cutting alum at .05 @7IPM is way too conservative. With my NM135 I dig at least 0.15 with any size endmill and well over 20IPM+ even for full slot passes. Two flute 35 helix uncoated carbide.
For profiling cuts just like those in your pics I use 1/8 since you would always have it full contact so to speak why cut more than needed. You would be wise to make a final pass full depth but alternatively (judging by your pic) polish the part afterwards for looks.
The problem you are experiencing (and I am just guessing here) is that when you do profiling in a few passes (e.g. taking away .05 one pass at a time until you cut through) is that many CAM software will use the same plunging speed as cutting speed for profile operations and that will not play out good for smaller carbide tools. Look at the Gcode file by hand, find all references to Z plunging and make sure they all have F2 after them (plunging Z level at 2IPM) and the next line must return cutting speed back to F25 for example.
With 2 flutes HSS 1/8 diam at 0.1" deep I can do 40 IPM in 6061 no problem. You would need 5500-6000 rpm though. Also coolant to lubricate or else then endmill will clog in seconds.  |