Hollow print intent not honoured

[PaulNaude01 0]

I wanted to print a hollow ball (from a solid STL model of a sphere) by using 0% infill and no supports, but in the preview I see a very strange few layers on the bottom inside that I can't explain and won't be able to remove afterwards.

See image attached.

Any idea what this can be?

 

I installed the new version 4.7.0

Faceted ball.stl

[GregValiant 1,251]

The stl file was generated as a low resolution file.  The facets would be much finer on a high resolution file.  Then your slicing pattern would be much closer to emulating a circle than what you have now which is that every layer essentially describes a square.

I'm attaching a project file with your low res ball and a 35mm ball that I generated as a high resolution stl file.  Open the file and slice it and then preview the first few layers.

Big Balls.3mf

[PaulNaude01 0]

Hi @GregValiant, thanks for your reply but no, the facets are intended and not the problem that I am describing.

In the image, both the faceted and spherical balls show the same problem: there are additional layers on the insides of the balls, but only at the bottom. With the chosen sizes and settings, both balls are suppose to have wall thicknesses of only 2 layers, but for some reason both show additional layers. In the new attached image, I  hope this detail is a bit clearer. I also attached the project file. The spherical file is very large because of its high resolution so I did not attach it, but it's just a solid sphere. 

WDI3M_balls.3mf

Edited August 28, 2020 by PaulNaude01

[PaulNaude01 0]

Hi @GregValiant, I now found the the problem, I missed one default setting to change for this case: The number of bottom layers!

 

[GregValiant 1,251]

Nice job catching it.  I looked at bottom layers but I already had it set to .8mm which was the wall thickness I was using.  That's likely why I wasn't seeing a problem.