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There's certainly no issue cutting AL on the Bot - thin sheet or thicker parts up to let's say 1.5" thick - that are held down well, can produce good results.
If you need to do production in thick AL or steel that requires lube & coolant - then farming it out or investing in a CNC mill like a Tormach is a wise decision...although I have to say, farming it out is no fun for guys who like tinkering or the occasional Saturday metal project.
With the Colombo, I use a spiral-O bit up to about 1/2" thick. If doing extensive area clears/pocketing, I will use a HSS end mill with a geometry suitable for milling AL. The HSS absorbs some of the harmonic vibration that you can get when milling AL with solid carbide end mills in certain diameters & feeds. Plus HSS will bend in situations where carbide will snap or shatter.
You can mill 2D and 3D in most non-ferrous metals with your router. As Jeff pointed out, you can't walk away when milling this stuff & you can't be asleep at the wheel while programming or operating.
-B
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We've been using Amana Tool's polishing flute aluminum cutters, and they work great.
We do roughing passes down to an onion skin 0.005 offset, then a cleanup pass with no offset and full depth. We run 1.5 IPS with .14" passes at 18,000 RPM with a 2.2 HP spindle.
Tabs hold like crazy in aluminum, so you don't need very many to keep the part in place while cutting this way.