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Bubbles of common problems in injection molding

Posted by: Mu Ju 2021-11-09 Comments Off on Bubbles of common problems in injection molding

According to the causes of bubbles, the solutions are as follows:

1) When the wall thickness of the product is large, the cooling speed of the outer surface is faster than that of the center part. Therefore, with the cooling process, the resin in the center part shrinks and expands to the surface, resulting in insufficient filling in the center part. This is called a vacuum bubble. The solutions are as follows:

a) According to the wall thickness, determine the reasonable gate and sprue size. Generally, the gate height shall be 50% – 60% of the wall thickness of the product.

b) Until the gate is sealed, a certain amount of supplementary injection material is reserved.

C) The injection time should be a little longer than the gate sealing time.

d) Reduce injection speed and increase injection pressure,

e) Adopt the material with high melting viscosity grade.

2) The solutions to the bubbles caused by the generation of volatile gases are as follows:

a) Sufficient pre drying.

b) Reduce the temperature of resin to avoid decomposition gas.

3) The bubbles caused by poor fluidity can be solved by increasing the temperature of resin and mould and the injection speed.


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