When I cut aluminum bar or t-slot extrusion on my bandsaw I am not happy with how "square" this edge is. I don't have a milling machine at home, and I have been told grinding aluminum is a very bad idea.
I used to build structures using the 80/20 aluminum extrusions , I used a mitre saw with a good aluminum cutting blade lubricated with stick wax (or any good cutting fluid). Makes beautiful square cuts with minimal burring. Be careful applying the stick wax to the rotating blade, otherwise your mitre saw will become a finger removing device by default :-(
Small very sharp teeth, hard blade, not too fast or the blade will flex, using wax was a good idea or plenty of lubricant. Make sure the blade is cutting perfectly square or you'll be chasing your tail. I'm the QM at an aluminum extruder (30 years), we cut millions of lbs a year (6xxx & 3xxx alloys). We have always used a lubricant called Boelube, made by Orelube Corp, it has a picture of a plane on the label. Dealing with burrs is tough. On our automated saws, dedicated to cutting parts for a major auto OEM, the blades are hundreds of dollars and we have to have them sharpened maybe every other month, but we can keep burrs below 0.010" on some of our more "regular" blades, they don't cost as many hundreds as the better blades. If you're just trying to get a flat edge, you might try sandpaper on a perfectly flat surface. Most aluminum sands relatively quickly and you're more protected from over-doing it.