1. Effect of molding process on shrinkage of plastic products
(1) The molding temperature is constant, the injection pressure is increased, and the shrinkage rate is decreased;
(2) keep the pressure increased and the shrinkage rate decreases;
(3) The melt temperature is increased and the shrinkage rate is decreased;
(4) The mold temperature is high and the shrinkage rate is increased;
(5) The holding time is long and the shrinkage rate is reduced, but the shrinkage rate is not affected after the gate is closed;
(6) The in-mold cooling time is long and the shrinkage rate is reduced;
(7) The injection speed is high, the shrinkage rate tends to increase slightly, and the influence is small;
(8) The molding shrinkage is large, and the rear shrinkage is small. The post-contraction is large at the beginning of two days and is stable for a week or so. The plunger type injection molding machine has a large shrinkage rate.
2. Influence of mold structure on shrinkage of plastic products
(1) The gate size is large and the shrinkage rate is reduced;
(2) The vertical gate direction shrinkage rate is reduced, and the parallel gate direction shrinkage rate is increased;
(3) The shrinkage rate away from the gate is smaller than that of the near gate;
(4) The shrinkage rate of the plastic part having the mold restriction is small, and the shrinkage rate of the unrestricted plastic part is large.