Cura adding skin in voids where it shouldn't

[peterlanoie 1]

I have this simple tube with a chamfer on it:

 

In Cura... prepare view looks fine.

 

 

But when I slice it, Cura is adding a full skin in the opening on the first few layers (the model in question is on the right of the next picture). It seems the extra skin is on the layers up to the depth of the chamfer. Interestingly, another similar tube (on the left) also with a chamfer does NOT get the superfluous skin, so I think I can rule out slicer settings.

 

 

If I  use the same model but without the chamfer as seen here:

 

 

and then slice without changing any slicer settings, it's fine (still the model on the right):

 

 

For more analysis... here are the 2 samples as seen in Windows 3d viewer. First no chamfer:
 

 

And WITH the chamfer. The STL doesn't seem to have anything that would suggest the need for the skin.
 

 

I have looked through all the slicer settings, re-exported the STL from the model, re-added the chamfer, but with no resulting change.

I have done several models previously with chamfers with no issue. I also did some test samples of this same tube, but only a short section of it (it was a hollow tube, open on both ends) and Cura did NOT add this extra skin.

Since perhaps it's relevant, the top of the tube is closed off, but has a 45 degree inner chamfer so it works without supports. Of note also, the second one that slices without the extra skin in the slice preview images above is basically the same geometry as the problem one with a closed off end.

 

I've run out of ideas. Hoping someone here has seen this problem before.

[GregValiant 1,251]

If you can post the STL file somebody can take a look.  I would guess that the surface of the chamfer is flipped the wrong way and it is indicating to Cura that it is an inside surface.  You can upload the STL to Service.Netfabb.com.  You will need to sign up for a free account.  It's a pretty good repair utility and takes but a minute and your file is ready to download.

[peterlanoie 1]

@GregValiant Thank you so much!! Clearly I'd been staring at the computer too long. I didn't notice that the bottom face of this piece was indeed a flipped face. I reversed it, recut the chamfer and it slices correctly. I'm irritated with myself that I didn't catch that. Thank you for the second set of "eyes".

 

Cheers!

-Peter

 

 

Edited April 2, 2021 by peterlanoie