overmolding vs insert molding

Two processes solve the same family of problems from opposite directions. Overmolding adds a second material on top of a finished plastic part; insert molding places a metal or plastic component inside the cavity and molds the part around it. Both eliminate assembly steps, both add tooling complexity, and both fail in predictable ways when the design rules are ignored. The value is easy to state. A soft-touch TPE grip over a rigid ABS housing replaces two parts, a glue line and a screw; a molded-in brass insert replaces a drilled hole, a tapped thread and a torque specification that a subcontractor has to meet. The cost sits in tooling, cycle time and the tight process window that a two-material part demands. This article sets out how the two processes differ, which material pairs actually...