Plastic Pipe and Tube Extrusion

Pipe and tubing come out of an extruder through a ring-shaped die with a pin in the middle: the melt flows round the pin and leaves as a hollow tube. Pressure inside the tube, or a vacuum sizer outside it, holds the diameter while it is cooled in water; a haul-off pulls it at a steady speed and a saw cuts it to length. PVC compound makes rigid pipe, plasticised (flexible) PVC makes clear vinyl tubing, HDPE makes pressure and drainage pipe. Aluminium is extruded the same way, cold enough to stay solid.