One sided drive?

[Jeremy]

Thanks very much for that, Irving.

The gantry members will be two lengths of 2" square x 10g wall 6082-T6 alloy box, with SBR16 fully supported rails screwed to them, so it should be pretty rigid.

I'm thinking of something similar to the layout shown on that Durham Robotics link, with the leadscrew outside the rail, so it should be OK, with luck. The main reason for using this configuration is the reduction in machine height and a possible increase in overall stiffness, as the gantry doesn't need an under-table drive. It also means that I don't need to add the complexity of a double leadscrew arrangement.

Jeremy

[irving2008]

Well given that 50mm square 10g (3mm wall) box section is stiffer than the 40 x 30 x 3 I postulated this should be plenty stiff enough for your needs...

That calculation assumes rigid corner joints and a cross member at each end between the Y-rails of the same stiffness.

The other racking issue is where the cutting forces cause the non-driven upright to rotate in the vertical plane relative to the driven one. Obviously gets worse as the cutter rises above the table, so you need to ensure torsional stiffness of the gantry in the Y-Z plane.