When you need to create neat bends in sheetmetal, nothing compares to a press brake. From dedicated units to simple angles mounted on a shop press, there's a wide range of possible designs. A few examples for your perusal:

How to Build a Press Brake by themetalschoolonline

Homemade Press Brake for Harbor Freight 20 Ton Shop Press by John Harmon - Cold Creek Works

diy press brake by T Jussilainen

Making Of a DIY Mini Press Brake by imbro84