Extrude "To Next" Not Working

[Anonymous]

Hi, I am trying to organise a model for an L4-L5 segment of the spine. I obtained STL files of the L4 and L5 vertebrae from CT data, which I used Mesh Enabler to turn into composites, then Sculpt to turn into solids. In the model I now have two separate solid bodies (the two vertebrae), and I am trying to create the two vertebral end-plates as a third solid body.

I have obtained a cross-section of each vertebral body and scaled them down to 70%, and placed these sketches around 1mm offset from the bottom of L4 and top of L5 (and named them "L4 Endplate Sketch" and "L5 Endplate Sketch" respectively). I wish to extrude these sketches to conform with the shape of their corresponding vertebra using the "Extrude To Next" command and selecting "New Solid" to extrude them as separate solid bodies from the other two vertebrae. However, when I try this, the extrude fails.

I have no idea why this won't work, and I have tried as many setting combinations as I think may be causing the problem (extruding as the same solid body, using different termination bodies, etc.). Only when I extrude "by distance" there is no problem, but when I specifically try to extrude "To Next", it can't create the extrusion. I imagine this may be due to a problem with the solid bodies of the vertebrae which arose after converting from the STL file, but no other ideas. Just very unsure what to do next.

[JDMather]

Can you get a quad mesh rather than a triangular mesh?

[johnsonshiue]

Hi Samuel,

I don't believe Inventor is the right tool for this task. The issue here is that the mesh data is imprecise (approximation of the actual geometry), while Inventor is a precise modeler. Every vertex, edge, and face have to carry design intent. Each mesh element by itself is meaningless. Only the entire mesh model shows how the design would look like.

As a precise modeler, Inventor does not have extensive tools handling mesh. I suggest you look into Mesh Mixer or Netfabb.

Many thanks!

[Anonymous]

I don't think I can. The STL files I obtained were not generated by an algorithm I wrote unfortunately.

[Anonymous]

Ok that makes sense. I figured that was possibly the case. I am not very familiar with Mesh Mixer. For what reasons would you suggest this application?

[johnsonshiue · Accepted solution]

Hi Samuel,

Mesh Mixer and Netfabb are very good at mesh modeling. I think you find a mesh modeler to create or edit the mesh geometry. Inventor is not the right tool to do that at the moment.

Many thanks!

[Anonymous]

That was it! I just converted my file to a solid through Mesh Mixer and that fixed all of the issues I was having with Inventor when I re-imported the STL file. Thanks a lot. It's crazy that it was just a problematic mesh I was dealing with before. I suppose that some of the faces may have been intersecting, or something along those lines.