Bubbles:
Cause: The bubble is easy to occur in the part of the forming
product wall thickness is thicker, the formation of the reason and
the forming product sag is exactly the same. Formed on the surface of the forming product for the depression, in
the forming product thick wall in the middle of the formation of
the cavity for bubbles. According to the causes of bubbles, the countermeasures are as
follows: when the wall thickness of the product is large, the
cooling rate of the outer surface is faster than that of the
center. Therefore, with the progress of cooling, the resin edge of
the center shrinks and expands to the surface, so that the center
is insufficient filling. This condition is called a vacuum bubble.
Countermeasure
1, according to the wall thickness, determine the reasonable gate,
runner size. Generally the gate height should be 50% ~ 60% of the wall thickness
of the product.
2. Until the gate is sealed, a certain amount of supplementary
injection material is left.
3. The injection time should be slightly longer than the gate
sealing time.
4, reduce the injection speed, improve the injection pressure, the
use of high melt viscosity grade materials.
5, due to the production of volatile gas caused by the bubble, the
solution is mainly: (1) full pre-drying. (2) Reduce the resin temperature to avoid the generation of
decomposition gas. The bubbles caused by poor fluidity can be solved by increasing the
temperature of resin and mold and increasing the injection speed.
6, warping, deformation of injection products warping, deformation
is a very tricky problem. It should be mainly solved from the aspect of mold design, and the
adjustment effect of forming conditions is very limited. When deformation is caused by residual stress caused by molding
conditions, stress can be eliminated by reducing injection
pressure, increasing mold temperature and making mold temperature
uniform, increasing resin temperature or adopting annealing method.
