What is Overmolding

Two injection molding: It is a special plastic molding process, also known as rubber coating. It is similar to the two-color molding process, but it is quite different from the two-color molding process. It is a process of molding a certain plastic raw material in a primary plastic mold, taking out the molded part, and putting it into the secondary molding mold to inject the same or another plastic material again. More complicated will be multiple molding, so that the appearance and process of plastic products meet the desired requirements, known as secondary injection molding.

Precautions 

In general, to strengthen the adhesion, the melting temperature of the covering resin should be the same as that of the substrate. If the melting temperature of the covering material is too low, the surface of the substrate cannot be melted. The bond between the two is not strong enough. However, or the melting temperature is too high, the substrate will soften and deform. In severe cases, the cover material can penetrate the substrate, causing the part to fail. Therefore, the choice of matching materials can ensure good adhesion. In general, matching materials should have similar chemical properties or contain matching composite components.

When the base material and the covering material do not match, usually only a mechanical interlocking effect can be formed. Not chemical bonding.

There are some issues to be aware of in multi-material injection molding. The most common include:

1. The chemical or mechanical bonding strength between the polymers is insufficient, and the material of the single or multiple parts is not completely filled;

2. Single or multiple material parts appear flashed.

3. The injection molding machine must maintain injection consistency.

In addition, the ratio of the shot volume of the injection molding machine barrel to the size of the injection molded part is also an important factor affecting the quality of injection molding. This ratio is critical for all injection molding operations and is especially important in overmolding.

The check device can separate the covering material like a sluice. The check device is easier to operate when the secondary injection material is metal. If it is a metal substrate and a more flexible plastic, the check device is more difficult to operate.