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Polymer Injection Moulding (PIM)

Polymer Injection Moulding is a process in which molten polymer is forced under high pressure into a mould cavity through an opening (sprue)

cogsHow does it work?

Polymer material in form of pellets is fed into an Injection Moulding machine through a hopper. The material is then conveyed forward by a feeding screw and forced into a split mould, filling its cavity through a feeding system with sprue gate and runners.

An Injection Moulding machine is similar to an Extrusion. The main difference between the two machines is in screw operation. In extruder screw rotates continuously providing output of continuous long product (pipe, rod, sheet). Screw of injection moulding machine is called reciprocating screw since it not only rotates but also moves forward and backward according to the steps of the moulding cycle.

It acts as a ram in the filling step when the molten polymer is injected into the mould and then it retracts backward in the moulding step. Heating elements, placed over the barrel, soften and melt the polymer.

The mould is equipped with a cooling system providing controlled cooling and solidification of the material. The polymer is held in the mould until solidification and then the mould opens and the part is removed from the mould by ejector pins.


Injection Molding is used for manufacturing DVDs; pipe fittings; battery casings; toothbrush bases; bottle lids; disposable razors; automobile bumpers and dash boards; power-tool housing; television cabinets; electrical switches; telephone handsets; automotive power brake; automotive fascias; transmission and electrical parts; mirror housings; steam irons; washer pumps; spoilers; butter tubs; moisture vaporizers; yogurt containers; toilet seats; cell-phone housings; cradles or bases for personal digital assistants; case of a notebook-computer; computer mouse; electrical connector housings; lawn chairs; automotive ashtrays; cookware appliance handles and knobs; aerosol caps; household items; bottle caps; toys

Sample handling requirements:

Availability of suitable split mould design. Identification of appropriate thermoplastic suitable for final application. (Common polymers used in injection moulding are Polypropylene, Polycarbonate, Acrylonitrile-Butadiene-Styrene and Nylon 6

Complementary techniques:

Thermoforming, Polymer Extrusion

Warwick Capability:

Various Battenfeldpressure and electric Injection Moulders


Claire Gerard: c dot gerard at warwick dot ac dot uk / 07385 145064

Polymer Injection Moudling Equipment

Typical results format, and sample:

Injection Moulded Polymer

Injection Moulded Polymer Output

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