Bevel gears 3D model Goal : create a pair of bevel gears for 90 degrees angle axles.

Context : the gears are designed with an OpenSCAD library (https://www.thingiverse.com/thing:1604369, function 'pfeilkegelradpaar'), then I try to modify them using TinkerCAD.

The problem : When printing the STL exported from OpenSCAD, everything seems fine. But when I import the STL in TinkerCAD, there is a separation where the angle changes, and I cannot seem to find a configuration that works.



Also, when previewing with Cura (tried with the older v14 as well as the latest v4), I get the same behavior : the exported STL creates a solid object, while the STL from TinkerCAD (even if not modified, just imported and exported) has a 'gap' of about 8 layers.



And, of course, everything fails afterwards.

Any help is appreciated. Thanks in advance.
I don't know how to explain how the problem is occurring with the STL post-processing tools you are using.  

Try loading the STL directly into a slicer and view the result, then slice and view the toolpath.  It is always helpful to eliminate steps in an attempt to narrow down where the problem is generated.

Were I to try to patch the OpenSCAD model, I would create a hub component that overlays where the crack is found.  This would be small cylinder with a hole that overlays the hub.

I have had success adding elements and holes to existing OpenSCAD models and imported STL files using OpenSCAD.