CNC Machining - Aluminum Material

With the continuous development of modern manufacturing technology, CNC machining has become one of the crucial processes in the manufacturing industry. Among the various available materials, aluminum is highly favored in CNC machining due to its lightweight, corrosion resistance, and excellent thermal conductivity. This article will delve into the advantages of aluminum materials in CNC machining, the aluminum alloys used by PCBWay CNC, the CNC machining process, and its applications in the industry.

The Advantages of Aluminum Material in CNC

While there is a multitude of aluminum alloys with various characteristic properties, there are also some fundamental features that apply to all aluminum alloys.

Machinability

Aluminum can be rapidly shaped, manufactured, and processed under various treatment processes. It can be easily cut by machine tools due to its soft and easily machinable texture, making it cost-effective and requiring less force compared to processing steel. These characteristics are significant advantages for both machinists and customers ordering parts. Additionally, the excellent machinability of aluminum means it is less prone to deformation during the machining process. Given its ability to enable CNC machines to achieve higher tolerance, and the precision is also enhanced.

Strength-to-Weight Ratio

Aluminum has a density of approximately one-third that of steel, making it relatively lighter in mass. Despite its lightweight nature, aluminum exhibits high strength. The combination of strength and weight is referred to as the material's strength-to-weight ratio. The high strength-to-weight ratio of aluminum makes it suitable for manufacturing many components needed in industries such as automotive and aerospace.

Corrosion Resistance

Aluminum demonstrates resistance to scratching and corrosion in typical marine and atmospheric environments. This characteristic can be further enhanced through anodization. It's worth noting that the corrosion resistance varies among different grades of aluminum, with the general-purpose CNC machining grade often exhibiting the highest resistance.

Low-Temperature Performance

Many materials lose some of their desirable properties below 0℃. For instance, carbon steel and rubber can become brittle in low-temperature conditions. In contrast, aluminum maintains its softness, ductility, and strength even at extremely low temperatures.

Conductivity

The electrical conductivity of pure aluminum is approximately 37.7 million Siemens per meter at room temperature. While aluminum alloys have lower electrical conductivity compared to pure aluminum, it is still sufficient for use in electronic components. On the other hand, if the ideal characteristic for a machined part is not conductivity, aluminum would not be a suitable material for it.

Recyclability

Since the CNC machining process involves subtractive manufacturing, generating a significant amount of chips or waste material, aluminum's strong recyclability is advantageous. Recycling aluminum requires relatively low energy, effort, and cost. This makes it highly favored among those seeking cost savings or aiming to reduce material waste. It also positions aluminum as a more environmentally friendly machining material.

Anodizing Potential

Anodizing, a surface treatment process that enhances wear resistance and corrosion resistance, is easily achievable for aluminum. This process also makes coloring of machined aluminum parts more straightforward.

Commonly Used Aluminum Materials in PCBWay CNC Machining

Commonly used aluminum materials in PCBWay CNC machining include Aluminum 6061, Aluminum 7075, Aluminum 5052, and Aluminum 2A12.

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Aluminum 6061

• Aluminum 6061 is widely known and has a profound impact, with its presence found in nearly every corner of the market today. Its popularity stems from its excellent corrosion resistance, weldability, machinability, and medium to high strength. Its chemical composition includes 0.6% Si, 1.0% Mg, 0.2% Cr, 0.28% Cu, and 97.9% Al, although these figures may vary slightly due to impurities and manufacturing methods.

• The density of 6061 aluminum is the same as pure aluminum (2.7 g/cm3, 0.0975 lb/in3), and it can be strengthened through heat treatment. 

• Some common conditions for 6061 aluminum are 6061-T6 and 6061-T4.

• This alloy's combination of good strength, machinability, and wear resistance makes it an ideal general-purpose alloy. 

• While 6061 aluminum may not excel in any particular field, it is a versatile material used in structural materials, ship frames, radiators, chemical equipment, and even soda cans.

More Details for Aluminum 6061 

Aluminum 7075

• 7075 aluminum is a high-strength aluminum alloy known for its excellent strength and toughness. It belongs to the 7000 series of aluminum alloys and is often referred to as "aircraft-grade" aluminum due to its common use in aerospace applications.

• The primary alloying elements in 7075 aluminum are aluminum, zinc, copper, and small amounts of other elements. The precise composition may vary slightly, but typical percentages include approximately 90.7% aluminum, 5.6% zinc, 2.5% copper, 1.6% magnesium, and trace amounts of other elements.

• 7075 aluminum is renowned for its high strength, with a tensile strength of approximately 572 MPa (83 ksi) and a yield strength of around 503 MPa (73 ksi). This makes it one of the strongest aluminum alloys.

• In addition to its high strength, 7075 aluminum also exhibits good toughness, making it suitable for applications that require a combination of strength and impact resistance.

• Due to its exceptional strength-to-weight ratio, 7075 aluminum is commonly used in aircraft structures in the aerospace industry, including wings, fuselage components, and other structural parts. It is favored in applications where high strength and low weight are critical. While aerospace is the primary application, 7075 aluminum is also used in other high-stress applications, such as high-performance bicycles, climbing equipment, and certain firearm components. Despite its high strength, 7075 aluminum is more challenging to machine compared to some other aluminum alloys. Precision machining requires careful attention, and the use of appropriate tools and cutting conditions is crucial. 7075 aluminum can undergo heat treatment to further enhance its mechanical properties, with common heat treatment methods including solution heat treatment and artificial aging. Although 7075 aluminum has good corrosion resistance, it is not as corrosion-resistant as other aluminum alloys like 6061. It is recommended to apply protective coatings or treatments in corrosive environments.

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Aluminum 5052

• 5052 aluminum alloy possesses some of the best welding characteristics, outstanding precision machining quality, and excellent resistance to saltwater corrosion, but it is not easily machinable. This alloy is non-heat-treatable and can only be strengthened using work-hardening processes, with 5052-H32 being the most common temper. 5052 aluminum is also considered one of the highest-strength non-heat-treatable alloys. For these reasons, 5052 aluminum is well-suited for use as sheet and plate metal, combining excellent formability and weldability with increased strength.

• Its density is slightly lower than pure aluminum, at 2.68 g/cm3 (0.0968 lb/in3), and its chemical composition includes 2.5% Mg, 0.25% Cr, and 97.25% Al. 5052 aluminum does not contain any copper, meaning it is not as prone to saltwater corrosion as some other aluminum alloys. This makes it an ideal choice for marine applications and is commonly used in electronic enclosures, hardware signage, pressure vessels, and medical equipment.

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Aluminum 2A12

• Aluminum 2A12 is a high-strength aluminum alloy belonging to the 2xxx series. Similar to other alloys in this series, 2A12's primary alloying element is copper, with small amounts of other elements included. Its chemical composition comprises aluminum, copper, and trace amounts of manganese, magnesium, and other minor elements. Specific compositions may vary, but typical percentages include around 90.7% aluminum, 3.8-4.9% copper, 1.2-1.8% manganese, 1.2-1.8% magnesium, and trace amounts of other elements.

• 2A12 is renowned for its high strength, comparable to certain steels. Its tensile strength typically falls between 490 to 540 MPa, with a yield strength of approximately 300 MPa. This makes it suitable for applications requiring a combination of strength and lightness. Like many high-strength aluminum alloys, 2A12 is commonly used in the aerospace industry, such as in aircraft structures, including wing skins, fuselage panels, and structural components. Its strength-to-weight ratio is crucial in aerospace design.

• Aluminum 2A12 exhibits good machinability and is suitable for various machining processes. However, like other aluminum alloys, heat may be generated during processing, emphasizing the importance of proper cooling and lubrication for optimal results.

• 2A12 is amenable to heat treatment, further enhancing its mechanical properties. Common heat treatment processes include solution heat treatment and artificial aging.

• While 2A12 is weldable, it should be noted that welding may impact its strength and heat-treatable properties. Therefore, appropriate welding techniques and post-weld heat treatment may be required.

• Aluminum 2A12 has good resistance to atmospheric corrosion. However, its corrosion resistance is not as high as other aluminum alloys, such as those in the 5xxx series. In corrosive environments, the application of protective coatings or treatments may be necessary.

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CNC Machining Process for Aluminum

CNC Milling

Milling refers to the use of computer instructions to move a rapidly rotating cutting tool along three or more axes. As the rotating cutting tool comes into contact with the workpiece, it systematically removes material. The cutting tool continuously traverses the workpiece surface until the workpiece resembles the desired part.

CNC Turning

We utilize CNC turning to manufacture cylindrical, round, and conical components. The machines used for CNC turning are called CNC lathes or CNC turning centers. They differ from CNC milling machines in that they rapidly rotate the workpiece in a chuck, but the cutting tool itself does not rotate. The cutting tool, mounted on a turret, moves around the rotating workpiece according to computer instructions and removes material as needed.

CNC lathes can cut the exterior of a workpiece or drill into it from the interior to produce tubular CNC machined parts.

CNC Post-Processing Procedures

After completing the machining of an aluminum component, specific processes can be applied to enhance its physical, mechanical, and aesthetic characteristics. The most widely used post-processing procedures are as follows:

Bead Blasting and Sandblasting

Bead blasting is a decorative finishing process. During this process, small glass beads are shot onto the machined part using high-pressure air, effectively cleaning the material and ensuring a smooth surface finish. The aluminum can have a glossy or matte appearance after bead blasting. Key operating parameters for bead blasting include the size of the glass beads and the pressure of the air. This process is suitable when tight size tolerances are not critical for the part.

Other Finishing Processes, including Polishing and Painting

In addition to bead blasting, there is sandblasting, where high-pressure sand is used to clean the material.

Coating

This process involves covering aluminum parts with coatings made of materials such as zinc, nickel, or chrome. This is done to refine the machining of the part and can be achieved through an electrochemical reaction process.

Anodizing

Anodizing is an electrochemical reaction process where aluminum parts are immersed in a dilute sulfuric acid solution, and voltage is applied at both positive and negative poles. This process effectively transforms the exposed surface layer of the part into a hard and non-conductive aluminum oxide coating. The density and thickness of the resulting coating depend on the viscosity of the solution, the duration of oxidation, and the current. Anodizing can also be used to color the parts.

Powder Coating

The powder coating process involves applying a coating of colored polymer powder to the part using an electrostatic spray gun. The part is then cured at a temperature of 200 degrees Celsius. Powder coating enhances strength and provides improved wear resistance, corrosion resistance, and impact resistance.

Heat Treatment

Parts made from heat-treatable aluminum alloys undergo heat treatment to improve their mechanical properties.

Application of CNC Machined Aluminum Parts in Industry

CNC machined aluminum parts find widespread applications in various industries, primarily owing to the excellent properties of aluminum such as lightweight, good thermal conductivity, and strong corrosion resistance. Here are some common industrial sectors where CNC machined aluminum parts are extensively used:

• Aerospace Industry: Aluminum alloys are widely used in manufacturing aircraft structures, wings, fuselages, and other components due to their high strength and lightweight characteristics. CNC machining can be employed to produce various complex aerospace parts, ensuring precision and quality.

• Automotive Manufacturing: In the automotive industry, aluminum parts are used in the manufacturing of body structures, engine components, suspension systems, and more. CNC machining is utilized for the production of high-precision, lightweight automotive parts, enhancing fuel efficiency and overall performance.

• Electronics Industry: Aluminum parts find widespread applications in electronic devices, including heat sinks, casings, connectors, and more. CNC machining enables the precise manufacturing of these parts to ensure effective heat dissipation and overall performance of the equipment.

• Food/Pharmaceuticals: Aluminum parts, being non-reactive with most organic substances, play a crucial role in the food and pharmaceutical industries.

• Sports Equipment: Aluminum is commonly used in the fabrication of sports equipment such as baseball bats and whistles.

• Low-Temperature Applications: Aluminum maintains its mechanical properties even at temperatures below zero degrees Celsius, making aluminum parts highly sought after for low-temperature applications.