The use of aluminum extrusion in product design and manufacturing has increased significantly in recent decades.
Perhaps you’ve heard of this manufacturing process and are wondering what it is and how it works.
Today we’ll discuss what aluminum extrusion is, the benefits it offers, and the steps involved in the extrusion process.
We’ll begin with the most basic and essential question.
What is Aluminum Extrusion?
Aluminum extrusion is a process by which aluminum alloy material is forced through a die with a specific cross-sectional profile.
Aluminum extrusion can be likened to squeezing toothpaste from a tube
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.
At a fundamental level, the process of aluminum extrusion is relatively simple to understand.
The force applied can be likened to the force you apply when squeezing a tube of toothpaste with your fingers.
As you squeeze, the toothpaste emerges in the shape of the tube’s opening.
The opening of the toothpaste tube essentially serves the same function as an extrusion die. Since the opening is a solid circle, the toothpaste will come out as a long solid extrusion.
Below, you can see examples of some of the most commonly extruded shapes: angles, channels, and round tubes.
On top are the drawings used to create the dies and on the bottom are renderings of what the finished aluminum profiles will look like.
Step #1: The Extrusion Die is Prepared and Moved to the Extrusion Press
First, a round-shaped die is machined from H13 steel. Or, if one is already available, it is pulled from a warehouse like the one you see here.
Before extrusion, the die must be preheated to between 450-500 degrees celsius to help maximize its life and ensure even metal flow.
Once the die has been preheated, it can be loaded into the extrusion press.
Step #2: An Aluminum Billet is Preheated Before Extrusion
Next, a solid, cylindrical block of aluminum alloy, called a billet, is cut from a longer log of alloy material.
It is preheated in an oven, like this one, to between 400-500 degrees celsius.
This makes it malleable enough for the extrusion process but not molten.
Step #3: The Billet is Transferred to the Extrusion Press
Once the billet has been preheated, it is transferred mechanically to the extrusion press.
Before it is loaded onto the press, a lubricant (or release agent) is applied to it.
The release agent is also applied to the extrusion ram, to prevent the billet and ram from sticking together.
Step #4: The Ram Pushes the Billet Material into the Container
Now, the malleable billet is loaded into the extrusion press, where the hydraulic ram applies up to 15,000 tons of pressure to it.
As the ram applies pressure, the billet material is pushed into the container of the extrusion press.
The material expands to fill the walls of the container.
Step #5: The Extruded Material Emerges Through the Die
As the alloy material fills the container, it is now being pressed up against the extrusion die.
With continual pressure being applied to it, the aluminum material has nowhere to go except out through the opening(s) in the die.
It emerges from the die’s opening in the shape of a fully-formed profile.
Step #6: Extrusions are Guided Along the Runout Table and Quenched
After emerging, the extrusion is gripped by a puller, like the one you see here, which guides it along the runout table at a speed that matches its exit from the press.
As it moves along the runout table, the profile is “quenched,” or uniformly cooled by a water bath or by fans above the table.
Step #7: Extrusions are Sheared to Table Length
Once an extrusion reaches its full table length, it is sheared by a hot saw to separate it from the extrusion process.
At every step of the process, temperature plays an important role.
Although the extrusion was quenched after exiting the press, it has not yet fully cooled.
Step #8: Extrusions are Cooled to Room Temperature
After shearing, table-length extrusions are mechanically transferred from the runout table to a cooling table, like the one you see here.
The profiles will remain there until they reach room temperature.
Once they do, they will need to be stretched.
Step #9: Extrusions are Moved to the Stretcher and Stretched into Alignment
Some natural twisting has occurred in the profiles and this needs to be corrected.
To correct this, they are moved to a stretcher.
Each profile is mechanically gripped on both ends and pulled until it is fully straight and has been brought into specification.
Step #10: Extrusions are Moved to the Finish Saw and Cut to Length
With the table-length extrusions now straight and fully work-hardened, they are transferred to the saw table.
Here, they are sawed to pre-specified lengths, generally between 8 and 21 feet long. At this point, the properties of the extrusions match the T4 temper.
After sawing, they can be moved to an aging oven to be aged to the T5 or T6 temper.