Extrusion is a process used for creating a product (an extrudate) by forcing a material through a die or an orifice to form a shape, or alternatively an extruder is used to produce semi-finished or finished products.
In a thermoplastic extrusion, the material is first softened by heating so that it can be shaped. This process is performed by the extruder, or extrusion machine. This heat softening is referred to by different names, such as ‘thermal softening’, ‘plasticization’, or ‘plastication’.
Most extruders are single screw machines. The screw is what forces the material towards, and then through, the die. Shape is imparted by the die, and/or by post-extrusion forming, and the product is then set to shape by cooling while maintaining its shape. The equipment used to perform this process is known as the post extrusion equipment, while the entire system is known as an extrusion line.
The extrusion products include:
- Plastic Film: This is generally used for packaging or sealed into bags.
- Plastic Tubing: Used for tubing and hose for laboratories, automobiles, etc.
- Plastic Pipe: Used for water, drains, gas, etc.
- Plastic Insulated Wire and Cable: Used in the industry and home for appliances, for communications, electric power distribution, etc.
- Feedstock for Other Plastics Processes: Extruders are widely used as compounders, or mixers. The output from an extruder compounder is chopped or granulated to form the feed for another process, such as extrusion or injection molding.
- Plastic Coated Paper and Metal: Used for packaging.
- Sheet: Used for lighting, glazing, signs, etc.
- Filaments: Used for ropes, twine, brushes, etc.
- Nets: Used for soil stabilization, packaging, etc.
- Profile: Used for home siding, gaskets, windows, doors, tracks, etc.