Plastics engineers use plastic extrusion machines to turn raw plastic granules or pellets into processed forms. Extrusion machines are optimal for creating plastic sheets, or long pieces like pipes and gutters. Plastic extrusion machines process at high volumes with little post-processing refinement.
The hopper is a large funnel that holds the raw plastic in either granular or pellet form. The hopper sends a continuous stream of raw plastic into the heating barrel of the extrusion machine.
The heated barrel of a plastic extrusion machine is a long, horizontal cylinder. The cylinder is heated internally through the use of a heating jacket. As the plastic is fed into the cylinder by the hopper, the plastic melts from the heat. A helical screw down the center of the cylinder rotates and pulls the molten plastic down its length.
Die and Mandrel
A water-cooled die is located at the end of the heated barrel. The intended shape of the plastic is cut into the die. Water passes along the metal die to cool the plastic as it passes and harden it into shape. A mandrel may also be located after the die to produce a hollow shape.
Read more: Parts of Plastic Extrusion Machines | eHow.com