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-   -   Named Selections Issue (http://www.cfd-online.com/Forums/ansys-meshing/84649-named-selections-issue.html)

vitor February 4, 2011 12:10

Named Selections Issue
 
Dear colleagues,

I have a question regarding the Named Selections in WorkBench Design Moldeler.
I'm using an IGES geometry projection to extrude my volume, so that I can switch the IGES geometry file and the Volume changes its shape automatically. The problem is that everytime I import a different IGES geometry the Named Selections report an error: "invalid due to model changes", which is obvious. My question is: is there a way to keep the Named Selections even after changing the model?

Thanks in advance,

Regards,

Vitor

PSYMN February 5, 2011 15:26

IGES is your weak link.
 
Yes, named selections are designed to help you keep everything persistent and parametric. They work by association with the underlying (hidden) entity names. All modern cad programs keep these names consistent (persistent), so you can parametrically update your model and the named selections and all the other downstream settings, loads, etc. would update automatically in ANSYS Workbench.

Your problem is IGES. IGES breaks the process by scrambling these entity names every time you output the file.

The solution is a direct CAD interface. Where do you make the geometry modification? Read that program's native geometry into ANSYS Workbench and the entity names will be preserved, parametric persistence will follow. Workbench actually has bidrectional CAD interfaces so you can use WB its self to drive the CAD tool's parametric engine.

If you can't do that and you only have an IGES file, then use a tool like SpaceClaim to parameterize and modify your model. Then send the SpaceClaim geometry into WB.

With all the hassle of IGES, and all the better "direct" technology out there, it is a wonder that anyone still uses IGES/STEP.

vitor February 7, 2011 11:55

Thank you, I'm truly grateful for your elucidative reply.

I'm using DesignModeler to build my model, the IGES geometry, which is the profile of a valve, is only imported to be used as a projection for the extrusion, in other words, I project the IGES geometry in a plane to get a sketch for the extrusion.

The reason why we are using IGES is because we already have a large repository with all geometries we need, it would take too much time to update them all.

Can you tell me more about this SpaceClaim?

Thaks again.
Regards,

Vitor

PSYMN February 7, 2011 12:01

SpaceClaim
 
SpaceClaim can help you by bringing dead iges geometries to life...

http://www.spaceclaim.com/

You basically parameterize your dead model and go from there. I think you will find lots of movies on this site, youtube and elsewhere...

At ANSYS we are so impressed by this tech that we actually worked out an OEM agreement (something ANSYS almost never does) with SpaceClaim. So, there is now a special version made especially for Workbench that you can buy from your ANSYS sales person...

vitor February 7, 2011 14:16

This software is really impressive. Its GUI reminds me the one of SolidWorks, and it seems very straightforward and intuitive.

Unfortunately, I think it would take too much time to license it and also get familirized with this tool...I was wondering, is there a way to solve the NS issue using only DesingModeler and the IGES geometry?

PSYMN February 7, 2011 15:30

Yes, SpaceClaim is very intuitive and very easy to learn.

As for just getting thru this with DM and your IGES files... It depends what you want to parameterize. Your problem with persistance comes from changing the iges file... But with a constant IGES file, you can parameterize any changes you make in DM.

I can't really make a good recommendation without understanding what you want to change, etc.

For a good parametric study, it may be worth rebuilding your model in DM or some other cad package (SolidWorks if you have it). Just think of your IGES files as a legacy library and do the work you need to do to recreate those profiles in CAD so you can move on without the IGES limitations.


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