This is a re-post from Idea Foundry members at ReFab Studio here is a link to the original
How to Shopbot Aluminum: We did some experiments with machining aluminum with The Columbus Idea Foundry’s Shopbot CNC machine. We had both success and failure (which itself is a success, when experimenting).
Here are the settings you may find useful when finding information on How to Shopbot Aluminum:
BIT USED Onsrud 63-622 (1/4″ diameter, single flute, upward spiral)
DEPTH OF PASS USED .109 (7/64″)
ROUTER SPEED USED 10,000 RPM
PLUNGE SPEED USED .10 IPS
TRAVEL SPEED USED .25 IPS
We have noticed that the alloy makes a big difference. Here is a guide to aluminum alloys from McMaster-carr:
Machinable alloys can be cut, drilled, shaved, turned, reamed, tapped, threaded, or otherwise machined.
Excellent—These alloys are ideal for machining. When cut, they will not require extensive post-machining cleaning and will produce very small broken chips.
Good—These alloys will have a good to excellent finish after machining and will produce curled or easily broken chips.
Fair—Alloys have a satisfactory post-machining finish and will produce continuous chips.
Poor—Difficult to get clean part after machining.
Reference: Mcmaster-carr website http://www.mcmaster.com/#about-aluminum/=fczose
The edges were fantastic, what you see in the pictures is straight off the Shopbot spoil-board with no modifications other than filing the tabs off.
Our lone mistake involved getting the bit too hot. We increased the depth of pass too high and it quickly got too hot. The basic rules to follow are that it should be relatively quiet, and the bit should not get hot and should even be cool to the touch shortly after the cut. I would change your settings at any signs of heat, like smell or discoloration.