Side dents in injection molds are caused by local internal shrinkage after gate sealing or out-of-material injection. The depression or micro-depression on the surface of the injection molded product is an old problem in the injection molding process. Dents are generally caused by a local increase in the shrinkage rate of plastic products caused by the increase in wall thickness. The degree of expansion and contraction depends on many factors, so how to deal with the side dents in the injection mold?
1. In the pressure holding process of the molded parts, additional plastic materials are injected into the mold cavity to compensate for the molding shrinkage. In most cases, the gate is much thinner than the rest of the part, and while the molded part is still hot and continues to shrink, the small gate has cured, and after curing, the holding pressure does not work on the molded part in the cavity.
2. The molded parts of semi-crystalline plastic materials have high shrinkage, which makes the dent problem serious; The molded shrinkage of amorphous materials is low and the dents are reduced; Fills and maintains reinforced materials with low shrinkage and less potential for dents.
3. Thick injection molded parts cooling time long, will produce greater shrinkage, so the thickness is the root cause of dents, design should be paid attention to, to try to avoid thick wall parts, if can not avoid thick wall missing, should be designed hollow, thick parts will be smooth to the nominal wall thickness, with a large arc instead of sharp corners, can eliminate or reduce the dents near the sharp corners.
