How does injection moulding work?

Material for the part is fed into a heated barrel, mixed, and forced into a mould cavity, where it cures and hardens to the configuration of the cavity. Moulds are typically made from metal, usually either steel or aluminium, and precision-machined to form the features of the part. They may need to split in a variety of ways to eject the finished part, or locate inserts that are bonded into the product. Most elastomeric thermoset polymers can be injection moulded, although custom compounding may be required in order to facilitate the process. Since 1995, looking across the entire range of thermoplastics, resins and thermoset types, the total number of available materials for injection moulding has increased dramatically at a rate of 750 per year. There were already approximately 18,000 materials available when that trend began, and injection moulding remains one of the most useful industrial processes ever invented.