10 TIPS FOR SUCCESSFULLY CUTTING ALUMINUM WITH A CNC ROUTER (PART 1)

People often ask if a CNC Router can cut aluminum. They usually see it used for wood and plastics. My answer to this question is always, “Yes, if done correctly.”

There are a few things to remember about how aluminum (and other metals) differ from wood or plastic. First, aluminum has a much smaller “sweet spot” for optimal feed rate and speed. If you miss this sweet spot, the cutter may chip, wear the material faster, and result in poor surface finish. In practice, there are several sweet spots depending on what you want to achieve:

Second, aluminum (and some other metals) has a “gumming” factor. Aluminum tends to stick to the cutting tool. In fact, it can act like it’s welding itself to the tool. Once aluminum builds up on the edges of your cutter, tool life drops significantly, especially at speeds of 20,000 RPM or higher.

Despite these challenges, you can cut aluminum successfully on almost any router. Here are 10 tips for cutting aluminum with a CNC Router:

1.      Don’t rush

A CNC Router can cut aluminum, but it is not ideal for aerospace parts like airplane wing beams. The price of success is to slow things down. This does not mean reducing feed rate and speed arbitrarily, but your material removal rate will generally be less than what a dedicated CNC mill could achieve.

So, relax and let the machine do its work. At minimum, a well-sized CNC Router will have a table large enough to handle more materials than any small CNC mill. You just need to start, press go, and let it run.

2.      Use a feed and speed calculator

You are likely approaching your machine’s limits. Cutting aluminum on a CNC Router is not simple—it must be done correctly. Tool behavior is critical. Endmills cannot maintain proper speed when navigating corners and pockets. Improper feeds and speeds can break cutters and ruin workpieces.

All CNC machines benefit from calculating cutting speed and spindle speed, but especially near edges, care is required. Key features for CNC Router users with a calculator like G-Wizard include:

– Minimum RPM settings: Calculators will not help if they keep you running slower than needed.

– Tool types: V-Bits, compression bits, and downcut bits matter. Ensure your calculator handles them correctly.

– Deflection: Tool deflection is real and causes breakage. A good calculator predicts it and provides ways to mitigate it.

– Chip load warnings: Cutting too slowly may cause chips to smear along the surface, generating heat that shortens tool life. Choose a calculator that warns about this.

– Thin chips: When cutting material narrower than half the cutter diameter, thin chips occur. Your calculation must account for this, or tools must be replaced sooner.

– Power reduction for weaker machines: See tip #10 in part 2 for details. Useful if your calculator supports multiple machine profiles.

Many CNC Routers have spindle speeds higher than typical CNC mills. A new router might reach 20,000 RPM while a new CNC mill may max out at 10,000 RPM. Tips below address this issue.

3.      Use coated carbide cutters

A way to achieve recommended RPMs is using high-speed cutters. Carbide cutters run faster than HSS. Forget HSS and cobalt. Coatings like TiAlN allow higher speeds. Invest in TiAlN-coated carbide cutters—they cost more but significantly improve results.

For example, cutting a 1/4″ slot with an HSS endmill may require 5,877 RPM (too slow for a 20,000 RPM router). Switching to TiAlN carbide raises the recommendation to 16,897 RPM with a surface speed of 1,106 SFM—much closer to router capabilities. For aluminum, I often run 20,000 RPM.

4.      Use smaller diameter cutters

Using a smaller diameter cutter increases RPM and reduces deflection. Move from a 1/2″ endmill to a 1/4″ or smaller. Carbide is much stiffer than HSS, reducing deflection and improving cut quality.

For instance, switching from a 1/4″ endmill to a 3/16″ endmill increases recommended RPM to 21,241, closer to a 20,000 RPM router. This balances tool and machine capabilities.

5.      Chip evacuation

This is critical. Don’t rely solely on dust collection unless you can ensure chips are cleared from deep cuts. More reliable is an air blower attached to the spindle, directed at the cutting area. You can also hold a nozzle or brush to keep the cut clear.

(To be continued in Part 2)

Source: http://blog.cnccookbook.com

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