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Polygon face/edge "skewed(?)" -> poor mesh

Pioneer
Pioneer

Hi all,

 

I hope someone can explain this issue for me. I have encounter this situation more than once and usually found a (time consuming) method to solve this by basically modelling the entire part again. Picture below shows a sheet model of a bend and with highlighted edge. The edge has this "zig-zag" line on the bottom part and "skewed" line on the top part. When meshing I usually get poor result.

 

Withoutmesh.jpg

 

The next picture shows the part with mesh. This is maybe not the worst situation I have encounter, but still makes some issues when meshing. I have tried auto heal and recreate & update, but I can not see that this will help. When I mesh again the same "edge" appears again. Maybe I am doing it wrong?

 

withmesh.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Can anyone explain to me how I can resolve this and what is the reason this is happening?  I am using NX10.

 

Thomas

 

 

 

 

 

 

5 REPLIES

Re: Polygon face/edge "skewed(?)" -> poor mesh

The question is how you created those surfaces.

 

Maybe the edges are not exactly coincident. Have you created both those problematic surfaces separately or this is a one divided surface / one body that has been splited later ?

 

 

Re: Polygon face/edge "skewed(?)" -> poor mesh

Legend
Legend

It's the polygonization of the geometry, not the geometry itself, that creates this issues.  It happens...

 

I'd update the polygon body (right mouse on it "recreate and update), then freeze the face and all problems will be gone...

Re: Polygon face/edge "skewed(?)" -> poor mesh

Pioneer
Pioneer

Hi,

 

Thank you all for reply. Have not tried to freeze face before, but when you say "freeze" the face you are talking about the "freeze geometry" command?  

 

Thomas

Re: Polygon face/edge "skewed(?)" -> poor mesh

Legend
Legend

Freeze Geometry is the one I'm talking about, yes Smiley Happy

Re: Polygon face/edge "skewed(?)" -> poor mesh

Siemens Phenom Siemens Phenom
Siemens Phenom

I would look at the original geometry to see if the swept faces are complete "cylinders" or not. If they are complete "cylinders", then this means that the meshing process is introducing seams on these periodic faces. Seams are required for meshing so that the faces can be unwrapped and meshed in parameter space, then the mesh is transformed back into 3D space. The image shows that the seams on adjacent faces didn't line up, and then some additional abstraction introduced a kink away from the circumferential edge. 

 

If possible, introduce the seams in the CAD model by dividing the "cylinders" two halves. This will eliminate the need for the meshing process to introduce the seams. Alignment of seams on this type of geometry was a development project for version 12. You will see much better results on this geometry in version 12, which is going into beta testing this Monday.

 

Regards,

Mark

 

Mark Lamping

Simulation Product Management

Simulation and Test Solutions

 

Siemens Industry Sector

Siemens Product Lifecycle Management Software Inc.

 

mark.lamping@siemens.com

www.siemens.com/plm