: : : R Heathcote, Plastic Injection Moulding : : :

	The Process The injection moulding machine consists of a heated barrel equipped with a screw (usually driven by a hydraulic motor), which feeds the molten plastic into a temperature controlled split mould via a series of channels. The screw melts (plasticises) the plastc granules, and also acts as a ram during the injection phase. The screw action also provides additional heating by virtue of the shearing action on the polymer. The pressure of injection is high, dependant on the material being processed; it can be up to one thousand atmospheres.
On most machines the mould is held closed by a combination of clamping and hydraulic pressure. This is known as the locking force. This can be up to thousands of tons and is spread over the area of the mould. To counteract the injection pressure, a moulding with a large surface area will therefore need a machine with a higher locking force than a moulding with smaller surface area
	Modern injection moulding machines, such as those that we use, are controlled by a built-in computer. This gives the superior consistancy and quality that discerning customers demand. To see an animation showing the process,click here.