Converting NAS file into STL, OB or ... 1

[VincentDillen]

Dear all,

I have a 3D model created in NASTRAN. The file extension is .nas . I need to import this model into another software (not a kind of FEM packages) for further processing. It suppports OBJ, STL and some other formats but not nas. Now I need to convert this file (mesh) into anyother formats, but how? Can anybody kindly direct me?

Best regards,

Sean

 

[BlasMolero]

Dear Sean,
You can use FEMAP pre&postprocessor to import the NASTRAN model, and then to export as STL.

Writing Stereolithography Files (STL)
FEMAP can also write Stereolithography files as well. FEMAP will ask you to select the elements to be translated. You will usually want to pick plane element types for this command, solids may be selected as well.. If you have quadrilateral plane elements, FEMAP will still write the triangular facets by first splitting these quads. This splitting procedure does not modify the elements themselves. FEMAP simply writes the triangular results to the STL file. If you choose solid elements, FEMAP will write each face as a triangular facet, splitting quadrilateral faces when required. If any plane elements are coincident with the face of solid elements, only one of these faces will be exported. Any line elements that are chosen in this procedure are simply ignored.

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/

 

[VincentDillen]

Many thanks Blas.
But just a quick question (maybe a stupid one, becuase I'm new in this area):when you say splitting, it means that I can select the elements I want to be translated to tirangulars or whatever i want?
Sorry, I don't even know does my question make sense or not.

Sean

 

[BlasMolero]

Dear Sean,

The facets in the StereoLithography file (*.stl) only support triangular faces, then this is the reason why any quadrilateral face element (say CQUAD4, CHEXA, etc ..) is splitted in two triangles, only for export, the FEMAP model remains unchanged.

Please note the main TYPICAL use of the STL command in FEMAP is reversed, is just to IMPORT a STL files: FEMAP IS ABLE TO CONVERT A STL FILE IN A FINITE ELEMENT MODEL!!. In addition to just translating the triangular facets, however, FEMAP can automatically merge all coincident points and split any facets that are necessary to eliminate free edges in the mesh. The options on this dialog box control merging, definition of short edges, as well as closing of gaps. This results in a valid finite element mesh, although typically with very bad aspect ratio elements. The facets can be remeshed with the Mesh, Remesh commands.

The following picture shows the sequence to follow:
1.- Typical look of a native STL CAD file, a disaster!!.
2.- The look of STL file imported in FEMAP after using command "Mesh > Remesh > Convert Facets" that lets you convert triangular facets for displaying graphics into triangular finite elements, generating automatically elements from the part's facets.
3.- Using Remeshing command you can remesh regions to end with better shaped triangular elements -- impressing!!.

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/

 

[VincentDillen]

Dear Blas,

Thanks a lot for your explanations, they are really informative and helpful. It gave me a better overview on what's happening in data translating. Thanks again.

Best regards,

Sean