, packing time, and cooling time. The injection molding process parameters namely melt temperature of 175 °C, mold temperature of 40 °C, injection pressure of 100 MPa, packing pressure of 100 MPa were fixed and polypropylene homopolymer of grade PP M108 was used in the study. The result shows that with increase in the injection time and packing time, gear shrinkage decreased but it increased with increase in the cooling time. The gear weight increased with increase in the injection time and no effect of packing and cooling time was observed. The minimum shrinkage of 1.657% and 1.972% was obtained in the experimental and numerical study respectively at injection time of 1.5 s, packing time of 15 s and cooling time of 20 s. Similarly, the maximum gear weight of 7.369 g and 7.350 g was also found at the same set of injection molding parameters in experimental and numerical study respectively.