Reversing polarity for aluminum can improve your cutting speed by a factor of 5, and radically improves cutting stability!
After a lot of experimentation, I figured out that the best way to cut Aluminum is by reversing the EDM polarity. The Workpiece should be negative and the EDM wire positive. This is really important, it will drastically improve cutting speeds, improve reliability (no more unexpected wire breaks) and improves the stability of the cut! I'm now cutting 25mm thick Aluminum at an amazing rate of 11 mm/min! Remember that if you reverse your polarity, the sense wires also need to be reversed, otherwise you might damage the generator!
More info here: https://www.youtube.com/watch?v=CcTQoy_tBp4&feature=youtu.be