Gantry design and FEA analysis

[JAZZCNC]

Your concentrating too much on deflection and not thinking about resonant vibrations which are the real killers of tools and finish. That Z-axis shown will resonate because the plate is too thin with a large gap between the rails acting like a trampoline.

Going back to the 50mm box section then I can tell you from experience building machines that it's not the best choice unless you use at least 6mm wall thickness and good bracing. The rectangular tube is much better when used in the correct direction and braced correctly, however you still need a thick wall to help with vibrations.

The simple FEA you are doing won't tell you anything about how the machine will perform in real life. You would be better advised to drop the FEA and put the time into reading builds and asking questions about any designs you like. By that, I mean directly asking the builder and not posting a thread asking the questions about a particular design as you'll get lots of conflicting advice and often from people with little experience or worse armchair experience.

Can't beat experience and to get the experience you need to get on with it so put the PC down and get the welder out.!!