Aluminium for CNC Machined Parts
CNC Machining of Aluminium
This article explores the processes, tools, parameters, and challenges involved in the CNC machining of aluminium and its alloys. It also discusses the properties of aluminium, the most popular alloys used in CNC machining, as well as aluminium application in various industries.
Aluminium is one of the most machined materials available today. In fact, aluminium CNC machining processes are second after steel in terms of frequency of execution. Mainly this is due to its excellent machinability.
In its purest form, the chemical element aluminium is soft, ductile, non-magnetic, and silvery-white in appearance. However, the element is not only used in the pure form. Aluminium is usually alloyed with various elements such as manganese, copper and magnesium to form hundreds of aluminium alloys with various significantly improved properties. The most commonly machined aluminium alloys and their designations by different standards can be found here.
Benefits of using aluminium for CNC machined parts
Although there are numerous aluminium alloys with varying degrees of properties, there are fundamental properties applicable almost to all aluminium alloys.
Aluminium is readily formed, worked, and machined using a variety of processes. It can be quickly and easily cut by machine tools because it is soft and it chips easily. It is also less expensive and requires less power to machine than steel. These characteristics are of immense benefits to both the machinist and the customer ordering the part. Furthermore, aluminium’s good machinability means it deforms less during machining. This leads to higher accuracy as it allows CNC machines to achieve higher tolerances.
Aluminium is about a third of the density of steel. This makes it relatively light. Despite its lightweight, aluminium has very high strength. This combination of strength and light weight is described as the strength-to-weight ratio of materials. Aluminiums high strength-to-weight ratio makes it favourable for parts required in several industries such as the automotive and aerospace industries.
Aluminium is scratch resistant and corrosion resistant in common marine and atmospheric conditions. You can enhance these properties by anodizing. It’s important to note that resistance to corrosion varies in different aluminium grades. The most regularly CNC machined grades, however, have the most resistance.
Performance at low temperatures
Most materials tend to lose some of their desirable properties at sub-zero temperatures. For example, both carbon steels and rubber become brittle at low temperatures. Aluminium, in its turn, retains its softness, ductility, and strength at very low temperatures.
The electrical conductivity of pure aluminium is about 37.7 million siemens per metre at room temperature. Although aluminium alloys may have lower conductivities than pure aluminium, they are conductive enough for their parts to find use in electrical components. On the other hand, aluminium would be an unsuitable material if electrical conductivity is not a desirable characteristic of a machined part.
Since it is a subtractive manufacturing process, CNC machining processes generate a large number of chips, which are waste materials. Aluminium is highly recyclable which means it requires relatively low energy, effort, and cost to recycle. This makes it preferable to those who want to recoup expenditure or reduce material wastage. It also makes aluminium a more environmentally-friendly material to machine.
Anodisation, which is a surface finishing procedure that increases the wear and corrosion resistance of a material, is easy to achieve in aluminium. This process also makes adding colour to machined aluminium parts easier.