Parts should be designed to release from the mold tool easily. Assembly Thermoplastic parts can be joined in many ways, for example, by using molded-in features, chemicals, heat, or fasteners. Molded-in assembly systems are fast, inexpensive, and need no other parts. Chemical bonding involves solvents and adhesives. Solvents join like or similar plastics by dissolving surfaces to form a weld when the solvent evaporates.
Adhesives join plastics to other plastics or other materials having bondable surfaces.
Thermal welding melts the interface between two parts to form a bond. Other thermal methods include hot plate, spin, induction, and radio frequency welding. Most mechanical fasteners used for metal parts work with plastics. Self-tapping screws are widely used with plastics, as are threaded metal inserts typically molded into bosses in the part. Although almost any shape, cavity, or projection can be molded, machining can create some features.