Plasticised polymer is extruded as a hollow pipe called a parison.  The parison is cut to length and clamped in the blow mould.  The blow mould is passed to the air pipe and the parison is given a blast of air.  The air inflates the hollow parison and forces it against the sides of the mould.  After a short cooling period, the moulding is ejected.  

The extruder produces a continuous flow of hollow section parison, so two or more moulds will be used to keep up with the flow of polymer.

Typical plastics used for extrusion blow moulding include:

• Polyethylene - Terephthalate (PET)

• Polypropylene (PP)

• Polyethylene (PE)

• Polyvinyl Chloride (PVC)