Gantry design and FEA analysis

[Neale]

Personal view here, but based on using my own machine for the last 2-3 years. It's described somewhere on this forum - search for "AVOR" and my username if you want to look it up. It's built mainly of 50x50x3 with some 100x50x3. Steel, all welded, various bits and pieces from 20mm Ecocast aluminium. I suspect that if you did a static FEA job on it, it would come out as being pretty stiff (for some definition of "stiff", anyway). It's not "Boyan bullet-proof" but it isn't bad. That 3mm box is strong enough - if well-braced. If I were doing it again, would I go the same route? No - it's strong enough but resonance is always a problem, and that's not something you can easily fix after the event. I should have gone for 5mm, I reckon, although there's not much else I would change. That would have meant that I could drill and tap directly into it for fixings instead of needing reinforcing strips or other workarounds.

So, what can t cut? Can it cut aluminium? Well, yes, probably, but it's horrible stuff to cut and with a plywood bed, I don't want to do "wet" cutting so I try to avoid it. Of course, it cuts wood/ply/mdf etc with no problem. But it also cuts - regularly - brass and steel. I use small (typically 2-4mm) carbide cutters which are happy to run at high speed and cut dry with no problem. No, I'm not carving engine blocks from large lumps of steel but I cut lots of fiddly little bits which would be difficult to do on the manual mill because of the detail needed - like a brass lost wax master for a lapel badge. One limiting factor is not machine strength or spindle capability but just work-holding - one area that I would revisit another time around is how to build a bed with clamping capability for the kinds of things I now do, as opposed to what I thought I would do when I first built it. Difficulty in just holding things firmly limits cutting forces you can apply.

I'm also in the "just put something plausible together, listen to comments based on experience, then fire up the angle grinder/welder" camp. The time you spend analysing you could cut and weld a couple more braces...