It seems that flexible objects just don't model well in many popular constructive solid geometry (CSG) CAD programs. Most CSG modelers seem to assume exclusively rigid bodies with sharply defined and constrained motions. Actually having fully dynamic unconstrained components seems mind-blowingly out of scope.

For example, there is a "collapsing string toy" from decades ago, that seems to be far beyond the ability of most CSG CAD to model and then dynamically simulate:

Google image search: collapsing string toy (also known as a "thumb puppet")

It is similarly exceptionally difficult for most CSG modeling software to accurately model and simulate the motion of a solid rectangular cube supported by two eye bolts, attached to two compound block and tackle rope pulleys.

two compound pulley blocks supporting a dynamic load

It is very limiting for a mechanical engineer to be locked into such an inflexible and rigid understanding of modeling.

So, what CSG modeling software is actually capable of simulating such dynamic complexity of motion?

  • $\begingroup$ Sorry, but resource requests such as this are specifically off topic here. $\endgroup$
    – Phil Sweet
    Commented Apr 14, 2018 at 3:34
  • $\begingroup$ I've often wondered what software these fellas used $\endgroup$
    – Phil Sweet
    Commented Apr 14, 2018 at 3:41
  • $\begingroup$ eh, I hate it when people make a claim that something is off topic and don't cite this anywhere. Where are the "rules" for this discussion category? There is nothing I can see anywhere. Also this is such specialized knowledge that it wouldn't hurt to share, as virtually no CSG can do it AFAIK. $\endgroup$ Commented Apr 14, 2018 at 3:52
  • $\begingroup$ It is because « resource hunting » questions become dated so rapidly. Such as if X is the software of the moment and is then no longer available, then the question and answer no longer help others. $\endgroup$
    – Solar Mike
    Commented Apr 14, 2018 at 9:15
  • 2
    $\begingroup$ Currently none of the cad applocations do this. I mean they can simulate the pulleys thats easy, but not the deformation all you really need is springs for the dynamics. They wont simulate the large displacement soft multibodies. You would need to move to either a FEM aplication that support large displacements like say Aabacus or use a MBS package like MSC adams. Even so the simulation of the defurmation is hard to set up but a nightmare to compute. Again pulleys easy deformation not, and animation of deformation not really in engineering scope. $\endgroup$
    – joojaa
    Commented Apr 14, 2018 at 9:34


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