According to the causes of bubbles, the countermeasures are as follows:
(1) When the wall thickness of the product is large, the cooling speed of its 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 condition is called a vacuum bubble.
The main solutions are:
a) Determine reasonable gate and gate size according to wall thickness. Generally, the gate height shall be 50%~60% of the product wall thickness.
b) Until the gate is sealed, a certain amount of supplementary injection material is left.
c) The injection time should be slightly longer than the gate sealing time.
d) Reduce the injection speed and increase the injection pressure.
e) Use materials with high melting viscosity grade.

(2) The main solutions to the bubbles caused by the generation of volatile gases are as follows:
a) Pre-dry fully.
b) Reduce the resin temperature to avoid decomposition gas.

(3) Bubbles caused by poor fluidity can be solved by increasing the temperature of resin and mold and increasing the injection speed.