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Aluminum Extrusions Industry Information
During the aluminum extruding process, the application
of pressure forces heated aluminum billets or logs through a metal die.
The die is an opening in the press shaped to resemble the final aluminum
part needed. The result is similar to the effect created when squeezing
toothpaste through a tube. The extruded
aluminum part reflects the die shape, just as the squeezed toothpaste
reflects the shape of the tube opening. Two methods of aluminum extruding
are direct extrusion and indirect extrusion. In the former process, the
die remains stationary while the ram forces the aluminum alloy through
the die opening. In the indirect extrusion process, the hollow ram houses
the die. The ram moves into the stationary billet from one end, forcing
the metal to flow into the ram and shaping the alloy with the die. An
almost infinite variety of shapes can
be produced at very close tolerances by the aluminum extruding process.
Extrusion dies can be either solid (flat) or hollow. Solid dies produce solid
shapes and may have one or more orifices through which the softened alloy is
forced. Hollow dies produce hollow or semi-hollow shapes. A single die may produce
shapes that have solid, semi-hollow and hollow sections. The bearing length of
the die is a critical characteristic of extrusion dies because it controls the
metal flow through the die. The longer the bearing length, the greater the resistance
to the flow of aluminum, and vice versa. All parts of the profile must
emerge from the die at the same speed. A well-designed die will slow the profile
through the thinner parts with shorter bearings in order to match the speed of
the profile through the longer bearings.
Aluminum is the best all-around extrusion metal due to its unique combination
properties. Although aluminum is one-third the weight of copper, brass or steel,
the extrusion process results in a very strong part because it can distribute
the metal to where it is needed. Aluminum is self-protected from corrosion by
its own thin transparent oxide film. Aluminum alloys can be easily joined by
welding, brazing and soldering. Conventional equipment can readily form or bend
aluminum extrusions. Aluminum also has high electrical conductivity and is a
good heat conductor and reflector, making it ideal for heat transfer and heat
shield applications.
Extruded
aluminum parts remain quite abundant and include aluminum
tubing, vehicle components, computer parts, window and doorway frames and
kitchen and other domestic appliances. Aluminum extruded products are often used
as feedstock for aluminum wire, drawn aluminum
tubing and rod and bar products. Aluminum extrusions range in size from one-millimeter
parts weighing a few ounces to parts several meters in length weighing one ton
or more. In addition to standard aluminum parts available in stock sizes and
shapes, aluminum extrusions meet specific customer needs in the construction,
automotive, medical, aerospace and telecommunications industries.
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