Factors Affecting The Plastic Shrinkage

- Sep 03, 2018-

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.