Aluminum is a major staple in most legitimate CNC machine shops. That’s because it’s extremely versatile, which means machinists can process it swiftly and efficiently. However, innate machinability is also what makes it difficult in many cases. Since aluminum is such a widely used metal, the machining space is highly competitive and not all services offer the same level of quality.
Why can aluminum be difficult to work with?
Machining aluminum comes with many challenges but hitting the required material removal rates without causing damage to your tools, workpieces, or machines is the trickiest. The process often takes high heat to complete, but too much heat can melt aluminum like butter. Meanwhile, the metal can also fuse to the equipment and halt manufacturing altogether. At that point, the machinist may have to do friction stir welding instead, and that could cost a lot more time and money.
What are the different types of aluminum?
Did you know that not all aluminum grades offer the same level of machinability? While some are easy to cut and mold, others become gummy when processed. That, in turn, can clog your equipment and make machining a nightmare. So, it’s important to understand the fundamentals of each aluminum type to prevent those otherwise avoidable issues.
For reference, here are the six main grades of aluminum most commonly used in CNC machining:
This is the most pliable metal grade of them all, with extremely poor corrosion resistance. So, it’s typically anodized for that reason.
This type of aluminum offers a superior weight-strength ratio, which is why you generally see it in applications where tension is applied.
This is an extremely soft metal, so it’s used a lot in forming or molding processes. Plus, it usually comes in sheet form and has excellent corrosion resistance.
This is the most common aluminum grade for modern machining because it’s easy to cut and gentle on the machines with only a slight risk of chipping.
Similar to 6061 in many ways, this type is more often used in extrusions because it’s less stiff. However, that also makes it gummier and a little harder for the machine.
This grade of aluminum is typically used for machining aerospace structural parts because of its durability, although it’s one of the hardest metals to finish.
Keep in mind that regardless of the grade, all-aluminum is highly machinable at the right machine shop. Most of the time, differences are only noticed if the tools and/or machines are working extra hard to keep up with demands. Simple or low volume production, therefore, usually doesn’t render as many negative results.
NOTE: There’s a major difference between wrought aluminum and cast aluminum. In general, the cast is always gummier but speak to your Pioneer Cuts machining team for more detailed information.
Which coatings are best for aluminum machining?
Usually, uncoated machining tools are ideal for processing aluminum. Standard tool coatings often do more harm than good, so be careful. You also won’t get a lot of performance out of special tool coatings either. Those are generally just a waste of time, money, and manpower. Here’s what else you need to know:
- AlTiN is a coating designed primarily for steel. The coating isn’t very smooth and there’s actually aluminum in it. That means the tool will likely weld itself to the workpiece without enough heat.
- ZrN is a reduced coefficient of friction, meaning it can help decrease chip flow while maintaining better surface temperatures on the workpieces and cutting tools.
- TiB2 is often preferred by experienced aluminum machinists for its low affinity to the metal, making it slide off the surface with little to no effort.
In most cases, the best tool coating for aluminum machining is just a polished, bare endmill. However, each project is different, so don’t be afraid to play around with the possibilities. Meanwhile, remember to check for industry certifications to ensure proper alignment with manufacturing regulations.
How do I fine-tune the aluminum cutting process?
Because friction and heat are the two primary concerns for machinists working with aluminum, it’s crucial to use proper cutting processes to fine-tune the production. Doing so not only helps clients understand lead times and pricing but it also allows the machining team to streamline their approach. For example, general-purpose cutting tools should never be used to machine aluminum, but only professional machinists understand why.
Check out these four ways that Pioneer Cuts experts can simplify aluminum machining even more:
1. Choose the right cutting tool and cutting tool material. Remember, carbide is always best because it can exceed high-speed steel even in non-performance applications.
2. Use a small grain size for optimal edge retention. Smaller grains create tougher materials that have better impact resistance.
3. Go with three flutes for solid carbide end mills because that provides the perfect balance between chip clearance and tool strength in most cases.
4. Pick the right helix angle. Slight angles can help reduce heat and cutting times but a higher helix can offer smoother slices and a better surface finish.
Well-equipped CNC machine shops have all the necessary tools and machinery to get the job done regardless of the type of aluminum that’s required. Plus, they can achieve extremely tight tolerances on projects with intricate geometries without sacrificing material integrity or project quality. For more information on how to achieve perfect results every time, contact someone at Pioneer Cuts.
A quick note on feeds and speeds for aluminum machining
Most CNC machine shops calculate their required RPMs with 1000 SFM but that’s not actually any faster than normal. Anything between 1000-1500 SFM is considered typical. However, you can increase speeds by as much as three times with harmonic testing. Talk to your design team to learn more.
Compared to many other materials used for rapid, accurate CNC machining, aluminum is relatively easy to work with. Not only does it respond well to most production approaches but it also comes in a variety of types for more customized outcomes. And while it can be cut at extremely high speeds, it’s still important to use the right tools, coatings, and machines to get the job done right.