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Aluminum, a non-ferrous metal, is the third most abundant element (8.23%) in Earth’s crust. Hans Orsted was the first to isolate it in 1827. Though it’s not that old compared to ferrous metals, it has been a popular choice across industries due to its strength, corrosion, and most importantly lightweight nature.
In high-stakes environments, such as aerospace and automotive manufacturing, precision is paramount. Every gram and precise dimension can impact overall performance and efficiency. So, aluminum has to undergo meticulous CNC machining processes to meet these exacting standards.
This detailed guide explains the Aluminum CNC machining process, the Aluminum alloys that are favorable for machining, and key applications of CNC Machined Aluminum parts.
CNC Machining Aluminium: Processes and Equipment
CNC Machining Aluminum refers to the use of computerized equipment (CNC machines) to cut and shape Aluminum sheets with extreme precision. Common machines employed for this purpose are:
CNC Milling Machines
CNC milling machines use a rotary cutting tool to cut, shape, and remove material from a workpiece. The tool bit has the flexibility to move in multiple axes (X, Y, and Z) to achieve the desired shape and dimensions. 3 to 5-axis CNCs are common for milling Aluminum.
Such machines are ideal for creating detailed surfaces, slots, and complex shapes – those required in automotive and aerospace. Rotary cutting tools (endmills, face mills, and ball cutters) are used for milling operations.
CNC Turning Centers
In CNC turning, a stationary workpiece slides against a rotating workpiece, shaping to design shape. This shaping is primarily for symmetrical, cylindrical aluminum parts like rods, shafts, and fasteners. A single-point cutting tool is used to trim the face and reduce the diameter.
CNC Laser Cutters
CNC laser cutter uses a highly powered light beam (laser) to vaporize the metal surface and create a sharp cut. Unlike mechanical tools, the spot size of the laser beam is hair thin and results in highly precise sharp cuts. However, the cutting thickness is limited.
Besides cutting, these tools can mark and engrave aluminum. So, ideal applications are marking devices in electronics and other industries.
Water Cutters
A waterjet cutter uses a high-pressure stream of water, mixed with abrasive particles, to cut through materials. It does not induce heat stress on the material, preserving the mechanical properties of aluminum.
Waterjet is used for cutting thicker aluminum plates and is favored in scenarios where thermal distortion must be avoided.
Why Choose Aluminum for CNC Parts?
Aluminum is the most abundant metal in the Earth’s crust. And it has all the desired characteristics that meet most of our product needs:
High Strength-to-Weight Ratio
Aluminum is known for its lightweight nature, but it boasts one of the highest strength-to-weight ratios among engineering materials. This attribute is precious in critical applications such as aerospace and automotive, where you need to reduce weight without compromising strength.
Great Machinability
Every metal requires some form of cutting and shaping through machines. In this aspect, aluminum behaves well. It’s soft and relatively easier to machine as it chips off easily. Also, it takes less amount of time, which in turn reduces machining costs.
Corrosion Resistance
Unlike ferrous metals that rust due to the oxide layer formation, many grades of aluminum are inherently corrosion-resistant. However, that trend varies across the series. The 6061 series is well-regarded for its resistance. Whereas, aluminum alloys containing copper are less resistant to corrosion.
Electrical Conductivity
On the conductivity chart of commonly used industrial metals, pure Aluminum just falls below copper. As per IACS, copper’s conductivity is in the range of 58 to 62 million S/m, while pure Aluminum is 35 to 38 million S/m. Iron, carbon steel, and stainless steel values are 10, 7, and 1.5 respectively. However, Aluminium alloys are less conductive.
Anodization Potential
Aluminum’s anodization is a unique advantage, particularly when durability and aesthetics are required. Anodization not only enhances the corrosion resistance of aluminum but also enables coloration, which can be beneficial for consumer products.
Recyclability
According to the International Aluminum Institute, 75% of all aluminum ever produced is still in use today. Moreover, around 30 million tons of aluminum are recycled annually, reducing the need for virgin aluminum production. This high recycling rate underscores aluminum’s role as a sustainable material choice.
Common Aluminum Series for CNC Machining
As per the International Alloy Designation system, all metallic alloy elements are represented by 4 digits which define the core metal and alloys present. An alphabet after the series name represents the surface treatment process.
Commonly, Aluminum comes in 7 different series, starting from 1000 to 7000. It begins with pure standard aluminum and then shifts toward alloys. A grade 8000 with rare-earth elements is also available but less common.
1xxx Series – Pure Aluminum
This series is purest, comprising 99% or more aluminum. It has all the inherent characteristics of Aluminum; excellent corrosion resistance and high electrical and thermal conductivity. That is why its common applications are chemical tanks and piping.
The tensile strength of these alloys falls between 69 to 186 MPa. 1xxx series alloys can be welded but are not heat-treatable.
2xxx Series – Al-Copper Alloys
The addition of copper improves the machining aspect and the tensile strength, taking it up to 420 MPa. It is predominantly used in aerospace where its high strength at various temperatures is crucial, though it often requires coatings for better corrosion resistance.
3xxx Series – Al-Manganese Alloys
This series enhances mechanical strength through the addition of manganese. They have a moderate tensile strength between 110 to 290 MPa and are also hot treatable. Common applications are food packaging, cookware, and sheet metal applications.
4xxx Series – Al-Silicon Alloy
4000 series are characterized by the inclusion of silicon, which lowers the melting points and improves fluidity in molten states, making it better suited for casting applications. Its major applications are cladding, welding fillers, and architectural extrusions.
5xxx Series – Al-Magnesium Alloy
Magnesium, the primary alloying element, lends high strength and excellent corrosion resistance to this series. The alloys are quite resistive to alkalis and readily weldable, which makes them perfect for marine applications. The series member, alloy 5083 is notable for its resistance to seawater and chemical exposure.
6xxx Series – Al-Magnesium-Silicon Alloy
This series is known for its formability, weldability, and corrosion resistance. They can undergo any heat treatment to achieve the desired characteristics. Alloy 6061 is quite a popular name (cost-effective as well), used for ebikes, boats, and truck frames.
7xxx Series – Al-Zinc Alloy
The strongest in the lineup, this series is alloyed primarily with zinc and is favored in aerospace and sporting goods for its exceptional strength-to-weight ratio and stress resistance. The alloys can be welded but extreme caution is required.
Popular Aluminum Alloys for CNC Machining
| Aluminum Alloys | Tensile Strength (MPa) **(Approx. Values) | Common Applications |
| Aluminum 2007 | 270-400 | Machine parts, bolts, rivets, nuts, screws, threaded bars. |
| Aluminum 2024 | 250- 400 | Aerospace structural components. |
| Aluminum 5052 | 170-305 | Marine environments, automotive fuel tanks, street signs. |
| Aluminum 5083 | 270-345 | Cryogenic equipment, marine applications, pressure equipment, chemical applications, welded constructions. |
| Aluminum 5754 | 190-240 | Welded structures, flooring, fishing equipment, vehicle bodies, food processing, rivets. |
| Aluminum 6060 | 190 | Construction, food processing, medical equipment, automotive engineering. |
| Aluminum 6061 | 180 – 270 | Highly loaded structures, scaffolds, rail coaches, machine parts, general-purpose applications. |
| Aluminum 6063 | 180 | Architectural applications, window frames, door frames, roofs |
| Aluminum 6082 | 290 | Offshore construction, containers |
| Aluminum 7075 | 500-572 | Bicycle frames, rock climbing equipment, weaponry, mold tool manufacturing, advanced engineering applications |
** These are just approximate values. The exact ones depend on the treatment process; Consult the manufacturer for precise values.
Key Considerations When CNC Machining Aluminum
When using Aluminum, these few technicalities need to be kept in mind:
Tool Material
Aluminum is soft, so it requires a hard-cutting tool like carbide. In carbide tools, the grain structure is also of prime importance. And it’s cobalt presence that helps achieve that fine structure. However, cobalt when reacts with aluminum, causes a gum build-up on the tool. So, an optimal ratio of 2 to 20% in the carbide tool is preferred.
Besides that, the coating also matters. Mill cutters with diamond, Titanium di-boride (TiB2), and Zirconium Nitride (ZrN).
Tool Design and Orientation
The end mills have flutes – their number decides the ease of machining operation. The recommendation is 2-3 flutes; two flutes offer optimal chip clearance, while three flutes balance chip clearance with tool strength.
The helix angle and clearance angle are also critical: a 35° or 40° helix angle is effective for roughing, and a 45° angle is better for finishing. Clearance angles should be between 6° and 10°.
Feed Rate and Speed
Cutting speed refers to the rotational speed of the cutting tool. It has to be chosen based on the type of Aluminum alloy. In general, a higher cutting speed is recommended to avoid built-up edges and reduce heat generation.
The feed rate is the rate of advancement of the tool. These rates differ based on the finish required; rough cuts might use a feed of 0.15 to 2.00 mm/rev whereas finishing cuts can use 0.05 to 0.20 mm/rev.
Cutting Fluid
Cutting aluminum dry is disastrous due to formation of build-up edges. Use undiluted mineral oils and avoid any fluids containing active sulfur or chlorine as they can stain aluminum.
Aluminum Parts: Finishing Techniques
A metal surface is prone to rust or corrode if left unfinished. Likewise, Aluminum undergoes some finishing techniques that only serve protective purposes but also add an aesthetic element.
Sandblasting
Sandblasting is blasting fine sand particles at high speeds onto the aluminum surface using compressed air. This process cleans the surface by removing any impurities or residues and creates a uniform, matte texture. It is useful for preparing the metal for further finishing or achieving a specific surface look.
Anodizing
Anodizing is an electrochemical process that thickens the natural oxide layer on the surface of aluminum parts. The added layer improves corrosion resistance, increases surface hardness, and allows for the dyeing of the aluminum.
Powder Coating
Powder coating applies a dry powder onto the aluminum. It is then cured under heat to form a thin layer. This coating is tough, protective, and available in many colors. The surface finish is of high quality and better than the standard paint.
Challenges in Machining Aluminum
Although aluminum is soft and lightweight, machining it presents some unique challenges:
Gum Build up
Aluminum has a low melting point (660°C) – the frictional heat generated during cutting or grinding can cause the metal to soften and adhere to the cutting tool, creating a “gumming” effect. To mitigate this, it is advisable to use hard carbide cutters accompanied by continuous lubrication through an ethanol mist.
Higher Costs Higher Risks
Aluminum is more expensive than many other common metals, so the costs associated with replacing/repairing damaged parts are significantly higher.
Contamination Risk
When exposed to the atmosphere, aluminum forms an oxide layer that can be detrimental if not removed prior to welding or machining. This oxide layer can lead to imperfections and porosity in the final product.
Cost Estimates for Aluminum CNC Machining
Cost is a critical factor in machining, particularly for large-scale production. Here are the main costs involved in the lifecycle of an aluminum product:
- Raw Material Cost: The price of aluminum varies depending on the thickness, grade, and size of the material. For a rough estimate, consider the common 6061 aluminum alloy. It’s priced at $12 and $15 per pound.
- Machining Cost: Operating costs for machines differ based on their capabilities. For a 3-axis CNC machine, the price is between $25 to $30 per hour. For more advanced 5-axis CNC machines, the cost falls between $40 to $50 per hour.
- Tool Cost: The carbide tool used in machining aluminum is approximately $2 to 5 per piece.
Applications of CNC Machine Aluminum Parts
Aluminum is one of the most used metals in the industry due to its favorable characteristics and ease of machining. Table 1 enlists Aluminum applications in major everyday sectors.
| Sector | Specific Applications | Aluminum Grades |
| Automotive | Engine components (pistons, cylinders) | 4032, 2618 |
| Transmission and structural | 6061, 7075 | |
| Aerospace | Aircraft structural frames | 2024, 7075 |
| Gear Components | 7075, 2024 | |
| Fasteners and fittings | 7075, 6061 | |
| Electronics | Heat sinks for thermal management | 6063, 1100 |
| Enclosures for electronic devices | 5052, 6061 | |
| Components for connectors and switches | 6061, 2024 | |
| Food and Packaging | Machinery components for food processing | 6061, 5052 |
| Packaging machine parts | 6061, 5052 | |
| Molds for food packaging | 3003, 6061 |
Choose RichConn for CNC Aluminum Machining Needs
Have a project that involves machining aluminum, or in need of custom aluminum parts? Choose RichConn’s Aluminum CNC Machining Services. We handle all aluminum alloy series with expertise.
Our team, with decades of experience, is ready to guide you from the initial step to final production. With state-of-the-art infrastructure and the latest CNC equipment, we deliver high-quality, standardized products more efficiently and swiftly. Contact us today and let’s discuss how we can support your CNC machining project.
