Side dents in the injection mold are caused by local internal shrinkage caused by gate sealing or missing material injection. The depression or depression caused by the surface of the injection molded article is an old problem in the injection molding process. The dent is generally caused by a local increase in the shrinkage of the product due to an increase in the wall thickness of the plastic article. The degree of expansion and contraction depends on many factors. So, how do the side dents of the injection mold be treated?
1. In the process of holding the molded part, a plastic material is additionally injected into the cavity to compensate for the mold shrinkage. In most cases, the gate is much thinner than the rest of the part. When the molded part is still hot and shrinks continuously, the small gate has solidified. After curing, the molded part in the cavity is not pressed. kick in.
2. The molded part of the semi-crystalline plastic material has a high shrinkage rate, which makes the dent problem more serious; the molding shrinkage of the amorphous material is lower, the dent is minimized; the reinforced material is filled and maintained, The shrinkage is lower and the possibility of dents is smaller.
3. the thick injection molded parts have a long cooling time and will produce large shrinkage. Therefore, the large thickness is the root cause of the dents. The design should pay attention to the thick-walled parts. If it is impossible to avoid thick walls, it should be designed. The hollow, thick parts are smoothed to the nominal wall thickness, and the large arc instead of the sharp corners can eliminate or minimize the dents generated near the sharp corners.