Extrusion is an operation consisting of extruding plastic melt continuously through an extrusion head into an open space. Extrusion technology is empolyed to manufacture final or semi-products. Extrusion technologies can be divided into the following three basic groups according to the shape of the final product or semi product:
• Production of pipes and sections
• Production of films and sheets
• Other (lining, production of fibres and coatings, etc.)
Usually, worm extruders are employed. They do not work separately; instead, they are installed in production lines where other equipment for calibration, take-off, splitting and, in certain cases, additional modification in shape or surface are applied.