Clean up curves, CAD split lines, for quad mesh 1

[enmo321]

Hi, new FEMAP user here.

I have a surface model imported from CAD which contains many split lines which I'd like to remove before meshing. I've found that the Mesh>Geometry Preparation dialogue is able to clean up a very small portion of the curves, slivers, small faces. Also using Geometry>Solid>Cleanup has not been able to do what I'd like when trying different settings for removing small features. Is there a way to manually clean up these curves? Or create a mesh which ignores all but certain curves for defining mesh size?

Thanks in advance.

 

[BlasMolero]

Dear Enmo321,
The first command I suggest to use is "Geometry > Solid > CleanUp" activating ON ALL options under "Cleanup Operation" form, not matter your geometry is a pure 3-D solid or 2-D Surfaces. This command will check the solid, and remove any extraneous features which are not part of the actual solid, but may have developed during export from a CAD package or from Boolean operations on it. If a portion of your solid appears inaccurate, or drawn incorrectly, use this command to see if you can remove it. And in general is better to answer NO when FEMAP detect problems like SLIVER GEOMETRY, is better to control yourself the changes.

"Slivers" are small faces that are created because of numerical inaccuracies in Boolean or other solid modeling operations. Typically these faces are much smaller than the other faces that define your solid. While they are small, they can cause great difficulties in meshing. They will often completely prevent a part from being hex meshed. FEMAP will try to removes these surfaces and attempts to restitch your solid without them. This option is only available with Parasolid geometry.

I have just imported in FEMAP a complex surface geometry from CATIA V5 in native format resulting isurfaceface body, yes, but with many patches, with many short edges (plot POINTs to see short edges), making impossible the shell meshing. The resource here I have followed is to re-create surfaces in FEMAP using command "Geometry > Surface > Edge Curves". Previously to get rid of very short edges I used repeatedly the API "CUSTOM TOOLS > GEOMETRY PROCESSING > Break Curves at Middle". To get only ONE curve edge I use command "GEOMETRY > CURVE - SPLINE > POINTS" and finally generate the new surface with "Geometry > Surface > Edge Curves".

Also, splitting large surfaces in smaller ones will help to get success when either "stitching" or generating "non-manifold" bodies. In this line take a look to comands like "GEOMETRY > CURVE - FROM SURFACE > PARAMETRIC CURVE", this is very useful to split surfaces at points that are not part of the proper surface to split, for instance a point in the edge belonging to other surface.

Yes, under MESHING TOOLBOX you have plenty of resources for more or less automatic fixing tools like "COMBINED/COMPOSITE CURVES" and "COMBINED/COMPOSITE SURFACES", also "FEATURE REMOVAL" and "FEATURE SUPPRESSION", but I am of those that like ful control of geometry changes and to perform myself all fixing and repairs, you can try and see the best approach to follow, all depends of the geometry complexity, upload a copy of the model and we can take a look, OK?.

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[enmo321]

Thank you Blas for your advice. I am able to use your advice to do the manual clean up by splitting curves, creating new splines and surfaces. However, in order to preserve geometry and time, I don't think this is efficient for the geometry I'm working with. I have attached an example of the surface with typical split lines, a by-product of the modelling. I'd like to know in more detail how to use the meshing toolbox to remove entirely the CAD split lines so that I may manually define curves for mesh control.

 

[BlasMolero]

Hello!,
If you run "Geometry > Solid > CleanUp" command activating ALL options you will see that you have invalid geometry, then FEMAP can not do miracles. You have sliver faces in your model.

Solid Cleanup
1 Solid(s) Selected...
Found Sliver Surface ID - 424
Found Sliver Surface ID - 427
Found Sliver Surface ID - 430
Curve 890 is invalid or corrupt.
Solid 12 failed Geometry Checking
Surface 430 has no facets
Surface 288 has no facets

Then the first suggestion is if you have access to the native CAD software used to create the part to try to remove the sliver faces, do as much as possible the clean process in you CAD system with the aim possed in to prepare a geometry for FEA meshing, not for manufacturing or drawing plans, then very small features should be removed compared with the mesh density you plan to use in your finite element model.

To learn how to use the MESHING TOOLBOX in FEMAP in order to repare & fix invalid geometry and let ready for meshing you have available the following videos from FEMAP experts at SIEMENS:
•

http://www.youtube.com/watch?v=qxZVafl2IZk

•

http://www.youtube.com/watch?v=wkWKlcwwHhc

•

http://www.youtube.com/watch?v=RCdbTzG5prg

•

http://www.youtube.com/watch?v=dvGGNMWCsrI

Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/

 

[mrfemap]

We have both automatic tools in FEMAP, and manual ones to help lay down an excellent mesh with geometry like this. With the manual tools (the Meshing Toolbox) one can really control how the mesh turns out. I created a short video showing how to do this on your geometry and have posted it to YouTube -

http://youtu.be/nbQu7yLVQzk

Since this is an excellent example of using FEMAP to mesh complicated geometry, are you ok with Siemens posting this on our YouTube channel?

Thanks,

Mark Sherman
sherman dot mark at siemens.com

 

[BlasMolero]

Dear Mark,
Excellentt job -- thanks!!.
By the way, I note this is the first time I give a star in the Femap forum, is good to have so valuable helpfulul members!!.
Best regards,
Blas.

~~~~~~~~~~~~~~~~~~~~~~
Blas Molero Hidalgo
Ingeniero Industrial
Director

IBERISA
48011 BILBAO (SPAIN)
WEB:

http://www.iberisa.com

Blog de FEMAP & NX Nastran:

http://iberisa.wordpress.com/