[Laxphan1525]

this isnt a real pretty way but if your good at machining you can cut a slot using a mill at the "correct" angle then bend it by hand and weld the joint to restore rigidity. However if you dont have a mill i have in the past cut a slot using an angle grinder and then welded the joint after. Again neither are that pretty but i have done both in the past and it works. It all depends on what angle you need and how accurate you need to be. Obviously they sell cnc benders and several large companies with access to these benders but most people dont have access to this type of equiupment. like people have said before tube benders work extremely well with aluminum and are an excellent tool for such a process.