Aluminum extrusion is the process of forcing heated raw aluminum (billet) through a pre-designed set of dies using pressure and heat. A ram applies the pressure. This process is similar to a hot glue gun. The raw aluminum (billet) comes in a cylindrical shape that is usually around 20 feet long with a varying diameter that depends on the custom aluminum extrusion manufacturer requirements. Below are the basic steps from beginning to end.
The billet is cut to the desired length based on the product specifications. The billet is then moved to a tunnel heater that heats the billet to about 900 degrees Fahrenheit. The exact temperature is based on what the make-up of the aluminum is.
After heating, the billet is coated with a lubricant to prevent sticking. It is then placed into a cradle. A set of dies that match the customer specification are placed in line. The billet is forced through these dies using a ram and anywhere from 1600 to 6000 tons of pressure. Maintaining a consistent temperature is key through this process.
The extruded pieces are then cooled for the stretching process. Cooling methods vary depending on the manufacturer. Air, water or both achieve cooling. This is key for the stretching process.
STRETCHING AND CUTTING
A gripper on both ends of the extruded pieces stretch the piece to ensure it is straight and then the stretched pieces are cut to customer lengths.
The pieces are then aged. They are heated up to about 350 degrees Fahrenheit for a minimum of four hours to harden the aluminum.