Modal Resonance Simulation - Fusion 360

[Tenson]

Hi ya'll,

I haven't been following this forum for some years since I built my machine and stopped thinking about upgrades for a while.

Since then, Autodesk Fusion 360 has become available for general use and with that its powerful simulation capabilities.

I was wondering if there has been much uptake with DIY designs here making use of the modal simulation functions?

I remeber I think Jonathan did some static load simulation with Solidworks when working out the best gantry shape, but milling machines are not about static loads, they are about resonance / structural modes. Everything is a spring, as they say.

Despite building what I thought would be a pretty solid machine frame (and for the most part it is, especially when considering static loads), there has always been some low frequency resonance that I couldn't track down because I'd braced all I could and it's too fast to see by eye other than 'it's wobbling'.

Using the modal simulation in Fusion 360 has been very telling about the effect of frame geometry, specifically bracing placement. I'm only just beginning to fiddle around, but so far it seems to match reality pretty accurately - for example I've found that cross-corner type of bracing is far less effective than diagonal-to-diagonal type.



I can also see that the layer damping I added to the short and long top beams was worthwhile, as they flex in the direction the damping is most effective :)