Aluminum extrusion is a process by which aluminum alloy material is forced
through a die with a specific cross-sectional profile.
Extrusion is defined as the process of shaping material, such as aluminum, by forcing it to flow
through a shaped opening in a die. Extruded material emerges as an elongated piece with the
same profile as the die opening.
A powerful ram pushes the aluminum through the die and it emerges from the
die opening.
When it does, it comes out in the same shape as the die and is pulled out
along a runout table.

STEPS IN THE ALUMINUM EXTRUSION PROCESS

1. Billets must be heated to approximately 800-925° F.
2. After a billet reaches the desired temperature, it is transferred to the loader
   where a thin film of smut or lubricant is added to the billet and to the ram. The
   smut acts as a parting agent (lubricant) which keeps the two parts from sticking
   together.
3. The billet is transferred to the cradle.
4. The ram applies pressure to the dummy block which, in turn, pushes the billet
   until it is inside the container.
5. Under pressure the billet is crushed against the die, becoming shorter and wider
   until it has full contact with the container walls. While the aluminum is pushed
   through the die, liquid nitrogen flows around some sections of the die to cool it.
   This increases the life of the die and creates an inert atmosphere which keeps
   oxides from forming on the shape being extruded. In some cases nitrogen gas is
   used in place of liquid nitrogen. Nitrogen gas does not cool the die but does
   create an inert atmosphere.
6. As a result of the pressure added to the billet, the soft but solid metal begins to
   squeeze through the die opening.
7. As an extrusion exits the press, the temperature is taken with a True
   Temperature Technology (3T) instrument mounted on the press platen. The 3T
   records exit temperature of the aluminium extrusion. The main purpose of
   knowing the temperature is to maintain maximum press speeds. The target exit
   temperature for an extrusion is dependent upon the alloy. For example, the
   target exit temperature for the alloys 6063, 6463, 6063A, and 6101 is 930° F
   (minimum). The target exit temperature for the alloys 6005A, and 6061 is 950° F
   (minimum).
8. Extrusions are pushed out of the die to the lead out table and the puller, which
   guides metal down the run-out table during extrusion. While being pulled, the
   extrusion is cooled by a series of fans along the entire length of the run-out and
   cooling table. (Note: Alloy 6061 is water quenched as well as air quenched.)
9. Not all of the billet can be used. The remainder (butt) contains oxides from the
   billet skin. The butt is sheared off and discarded while another billet is loaded and
   welded to a previously loaded billet and the extrusion process continues.
10. When the extrusion reaches a desired length, the extrusion is cut with a profile
    saw or a shear.
11. Metal is transferred (via belt or walking beams systems) from the run-out table to
    the cooling table.
12. After the aluminum has cooled and moved along the cooling table, it is then
    moved to the stretcher. Stretching straightens the extrusions and performs ‘work
    hardening’ (molecular re-alignment which gives aluminum increased hardness
    and improved strength).
13. The next step is sawing. After extrusions have been stretched they are
    transferred to a saw table and cut to specific lengths. The cutting tolerance on
    saws is 1/8 inch or greater, depending on saw length.