Solutions for Stress Marks in Plastic Molded Products

In the previous article, we introduced the main causes of stress marks in plastic molded products and whether we should find ways to avoid internal stress. By consulting our senior engineers, the solution is as follows:

1. Plastic injection product design:

(1) The thickness of the plastic product is too thin or the thickness of the flow end is too thick, resulting in excessive filling pressure and holding pressure. Gum addition or end-of-flow subtraction is required. That is to say, when the holding pressure is reduced, it depends on whether the shrinkage can be reduced and improved. If not, it is necessary to add glue in a large area;

(2) Try to avoid the difference in meat thickness, if there is, it needs to be differentiated, and the transition should be smooth, and there should be no steps for digging;

(3) Avoid too large bone position of the male model, which will cause stress marks on the bone position of the female model.

2. Plastic injection mold design

(1) The gate is too small or too few, and the distribution is uneven, adding cold wells or overflow troughs;

(2) Loose mold matching of moving parts or unreasonable waterway configuration, resulting in high mold temperature;

(3) The plastic injection mold flow channel and cavity exhaust should be good to reduce the stress and pressure of the cavity;

(4) The thickened line on the glue-reducing side is helpful for mold exhaust and product adhesion.

3. Injection molding conditions

(1) Reasonably set the holding pressure and time;

(2) Lifting and lowering of plastic injection molds;

(3) Increasing the speed is beneficial to reduce the residual orientation stress;

(4) Increasing material temperature, back pressure, and screw speed has little effect on stress marks.