Overmolding is an injection molding process where two materials are molded together. Types of overmolding include two-shot sequential overmolding, multi-shot injection molding or insert overmolding.
Two-shot sequential overmolding is where the molding machine injects the first material into a closed cavity, and then moves the mold or cores to create a second cavity, using the first component as an insert for the second shot using a different material.
Multi-shot injection molding injects multiple materials into the cavity during the same molding cycle.
Insert overmolding uses a pre-molded insert placed into the mold before injecting the second material.
Overmolding is not an easy process – its complexity requires us to adhere to the strictest tolerances. Generally speaking, the overall concept of overmolding is almost the same as that of insert molding, yet it allows much more chances for mistakes and a much narrower margin for tolerances.
After the overmolding process, the materials we use will cool down and thus shrink, so we must give special consideration to the molds that we create. In addition, in the overmolding process, we need to use a variety of diversified materials. Due to the different cooling/shrinking properties of these materials, it is critical for us to create our molds that match the particular properties of the different materials to be used. To meet the exact needs of your overmolding project, our mold designers will match the mold specs to your specific requirements.
The plastic overmolding process provides a number of benefits that include:
- Secondary operation, assembly and labor costs are effectively reduced (as a single assembly is molded)
- In the manufacturing process, bonding steps are eliminated (component reliability is thus improved)
- Components that are plastic overmolded are able to ensure proper alignment and avoid loosening, while the plastic resins can offer improved resistance to shock and vibration
- Parts structure and strength are improved
- Design flexibility are enhanced and multi-material components are allowed (custom plastic overmolding makes it possible to produce molded parts with multiple different thermoplastic materials)
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