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.
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.
Machinability
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.
Strength-to-weight ratio
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.
Corrosion resistance
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.
Electrical conductivity
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.
Recyclability
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 potential
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.
Popular aluminum alloys for CNC machining
From our experience at Xometry, the following 5 aluminium grades are one of the most often used for CNC machining.
EN AW-2007 / 3.1645 / AlCuMgPb
Alternative designations: 3.1645; EN 573-3; AlCu4PbMgMn.
This aluminium alloy has copper as its main alloying element (4-5%) of copper. It is a short-chipped alloy that is durable, light, highly functional, and has the same high mechanical properties as AW 2030. It is also suitable for threading, heat treatment, and high-speed machining. All these properties make EN AW 2007 widely used in the production of machine parts, bolts, rivets nuts, screws, and threaded bars. However, this aluminium grade has low weldability and low corrosion resistance; therefore it is recommended to carry out protective anodising after part machining.
EN AW-5083 / 3.3547 / Al-Mg4,5Mn
Alternative designations: 3.3547; Alloy 5083; EN 573-3; UNS A95083; ASTM B209; AlMg4.5Mn0.7
AW 5083 is renowned for its excellent performance in severe environments. It contains magnesium and small traces of chromium and manganese. This grade has very high resistance to corrosion in both chemical and marine environments. Of all the non-heat treatable alloys, AW 5080 has the highest strength; a property which it retains even after welding. While this alloy should not be used in applications with temperatures higher than 65°C, it excels in low temperature applications.
Due to its set of desirable properties, AW 5080 is used in numerous applications including cryogenic equipment, marine applications, pressure equipment, chemical applications, welded constructions, and vehicle bodies.
EN AW 5754 / 3.3535 / Al-Mg3
Alternative designations: 3.3535; Alloy 5754; EN 573-3; U21NS A95754; ASTM B 209; Al-Mg3.
Being a wrought aluminium-magnesium alloy with the highest % of aluminium, AW 5754 can be rolled, forged, and extruded. It is also non heat-treatable and can be cold-worked to increase its strength, but at a lower ductility. In addition, this alloy has excellent resistance to corrosion and has high strength. Considering these properties, it is understandable that AW 5754 is one of the most popular CNC machined aluminium grades. It is typically used in welded structures, flooring applications, fishing equipment, vehicle bodies, food processing, and rivets.
EN AW-6060 / 3.3206 / Al-MgSi
Alternative designations: 3.3206; ISO 6361; UNS A96060; ASTM B 221; AlMgSi0,5
This is a magnesium and silicon containing wrought aluminium alloy. It is heat-treatable and has average strength, good weldability, and good formability. It is also highly resistant to corrosion; a property which can be improved even further through anodising. EN AW 6060 is often used in construction, food processing, medical equipment, and automotive engineering.
EN AW-7075 / 3.4365 / Al-Zn6MgCu
Alternative designations: 3.4365; UNS A96082; H30; Al-Zn6MgCu.
Zinc is the primary alloying element in this grade of aluminium. Although EN AW 7075 has average machinability, poor cold forming properties, and is not suitable for both welding and soldering; it has a high strength-to-density ratio, excellent resistance to atmospheric and marine environments, and strength comparable to some steel alloys. This alloy is employed in a very wide range of applications including hang glider and bicycle frames, rock climbing equipment, weaponry, and mold tool manufacturing.
EN AW-6061 / 3.3211 / Al-Mg1SiCu
Alternative designations: 3.3211, UNS A96061, A6061, Al-Mg1SiCu.
This alloy contains magnesium and silicon as its major alloying elements with trace amounts of copper. With a tensile strength of 180Mpa, this is a high strength alloy and is very suitable for highly loaded structures such as scaffolds, rail coaches, machine and aerospace parts.
EN AW-6082 / 3.2315 / Al-Si1Mg
Alternative designations: 3.2315, UNS A96082, A-SGM0,7, Al-Si1Mg.
Typically formed by rolling and extrusion, this alloy has medium strength with very good weldability and thermal conductivity. It has high stress corrosion cracking resistance. It has a tensile strength that ranges from 140 – 330MPa. It is heavily employed in offshore construction and containers.
Post time: Jul-29-2022
