An extrusion machine is a device which pushes or pulls a material through a shaped die to form a continuous length of product with a preset cross section. The extrusion process is used to produce a large number of commercial products which include steel or copper wire, plastic tubing, plastic sheets, and many food types. Extrusion as a manufacturing process offers many benefits such as the wide range of complex cross sections possible and the ability to form brittle materials. Depending on the material used, an extrusion machine may form the material cold or hot with some types of materials being completely melted prior to extrusion.
The simplest example of an extrusion machine is a bakers piping bag. The bag is filled with icing and a fitted with a decorative piping nozzle. If the bag is squeezed, the icing fills the nozzle and is forced out or extruded as a continuous length with the same cross section as the shape of the nozzle opening. This is the same basic principle as industrial extrusion machines used to form many products using plastics, metals, and food or pharmaceutical ingredients. The only real departure from this simple example is in the complexity of the cross sections, the inclusion of hollow cores, and the fact that some machines draw the material through the die rather than pushing it.
An extrusion machine can be used to produce a wide variety of products from an equally large range of raw materials. It is also an attractive alternative to other manufacturing processes as it allows for a larger selection of profiles and is suitable for use with brittle materials. In industrial applications, plastics are extruded to produce food packaging film, cladding sheets, insulation, automotive parts, and tubing products such as electrical conduit and plumbing pipes. Steel and alloys are extruded to form rods, pipes, and wires as well as steel conduits and construction members for light engineering. The food and pharmaceutical industries also make extensive use of extrusions in the production of products such as pasta, cereals, cookies, and several drug carriers.
In several extrusion applications, particularly those using plastics, the material to be extruded needs to be heated to melting point prior to being used. These applications typically use a screw feeder mechanism similar to those used in the injection molding process to heat and feed the material. Cold extrusion is also a common extrusion process and is normally limited to metals such as tin, lead, steel, aluminum, and copper. Cold extrusion has several benefits over the hot process such as a lack of oxidization, better surface finishes, and quicker extrusion times. A cold extrusion machine is used to produce items such as automotive pistons, steel cylinders, tubing, and gear blanks.