The extrusion process
The extrusion process begins with aluminum Log or Billet. These logs are 22ft long and weigh on average 1200 lbs. Logs are available in 7”, 8” and 10” diameter with alloys such as 6063, 6005, 6463 and 6061. The Log or Billet is fed into an oven which heats the aluminum up to around 900 degrees Fahrenheit; this brings the billet to a ‘plastic’ state where it is malleable under extreme pressures, but not molten. The Log exits the oven and is sheared to an extrudable length – usually around 30” depending on the shape being extruded. The hot 30” billet is fed to the extrusion presses by the extrusion loader. The loader places the billet in front of the container. A large ram then pushes the billet into the container and applies as much as 3000 tons of pressure which squeezes the aluminum through the steel extrusion die. When the hot aluminum is forced through the extrusion die the aluminum takes the shape of the profile in the steel die and exits as a long stock length aluminum extrusion. The entire process is monitored with a digital readout and all data is stored on servers which are used to develop extrusion recipes for each specific profile.
As the hot aluminum extrusions exit the press an Extrusion Puller grips the end of the extrusions and guides the parts along the run-out table. This keeps the 900 degree extrusions from twisting and touching each other. On the run-out table a series of fans will cool the parts to room temperature. At this point in the process the aluminum extrusions are at a “soft state” T4 temper. Post artificial aging is used to reach harder tempers such as T5 or T6 tempers. There are other forms of cooling during the extrusion process such as water quenching which allow for harder strength tempers through artificial post aging.
Once the aluminum is extruded to the 150ft. table stock length each piece must be separated from the continuous extrusion process by cutting with special movable Hot Saws. After separation the extrusions are transferred to the cooling table where it is allowed to cool. As the aluminum extrusions cool they shrink and distort. After the parts reach room temperature the next process stretches the aluminum back to its non-distorted condition. The stretching operation is achieved by gripping the extrusion on both ends, and stretching the aluminum approximately 3% of its total length. This straightens and brings all dimensions and tolerances into spec. Then the parts travel to the finish saw which will cut the long table length extrusions into pre-determined stock lengths 20ft or less. The extrusions are then loaded onto aging carts and are fed into an artificial age oven which gives the parts a T5 or T6 temper hardness.
An extrusion die made of H13 steel and comes in various sizes and with a varying number of profile holes. Some dies are as large as 15” in diameter, and can have between 1 and 8 profile holes depending on desired extrusion design pressures. Today Custom Aluminum Products has produced 12,000 custom designed profiles. Please allow Custom Aluminum Products to assist in the die design process. By working together we believe we can reach the best possible design at the lowest cost to our customers.
To learn more about our extrusion capabilities or how to use best design practices to design the perfect aluminum extrusion profile, please contact our sales team for a copy of our Engineering Guide for Aluminum Extrusions.