Gantry design and FEA analysis

[Voicecoil]

Well sort of.... The direct fixing of the rails thing was more aimed at how you're spacing the front and back Z plates apart. Currently you have the carriages fixed hard onto the back plate, and then some bits of square bar lifting the rails off the front plate presumably to clear the ballscrew bits. This will make the front plate wonderfully stiff front to back, but it would be worth doing your FEA to see what lateral/twisting rigidity is like. The other option would be to have the rails direct onto the front plate, and lift the carriages on a couple of bits of rectangular plate, if this leaves the front plate assy. too bendy, stick the stiffening bars onto the front plate instead of the back. My gut feeling tells me that getting the front plate stiff is more important as it's that that will be dangling down at maximum Z extension. It will be interesting to see what the FEA predicts for the different options.

PS do think about the locations of the fixings for both X and Z carriages - get them overlapping and you might end up with a wonderfully rigid assembly that it's impossible to assemble And also think about making sure there's a way of tramming the Z-axis (adjusting it so it's perpendicular to the bed)