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Struggle generating 3D-Mesh of rather complicated structure

Posted by Maike Schick at November 08. 2019

Hello everyone,

I want to generate a 3D-Mesh of the six STL-Files that can be found here: https://www.dropbox.com/sh/3mhyc34ydso777q/AAD5CwsB6vKjCRgl5nd-6WG_a?dl=0

It is a woven structure out of six wires. My strategy so far was

1. Import in Geometry Mode

2. Build Solid of every STL

3. Make Partition of the Solids

4. Go to Mesh Mode and Create Mesh with NetGen 3D-2D-1D (Min 0 - Max 0,05)

The Mesh has now been computing for a week and it still is at 4 %.

Instead of NetGen 3D-2D-1D, I also tried NetGen 3D and NetGen 2D-1D seperately, but the 3D-Mesh Computation fails, but only for two of the six wires. Then, if I build a Compound and try to apply NetGen 3D on it again, it only meshes the other two wires. I am very confused by this.

What is also funny, is that the same structure just smaller, consisting of four wires, was meshed with the same strategy described above within two hours!

Thank you for your help.

Sincerely,

Maike

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Saint Michael at November 08. 2019

Hi Maike

I propose the following approach:

1. Import all meshes in Mesh module

2. Make a Compound mesh -  Mesh > Build Compound

3. Invert orientation of mesh faces - Modification > Orientation

4. Edit the compound mesh to add NETGEN 3D

5. Compute the mesh in ten seconds.

St.Michael

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Maike Schick at November 08. 2019

Thank you so much! If you only knew how much time I've wasted on this..

What approach would you suggest to refine the mesh in the areas where the wires cross?

As far as I know, in "NetGen 2D Parameters - local sizes" you cannot choose a mesh group as faces. So what I am considering on doing now would be:

1. Import STL's to Geometry Mode

2. Define the areas of interest as Face Groups

(I've tried this and faced some problems: 1. this takes so much more time than defining them in Mesh Mode, 2. when I select the faces of one side of the wire also the faces of the back side of the wire are selected)

3. Go back to Mesh Mode and Mesh each of them with NetGen 2D-1D and local sizes as parameter

4. Then use your approach from above

Would you agree on that?

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Saint Michael at November 09. 2019

To refine the mesh I propose to apply NETGEN 2D to the Compound mesh, the same way as I applied NETGEN 3D. It ramains only to create geometry to specify Local size. I suggest the following approach.

1. Create group of nodes Group_1 located at wires contact by creating a Group on Filter "Double Nodes", with Tolerance 3e-2, if I am not mistaken. I select the tolerance using Merge Nodes dialog, manual mode.

2. Create Group_2 of triangles including nodes of Group_1. Mesh > Group based on nodes of other group, Element type = Face, Number of nodes = At least one.

3. Fill holes in Group_2 by creating another group Group_3, the same way as Group_2, using Group_2 as input.

4. Export Group_3 in a STL file.

5 Import the STL file in Geometry module. After that it is ready to specify Local size for NETGEN 2D.

St.Michael

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Maike Schick at November 11. 2019

Thank you for your answer!

I already tried the approach I described above and I now I have a refined 2D-mesh of each wire. But now the 3D-meshing of the Compound mesh fails with "NgException: Stop meshing since too many attempts."

I uploaded the refined STL's here: https://www.dropbox.com/s/jgrt5w59vpbu3fg/3x3_contactRefined.zip?dl=0

Maybe you can get it meshed in 3D again.

I will start trying your approach now anyway

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Maike Schick at November 11. 2019
I tried your approach and everything worked until step 5. I imported the STL of Group_3 in Geometry Mode.
Then I went back to Mesh Mode and tried to edit Compound_Mesh_1 - NetGen 2D, but I cannot select Group_3 as faces in Local Size.
 
Sincerely
Maike

Re: Struggle generating 3D-Mesh of rather complicated structure

Posted by Maike Schick at November 11. 2019

Nevermind, I was able to select the groups I defined and then used your approach (First, NetGen 2D with refinement on the Compound mesh and then NetGen 3D) and it worked.

Thank you so much!

Maike

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