Aluminium extrusion is a metal fabrication process used to create a wide variety of components and products, including aluminum alloy rails, casings, tubes, housings and blocks. The specifics of the process are highly dependant on the design of the eventual product, and the machines and additional operations involved will be determined by the necessities of the product.
An aluminum extrusion requires a billet, which is the original aluminum alloy stock that will be extruded into the required profiles. The billet is heated until softening and then inserted into the extrusion machine, where a ram pushes it through a shaped opening. The opening, or die, is designed in accordance with the original product design, and the shape that emerges from the extruder has the same cross section as that of the die. The ram is powered by a high-pressure system capable of forcing the softened aluminum through the die. Billet stock can range from solid aluminum bars to powder.
Temperatures involved in aluminum extrusion can reach more than 500 degrees Celsius, which is still lower than the melting point of aluminum alloys. This means that the aluminum stock is still a solid when forced through the die (a much softer solid than room-temperature aluminum). A typical direct extrusion process leaves approximately one-tenth of the original stock in the extruder, although this material can be later recycled.
A number of finishing treatments are performed on aluminum extrusions. These include anodizing, which allows color to be added to the surface and which enhances the strength of the natural oxide coating; powder coating, an environmentally safe and effective option; and liquid coating, which includes various synthetic sprays and films. Each process creates a coating with different aesthetic and practical characteristics.
Among the many benefits of aluminum alloys are their strength, light weight and corrosion resistance. These attributes, coupled with the relative ease with which it can be machined and extruded, make aluminum one of the worlds most widely used metals. Aluminum extrusions are found in an endless range of industries, from aerospace to home appliances.