Precautions for secondary injection molding

Generally speaking, to enhance adhesion, the melting temperature of the covering material resin should be the same as the base material. If the melting temperature of the covering material is too low, it will not melt the surface of the substrate. The bond between the two is not strong enough. However, if the melting temperature is too high, the base material will soften and deform. In severe cases, the covering material will penetrate the base material, causing component processing failure. Therefore, choosing matching materials will ensure good bonding. Generally speaking, matching materials should have similar chemical properties or contain matching composite components.
When the base material and covering material do not match, usually only a mechanical interlocking effect can be formed. rather than chemical bonding.
Multi-material injection molding also needs to pay attention to some issues, the most common ones include:
1. The chemical or mechanical bonding strength between polymers is insufficient, and the material filling of single or multiple components is incomplete;
2. Flash flash appears on single or multiple material components.
3. The injection molding machine must maintain injection consistency.
In addition, the ratio of the injection 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, but is especially important in overmolding.
The non-return device can separate the covering material like a floodgate. It is easier to operate the non-return device when the secondary injection molding materials are all metal. However, it is more difficult to operate the non-return device if it is a metal base material and a more elastic plastic.