Watertightness in mesh

Question

Watertightness in mesh

mechy20 (Mechanical)

(OP)

9 Sep 07 18:11

Hi All,
I am having problems with a complicated solid model that I am trying to automesh. It is a big assembly and one of the parts gets flagged as it was not successfully surface meshed. However this part is able to solid mesh without any hassles.

However a part that did not get flagged initially during surface mesh is not solid meshing as the surface mesh is not watertight.

As my geometry is complicated I am unable to identify the surface or nodes near the problem area.

I have played with a whole bunch of mesh size settings and the only case where it worked I ended up with an extremely small mesh size and more than 130000 nodes (which would kill my computer)

Any suggestions on how to mesh this? I cannot hand mesh something as complicated as this.

Thanks in advance

GBor (Mechanical) · Answer 1 · 2007-09-10 09:16:12

It would be helpful to see the model on this one, but could you de-select the problem part for meshing and hand mesh just that one part after the rest has been solid meshed?

The problem comes from the solid model information. What CAD system did you use to generate the original model?

Also, 130,000 nodes on a solid model doesn't sound like too much for today's computers. Bricks only have 3 degrees of freedom, so it doesn't seem that this should be too complicated unless you are trying to run an Event Simulation with multiple areas of contact.

Garland E. Borowski, PE
Borowski Engineering & Analytical Services, Inc.
Lower Alabama SolidWorks Users Group
Magnitude The Finite Element Analysis Magazine for the Engineering Community

mechy20 (Mechanical) · Answer 2 · 2007-09-10 16:04:33

GBor, As always thanks for your response.

Unfortunately due to restrictions am unable to share the model. The solid model was built in Solidworks and all the features such as fillets, chamfers, drafts (ah ! yes it is Plastic)were removed.

However this one part that comes up with the watertightness is the most complicated part of the assembly.

At this point I am trying with the fine meshed model, it may be ok as you say, since this is not MES.

Thanks again.

GBor (Mechanical) · Answer 3 · 2007-09-10 17:28:18

SolidWorks is wonderful software, but you need to make certain that you set the export options to a high precision. I think default for SW is something like 1e-7 in the IGES export. Algor recognizes gaps down to about 1e-15 (double precision), I think. Not 100% certain if those numbers are entirely correct.

You may want to try to perform the surface mesh, global snap the model, and then solid mesh. This may close up any gaps. Not sure what this will do with the part that didn't originally surface mesh, but it may resolve the issues with the lack of watertightness in the part that did surface mesh.

mechy20 (Mechanical) · Answer 4 · 2007-09-11 14:58:01

Thanks GBor. I will try that and let you know.

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Watertightness in mesh