Injection molding is a manufacturing process for producing parts from both thermoplastic and thermosetting plastic materials.  Material 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, molds are made by a mold maker (or toolmaker) from metal, usually either steel or aluminum, 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 component to entire body panels of cars.  Injection molding is used to create many things such as wire spools, packaging, bottle caps, automotive dashboards, pocket combs, some musical instruments (and parts of them), one-piece chairs and small tables, storage containers, mechanical parts (including gears), and most other plastic products available today.

Injection molding is the most common method of part manufacturing.  It is ideal for producing high volumes of the same object.  Some advantages of injection molding are high production rates, repeatable high tolerances, the ability to use a wide range of materials, low labor cost, minimal scrap losses, and little need to finish parts after molding.  Some disadvantages of this process are expensive equipment investment, potentially high running costs, and the need to design moldable parts.