Difference Between "Stitch" and "Non-Manifold Add" in Solid Geometry Creation 3

[Cheyne]

When dealing with surfaces, can someone tell me the difference between "stitch" and "non-manifold add?"

My own theory is that with "stitch," there is a cleanup process that closes gaps between the surfaces of interest. As opposed to "non-manifold add" that has no cleanup process, and only works if the two surfaces are touching, having no gaps.

Can someone confirm, or clarify?

http://www.martinezandturek.com

 

[BlasMolero]

Hello!,
Using GEOMETRY > SOLID > STITCH allows you to close a solid body, or sheet body, giving the option to CLEANUP MERGEABLE CURVES + enter A GAP TOLERANCE. This is pure PARASOLID operations. It creates a solid from a series of surfaces. The only inputs required for this command are the surfaces themselves, a stitching tolerance, and whether “mergeable curves” should be cleaned up. The tolerance can be adjusted to facil­itate the closing of gaps between surface edges. This is a very useful command when reading trimmed surfaces from an IGES file. You can read an IGES file, and then use this command to generate a Parasolid solid from the IGES surfaces. You can then manipulate this solid just like any other solid you would have created in FEMAP, this is the main advantage, you can extend surfaces by edge, remove faces, using MESHING TOOLBOX, etc.. This is my favorite command.

When Cleanup Mergeable Curves is “on”, which is the default, FEMAP will remove all internal curves which are redundant. The “stitched” geometry will contain as few surfaces as possible by removing curves which are not needed to define the overall topology of the geometry. When “off”, all of the surfaces being stitched together will remain in the geometry.

Apparently you can do the same with GEOMETRY > SURFACE > NonManifoldAdd .... but the diference is notable. THE NonmanifoldAdd entity allows to define a sheet body with T-SURFACES, is perfect, if you try to stitch two surfaces in "T" you will receive an error message, but is possible using nonmanifoldAdd command.

This is the only command in FEMAP which allows you to create “Non-Manifold Solid Geometry”, an option in the Parasolid modeling kernel which creates “General Bodies” as opposed to regular solids (FEMAP solids) and sheet solids (FEMAP surfaces). The command allows you to Boolean Add sheet solids to one another, as well as add “sheet solids” to Parasolid “solids”. The “Non-Manifold Add Tolerance” may be adjusted in an attempt to have more solids and sheet solids combined into as few “general bodies” as possible.

The use of Non-Manifold Geometry can be very useful in creation of mid-surface models with “T-Junctions”, mod­els where shell elements (2-D) and solid elements (3-D) need to be connected and portions of the shell mesh are embedded into the solid mesh, and “solids” with internal “surfaces” used in certain types of analysis.

The main limitation of Non-manifold geometry is that body is "untouchable", many of the other commands on the Geometry, Solid... menu will not function as they did before the geometry was changed from regular geometry to “general body” geometry. A good idea is to have both the surfaces and solids “ready to go” before using the “NonManifold Add” command.

Try both commands, and you will realize of advantages & limitations, use the best of both!!.

Best regards,
Blas.





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

IBERISA
48011 BILBAO (SPAIN)
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Blog de FEMAP & NX Nastran:

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[Cheyne]

Wow!

Thanks for the thorough response, Blas. Will do!

Cheyne

http://www.martinezandturek.com

 

[trainguy]

Blas,

Thanks for the "solid" explanation...

tg

 

[mrfemap]

Non-Manifold Add is being updated for FEMAP 11.1. We worked with the Parasolid team and non-manifold add is much more "tolerant" than it was in the past. Similar to how stitching can use a tolerance to bring edges together, non-manifold add will be able to do so in the next release. If anyone has any test cases they would like me to test in the development version of adding together surface geometry that was not possible in the past, please send it to me -

sherman dot mark at siemens dot com