Continuous extrusion metals

Typical arrangement of a cold extrusion machine for metals 

Production rates high but are dependent on size and complexity. Continuous lengths up to 12 m/min. Cut extruded length up to 1000/h is possible. 

Extruders often run below their maximum speed for trouble-free production. 

Can have multiple holes in die for increased production rates and lower wear rates. 

Extruder costs increasing steeply at the higher range of output. 

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Continuous Extrusion (Metals) 7.9 Solid State Welding... 

CC Continuous extrusion (metals) process capability chart. 

Two notable methods to produce microcellular foams include gas supersaturation in combination with an extrusion process developed by MIT/Trexel [84-86] and the continuous extrusion process by Dow [87,88]. Super-insulating materials are made by the encapsulation of a filler material inside a barrier film, aluminum foil, or metallized film. These materials exhibit 5-7 times the R-value of typical nonvacuum insulating materials depending on vacuum level and barrier and filler type. Uses for these VIPs (vacuum insulation panels) include refrigeration and controlled-temperature shipping containers. 

Corrugated plastic can have a double-faced or single-faced construction. The double-faced construction has two linerboards separated by a fluted center. The single-faced construction allows one to form tubes or to shape the material around most cylindrical or round products. Profile plastic is produced as a continuous extrusion with two outer linerboards separated by a vertical flute. Inhibited corrugated and profiled plastics are used for boxes, dividers and partitions between metal surfaces. 

Like the extrusion of metals, the extrusion of plastics involves the continuous forming of a shape by forcing softened plastic material through a die orifice that has approximately the geometric profile of the cross-section of the work. The extruded form is subsequently hardened by cooling. With the continuous extrusion process, such products as rods, tubes, and shapes of uniform cross-section can be economically produced. Extrusion to obtain a sleeve of the correct proportion almost always precedes the basic process of blow molding. 

Compare the processing of metals and plastic by continuous extrusion and explain the differences involved. 

The most chemical-resistant plastic commercially available today is tetrafluoroethylene or TFE (Teflon). This thermoplastic is practically unaffected by all alkahes and acids except fluorine and chlorine gas at elevated temperatures and molten metals. It retains its properties up to 260°C (500°F). Chlorotrifluoroethylene or CTFE (Kel-F, Plaskon) also possesses excellent corrosion resistance to almost all acids and alkalies up to 180°C (350°F). A Teflon derivative has been developed from the copolymerization of tetrafluoroethylene and hexafluoropropylene. This resin, FEP, has similar properties to TFE except that it is not recommended for continuous exposures at temperatures above 200°C (400°F). Also, FEP can be extruded on conventional extrusion equipment, while TFE parts must be made by comphcated powder-metallurgy techniques. Another version is poly-vinylidene fluoride, or PVF2 (Kynar), which has excellent resistance to alkahes and acids to 150°C (300°F). It can be extruded. A more recent development is a copolymer of CTFE and ethylene (Halar). This material has excellent resistance to strong inorganic acids, bases, and salts up to 150°C. It also can be extruded. 

Extrusion coating is ideal for rods, tube and wire. The article is passed through a paint reservoir and then out via a die, which leaves only the correct thickness of paint in place. There are further techniques suitable for flat articles in sheet or web form. Knife coating is ideal for very thin coats, especially on continuous paper or plastic webs. The knife is either a metal doctor blade or a curtain of high velocity air (an air knife) directed onto the surface and it removes surplus material applied previously. 

Extrusion of Metals, Plastics, Explosives and Propellants. Extrusion is the process of forcing (by using pressure) a material in softened (plastic) condition thru a suitable orifice in order to produce a body of uniform desired cross-section, continuously. In order to render the material plastic, it is either preheated (as in (he case of plastics, solventless smokeless propellant and some metals) or softened by adding a plasticizer (as in die case of some plastics and smokeless propellant). Extrusion may be considered as one of the branches of size adjustment... 

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