Extrusion Processing of Plastic
One of the most common methods of processing plastics is Extrusion using a screw inside the barrel. The plastic, usually in the form of granules or powder, is fed from the hopper on to the screw. It is then conveyed along the barrel where it is heated by conduction from the barrel heaters and shear due to its movement along the length of the screw flights. The depth of the screw channel is reduced along the length of the screw so as to compact the material. At the end of the extruder the melt passes through a die to produce an extrudate of the desired shape.
