CNC (Computer Numerical Control) machining is a versatile machining process that uses computers programs in either prototyping or full item production of engineering materials. Unlike the conventional machining process where the machinist controls the lathes manually, the CNC machining process is controlled by a computer program. Aluminum is a popular machined material because of its easy machinability and its availability in numerous grades.
Most manufacturers choose aluminum machining, mainly due to the excellent machinability of the aluminum materials and the fact that it exhibits excellent thermal and mechanical properties. CNC aluminum machining is not only beneficial to the manufacturers as CNC machined aluminum parts are usually found to be lightweight, which eases the usability of the machined parts by the end-users.
Benefits of Using Aluminum for CNC Machined Parts
Some properties of the aluminum alloys are to be considered beneficial while machining aluminum parts. Although different aluminum alloys with varying properties are used in aluminum machining, listed below are some fundamental properties that apply to almost all aluminum alloys.
- Corrosion resistance.
- Strength-to-weight ratio.
- Performance at low temperature.
- Anodization potential.
- Electrical conductivity.
Aluminum is known to be a soft metal; therefore, it can be easily formed, worked, and machined using various processes. Since it is soft, it can also be cut easily and quickly by machine tools. Aluminum does not require much power to machine, and it is known to have high accuracy during the machining process due to its low deformation rate.
Regarding corrosion rate consideration in metals, aluminum materials are known to be of high corrosion resistance. However, the corrosion resistance varies in different aluminum grades, but the most used aluminum grades for the CNC aluminum machining process have considerably high corrosion resistance.
When compared to other metals, aluminum is seen to be very light weighted and with high strength. The measure of the strength of a material and its weight is tagged as the strength-to-weight ratio. The strength-to-weight ratio of CNC machined aluminum parts is considered favorable in several industries due to its lightweight and high strength.
Performance at low temperature
Unlike other materials, aluminum tends to retain its desirable properties even at low temperatures. Since it retains its properties like ductility, softness, and strength at low temperatures, it is preferred in industries for production purposes.
Anodization is a surface finishing process. It is used to improve the surface of materials and increase their resistance to corrosion and wear. It also makes adding color to the surface of the material easy. Aluminum is known for its anodization potential.
Aluminum, in its pure state, has an electric conductivity rating of around 36.9 × 106 Siemens/m. Therefore, aluminum alloys might have lower electrical conductivity, but they are very suitable for machined parts used in components that require electrical conductivity.
The CNC machining process results in the production of many chips, which can be seen as wastage. Since aluminum is a material that is easily recycled, the waste materials (aluminum chips) can be transferred or sold as scrap to industries that recycle aluminum scraps.
Popular Aluminum Alloys Used For CNC Machining
Aluminum alloys are mostly considered for CNC machining because of some of the beneficial properties discussed above. However, aluminum alloys are of different grades and definitely with distinct mechanical specifications. Some of the famous aluminum alloys that are used in the production of aluminum CNC parts are discussed below;
Aluminum 6061 is one of the most popular aluminum for machining, containing magnesium and silicon as its major alloying elements. It is known to be very versatile compared to other aluminum alloys, making it a top choice for CNC machining. The grade is also known for its superb mechanical properties, most especially for its excellent weldability. The major drawback of this alloy is that it does not suit well for high-stress applications.
Some common applications include; automotive parts like chassis, truck bodies, aircraft parts, valves, pipes, computer parts.
- Hardness: 60 HRB
- Ultimate Tensile Strength: 124 – 290 MPa
- Modulus of Elasticity: 68 GPa
- Elongation at break: 12-25 %
- Melting Temperature: 585oC
7075 aluminum alloy is one of the most common aluminum alloys for CNC machining used for highly stressed structural applications. It contains zinc as its primary alloying element and has excellent mechanical properties. Despite being known for its high strength and excellent mechanical properties, the major drawback of the 7075 aluminum alloy is that it is more susceptible to embrittlement than many other aluminum alloys.
It is commonly applied in aerospace industries for aircraft parts, transportation industries for vehicles, and weapons production.
- Hardness: 87 HRB
- Ultimate Tensile Strength: 572 MPa
- Modulus of Elasticity: 71.7 GPa
- Elongation at break: 11%
- Melting Temperature: 477oC
Aluminum 2024-T4 is an aluminum alloy with copper as its primary alloying element. It is a moderate to high strength alloy and can be applied in areas that require a high strength-to-weight ratio and good fatigue. 2024-T4 aluminum alloy is known for its poor corrosion resistance and is often clad with aluminum for protection.
Common applications of aluminum 2024-T4 include aircraft fuselage, wing tension members, and vehicle parts.
- Hardness: 70 – 120 HB
- Ultimate Tensile Strength: 200 – 540 MPa
- Modulus of Elasticity: 73 GPa
- Elongation at break: 14 – 20 %
- Melting Temperature: 500oC
Aluminum MIC 6
Aluminum MIC 6 is a unique blend of specific alloys resulting in a cast aluminum plate known for its high tolerance and stability. It has high machinability properties, coupled with impressive stress-relieving properties. The major setback is that MIC 6 alloy threads are not very strong, and particularly fine threads can lead to thread failure.
MIC 6 CNC machined parts can be seen in electronic applications, machine components, and laser technology.
- Hardness: 65 HB
- Ultimate Tensile Strength: 166 MPa
- Modulus of Elasticity: 71 GPa
- Elongation at break: 3%
Aluminum 6082 is an alloy in the wrought aluminum-magnesium-silicon family. It is known for its high strength property, and it is mostly preferred when high-strength materials are needed. The drawback is that it is difficult to produce thin walls using aluminum 6082.
Some areas where the application of aluminum 6082 is required are constructing bridges, trusses, and towers.
- Hardness: 35 – 56 HRB
- Ultimate Tensile Strength: 140 – 330 MPa
- Modulus of Elasticity: 71 GPa
- Elongation at break: 6.3 – 18 %
- Melting Temperature: 555oC
The benefits of CNC aluminum machined parts cannot be overemphasized, as it has been proven to be beneficial both to the machinists and to the end-users. These benefits are primarily due to the aluminum alloys' great properties, such as the excellent machinability and the great weight to strength ratio.