Importing .stl files into Creo Parametric 3.0 and then converting to solid.

[ptc-4680137]

Hi there,

The context of my question is this:

I have an existing model model on OpenVSP, an aerospace prototyping software. I have exported a mesh from Openvsp into a .stl file.

I imported the .stl file into Creo Parametric 3.0, which resulted in a facet feature.

Despite being a facet feature, when I go Analysis>mass properties>preview, It gives me a volume and a mass. I don't understand this as I thought I just imported a "mesh" type file which does not have an assigned volume. The only explanation I can think of is that Creo automatically assigned a volume when I imported the file. How do I fix this?

My goal is to add a specific thickness to the surfaces and assign densities for a mass model.

To do this, I assume I have to somehow convert the facet into a solid, which I'm not sure is possible or not?

Thank you,

Joe

[dschenken]

A typical stl file will have facets that enclose a volume. Creo used that to solidify it for you; it would not report a mass for a surface model.

.

You might be able to use the Shell operator to create the thickness changes you want. Alternatively mesh-based editors like Blender allow thickening of mesh based geometry.

[DavorGranic]

Or you use restyle to turn it into proper surfaces and then solidify or thicken. This is actualy longer way to your goal.

[ptc-4680137]

Thanks for the replies. Restyle does not seem to work. As in, when I click on it, nothing actually happens The shell operator does not work either.

I will try to use blender to create the thickness. If I import a .stl file into blender, will I get the same issue as when I import it into creo?

[MartinHanak · Accepted solution]

Joseph,

if you have time to experiment, you can use FreeCAD:

1. open STL
2. change working mode to Part
3. click Part menu and apply Create shape from mesh command
4. select blue solid in the left pane
5. use File > Export to save IGES or STEP file

You can open IGES or STEP file in Creo Parametric. This way you will get standard solid/surface model...

Martin Hanak

[ptc-4680137]

I will try this. This sounds like it will work, thank you!!

[tkassenaar]

FreeCAD works but the drawback is that the IGES- or STEP-model is still a facet model with flat, triangular, first degree NURBS surfaces. The end result is a model with just as many facets as the original model. It's completely identical in shape to the original. That's fine if you don't mind but if you want a smooth model with less surface patches this is not the way. I find this cheating. Adding wall thickness to such a model normally fails because mesh surfaces are noisy, not smooth. Especially scanned meshes.

Inventor has an add-in named Mesh Enabler which does the same but is limited to 5000 facets.

MeshLab is great open source to repair, smooth and simplify mesh models, especially from 3D scans.

Mesh to Single Nurbs from Resurf converts a mesh model to one single NURBS but only for not-too-complex surfaces of course.

Rhino has an option to convert a mesh to real, smooth, curved NURBS surfaces. But it involves hand editing. It's a bit like the DataDoctor in Creo.

Materialise claims to have conversion software called 3-matic but I have not tried it and they are foggy about downloading and using it. I guess that hand editing of the mesh is involved.

Hey, where are your mesh-to-NURBS options PTC?

[pimm]

We are really getting stuck with this.

Of course we can bring an STL into Creo, but we haven't been able to turn this model into anything usable.

We tried the FreeCAD option, but perhaps the STL scan is too large.  Even though FreeCAD makes the export it won't import into Creo or our other CAD system.

This is an area that more and more we are needing to find a no cost added way of converting an STL to something usable.

[tkassenaar]

Try to reduce the number of polygons of your scanned STL with MeshLab

Polygon Reduction with Meshlab - Shapeways

[pimm]

Within our Polyworks software we can reduce the size of the STL.  We just are having difficulty in converting this to usable CAD data.

I did download and looked at the MeshLab application.  I didn't see any option to convert to IGES or STEP surfaces.

It wasn't evident what I could do with the STL model within MeshLab.  It would be nice if it could remove the STL faceting, but it still wouldn't solve the conversion to surfaces issue.