Aluminum CNC Machine: Benefits and Possible Alternatives
For CNC machining projects, aluminum is one of the most popular material choices due to its desirable physical properties. It is strong, which makes it ideal for mechanical parts, and its oxidized outer layer is resistant to corrosion from the elements. These benefits have made aluminum parts common across all industries, though they are particularly favored in the automotive, aerospace, healthcare and consumer electronics spheres.
Aluminum also offers specific advantages that simplify and improve the process of CNC machining. Unlike many other metals with similar material properties, aluminum offers excellent machinability: many of its grades can be effectively penetrated by cutting tools, chipping easily while being relatively easy to shape. Because of this, aluminum can be machined more than three times faster than iron or steel.
This article explains some of the key advantages of aluminum CNC turning — reasons why it is one of our most widely requested prototyping and production processes — but also suggests machining alternatives to aluminum.
Other metals and plastics can provide similar benefits to aluminum, in addition to the unique benefits of their own.
One of the main reasons why engineers choose aluminum for their machined parts is because, quite simply, the material is easy to machine. While this would appear to be more of a benefit for the machinist manufacturing the part, it also has significant benefits for the business ordering the part, as well as the end-user that will eventually use it.
Because aluminum chips easily, and because it is easy to shape, it can be cut quickly and accurately with aluminum CNC milling. This has some important consequences: firstly, the short timeframe of the machining job makes the process cheaper (because less labor is required from the machinist and less operating time is required from the machine itself); secondly, good machinability means less deformation of the part as the cutting tool goes through the workpiece. This can allow the machine to meet tighter tolerances (as low as ±0.025 mm) and leads to higher accuracy and repeatability.
Different aluminum grades differ greatly in their resistance to corrosion — the degree to which they can withstand oxidization and chemical damage. Fortunately, some of the most popular grades for brass CNC turning are the most resistant. 6061, for example, offers excellent corrosion resistance, as do other alloys on the lower end of the strength spectrum. (Strong aluminum alloys may be less resistant to corrosion due to the presence of alloyed copper.)
Aluminum has desirable physical properties that make it ideal for both mechanical and aspect parts. Two of the most important are the metal’s high strength and its lightweight, both of which make the material favorable for critical parts such as those required in the aerospace and automotive industries. Aircraft fittings and automotive shafts are two examples of parts that can be successfully machined with aluminum.
However, different grades of aluminum serve different purposes. Because of their favorable strength-to-weight ratio, general-use grades like 6061 can be used for a wide variety of parts, while notably high-strength grades like 7075 may be preferred in aerospace and marine applications.
CNC machined aluminum parts can be useful for electrical components due to their electrical conductivity. Though not as conductive as copper, pure aluminum has an electrical conductivity of about 37.7 million siemens per meter at room temperature. Alloys may have lower conductivities, but aluminum materials are significantly more conductive than, for example, stainless steel.
Machined aluminum parts are especially popular in the consumer electronics industry, not just for strength and weight demands, but because of important aesthetic considerations. As well as being receptive to paints and tints, aluminum can be treated with anodization, a surface finishing procedure that thickens the protective and oxidized outer layer of the part.
The anodization process, which generally takes place after machining is completed, involves passing an electric current through the part in an electrolytic acid bath and results in a piece of aluminum that is more resistant to physical impact and corrosion.
Importantly, anodizing makes it easier to add color to a machined aluminum part, since the anodized outer layer is highly porous. Dyes can find their way through the porous sections of the outer layer and are less likely to chip or flake since they are embedded within the tough exterior of the metal part.
Another benefit of aluminum is its high recyclability, which makes it preferable for businesses seeking to minimize their environmental impact or for those who simply want to reduce material wastage and recoup some of their expenditure. Recyclable materials are particularly important in CNC machining, where there is a relatively large amount of waste material in the form of chips from the cutting tool.
Alternatives to aluminum in CNC machining
Businesses may seek alternatives to aluminum for brass CNC milling for any number of reasons. After all, the metal has a few weaknesses: its oxide coating can damage tooling, and it is generally more expensive than alternatives like steel, partly due to the high energy costs of aluminum production.