Causes and solutions of bulge defects in injection molding

Bulge defects of plastic products are very common in the process of injection molding. It not only affects the beauty and appearance of products, but also leads to uneven thickness of products, reducing the strength and practicality of products. This paper will analyze the causes of injection molding bulge defects, and put forward the corresponding solutions, so that readers in practice reference and improvement.

Cause description

In the process of injection molding, after the molten plastic enters the mold cavity, if the heat is uneven or the injection pressure is insufficient, the bulge defect will be formed. Specific performance for the product surface convex or concave phenomenon, affect the product smoothness and smoothness. The causes of bulge defects mainly include material ratio, mold temperature, product size and other factors.

solution

In order to avoid injection molding bulge defects, the following solutions can be adopted:

1. Adjust the material ratio: increase the filler and glass fiber additives, improve the rigidity and toughness of plastic products, reduce the generation of bulge defects.

2. Control mold temperature: keep mold temperature consistent with plastic flow temperature to avoid premature solidification or crystallization of plastics in the cavity.

3. Optimize the injection process: appropriately increase the injection pressure and pressure holding to ensure that the plastic cavity is fully filled. At the same time, the cooling time should be set reasonably to avoid bubbles and bulges inside the products.

4. Control product size: plastic shrinkage rate should be considered in product design to ensure product size meets requirements and reduce the appearance of bulge defects.

According to the plastic material and process conditions, choose the appropriate material temperature and die temperature. Generally speaking, the material temperature should be higher than the plastic flow temperature, mold temperature should be higher than the material temperature. Reasonably adjust injection speed and pressure to ensure that the plastic is fully melted and the cavity is filled. Rapid injection and high pressure injection should be used in general. Under the premise of ensuring the strength of the product, the dosage of filler should be properly reduced to improve the crystallization rate and degree of plastics, so as to reduce the generation of bulge defects.