Solutions for bubble problem in the Injection Process
According to the cause of the bubble, the solution to the problem is as follows:
(1) When the wall thickness of the product is large, the outer surface is cooled faster than the center portion. Therefore, as the cooling progresses, the resin at the center portion is expanded toward the surface while being shrunk, so that the center portion is insufficiently filled. This condition is called a vacuum bubble. The main solutions are:
a) Determine the proper gate and runner size based on wall thickness. Generally, the height of the gate should be 50% to 60% of the wall thickness of the product.
b) A certain amount of supplementary injection material is left until the gate is sealed.
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 a material with a high melt viscosity rating.
(2) The bubbles caused by the generation of volatile gases are mainly solved by:
a) Adequate pre-drying.
b) Lower the resin temperature to avoid decomposition gases.
(3) Bubbles caused by poor fluidity can be solved by increasing the temperature of the resin and the mold and increasing the injection speed.