Errored surfaces.

The left part of the first picture is giving an inverted circle when lying flat, but the right part of the first picture is how it should be. Same STL for both slice orientations. I tried toggling union overlapping volumes with no luck. I tried to invert face normals with Blender with no luck either.

This gives the error: The highlighted areas indicate either missing or extraneous surfaces. Fix your model and open it again into Cura.

Here is a link to the model, this is another link.

I have tried

  • manually repairing faces with Blender,
  • repairing the model with Autocad Meshmixer

both without success.

  • 1
    $\begingroup$ Cura is explicit on your model, it is broken. A valuable tool was the online Netfabb STL repair service, this now appears to be integrated in Fusion 360. $\endgroup$
    – 0scar
    Mar 3, 2022 at 12:12
  • $\begingroup$ That's a model error - the bores have inverted faces. $\endgroup$
    – Trish
    Mar 3, 2022 at 22:13
  • $\begingroup$ Windows 10 3DBuilder wipes out the counterbores and turns the surface into a flat area, as does Meshmixer. The creator (you?) created a non-manifold object that resists repair. $\endgroup$
    – fred_dot_u
    Mar 3, 2022 at 23:22

1 Answer 1


I've discovered via Meshmixer that there are duplicate cylinders for the counterbores. I selected "separate shells" which generated two sets of cylinders in the Objects Browser as well as the main body. Selecting each flawed entry in the browser left behind the main body, which is manifold and passes the Analysis/Inspector test sequence.

You can have the repaired file from my Dropbox, public folder, or you can perform the process on your own. If you select the former, please let me know when it's retrieved, as I endeavor to keep my space in the free category on Dropbox.


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