The link between alloys and tolerances

Aluminium is aluminium, right? Well, yes. But there are hundreds of different aluminium alloys. It is important to start your project by carefully considering the choice of alloy. This is what you need to know.

There are easily extrudable alloys, such as 6060 or 6063, and slightly less extrudable alloys, such as 6005 and 6082. And they run up to strong alloys that are difficult to extrude and approach the mechanical properties of steel.

The alloys with higher classifications are stronger, but they are also more expensive. For that reason, it is important to start your project by carefully considering the choice of alloy.

Alloy components affect the production process

There is a specific production method for each type of alloy. While one alloy needs only a little cooling after the extrusion process, the other one needs more, extending even to water rather than air cooling. These cooling methods have an important effect on tolerances and on the ability to give a profile a certain shape – and create restrictions, especially for the alloys that are more difficult to extrude.

And then there are the chemical elements that an alloy contains. Elements such as manganese, zinc, iron, copper and vanadium are found to a greater or lesser extent in the heavier alloys in particular. Vanadium is important for the crash-absorbing alloys found in the car industry. These heavy elements also influence significantly the wear of the dies, and as a result, they influence the dimensions of the profiles – especially the tolerances – with greater deviation the longer the die stays in place.

Tolerances are important

Why are tolerances so important? These are the main reasons:

• Meeting the desired functional requirements
• Determining the maximum permissible die wear
• The ability to produce the desired shape of the extrusion, which is influenced by the complexity of the profile and whether it’s open or closed
• Establishing the necessary press technical conditions, such as cooling, run-out side and start-up temperature