What should I do if plastic products have dents?

Aug. 10, 2020

Causes of dents

1. The thickness of each part of the product is different

2, the internal pressure of the mold is insufficient

3. Insufficient mold cooling

4. Deformation due to insufficient cooling time

Associated knowledge

1. In the process of producing products, dents are the most frequent occurrence of undesirable phenomena. The plastic injected into the mold shrinks in volume when it is cooled. The early cooling part means that the surface hardens first, and bubbles will be generated inside. The so-called dents are cooling. The slow part creates a conspicuous concave surface in the direction of bubble shrinkage.

2. Materials with large shrinkage are also prone to dents. 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 this may cause residual internal stress.

3. Because the dents are better to be inconspicuous, if they do not affect the appearance, they are deliberately processed into a corroded pattern on the mold, such as grains, grains, etc. Also, if the molding material is HIPS, it is also effective to lower the mold temperature to reduce the finish. However, once dents occur in these methods, it is difficult to repair polished products.


The solution

1. Immediately: increase the injection pressure, prolong the injection holding time, reduce the barrel temperature and mold temperature, and force cooling where the dents are generated.

2, short-term: fill up the flow edge where the dent is generated. When the material in the dent area has a narrow place, make this part thick.

3. Long-term: The difference in thickness of the designed product should be completely avoided. For ribs that are prone to dents, the long and narrow shape should be as short as possible.

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