I went through the process when cutting some old signs (2mm aluminum) for my struts.
Suggestions:
- Trochoidal milling as suggested is great, especially for thicker material, although if you are cutting very thin (2mm or less) sheet, it is possible to use straight milling instead. Trochoidal is VERY slow in comparison.
- An Air-Mist sprayer using IsoPropyl Alcohol (IPA) for cooling of the end mill and chip evacuation is helpful
- Aluminum is very sticky, so it is easy to weld chips to your end mill. Feeds and speeds to ensure no rubbing are critical (as is chip evacuation)
You can check out my build thread, starting at the linked post, and then for the next 5 or 6 posts for some info on the setup, feeds and speeds, etc. that I used.
This thread has some info on the Air-Mist system, with a few links to threads about cutting aluminum and making a holder to attach the sprayer to the LR3.
Amazon has a ton of the sprayers for a pretty cheap price. IPA is available at most pharmacies, or even Costco.