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Problem with Face Edges selection

Creator
Creator

Hello,

 

I am trying to select the edges of the face of a solid for a Section Inertia Analysis. However, the selection does something strange at a very small part of the selection. Given that little something, it is not possible to get the solid analysis and instead it gives me a hollow analysis. Here are some screenshots of the problem.

 

error1.JPGerror2.JPGerror3.JPG

 

Is there a way to prevent NX from doing this? I am using NX 11

 

I appreciate your help.

 

Jorge

13 REPLIES

Re: Problem with Face Edges selection

Siemens Phenom Siemens Phenom
Siemens Phenom

The screenshots show you may have an issue with the quality of the geometry.

 

Have you tried running Examine Geometry to check for issues?

 

Can you provide the part file so we can have a closer look?

Re: Problem with Face Edges selection

Creator
Creator

Hi,

 

Thanks for your answer. Yeah I tried with Examine Geometry and everything seems to be OK.

 

error4.JPG

 

Here is the part file.

 

 

Re: Problem with Face Edges selection

Siemens Phenom Siemens Phenom
Siemens Phenom

If you are looking for the radius of gyration, try using the Measure Body command.

 

Otherwise, someone more familiar with section inertia analysis will need to chime in.

Re: Problem with Face Edges selection

Creator
Creator

Hi,

 

No I am not looking for the radious of gyration. Actually, I am doing something else in NX Open, but I call Section Inertia Analysis to get some information. The problem is not the tool, it is the edges and how they are mishandled by the selection command. I don't know what causes that unwanted approximation that leaves the section open. If I try to select edge by edge, the little curve is unselectable, so it seems NX is uncapable of processing it properly so it tries to compensate for it (unsuccesfully).

 

error5.JPG

 

As you can see in this picture, I had the diagonal line and the vertical lines selected, but when I select the horizontal line, the vertical line gets deselected and turns blue. It cannot be selected again.

 

Thanks again for your responses.

Re: Problem with Face Edges selection

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

Try tightening up your selection tolerance?

Ken Akerboom Sr CAx Systems Engr, Moog, Inc.
Production: NX10.0.3.5 MP16/TC11.2
I'd rather be e-steamed than e-diseaseled


Re: Problem with Face Edges selection

Creator
Creator

Hi,

 

I tried that in my extrude and unite operations. Also on the customer defaults I increased my tolerances from 0.01 mm to 0.001 mm and 0.5 degrees to 0.05 degrees and it didn't work.

 

Thanks for your response.

Re: Problem with Face Edges selection

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

There is a small "sliver" cut where one of the rectangles doesn't quite meet up with the rail. If you eliminate the sliver (I used replace face), it will let you do a solid section analysis.

 

section_01.png

section_02.png

Re: Problem with Face Edges selection

Creator
Creator

I am aware of that "sliver" and I know it is the reason the section is open. But, is there away to make NX get the selection right with the "sliver" in it? I am asking because that geometry is the result of an automated process made with NX Open, so that it is just a step in the process. So, user interaction with the solid is far from ideal. 

Re: Problem with Face Edges selection

Gears Esteemed Contributor Gears Esteemed Contributor
Gears Esteemed Contributor

I'd guess that the section inertia analysis tool has a minimum edge length tolerance that is causing the smalll edge to be ignored. This suspicion needs to be confirmed by someone with more knowledge of the internal workings of the section inertia command.

 

Have you tried the "advanced mass properties -> area using curves" command? It provides many of the same values as the section inertia command but it doesn't seem to choke on the small edge. I don't know the API command equivalent, but it's probably buried somewhere in the UF functions.