Crystalline plastics shrink than conventional non-crystalline plastics. When processing, the amount of material should be increased appropriately, or a replacement agent should be added to the plastic to accelerate crystallization and reduce shrinkage and depression.
(1) The temperature of the cylinder is too high, and the volume changes greatly, especially the temperature of the front furnace. For plastics with poor fluidity, the temperature should be properly increased to ensure smoothness.
(2) The injection pressure, speed, back pressure is too low, and the injection time is too short, so that the amount or density is insufficient and the contraction pressure, speed, back pressure is too large, and the time is too long, causing the flash to shrink.
(3) The feeding amount means that the injection pressure is consumed when the cushion is too large, and when the amount is too small, the amount of the material is insufficient.
(4) For parts that do not require precision, after the injection pressure is maintained, the outer layer is basically condensed and hardened, and the part with the sandwich part is still soft and can be ejected, and the mold is released early, and it is slowly cooled in air or hot water. It can make the shrinkage depression smooth and not conspicuous and does not affect the use.