The shrinkage of the plastic cap is mainly due to the f […]
The shrinkage of the plastic cap is mainly due to the fact that the surface material at the wall thickness is pulled in due to the volume shrinkage, and a dent mark appears on the surface of the finished product after cool. Shrinkage is the most common occurrence of defects on the surface of the finished product, but most of it occurs to the wall thickness.
1, process factors
(1), The holding pressure is not enough to overcome the strong resistance of the flow path to the pressure keeping stage so that the pressure in the film is insufficient and the effective feeding cannot be performed. ,
(2), The injection speed and the pressure holding speed are too slow so that the fluidity of the melt is not enough, and the speed is relatively slow. The solution that enters the cavity first cools faster, and it is too late to use the pressure-holding to carry out the feeding. Injection pressure.
(3), The holding time is too short, so that the melt reverses before the gate solidifies, resulting in insufficient product shrinkage.
(4), the back pressure of the storage material is not enough, the screw retreats fast, the melt is not dense, and the product shrinks space.
(5), The mold temperature and hot runner temperature are too high, the cool time is prolonged, and when the cool is insufficient, the shrinkage of the product is large.
2, the mold factor
(1), The mold is trapped and exhausted, resulting in residual air in the cavity, less melted material, and large product shrinkage. The mold should be maintained and the exhaust groove should be increased.
(2), the mold release is not smooth, resulting in the product being trapped, dents, maintenance of the mold, polishing the mold or adding a thimble.
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