Input shape is null with imported STL

[KDM]

I was too lazy to make a thread, so I imported an old one I made in another software package. When I try to operation on it, for example, merging it with a cylinder "Bolt Internal," I'm told "Input shape is null."

Why is this shape null and how can I make it more than null, please?

Thanks as always!

[heda]

shape is null, because a mesh is a mesh, which is not the same as a brep (the "normal" fc shape).

in this case you don't want to make it a shape, you are better off learning how to do threads...

Snip macro screenshot-514bb5.png (4.16 KiB) Viewed 1141 times

the yellow/red are all points (from analyze mesh) that need fixing in the mesh for it to be usable as a geometry for anything else than looking at it...
just not worth it in this case.
badly formed stl's are utterly useless, maybe this one could be repaired by hand if one spent hours on it...

there is a tutorial on how to make threads, or take one from another model that you find online (in step format)...
or try ThreadProfile_Workbench

[adrianinsaval]

STL is terrible as exchange format, you should use it only where needed, use step whenever possible instead.
To answer the question, an STL is not an actual BREP shape (the kind of shape most parametric CAD use), it's just a mesh. In FreeCAD you would need to make a shape from the mesh and probably then a solid from the shape in order to make a boolean operation. I strongly advise against this approach as it would have terrible performance since instead of an actual thread you would have a lot of triangles that approximate it.
Either model the thread again in FreeCAD (recommended) or, assuming it is also a brep based CAD (if it's mesh based this would be useless), go back to whatever you used for it an export as step instead.

[KDM]

shape is null, because a mesh is a mesh, which is not the same as a brep (the "normal" fc shape).

I was rather hoping I could treat the completely closed mesh as a surface and make a solid. I thought it might be a shortcut.

in this case you don't want to make it a shape, you are better off learning how to do threads...

Quite correct. Just not last night!

there is a tutorial on how to make threads, or take one from another model that you find online (in step format)...

That'll be today's entertainment. Thank you.

[KDM]

STL is terrible as exchange format, you should use it only where needed, use step whenever possible instead.

Yep. Learning that!

To answer the question, an STL is not an actual BREP shape (the kind of shape most parametric CAD use), it's just a mesh. In FreeCAD you would need to make a shape from the mesh and probably then a solid from the shape in order to make a boolean operation. I strongly advise against this approach as it would have terrible performance since instead of an actual thread you would have a lot of triangles that approximate it.

I wasn't thinking of performance. I figured, the 3D printer slicer is going to approximate it to a bunch of flat ovoids made up of triangles, anyway, so didn't quite grasp what the big deal would be. I hear you, though: I would like the shape to perform when when being manipulated in FreeCAD, so I'm taking that on board.

Either model the thread again in FreeCAD (recommended) or, assuming it is also a brep based CAD (if it's mesh based this would be useless), go back to whatever you used for it an export as step instead.

Nah. I was previously working in Microsoft 3d Designer, and it looks like all the output formals are mesh types.

Today is "learn to make a thread" day!