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STL file with equilateral triangles


Hello, I`m not sure if this is the correct forum for this question…

Our company has written a custom flow analysis program.

And our simulation department wants to have a STL file with equilateral triangles (equal side length).

The STL export in Catia has this option.

So now our simulation department want to import a step file in Catia and export the above mentioned STL.

But the translation doesn’t work well because flow surfaces are mostly freeform faces.


We do have advanced simulation licenses in NX.

So my question is if there is a way to export a STL with equilateral triangles from NX?






Re: STL file with equilateral triangles

Siemens Legend Siemens Legend
Siemens Legend

Hi Klaus,


when I understand you right your problem is, that an STL export of a CAD File generates facets that depend strongly on the surface curvature and for example in planar faces you get larger elements than in curved areas.

If you use Advanced Simulation I could think of the following process:


- Generate a FEM file for the geoemtry

- Mesh the body with a triangular surface mesh. You can control the mesh size and if you turn the "Curvature Based Size Variation" to 0.0, you will get a quite homogenious mesh.

- Export the Mesh


The export cannot be done to STL directly. The following could be done:

- Export a JT File (Export -> JT). This JT File can be opened in Modeling and exported as STL from there. The facets will be like the Mesh in FEM and you should be able to use it in your application.


If you want to have more automation and if you are able to work with NX Open you could:

- Automate the above import/export process using NXOpen to have a single Export Step

- Export a Nastran Bulk file (File->Export->SImulation in FEM File) and maybe you find a Nastran 2 STL translator

- Write an NX Open Script to export the Nastran Surface Elements as STL Facets


I hope that helps



Re: STL file with equilateral triangles

Hello Boris,

Tanks fort this detailed answer.
I will try the manual export and give it to our simulation guys.