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?

[hodshon]

Martin,

I just tried your technique.

It worked great!

thanks

fred

[hodshon]

FreeCAD STL to STEP worked PERFECTLY into Creo 3/4 !!!

Thank you.

[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.

[tkassenaar]

MeshLab cannot convert STL to IGES or STEP. It can only repair, smooth and simplify mesh models. MeshLab has no user manual so you have to Google a lot to find out how to use it. The user interface is discouraging. I have used it to reduce the mesh count, and to smooth surfaces with the not so obvious command Filters/Remeshing, Simplification and Reconstruction/Surface Reconstruction:Poisson. MeshLab is a tool for mesh guru's which most of us are not.

Resurf has software to convert STL to IGES, for instance "Automatic surface from mesh". I tried it on the scanned model of a human heart but the result was rather disappointing.

[pimm]

Thank you Tom.

We still haven't figured out the best way to get our large patchy STL to surfaces but if we do find a way perhaps Mesh Lab would be able to clean this up some.

It really is disappointing that STL conversion isn't a base tool with Creo.  This is a tool included in our much cheaper software and also in freeware such as FreeCAD.

[rthapa]

Hello Joseph,

I have been working with similar projects. Converting scanned hand .stl which is surface model into solid 3D printable .stl file. Were you able to fix this? Can you share with me if any?

It would be of great help!

Thanks!

[Jose_Costa]

I've never done this but some videos on youtube show some guys doing this with the Restyle module:

Also, this can done "automatic" just saving a Shrinkwrap file, but, it produces a lot of tiny surfaces:

[spicer_g]

You can also 'save a copy' and select Shrinkwrap from your pull down. When the dialogue box comes up select 'Faceted Solid' (You may need to uncheck some boxes i.e. 'fill holes') and set your quality level 0-10 and click OK. It will produce a solid part.