Are you turning the crossfeed by hand or using the leadscrew?
What kind of tool are you using? What radius is the tip? Where did you get it or what brand is it? Did you grind it?
What depth of cut?
What kind of aluminum is it? Where did you get the aluminum?
Looks like higher RPM, slower and/or smoother feed, larger tool tip radius (or better quality tool) and maybe some cutting oil might help. WD40 is good on aluminum. With a decent cutting tool and some WD40, you should be able to use the lead screw and get a very nice cut, unless it's crap aluminum.