The next time you see a sleek phone or a light airplane part, think of aluminum. It starts as a soft, silvery, non-magnetic element, but its real-world magic happens when it’s mixed with other elements like copper, magnesium, or manganese to create aluminum alloys. These play essential roles in modern engineering, boasting properties that are hard to beat in CNC machining.
Why Machinists Love Aluminum
Aluminum isn’t just a strong material, it’s a practical and efficient one. Here are the core advantages that make it a favorite on the factory floor:
Machinability: Aluminum is incredibly easy to cut, meaning CNC machines can shape it fast and with less effort than materials like steel. This speed saves both time and money. Plus, because it’s so cooperative, aluminum allows for tight tolerances and is less likely to deform during the milling process, leading to more accurate parts.
Specific Strength: Aluminum is about one-third the density of steel, making it remarkably light. Crucially, it doesn’t sacrifice strength for weight. This powerful combination—known as specific strength—is essential for industries like aerospace and automotive, where every ounce matters.
Corrosion Resistance: Aluminum naturally resists rust and degradation from air and water. This defense can be made even stronger with anodizing, a common surface treatment that creates a durable, protective layer.
Low-Temperature Performance: While many materials get brittle and weak in the extreme cold, aluminum stays soft, flexible, and strong, maintaining its high performance even in icy conditions.
Electrical Conductivity: Pure aluminum is an excellent conductor of electricity. Although its alloys are slightly less conductive, they are still widely used in electronic components.
Recyclability: Because CNC machining involves cutting away material, it produces a lot of scrap metal. Aluminum is highly recyclable, requiring little energy or expense to reuse. This makes it a great choice for companies trying to cut waste and be more environmentally responsible.
How Aluminum Parts Are Made
Aluminum is versatile and can be shaped using any standard CNC machining process. The most common methods are:
CNC Milling: A multi-toothed spinning tool removes material from a stationary block, perfect for creating complex 3D shapes and features like pockets and grooves.
CNC Turning: The piece of aluminum spins rapidly while a stationary cutting tool shaves material off to create parts with cylindrical shapes.
Drilling and Facing: These are used to punch precise holes and create smooth, flat surfaces on the part.
Getting the Cut Just Right
Machining aluminum isn’t a simple hack-and-slash job. To get a perfect part, machinists must fine-tune their tools and settings:
The Right Tools: Due to the material’s softness, tools need to quickly clear the large aluminum chips they create. Carbide cutters with a low number of flutes (usually 2 or 3) are preferred. Also, special coatings like Diamond-Like Carbon (DLC) are often applied to the tools to prevent aluminum from sticking and welding itself to the cutter’s surface.
Speed is Key: Aluminum can handle extremely fast cutting speeds. Running the machine as fast as possible is actually better because it reduces heat, prevents sticking, and produces a smoother finish.
Use Coolant: Aluminum should never be cut dry! Proper coolants (oil emulsions or mineral oils) are essential for carrying heat away and preventing the aluminum from building up on the tool’s edge.
Surface Finishing
Once the CNC machine is done, aluminum parts manufacturers will add finishing touches to improve durability and appearance.
Anodizing: This is the most popular finish. The part is submerged in an acid solution and electrified, turning the outer surface into a hard, protective layer of aluminum oxide. This process is also a great way to add color to the part.
Bead Blasting: Small glass beads are sprayed at the part at high pressure, cleaning the surface and giving it a uniform, matte, or satin look.
Powder Coating: A colored polymer powder is sprayed on and then baked. This creates a very tough, thick shell that protects against wear, corrosion, and impacts.
Heat Treatment: Certain aluminum alloys are heated and cooled in specific cycles to greatly improve their structural and mechanical performance.
Applications of Aluminum
Thanks to its versatility, you can find CNC machined aluminum everywhere, from your kitchen to the stratosphere:
Aerospace: For lightweight, high-strength aircraft structures.
Automotive: For lighter engine and body components.
Electronics: For casings and internal components due to their conductivity.
Medical/Food Industries: Because it does not
react with most organic materials.
