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Advance Mass Properties for NX Assembly based on WCS

Hi,

I am currently using the UF_WEIGHT_estab_part_props to get the Center of Mass and Moments of inertia for assemblies. This API is returning me the values based on absolute co-ordinate system.


The menu command in NX (Analysis->Advanced Mass Properties->Advanced Weight Management) gives the results based on the currently used WCS.

I also need to get the results based on the the WCS using a API.
Any suggestions would be helpful.

Regards,
Santosh

Regards,
Santosh
5 REPLIES

Re: Advance Mass Properties for NX Assembly based on WCS

[ Edited ]
Well you could take the ACS answers and map them to the WCS. Volume, mass, and surface area are obviously independent of coordinate system. Centroid is just a point, so it's easy to map. Moments of inertia are more complicated, but the change-of-coordinates techniques are taught in physices and ME courses everywhere.See here for example: https://en.wikipedia.org/wiki/Moment_of_inertia#Calculating_moment_of_inertia_about_an_axis To do the basic mapping of point and vectors, you can use functions like NXOpen.UF.UFCsys.MapPoint or Snap.NX.CoordinateSystem.MapAcsToWcs.
山田
yamada

Re: Advance Mass Properties for NX Assembly based on WCS

I am actually using a formula to calculate the translation rotation of WCS and then calculating the Moments of Inertia Tensor, which will also give me products of inertia.

This is a big calculation and took me a while to complete only the partial (i.e., rotation) solution. I was wondering that if there is any API to do this for me.

I ll try the method you suggested.

It would be really helpful if there was a boolean flag which gives us the values in desired CSYS.

Regards,
Santosh

Re: Advance Mass Properties for NX Assembly based on WCS

Actually, now that I think about it, the function NXOpen.UF.UFModl.AskMassProps3d *does* return its answers relative to the WCS. Personally, I consider this to be a bug, since the rest of NX/Open uses the ACS almost exclusively. But, bug or not, it's documented, and it probably won't change, so it's safe to use it, if it helps.
山田
yamada

Re: Advance Mass Properties for NX Assembly based on WCS

But even there the inputs to that API is too much.
It does not take part/assembly tags, instead it takes solid bodies.
Also need to provide the type of the solid body which is not available directly.

Considering a large vehicular assembly doing such kind of operation is not possible as it might contain sheetmetal/surface/solid..etc bodies.
Regards,
Santosh

Re: Advance Mass Properties for NX Assembly based on WCS

>> It does not take part/assembly tags, instead it takes solid bodies.

If you would like to assert values (e.g. enter them manually), then the API does take part / component tags.

 

There is also an option to define a reference set containing the bodies for which to calculate the weight data with; see UF_WEIGHT_set_part_ref_set.

Marc Prosl
NX Software Developer