Injection molding processing insert design points of attention

Injection molding is an efficient and economical production method, widely used in the manufacture of plastic parts. In the injection molding process, the rationality of the insert design has an important impact on the final product quality and production efficiency. In this paper, we will elaborate on several key points in the injection molding process that should be noted in the design of inserts to ensure that the product can be molded smoothly, while achieving the expected performance requirements.

Inserts refers to the plastic injection molding process pre-positioned in the mold of some parts, these parts can be metal, plastic or other materials, with the molten plastic together with the solidification of molding, become part of the product.

In the design of inserts, what issues need to pay attention to?

1. Material selection for inserts. The material needs to have good compatibility with the plastic substrate to avoid stress concentration due to material mismatch, which can lead to cracking or deformation of the finished product. Metal inserts usually require special treatment, such as plating or coating, to enhance the bond with the plastic.

2. Design of insert geometry. The dimensional accuracy of the insert will directly affect the overall dimensional accuracy of the injection molded part, so its tolerance range should be strictly controlled during design. In addition, the edges of the inserts should be designed as a smooth transition, avoiding sharp corners, which can reduce the shear stress of plastic flow and prevent cracks or warping.

3. Positioning and fixing method. Inserts must be accurately positioned in the mold to prevent deflection during injection. Commonly used fixing methods are snap type, press-in type or magnetic adsorption, etc., the specific choice of which method should be based on the size and shape of the inserts and injection pressure and other factors to be considered.

4. Thermal expansion factors should not be ignored. Due to the different coefficients of thermal expansion of plastics and insert materials, the design should take into account the two in the heating and cooling process of dimensional changes, leaving appropriate gaps or structural measures to absorb the difference in thermal expansion.

5. Runner design is also a crucial part. Runners should be able to guide the plastic to fill the mold cavity smoothly, and ensure that the melt can be uniformly wrapped around the insert. When designing the runners, the location and shape of the inserts should be taken into account to avoid dead spots or stagnant areas.

6. Equally important is the exhaust design of the mold. When the plastic is injected into the mold cavity, if the air inside the mold cavity cannot be discharged in time, defects such as bubbles or short shots will be formed. Therefore, the mold design should include a reasonable exhaust system, such as exhaust slots or venting pins, to ensure that the gas can be discharged smoothly.