Cura Filling in the bottom layer?

[Dacraun 0]

FYI, I'm using Cura 4.12.0.

 

I've never had an issue while slicing before where I stood as clueless as now...
I've recently downloaded a lovely cat-shaped cookie-cutter from thingiverse and endeavored to print it.

However, for some obscure reason, Cura seems hellbent on filling in the entire bottom layer with filament, where it should be just an outline.

I've printed circles and cylinders and various other hollow shapes before, without a hint of an issue, but this somehow eludes me.

 

It looks hollow on the preview, it looks hollow if I try to open the STL on solidworks, but as soon as it's sliced... Look for yourself, I've attached pictures.

 

 

I've tried using some of the default slicing settings, thinking it might be something I changed by accident, but the default cura settings result in the same thing...

I've attached the STL file as well, in case you want to give it a try on your own.

 

Ausstecher_katze.stl

[ahoeben 1,767]

The problem is that the model has conflicting "normals". The top of the model (the "walls") has the normals facing outward, the bottom (the modeled "brim") has the normals facing inward. This confuses Cura. You can sort of see this because the top section has a red "overhang" indication on top, instead of on the bottom.

 

The easiest fix is to download the Mesh Tools plugin from the marketplace (if you don't have it already), select the model and right-click. Then select Mesh Tools -> Fix model normals. After that the model will slice properly.

[ahoeben 1,767]

If you look carefully at this image (that you posted yourself), you can also see that there is an issue with the normals. Looking at the small section between the tail and the head of the cat from below, you see that you are looking "through" the wall as if it did not exist, and then instead you see the insides of the wall. It looks asif you are staring into a box, as it were. This is due to what is called "backface culling"; the application that made this image did not draw the "back" of the faces. Since all the faces are "inverted", only the "insides" of the walls get drawn.

[Dacraun 0]

That did the trick.
I didn't really flinch at the strange representation in SW, since it sometimes loads models that actually slice correctly in a strange manner. But the Mesh Tools extention with 'Fix Normals' did indeed fix the stl model for slicing.

So you're definitely right.

 

Thanks a lot for your help. ❤️