Injection molding is a manufacturing process for producing parts by injecting material into a mold. Injection molding can be performed with a host of materials mainly including metals, (for which the process is called die-casting), glasses,  elastomers, confections, and most commonly thermoplastic and thermosetting polymers. Material for the part is fed into a heated barrel, mixed, and forced into a mold cavity, where it cools and hardens to the configuration of the cavity. After a product is designed, usually by an industrial designer or an engineers, molds are made by a mold-maker (or toolmaker) from metal, usually either steel or aluminium, and precision-machined to form the features of the desired part. Injection molding is widely used for manufacturing a variety of parts, from the smallest components to entire body panels of car. Advances in 3D printing  technology, using photopolymers which do not melt during the injection molding of some lower temperature thermoplastics, can be used for some simple injection molds.

Parts to be injection molded must be very carefully designed to facilitate the molding process; the material used for the part, the desired shape and features of the part, the material of the mold, and the properties of the molding machine must all be taken into account. The versatility of injection molding is facilitated by this breadth of design considerations and possibilities.