Help - No naked edges but can't close polysurface


I’m currently trying to create a close to replica model of a dragonfly wing for 3D printing and having problems with creating a closed polysurface. Admittedly my model isn’t wonderful, lots of overlapping parts etc. but its for my masters thesis and I’m running out of time, so starting from scratch really isn’t an ideal option. I’ve tried converting it to a mesh but when I sent the STL file through for printing it turned out the file was just a shell, so I’ve gone back to trying to fix the ‘solid’ model.

I’ve fixed all my naked edges but the main part still shows as an open polysurface, any ideas for why this is or how I fix it?

Any advice would be much appreciated
Thank you,

If you can, please post the model. If you run the selClosedPolySrf on your file, is the model selected? If it isn’t, does DupBorder give you a or multiple curves?

I don’t think I can upload it unfortunately. Model isn’t selected when I run selClosedPolySrf and DupBorder doesn’t highlight anything either.

Thank you though!

That’s all an .stl ever is - just a shell - there’s nothing “inside”. The shell needs to be completely closed for 3D printing is all. With some 3D printing systems, there can be overlapping parts if they are all closed, the software will merge them. With others you will need to merge all the volumes into one closed shell first before running it through the printing software.

If you are sure there are no naked edges and it still doesn’t say closed, then you probably have a non-manifold area somewhere in the model. If you type SelNonManifold, does the model select? Also, you can go to Analyze>Edge tools> Show edges and check Non-Manifold edges and see if any show up…


1 Like

Yes there are a few, I’ve just exploded my model in an effort to try and fix them but that also means re-joining all my edges. Is the right thing to do?

  • Bridie

Fixing non-manifold edges can be a bit tricky. I would not explode the model at first. Find the edges with the edge tools, then use ExtractSrf extract the surfaces around the non-manifold edge. (Non-manifold edges are edges that have more than two surfaces attached to the same edge, like a “T” joint - a structure that is “legal” for some things but not supposed to happen in Rhino normally - it does however… Non-manifold edges are stictly “illegal” for 3D printing, as there always needs to be a continuous closed shell with no branching).

If you are lucky, just one of the extracted surfaces will be superfluous, and you can delete it and join stuff back up again. However, often it will also require some minor fixing of the surrounding surfaces to get everything to join up closed and manifold. There are unfortunately no hard-and-fast rules for this stuff.


Super I now have no open polysurfaces!