Why are there dents in blow molded products?

In the production process of blow-molded products, dents are one of the most frequent occurrences of adverse phenomena, because the plastic injected into the mold shrinks in volume during cooling, and the surface of the early cooling part hardens first, and then bubbles are generated. That is to say, we say dents. What are the reasons for this phenomenon of steaming?

1. Possible causes of dents

The thickness of each part of the product is different, the internal pressure of the mold is insufficient, the cooling of the mold is insufficient, and the deformation caused by insufficient cooling time may cause dents on the surface of the blow-molded product, and materials with high shrinkage are also prone to dents.

2. How to crystallize products with dents.

Increase the injection pressure, prolong the injection pressure holding time, reduce the barrel temperature and the mold temperature, force cooling in the place where the dent is generated, and make up the flow edge where the dent is generated. If you want to improve the dent problem in the long term, the difference in the thickness of the designed product should be completely avoided. Reinforcing ribs that are prone to dents should be as short as possible.

For dents caused by material locks with high shrinkage, when changing the molding conditions to eliminate dents, the setting conditions should be set in the direction of small shrinkage. That is, the mold temperature and barrel temperature decrease, and the injection pressure increases, but it should be noted that residual internal stress may be caused by this.