Injection molding

njection molding (British variant
spelling: moulding) is a manufacturing technique for making parts from
both thermoplastic and thermosetting plastic materials in production.
Molten plastic is injected at high pressure into a mold (British variant spelling: mould), which is the inverse of the
product"s shape. After a product is designed by an Industrial
Designer or an Engineer, molds are made by a moldmaker (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 component to entire body panels of cars.
Injection molding is the most common method of production, with some commonly
made items including bottle caps and outdoor furniture. Injection molding
typically is capable of an IT Grade of about 9-14.

Materials: The most commonly used
thermoplastic materials are polystyrene (low cost, lacking the strength and
longevity of other materials), ABS or acrylonitrile butadiene styrene (a ter-polymer or mixture of compounds used for everything from Lego parts to
electronics housings), nylon (chemically resistant, heat resistant, tough and
flexible - used for combs), polypropylene (tough and flexible - used for
containers), polyethylene, and polyvinyl chloride or PVC (more common in extrusions as used for pipes, window frames, or as the insulation on wiring where it is
rendered flexible by the inclusion of a high proportion of plasticiser).

Injection molding can also be used
to manufacture parts from aluminium or brass. The melting points of these metals are much higher than
those of plastics; this makes for substantially shorter mold lifetimes despite
the use of specialized steels. Nonetheless, the costs compare quite favorably
to sand casting,
particularly for smaller parts.