Just finishing up my build of a 1000x1000 Workbee , one thing that concerns me is the rotational stiffness of the X axis Cbeam , there is quite a lot of movement if any force is applied to the z axis motor ( to simulate cutting forces). About half the movement is in the z axis wheels and the rest in the X CBeam twisting. My thought were to add a 20/80 to the rear of the cbeam bolted on resulting on a 80x60 box channel ,move the back wheels back to also widen the footprint on the x gantry and move the lead screw to the back of the plate. I know I will need to make new plates but that is ok. Or use 2 Cbeams bolted together as a tube. - the worry is having such a wide x gantry will cause flex in itself due to the longer bolts. For the Z the thought was to add a extra set of wheels higher up and a plate across the front to support the wheel bolts from spreading or convert to a linear rail system . Anyone done this that can give some feedback
Rather than putting 2 beams back to back would I be better off using 2 beams but spaced one above the other with a gap between for the lead screw ? Would more gap increase the torsional rigidity ?
Yes and yes but no reason to raise the lead screw to the space between the gap. Keep it as low as possible as this keeps the force close to the resistance.