dynamic simulation, separate a part from a 'welded group' for FEA

[nac69]

Hi All,

I am doing a dynamic simulation in which I have a shaft attached to a gear by some screws, so when the gear rotates the shaft rotates as well. Then when I carry out a dynamic simulation, both the gear and shaft appear as a welded group, but I want to export only the shaft for a FEA. Currently this is not possible because this cannot be done with welded parts (that is the error message I get).

How do I take out the shaft out of the welded group so I can do the FEA?

[JDMather]

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@nac69 wrote:
 But the dimensions are accurate and I set the material so wood, so again the resulting mass should be approximately correct.

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Actually, you set the Appearance to wood, not the material.  The material is set to Default (which is same mass as water).

[nac69]

Ok I'll edit that.

Also regarding the holes made for the fasteners, I am getting interference between the fasteners and the holes I made. For example the M6's, the diameter on the outside of the thread is 6mm so I modeled it from a 6mm cylinder. For the threaded holes, I used the hole feature and let Inventor calculate the required hole size for an M6 (like you said some posts above). Now using the inteference check I get some interference between the screw and the hole, is this correct? either:
1. Because inventor does not model the actual threading, it takes it as a cylinder entering in a hole. In this case the interference makes sense.
2. There is an error on how I modeled either the screw of the hole.

thanks

[JDMather]

You should get interference since the threads are cosmetic rather than cut.  The cut threads will engage providing the clamping force.

[nac69]

Hi JDMather,

I've been trying to improve my dynamic simulation model because there were some redundancies and some times the automatic constraint generator created constraints that made no sense. By doing this I came along this two different Dyn.Sim. set-up however I'm not sure which one would be correct.

This one has all the shaft components, fasteners, and other parts, as mobile parts. (From my experience so far it's easier to do FEA on mobile parts):

But then on this one, the other set of fasteners is mobile and the big gear, among other parts:

So my questions is how should it look to know that it was done correctly? or are there different ways to set this up? So that I can stick to one set-up and focus on getting that one right.

At the moment I think the first one looks more correct than the second one.

Thanks