I havent milled aluminum in decades but this shouldnt have changed much.
I would answer better if I knew your endmill size and feed rate settings, and how the workpiece will be clamped onto the machine. That said, Ive seen it done really fast, both spindle and bed speeds. But you need sane advice, not production level speeds. How many do you plan to cut? If just one, then no room for mistakes on final cut? Then plan on 3 passes. Roughout, Mostly finish, and Final Pass pretty pass. I might do final pass to just remove the last ten or fifteen thousandths. Esp if I dont know how well I can trust the machine ive never used.
Your roughout is the speed limited cut but 5 to 20 ipm with spindle sleeds of 500-2000 will work. Presuming one inch four flute endmill. Faster spindle with a two flute. A machinist will look at the clearances on his or her endmill, and decide on spindle speed based on sharpness condition, and clearance on backside of cutter. Then select a table speed at the low end, but speed up travel if the chips show gumming. Any speed that gives clean chips is a good speed. But put up a shield to protect neighboring spaces please, if it throws them very far…
Im a chemist and Im here mostly for 3D printing stuff. Maybe ceramics. But I have an old machinist toolbox with tools I would sell after moving and never using them in 40 years.