CNC (Computer Numerical Control) is a group of machining processes involving several types of machines; turning and milling. The versatility of the process allows it to be used either for prototyping or mass production.
Aluminum is very common in the manufacturing sector because of properties that give it excellent machinability. Today we are going to look at the full process and the benefits of CNC machining Aluminum.
The use of aluminum in the CNC machining process has grown immensely, the production of CNC automotive parts and other CNC parts that are lightweight has been intense.
Following are just a few of the things you may not have known, including how we produce the highest quality of machined aluminum parts.
Aluminum Material: CNC Aluminum Machining
Aluminum is a soft, lightweight, malleable, and durable metal. It’s strength to weight ratio lends itself to finished parts for the automotive and aerospace industries.
In its pre-finished state, the metal is silver or dull gray, depending on the roughness of the surface.
Aluminum Properties
- Lightweight
- Strong
- High Conductivity
- Thermally Conductive
- Non-Toxic
- Reflective
- Easy Surface Finishing
- Ductile
- Miscible
- Relatively Cheap to Produce
- Recyclable
- Corrosion Resistance
Grades of Machining Aluminum
Although there are many grades used in the CNC Machining of aluminum, it is important to remember that all of them are highly machinable.
2011
This has been described as ‘the butteriest of butter’. Perhaps the most machinable of all the grades of aluminum. The drawback to this grade is it’s low corrosion resistance, that’s why it’s best to apply an anodized finish to it.
2024
The alloy is predominantly used in the military and aerospace sectors. This is because of its mechanical properties, like great wear resistance, and high strength. The downside to this grade is that it has bad welding properties and low corrosion resistance.
5052
Typically used in forming applications because of its softness. Sometimes found in marine applications, since it has excellent corrosion resistance.
6061
A grade with very good mechanical properties including excellent weldability. Ideal for use in the extrusion process due to good toughness, medium to high strength. This grade is commonly used for 5 axis CNC machining.
6063
Similar in function to 6061, but this is more common to see in extrusions. However, it isn’t quite as stiff. This makes 6063 a little harder to machine; it’s softer and gummier.
7075
This grade is known for its exceptional fatigue strength. Not suitable for welding. Commonly used in parts that require it to be tough such as fuselages, bicycle parts, rock climbing kits, and aircraft wings. This alloy also better in corrosion resistance.
CNC Machined Aluminum Components and Parts
CNC machined aluminum is used to produce many parts and components that aid in a wide range of services. Today, well machined CNC aluminum parts are growing in popularity in the engineering sector.
The following are some of the CNC machined aluminum parts:
- Front panels
- Dowels Pins
- EMI-Housings
- Spline Shafts
- Medical Devices
- Lighting Fixtures
Aspects of CNC Machining Aluminum
Aluminum and Steel are both metals and some machine shops treat them as such. But as specialists in machining, we know that they have to be treated differently. Aluminum requires different processes and different tools.
Cutting Tools for Aluminum
Carbide Only
Technically, tools used for CNC machining steel can be used for CNC machining aluminum, but for the best finish, we only use specialized tools. Essentially we just need to understand what we want out of a tool. Aluminum is soft cutting, meaning that the tool doesn’t undergo hard impact forces as it cuts.
What’s critical is maintaining a razor-sharp edge. For this reason, we would choose hardness over toughness for material characteristics.
There are two main things that affect this property: carbide grain size and binder ratio. For grain size, larger grain produces a harder material, whereas smaller grain produces a more impact-resistant, tough material.
For aluminum, we want to maintain that edge sharpness, so we want a small grain size for maximum edge retention.
The other factor iin CNC machining aluminum is the binder ratio. For carbide cutting tools, the binder is cobalt. This could have anywhere from 2%-20% cobalt content. Since cobalt is softer than the carbide grains, more cobalt means a tough tool, less cobalt means a harder tool.
So we’re basically just looking for a carbide cutter that has a large grain size and low cobalt content.
Flutes
3 flutes are the sweet spot for solid carbide endmills 98% of the time. Chip clearance is the name of the game for aluminum, and 3 flutes give that perfect balance of tool strength and chip clearance.
2 flutes can be a viable option also; where cutting forces are lower and chip clearances are more of a factor. One area where this makes sense is when you have a very long tool that is prone to vibration.
At the end of the day, though, 3 flutes are the industry standard for CNC machining aluminum and that is what we use.
Helix Angle
The helix angle of a tool is measured by the angle formed between the centerline of the tool and a straight line tangent along the cutting edge. Cutting tools for aluminum typically feature higher helix angles than standard end mills.
Specialized helix angles for Aluminum are typically either 35°, 40°, or 45°. Variable helix tools are also available and make a great choice for reducing chatter and harmonics while also increasing material removal rates.
Clearance Angle
Clearance angle is another important factor in CNC machining aluminum for the proper functioning of a tool. An excessively large angle would cause the tool to dig into the work. On the other hand, too small an angle would cause friction between the tool and the work.
Clearance angles between 6° and 10° are best for aluminum CNC machining.
Feeds and Speed
The softer the material being machined, the faster the recommended cutting speed. At 900-1800 feet per minute (using a carbide tool) aluminum has a similar cutting speed to wood. But unlike when cutting wood, the optimal feeds and speeds set-up will be in a much tighter range.
CNC Machining aluminum is often characterized by a high spindle speed. We have to be wary of combining high spindle RPMs with feed rates that are too slow.
As the tool will spend more time rubbing against the aluminum than cutting it. This will increase the working temperature and drastically reduce the tool life.
Aluminum CNC Machining Processes
We can machine aluminum using several CNC machining processes available today. Some of these processes are as follows.
Turning
In CNC turning operations, the workpiece rotates, while the single-point cutting tool stays stationary along its axis. Depending on the machine, either the workpiece or the cutting tool carries outfeed motion against the other in order to achieve material removal.
You can read more about how we use CNC Turning Here.
Milling
Milling operations are perhaps the most commonly used in CNC machining aluminum parts. These operations involve the rotation of a multi-point cutting along its axis, while the workpiece stays stationary along its own axis.
Cutting action and subsequently, material removal is achieved by the feed motion of either the workpiece, the cutting tool, or both of them combined. This motion can be carried out along multiple axes.
Read more about Milling here.
Pocketing
Also known as pocket milling, pocketing is a form of CNC milling in which a hollow pocket is machined in a part.
Facing
Facing in machining involves creating a flat cross-sectional area on the surface of a workpiece through either face turning or face milling.
Drilling
Drilling is the process of making a hole in a workpiece. In this operation, a multi-point rotating cutting tool of a particular size moves in a straight line perpendicular to the surface to be drilled, thereby effectively creating a hole.
Industries using CNC Machined Aluminum Parts
- Aerospace: due to its high strength to weight ratio, several aircraft fittings are made from machined aluminum;
- Automotive: similar to the aerospace industry, several parts such as shafts and other components in the automotive industry are made from aluminum;
- Electrical: having high electrical conductivities, CNC machined aluminum parts are often used as electronic components in electrical appliances;
- Food/Pharmaceutical: because they do not react with most organic substances, aluminum parts play important roles in the food and pharmaceutical industries;
- Sports: aluminum is often used to make sports equipment such as baseball bats and sport whistles;
- Cryogenics: aluminum’s ability to retain its mechanical properties at sub-zero temperatures, makes aluminum parts desirable for cryogenic applications.
In Summary
Aluminum is a versatile material with a high level of machinability. We have a full understanding of its capabilities and machining requirements. Use our inquiry form if you require CNC Machining or contact us for any questions that you may have.
