Overmolding is an injection molding process where one material is molded on top of another. Types of overmolding include two shot sequential overmolding, and multi-shot 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. Different materials are used for the two shots.
- Multi-shot overmolding uses more than two materials to manufacture the final part.
Two shot sequential overmolding analyses consist of a two step process, where a
Fill+Pack analysis is performed on the first cavity (first component stage), and then a
Fill+Pack analysis or a
Fill+Pack+Warp analysis is performed on the overmolding cavity (overmolding stage). The overmolding stage on the second cavity uses a different material from the first component stage. Mold and melt temperatures used in the overmolding stage are initialized by the temperatures recorded at the end of the first component stage.
Materials are usually chosen specifically to bond together, using the heat from the injection of the second material to form that bond. This avoids the use of adhesives or assembly of the completed part. It can result in a robust multi-material part with a high quality finish. When designing an overmolded part, wall thicknesses of both the insert and the overmolded component should be as uniform as possible to ensure an even and robust bond. Avoid ribs and sharp corners to reduce flow problems.
Tip: You may find it less time consuming to model your part in two separate studies, one for the first component stage and one for the overmolding stage. You can then add these two stages together in one model.