CNC milling on aluminium

Aluminium is one of the most used materials when working with the CNC milling machine.

This material has several characteristics that make it particularly suitable for various types of projects. Depending on the alloys, in fact, it is possible to obtain technical characteristics more or less suitable for certain processes.

In this article we delve into the technical characteristics of aluminium and the elements to consider when choosing the right alloy for CNC milling.

CNC machining

CNC machines are an evolution of traditional milling to which a computerized numerical control system has been integrated, that is, a computer that automates the operations of the machine simplifying the work of the operator.

This system guarantees a high level of precision, since the processing is no longer entrusted to the manual skill of the person. In addition, CNC machines are able to process the blank quickly while maintaining the versatility of production.

In addition to the milling machine, machines have also been automated with a CNC system over the years. The most common are: lathe and drilling machines, laser and plasma cutting machines.

Of all the CNC machines, the milling machine is certainly the most widely used, as it allows different processes, on a wide range of materials, in a short time and at limited costs. The CNC milling machine uses cutting tools that, by means of a rotary movement, separate part of the material from the main block.

The machining centre governs the movements of the tools around the material and ensures the production of the piece according to the information entered in the computer. 

In general, CNC milling can be performed on different materials. Aluminium is one of the most widely used for this type of processing thanks to its important specific technical characteristics. 

Technical characteristics of aluminium

Aluminium is a material that lends itself to processing using different techniques. 

The reasons why this material is among the favourites for CNC milling are:

• malleability
• corrosion resistance
• non-magnetic
• excellent thermal and electrical conductivity

Although pure aluminium can sometimes be unsuitable for some applications, the advantage of this material comes from the possibility of improving its mechanical characteristics by combining it with other elements such as copper, lithium, magnesium, silicon, zinc and other elements, to create high-performance alloys. 

For CNC milling, the most commonly used alloys can be reduced to three:

1. Cast aluminium alloys, i.e. cast and bonded when these elements are in the liquid state. This type of material is particularly versatile, lightweight, durable and above all economical. 
2. Aluminium-lithium alloys (Al-Li), where thanks to the lightness of lithium, the alloy is suitable for the aerospace industry and racing machines.
3. Beaten aluminium alloys, i.e. alloys cast in the solid state. This type of material is the most used for machining with CNC machines thanks to the ease of modelling and machining. This allows you to obtain precise results even in the edges.

Parameters to consider for CNC milling

When looking at production, whether in series or in small quantities, there are usually four criteria for choosing the aluminium and alloy most suitable for CNC milling: 

• Cost: mild and carbon steels are among the cheapest compared to aluminium, while stainless steel is more expensive. However, it is important to keep up to date on prices, as the cost of steel varies daily based on the supply and demand of raw materials.
• Corrosion resistance: while stainless steel and aluminium have no problems, other types of materials may have rust after processing. Therefore, in the case of choosing materials other than aluminium and stainless steel, the piece must then undergo subsequent processing so as not to compromise the material itself and the final result. 
• Weight: the great advantage of aluminium is its extreme lightness compared to other types of materials, while maintaining excellent performance during processing.
• Resistance: steel is definitely better performing than aluminium, which if subjected to heat sources could deform. Aluminium is also more prone to scratches and dents. Carefully evaluate the result and end use.

Conclusions

In conclusion, when it comes to machining aluminium with a CNC milling machine it is important to know the technical characteristics of the alloy and its performance during machining. Aluminium has the advantage of cooling quickly and being able to be processed several times compared to other materials, however it may not be suitable for the final use of the part made. So carefully evaluate the objective of your project and which parameters to prioritize, in this way you will be sure to make the right choice