Why do you rub your hands together vigorously in winter when your fingers are cold? Because rapid rubbing converts kinetic energy into heat. And it is precisely this physical phenomenon that is utilised in plastics processing, the Injection moulding process, to take advantage of this in several ways.
We remember in the explanation of the concept of Rheology, that the plastic granules are melted and homogenised in an externally heated injection moulding cylinder. This is achieved by the rotary movement of the screw, during which the hard and still cold granulate rubs against the hot barrel wall, melts there and the mixture of already hot melt and still cold granulate is pushed forwards to the tip of the screw with a great deal of force. The pellets rub against each other and are squeezed through narrow gaps between the screw flight and the hot barrel wall. Additional frictional heat is generated. The injection moulding barrel therefore needs to be heated less from the outside.
During the subsequent injection process, the hot melt is chased through narrow distribution channels and injection points on its way to the mould cavity, which in turn generates useful frictional heat that keeps the hot mass flowing until it cools down in the cooled mould and can be demoulded as a plastic part.
And when, after all the friction, the customer receives a precise plastic moulded part from us that fully meets his requirements, he may even rub his hands together for a moment.