Unexpected holes in shell (Cura 3.2.1)

[dhscord 0]

I get some unexpected holes in my shell in Cura 3.2.1. Anyone got any thoughts? I have exported the shell from Cura as STL and checked it. Cura is definitely recognising it as solid so must be something happening in the slicing? I'm guessing some weird combination of settings...

 

Attached images are of shell view and sliced view (which shows the missing shell [top surface] in the middle of the "6" and "4"...

Edited December 19, 2018 by dhscord

[burtoogle 513]

It could well be a problem with the model, can you post the model file?

[gr5 2,167]

I think that behavior is mostly expected.  I don't understand why the missing surface doesn't match the 6 and the 4 more perfectly but the "top layer skin" shouldn't appear and those spots where the 6&4 are because - well - that's not a top surface.

[kmanstudios 1,120]

The last time I saw something like this, it was that the person who was slicing did not state that they were slicing for a non-UM printer. I did notice it a bit later way deep in the screen caps. But, it would make things easier if it was mentioned as to what printer it is aimed at without digging through teeny graphics :).

 

Edit: And I do agree with @gr5about the lead in to the raised lettering. If the model is not parts combined objects (base, and separate numbers), but rather a contiguous shell, then the structure would generally just be infill up to the next level of surfaces.

Edited April 21, 2018 by kmanstudios

[gr5 2,167]

58 minutes ago, kmanstudios said:

then the structure would generally just be infill

I think the next layer up probably had shell around the 6 & 4.

[kmanstudios 1,120]

9 minutes ago, gr5 said:

I think the next layer up probably had shell around the 6 & 4.

I agree. I have noticed the same thing when I have a perfect shelled/solid objects with such features rather than 'stacked objects.'

[dhscord 0]

 

17 hours ago, smartavionics said:

It could well be a problem with the model, can you post the model file?

 

I've uploaded the STL... I have checked it in multiple apps and it seems to be interpreted correctly.

 

16 hours ago, gr5 said:

I think that behavior is mostly expected.  I don't understand why the missing surface doesn't match the 6 and the 4 more perfectly but the "top layer skin" shouldn't appear and those spots where the 6&4 are because - well - that's not a top surface.

 

I don't understand what you mean by "not a top" surface... I have included a screenshot from Cura 15 which gets the shell correct. While the 6 itself is not a top surface, the hole in the 6 IS a top surface. In fact, Cura knows it is because, if I enable ironing, it tries to iron that part but there is no shell to iron! I've included a sceengrab of the ironing layer with ironing enabled.

 

14 hours ago, kmanstudios said:

The last time I saw something like this, it was that the person who was slicing did not state that they were slicing for a non-UM printer. I did notice it a bit later way deep in the screen caps. But, it would make things easier if it was mentioned as to what printer it is aimed at without digging through teeny graphics :).

 

Edit: And I do agree with @gr5about the lead in to the raised lettering. If the model is not parts combined objects (base, and separate numbers), but rather a contiguous shell, then the structure would generally just be infill up to the next level of surfaces.

 

I am indeed slicing for a non-UM printer. Does that matter? I am slicing for an Anet A8. The STL is a contiguous shell but, as stated above, their should be some horizontal shell in the hole inside the 6. Instead, Cura just leaves this open (and you can see the infill). I've also included close-up of the printed 6 which has the shell inside the 6 missing. You can indeed see directly into the solid object.

 

UPDATE: Well, I've selected a different print profile and Cura get's it right! So, I guess one of my settings in my custom profile is causing this... any ideas which one? Can I send my my settings through?

 

I'll try to recreate the profile from the default 0.2mm layer height profile and see where it goes wrong,

 

 

 

custom-hayesmaker-solid.stl

[dhscord 0]

SOLVED: "Minimum Infill Area" was set to 10mm2. Changed to 0mm2 and fixed.

[gr5 2,167]

There was a basic misunderstanding of the word "shell".  We think of parts as 3 dimensional but the slicer mostly thinks of just slices where "shell" is the pass or passes that separate inside from outside HORIZONTALLY.  What you point out I don't call "shell" but I consider to be a "top layer".  I think Cura terminology is the same.

 

Anyway I'm glad you figured it out - this is useful for the future if someone else has the same problem.

[burtoogle 513]

The Minimum Infill Area was originally intended to stop little areas of infill appearing within an area of skin. It worked OK. More recently, this setting seems to have changed its behaviour and now it seems to do nothing useful and, indeed, tends to break things by making unwanted holes in the skin layers. EDIT - actually, I'm not sure that the behaviour really has changed but it does seem to conflict with with the skin shrink/expand feature.

 

This setting is now redundant anyway as the settings for shrinking/expanding skin regions provide better control. I recommend setting the min infill area to zero and ignoring it.

Edited April 22, 2018 by burtoogle

[dhscord 0]

6 hours ago, gr5 said:

There was a basic misunderstanding of the word "shell".  We think of parts as 3 dimensional but the slicer mostly thinks of just slices where "shell" is the pass or passes that separate inside from outside HORIZONTALLY.  What you point out I don't call "shell" but I consider to be a "top layer".  I think Cura terminology is the same.

 

Anyway I'm glad you figured it out - this is useful for the future if someone else has the same problem.

 

Yeah, sorry about that. When modelling objects I think of the shell as the external surface of the object.

 

6 hours ago, smartavionics said:

The Minimum Infill Area was originally intended to stop little areas of infill appearing within an area of skin. It worked OK. More recently, this setting seems to have changed its behaviour and now it seems to do nothing useful and, indeed, tends to break things by making unwanted holes in the skin layers. EDIT - actually, I'm not sure that the behaviour really has changed but it does seem to conflict with with the skin shrink/expand feature.

 

This setting is now redundant anyway as the settings for shrinking/expanding skin regions provide better control. I recommend setting the min infill area to zero and ignoring it.

 

Not sure how or when I changed that setting... I have been trying to solve issues with small gaps in prints (I print quite small objects) and changed a bunch of things to fix that. Anyway, I think I have honed my settings quite nicely. And now I am also signed up to this forum so that's a bonus too!