They are used largely in the metals, plastics, and composite-forming industries. These extrusion machines are also used in construction, automotive, and aerospace applications.
Transforming or converting thermoplastic resin, usually in pellet form into roll or sheet stock through a combination of pressure and heat, is the purpose of sheet extrusion. The sheet may then be processed into shapes through pressure forming or thermoforming.
The plastic pellets are fed from a hopper into the barrel of the extruder where the pellets are slowly melted by mechanical energy generated by a turning screw and by heaters arranged along the barrel. The molten polymer is forced through a die which forms the extrudate into products.
"PET sheet is traditional plastic package material; it has high transparency, there is no ripple, crystal and the white creases after folding the surface. It remains good performance for oil and chemical resistance, high toughness and strength, good impact resistance. This product is widely used after thermo forming for cosmetics, food, toys, folding boxes and printing etc". The typical plastic materials that are used in extrusion but are not limited to are - polycarbonate, acrylic, acetal, polypropylene, nylon (polyamides), acrylonitrile butadiene styrene (ABS), polyethylene, polystyrene, and polyvinyl chloride (PVC).
