Plastic Injection Moulding – A Detailed Overview

Raw Materials

There are several kinds of raw materials used for the manufacturing of the plastic injections. However, the thermosetting plastic, elastomers and thermoplastic polymers (resins) are widely used in the production process due the presence of greater viscosity in these materials.


The Plastic injection moulding machines have basic component parts such as material hopper, heating unit, plunger etc. These machine parts are used to build pressure and keep the moulds in proper order to give the perfect shape once the molten material is poured inside it. They are also called presses, working in accordance with the tonnage ratings. Tonnage is the capability of the machine to exert clamping force during the manufacturing process to keep the moulds in closed position. The tonnage may range between 5 tons to more than 9000 tons depending upon the rigidity of the raw materials and the projected area of the moulding parts.

Plastic Injection Moulding Process

Melting Polymers: There is a broad and cylindrical melting unit in the injection-moulding machine, where the polymer is converted into liquid under high temperature and pressure. The polymer is filled in an auger, which has an opening at the bottom. The auger is introduced into the melting unit using a hydraulic motor. A valve system at the bottom of the cylinder restricts the passage of the liquid into moulds.

Pouring the Liquid Material into the Moulds

Once the heating process is over, the auger is pushed further to pour the liquid polymer in to the moulds to give the requisite shape to the injections. The moulds are compressed under huge pressure to keep them intact and in proper position. During this process, the liquid is poured twice or more to ensure there are no air spaces left.


After the moulding, the entire mould is introduced to cooling for compact solidification of the plastic injections, which consumes the major time-period during the entire manufacturing process. The cooling is done by passing air or water over the heated moulds or introducing cold water through small holes on the mould surface.


Once the cooling process is over, the compact plastic injections are ready for removal from the moulds. The clamp on the mould is unlocked to open the mould and derive the injection. The entire process is completed and the mould is now ready for the next unit manufacturing.

Plastic injections are affordable compared to other forms of injection. The cost of production mainly depends on the type of machineries. In the long run, this is a lucrative business. The plastic injection moulds are widely used in the manufacture of a number of other plastic products.

Post time: 05-09-2017