STL misshapen

When I export a file to STL, I’m getting some parts of the model badly misshapen. Everything looks great in 3DM, but the STL file bears no resemblance. The model pictured is a simple extrusion from surface created by offsetting a curve. The curves in small legs come out fine in STL, but the back corners get turned into weird angle.
Screen Shot 2020-06-30 at 4.56.45 PM

I’m working with Rhino 6 on a Mac Air. I haven’t had any trouble with previous files. But discovered an issue with a just completed model and decided to just start from scratch and having the same issues.

It appears my photos didn’t load, so trying again.

Try running DivideAlongCreases with SplitAtTangents=Yes on your surface model. Does the STL look any better after? If not, it could also be your STL export settings or the model size or it being very far from the origin…

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I get a “one object could not be divided” message.

Can you post the object here?

That’s what the images are of. What’s odd is that I have an identical piece that slips just outside this one (an inner and outer wall), created the same way and the stl. for it looks fine.

George Sebastian-Coleman

Yes, but nobody can check to find a reason/solution without having a Rhino file to look at.

Sorry, misunderstood your request. The upper shell is the one that turns out fine as an stl, the lower one is the one that produces the results shown above.
11’6".Tender.v3.3dm (3.7 MB)

Ouch, there are quite a few problems with that one, a number of non-tangent spots and some bad surfaces when I explode, rebuild edges and join… So I just extracted the outer profile, fixed that using clean lines and arc fillets, offset by 0.60 and re-extruded it the two profiles… Finally I used DivideAlongCreases > SplitAtTangents=Yes (don’t preselect the objects). I think it should make a good mesh (STL) now.

Tender-RevMSH.3dm (863.0 KB)

Thank you for the revision! Now I just need to figure out why it was so bad to start with.

George Sebastian-Coleman

Thanks, again, I just tried the DivideAlongCreases on the completed model without pre-selecting and it solved the issues that had me starting over. Much appreciated tip!

George Sebastian-Coleman