Overmolding uses plastic injection molding to create a part from multiple materials. This process adds an injection-molded layer of material over an existing injection-molded workpiece. The overmolding process produces chemically bonded parts made using multiple materials.
Overmolding is often cheaper and more effective than other manufacturing approaches that require creating and assembling component material parts separately. The process can also be used to build layered parts from scratch or to add a resistant outer layer to existing plastic parts and tools, providing a more rugged exterior. Toothbrushes consisting of a solid plastic body and rubberized grip are a common example of an over-molded product.