You may be familiar with the process of creating extruded aluminum shapes, but there is a lot more than simply pressing an aluminum billet through a die. A great deal of planning and work goes into this method and some of it requires precision. Here is a closer look at aluminum extrusion from raw aluminum to finished product.
Casting
Did you know the first step in creating extruded aluminum shapes starts with casting? First, the billets must be created and to do this, aluminum is melted and added with different metals to form aluminum alloys. For example, to create 6061 aluminum, magnesium and silicon are included.
The metals are all melted together and the molten aluminum alloy pours from the melting oven into a filtration area which purifies the aluminum by taking out impurities and gases. Next, it flows into molds and is cast into aluminum logs, which can be as long as 30 feet. The logs are then cut into billets of varying sizes, to be used for extrusion.
Extrusion
The first step in making extruded aluminum shapes involves heating the billet to make it soft. Depending on the alloy used, it can take temperatures as high as one thousand degrees Fahrenheit. Special heating methods are used to ensure even heating throughout the entire billet. This is essential to the extrusion process.
Next, extrusion dies are also heated and the heated billet is then placed into a press section. A ram mechanism pushes the billet through a chamber which contains the die. The aluminum material then passes through the die and comes out in a wide range of extruded aluminum shapes, depending on the die.
The extruded aluminum is still very hot and it is rapidly quenched. This is the direct extrusion method. However, for some types of extruded aluminum shapes, an indirect extrusion method is used.
Indirect extrusion is similar to direct. A billet is placed in a container and both the container and billet pass through a hollow ram to form extruded aluminum shapes. This is sometime called backward extrusion, and is more energy efficient because much less friction is created.
After extrusion, the aluminum pieces are stretched to get rid of distortion or warping, and then cut into the proper size. Next, the aluminum is aged either naturally or in a heated environment to harden the metal. Before the finished product is shipped to the customer, it is carefully checked and measured to ensure accuracy and quality.
