Joe's 1000x600x200 steel and aluminium router started

[devmonkey]

So I just did some maths, if 've got all my units correct, a 100N force on the cutter exerted at 300mm below the centroid of the gantry cross section and half way along the 1000mm Y axis would cause a deflection at the tool of approximately:

160x80x16mm channel is 39cm^4 - deflection 0.22mm
160x80 ITEM heavy profile 390cm^4 - deflection 0.022mm
160x80x16mm box is 1400cm^4 - deflection 0.006mm

I guess that 100N is unrealistic and would break the cutter first.

I'm going to have to drill all the holes anyway, is the bog standard 6" x 3" x 3/8" aluminium extruded box section flat and twist free with parallel sides?

I was looking at the Item profile extrusion since I thought it would give me parallel flat sides without having to process it. My mill table is only 700mm long, not quite enough to surface the entire gantry without re-locating the work which is difficult to do accurately in plane.

I'm also sure I've seem some pictures on here of peoples gantries constructed from plate?