Importing and manipulating 3D scans.

max_thelion

Thanks in advance for any advice on this:
I have a medical problem that I'm trying to solve with a device that exists elsewhere but is not available in my country, so I need to produce something that does the same job. The device is a gumshield that features an air duct from an inlet at the front, to outlets at the rear end of the jaw, to route air around an enlarged tongue to facilitate breathing whilst asleep.
I have a basic appliance that does not have the air duct and I also have a physical model of my teeth from impressions that were taken.

I'm trying to 3d scan, using photogrametry, and then edit the model to add the duscting, and then to 3d print the new appliance. I'm able to 3D scan into Meshroom, then decimate the scan to 5000 facets in Meshlab and export the scan as an STL or an OBJ. I can then get the object into Onshape but it shows as a surface rather than a solid, so I can't edit it as you would a solid. I've tried importing into Solidworks(which will make it a solid) and then into Onshape as a Solidworks file, but Onshape hangs when trying to import it.

Can anyone offer any advice on how to make these scans solid and editable in Onshape (or Solidworks, but my preference is for Onshape)

tim_hess427

When you import a scan into Onshape, it'll come in as "mesh" file. Onshape doesn't have the ability to edit mesh files. What you can do, however, is use the mesh as a reference and re-create the geometry using the onshape tools (sketch, extrude, revolve, etc..) to create the solid shape that you need. 

This thread has an example of someone designing parts around 3D scans to make a motorcycle part.  Here's a video explaining the process as well - Rusty Shed.

max_thelion

Thanks, I'm aware of that method, but it's not really any use for the very complex organic geometry of a set of human teeth. I'm aware this is a difficult problem to solve, but it must be possible (even if I have to go outside OS) as there are plenty of 3D printed custom medical devices out there.

Ideally I would turn the 3D scan into a 3D thickened solid, which I would then import and merge with a more conventionally created lower section created within Onshape.

tim_hess427

That makes sense. It sounds like Onshape is not the right tool for the job. I was looking into other options a while back and didn't find much that was inexpensive or free.

Rather than trying to import a mesh body into onshape, you'd probably be better off exporting the lower section from Onshape (as .obj or .stl) and doing the boolean operation in your mesh editing software.

You might try using meshmixer. I believe it's still free, but I don't know if it would be any better than Meshlab.

steve_shubin

@max_thelion

You mentioned how you were able to convert your scan into a solid using SolidWorks. I wonder if exporting that solid out of SolidWorks in a different file format such as SAT, and then importing or opening that up
in Onshape would help ?

max_thelion

Hi Steve, yes I've converted it into a solid using Solidworks and saved as the native SW format, .SLDPRT. This imports and translates in OS successfully, but in OS I can't edit it because OS appears not to be able to cope with the triangular mesh. 

I really like Tim's idea of using the mesh editing software to add a lower section created in OS as a workaround, though my skills in mesh editors such as Meshlab, Meshmixer and Blender are rudimentary.

Also, I have found that Fusion 360 appears to have functionality that supports mesh editing and turning the mesh into a Parametric with quads rather than triangles, which may then be edited more conventionally (in a CAD sense). I just got out of Fusion though after their crappy treatment of their hobbyist users, and really want to stay loyal to OS because of their far better treatment of their userbase.

max_thelion

For those that are interested in this issue - I have reinstalled Fusion360, and following the great advice given above, went back to Meshmixer, took an open (as opposed to closed/solid) version of my 3d scan mesh, and did some basic planar trimming, then used the extrude function in Meshmixer to give the mesh thickness. I was then able to import as a mesh into F360 and convert from a mesh into a Brep (not sure what that's short for) and then further edit the thickened mesh in conventional CAD ways, adding air ducting by extruding from a sketch plane up to the complex surface of the original thickened mesh. 

I'm still having problems with extruding a cut into a surface that combines the mesh geometry and a curved surface added via normal CAD means, but that's one for an F360 forum rather than this one.

I'm still an OS devotee, and I really hope the package develops in a direction that will support working with meshes. Once this task is over I'll be dumping F360 and reverting to OS for everything else I do that doesn't involve complex organic meshes.