Quote Originally Posted by Voicecoil View Post
You'd certainly need those brackets to make something that's rigid, going for a thicker extrusion would help. I don't have any figures for 45x180, but looking at the moments of inertia of 40 x 160 they're 53x & 731y, whereas an 80 x 160 it's 362x & 1232y - 6x stiffer across the smaller dimension and nearly twice as stiff across the larger.
Don't even need 80 x 160 for a machine this size, 80 x 120 is massively stiff enough. I fit this size on medium-duty 8x4 machines and it makes for a very rigid gantry.