Aluminium extrusion is a process of transforming aluminium alloy into objects with a definitive cross-sectional profile for a wide range of uses. The extrusion process makes most of aluminium’s unique combination of physical characteristics. A powerful ram pushes the aluminium 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.
Main categories of extruded shapes are:
- Solid; with no enclosed voids or openings
- Hollow; with one or more voids
- Semi-hollow; with a partially enclosed void
The process of aluminum extrusion consists of the following steps:
- After designing and creating the shape of the die, a cylindrical billet of aluminum alloy is heated to 500°C
- The aluminum billet is then transferred to a loader, where a lubricant is added to prevent it from sticking to the extrusion machine, the ram or the handle.
- Substantial pressure is applied to a dummy block using a ram, which pushes the aluminum billet into the container, forcing it through the die.
- To avoid the formation of oxides, nitrogen in liquid or gaseous form is introduced and allowed to flow through the sections of the die. This creates an inert atmosphere and increases the life of the die.
- The extruded part passes onto a run-out table as an elongated piece that is now the same shape as the die opening. It is then pulled to the cooling table where fans cool the newly created aluminum extrusion.
- When the cooling is completed, the extruded aluminum is moved to a stretcher, for straightening and work hardening.
- The hardened extrusions are brought to the saw table and cut according to the required lengths.
- The final step is to treat the extrusions with heat in age ovens, which hardens the aluminum by speeding the aging process.