Inventor, COG 2

[mrsharpe58]

"Using Autodesk Inventor, why does the COG shift off centerline in my model of a pipe when I cut threads into it?" It shifts off center of the center line. A shift length ways I could understand.

 

[btrueblood]

Because there is a start and end to the thread, and if not perfectly opposed (i.e. symmetric), leads to a slight offset of the c.g. Probably can be ignored for most instances, since the pipe itself is not controlled to a level of symmetry to make the threading offset apparent. The change should be pretty minimal...

 

[MintJulep]

Is there really a need to include pipe threads in your model?

 

[mrsharpe58]

That makes sense btruebood, but I can't see it changing the COG as much as it's changing it. It's a dramatic change.
Good logical answer though.

 

[3DDave]

The way the COG is calculated (the algorithm) is to project little triangles from the surface of the part onto a plane. If the normal to the triangle is away from the plane the projected volume is added. If towards the plane, it is subtracted. For each volume a CG is calculated. At the end, the volumes and CGs are taken together to generate a net CG for the part.

I would guess that the threads add a huge number of little triangles and there are errors that accumulate.

 

[JohnRBaker]

Perhaps it might be better to post this in the Autodesk: Inventor forum.

John R. Baker, P.E.
EX-Product 'Evangelist'
Irvine, CA
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The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[mcgyvr]

post the ipt?
version of Inventor?
up to date on updates/service packs?

And last but certainly not least...
Why are you actually cutting real threads vs just using the cosmetic representation of them?