Aluminium Extrusion 101

The basics of the aluminium extrusion process

What is an Aluminium Extrusion?

Aluminium extrusions are the end result of a process used to transform aluminium alloy into useable bar length components that have a defined cross sectional profile, suitable for the required end application.

Their are many standard profiles available such as angles, channels etc. It is also possible to design your own profile in a cost effective way, that is our specialism.

They are used for a wide range of applications all around us - at work on your desk, office screening, whiteboards, heat syncs in your laptop. In your car - treadplate, grills, interior trim. At home - in your kitchen appliances, bathroom tile trims etc.

Different Aluminium Profiles.jpg

How are Aluminium Extrusions Made?

Step 1 - Take an Aluminium Ingot or Log

Before extrusion can begin you'll need some aluminium ingot. These are usually round in shape and up to 7 meters long - very heavy indeed. They come in a variety of alloys and thicknesses. These ingots are heat treated in process called homogensiation, that ensures it can be heated uniformly during extrusion before being supplied to an extrusion plant.

Step 2 - Cut a Bit Off and Warm it Up

A small slice, of the ingot is shaved off to suit the size of the press being used and the final extruded length required,  this cut is usually between 300mm and 1000mm long. This cut of the ingot is called a billet. The billet is now fed into a billet heater and its fired up to somewhere between 400-500 degrees celcius however, the precise temperature will depend of a number of factors such as complexity of shape, alloy, etc.

Step 3 - Squeeze it

This step is where the magic happens. The pre-heated billet is then loaded into a chamber and pushed at force through the opening of a die. The die has a wider opening on the rear face and the final shape/profile required by the customer on the front.

Playdough extrusion

Imagine a kids playdough machine, fill it up with dough, stick a star shape on the front, press the handle down and voila, star shaped playdough.

So much force to causes the aluminium to flow and exit the die at speeds between 5-80 m/min.

 

The extruded length may be as long as 50 metres and may consist of one or multiple strands of the same profile. Usually extrusions of most commerical alloys will be cooled or quenched as they leave the press, to bring them down from the 500 degree celcius temperature used during extrusion.

Step 4 - Cool it

Extrusion has to be cooled to enable it to be handled and stretched. This is acheieved using air, water or a mixture of both.

Cooling is also used as the first part of the heat treatment of age-hardening alloys. 

Step 5 - Stretch and Cut to Length

The super long lengths of extrusion are moved along the press table to an extrusion stretcher. The jaws of the stretcher are clamped to either end of the long lengths. The long lengths are then stretched to help improve overall straigtness.

The nice striaght lengths are now shuffled off to a conveyor saw, that trims the super long lengths into an easier to handle size (usually between 2 and 6m long). This makes all downstream treatment and handling much simpler - try loading a 50m length onto a lorry - not gonna happen!

Step 6 - Age it

Most extrusions are then articially age hardened, this involves baking extrusions in an oven a speicifc temperature between 170 and 190 degrees celcius for between 4 and 8 hours depending on the hardness property (called temper) required. Ageing develops the mechanical properties of the extrusions, most notably the profiles strength.

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