Insert molding is like overmolding, but the base part doesn't have to be plastic or made by injection molding. For example, it can add a plastic coating to a metal part. It's often used for tools like scalpels, where a metal blade is embedded in a plastic handle, or for parts with bushings, clips, and fasteners placed inside the mold.

Overmolding is a process that creates chemically bonded multi-material components by adding a layer of injection-molded material onto an existing part. After the first injection molding process, the product is removed once it has cooled and is then placed into a second mold for a second injection. This causes the two plastic parts to be encapsulated together. It can be used to build layered components or to add a durable outer layer to existing plastic parts. This method is more cost-effective than separately manufacturing and assembling the parts.