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Exporting from rhino to solidworks and prototyping(cutting on cnc 5 axis machine)

Question asked by Michael Mitford on Jun 21, 2014
Latest reply on Nov 18, 2014 by John Brock

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Hi guys, i have an issue where i have a model i created in rhino and tested it with the volume analytics and surface edges and naked edges and it all checks out ok. i want to import it into solidworks but when i do i have errors which take forever to heal. is there a specific way to do this and get best results? also this file will be cut cut on a cnc 5 axis machine so what format is best for this since my model is already watertight and all set to go from rhino 5. are files made in rhino good to go for cnc prototyping?

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Chris Dordoni Jun 21, 2014 9:59 PM
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Michael,

Rhino files can contain meshes as well as nurbs surfaces. Do you know what type of surfaces are in your file?

I don't know if SolidWorks will read the meshes in a Rhino file as I do not use that format. In general, SolidWorks can open only very small meshes as solids (15,000 or so triangles). Larger meshes can be opened as graphics bodies but are only useable as modeling references.

If you have all nurbs surfaces, SolidWorks should open your Rhino file as a 3DM, but you can try using STP as well.

Can you be more specific about the errors, or post the file?
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- Michael Mitford @ Chris Dordoni on Jun 22, 2014 5:31 PM
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  Hi Chris, the rhino file i have is a nurbs surface no meshes first i exported to a step file but it really takes some time to correct the errors, i tried what you suggested about opening 3dm files but it says no surface/solid found which is totall weired since the file is created in rhino and in the file properties its a closed polysurface.
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  - Chris Dordoni @ Michael Mitford on Jun 22, 2014 6:45 PM
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    How did you create the model in Rhino ... did you draw the curves in Rhino and use the Rhino's surfacing tools? If you did, you should at least have nurbs surfaces, if not a nurbs solid.
    
    The one thing that leads me to believe you actually have a mesh instead of nurbs is that Rhino is calling it a polysurface. This usually means polygons, which is the same thing as a mesh.
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    - Michael Mitford @ Chris Dordoni on Jun 22, 2014 7:19 PM
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      actually what i did was i first imported the cad file into rhino and then from that i used the linework to create a closed spline then extruded from those lines to create the solid i want. for some complex shapes i made the model in 3ds max, exported to autocad and converted to nurbs. then i exported it as a iges file which i imported in rhino then joined those surfaces. with the extruded models i have in rhino i used the usuall bollean tools to get the final model need. funny thing is when i do import a obj mesh file for example in rhino it does not look like a polysurface model instead like the original mesh and also rhino properties tell me also that it is indeed a mesh file and not a poly surface.
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      - Chris Dordoni @ Michael Mitford on Jun 22, 2014 7:35 PM
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        It sounds like parts of your object are a mesh and other parts are nurbs. Maybe polysurface in Rhino means a hybrid surface.
        
        If your file has more than 15,000 or so surfaces, SolidWorks will not be able to join them into a solid.
        
        Find out how many triangles were in the portion that you used 3dsMax for. If there are more than 15,000 triangle there, then that is the problem.
        
        The triangles in the mesh were probably converted into separate triangular nurbs surfaces in IGS, so you probably have way more than SolidWorks can handle to join into a solid or connected surface.
        
        If you have thousands of flat surfaces, putting a toolpath on them will be an issue. Though your model may be in a nurbs format, the machining service will likely refuse it.
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        Michael Mitford @ Chris Dordoni on Jun 22, 2014 7:42 PM
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        Idk at this point and no the model exported from 3ds max where actually very simple with not many triangular faces involved, each object couldnt have more than 100.
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        Michael Mitford @ Michael Mitford on Jun 22, 2014 7:53 PM
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        i tried importing a few of the pieces exported from autocad into solidworks and it came in with few issues with faces and i repaired them successfully then saved the solidworks file as a part file then imported them in rhino and it imported as a polysurface, also i created an object from scratch in solidworks then imported in rhino and everytime i imported that solid it imports as a poly surface so it seems it deals with nurbs objects as polysurface and mesh as meshes because as i can see you cannot combine meshes and surface objects so a poly surface cannot be made of meshes
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        Chris Dordoni @ Michael Mitford on Jun 22, 2014 8:17 PM
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        Michael,
        
        Are you able to get the surfaces you repaired in SolidWorks, into Rhino with the other surfaces, and then back into SolidWorks?
        
        If you used subdivision in 3dsMax, your triangle count would go up. So if you initially had a few hundred triangles, that could easily become thousands and you might not be aware of it unless 3dsMax has a way of showing you how many triangles are in the subd surface.
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        Michael Mitford @ Chris Dordoni on Jun 23, 2014 3:01 AM
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        Chris,
        
        No i didnt use subdivision in 3ds max and yes it does have a way to show you tri count in design for video games also so i know 3ds max very well. i just exported enough geometry so when i take it into autocad and convert it into nurbs then it automatically gives me the smoothing i like.
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        Chris Dordoni @ Michael Mitford on Jun 23, 2014 9:31 AM
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        So the problem is most likely not the number of surfaces.
        
        You were able to repair the surfaces in SolidWorks and export them. Were you able to import them into Rhino to combine with the rest of your work?
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John Brock Nov 18, 2014 2:15 PM
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Hi
If you can post your file, I'm happy to look at it in Rhino to make double sure it's OK for export.

Generally this means setting your Rhino tolerance settings appropriate for SolidWorks. An Absolute modeling tolerance of 0.0005" or 0.01 mm, and an angle tolerance of 0.5º. Never use the JoinEdge command in Rhino as it overrides the tolerance.

Run SelBadObjects to make sure all the data structures are clean.

Use the What command to make sure you are exporting "Closed, Solid, Polysurfaces". A good double check is to Explode your Solids in Rhino and Join them again making sure you get closed polysurfaces again with no naked (unjoined) edges.

John Brock
Rhinoceros
Seattle
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Exporting from rhino to solidworks and prototyping(cutting on cnc 5 axis machine)

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