(1) The design of the part should make the wall thickness uniform and ensure uniform shrinkage.
(2) The cooling and heating system of the car plastic injection mould must ensure that the temperature of each part is consistent.
(3) The gating system must be unobstructed and the resistance must not be too large. For example, the dimensions of the main runner, runner, and gate must be appropriate, the smoothness must be sufficient, and the transition zone must be arc-transitioned. Professional plastic knowledge exchange WeChat group plus editor WeChat: NB58250988
(4) The temperature should be increased for thin parts to ensure smooth material flow, and the mold temperature should be lowered for thick-walled parts.
(5) The gate should be opened symmetrically and should be opened in the thick wall part of the product as much as possible, and the volume of the cold slug well should be increased.
2. For machines:
(1) The nozzle hole is too large to cause the melt to flow back and shrink, and the resistance is too small and the amount of material is insufficient to shrink.
(2) If the clamping force is insufficient, the flash will also shrink. Check whether there is any problem with the clamping system.
(3) If the amount of plasticization is insufficient, a machine with a large amount of plasticization should be used to check whether the screw and barrel are worn.
3. In terms of plastics:
Crystalline plastics are more harmful than non-crystalline plastics. The amount of material should be appropriately increased during processing, or a replacement agent should be added to the plastic to accelerate crystallization and reduce shrinkage.
4. Processing aspects:
(1) The temperature of the barrel is too high and the volume changes greatly, especially the forehearth temperature. For plastics with poor fluidity, the temperature should be appropriately increased to ensure smoothness.
(2) The injection pressure, speed, back pressure is too low, and the injection time is too short so that the material volume or density is insufficient and the contraction pressure, the speed, the backpressure are too large, and the time is too long to cause flashing and contraction.
(3) The feeding amount means that the injection pressure is consumed when the cushion is too large, and the amount is insufficient when it is too small.
(4) For parts that do not require precision, after the injection and holding pressure, the outer layer is condensed and hardened, and the sandwich part is still soft and can be ejected, and the parts are ejected early and allowed to cool slowly in the air or hot water. , Can make the contraction depression gentle and not so conspicuous without affecting the use.