thin walls not always filled with single extrusions

[blackbird2016]

I may have discovered an other one here.
Sometimes thin walls are not filled as expected by single extrusion.
No matter how high I set the infill there is just nothing in between inner and outer perimeter.
Playing with nozzle sizes (which I do not want) eventually I will at least get a solid infill at the top.

Only if setting 3 perimeters I will get a single extrusion infill.

Same goes for the cargo hold at the benchy where the gap is clearly visible in both the preview and the printed model.
Only with 3 perimeters it will get closed by single extrusion, but then I will have a benchy/object with 3 shells everywhere,
at least if not splitted in different processes.

I happily would provide a factoryfile which is already on my desktop.
But still I can not attach a 6mb file but getting an error for file being to big.

[blackbird2016]

With a single wall the factory file got small enough to be attached.

Picture 1 is with 0,44 extrusion width (S3D auto determines 0,48!).
No matter what infill-settings, bottom and top layers are missing. No fill / infill.
Gaps are clearly visible in both the preview as well as in the actual print.

Picture 2 is with 0,4 extrusion width
Top and bottom layers are present but with diagonal top-layer-lines whereas this is the perfect case for single-extrusion fill.
Infill is present as a line.

Picture 3 is with 0,44 extrusion width but 3 shells.
Single extrusion fill present but over the complete height.
Can be used as a workaround but not suitable for all models
if you do not want to have 3 shells everywhere. (printing time)

[blackbird2016]

And here is the factory file

[blackbird2016]

Bump...

[S3D-Alex]

Apologies for taking a couple days blackbird. Thank you for documenting this so well and bringing it up. This is sort of a grey area though as there are multiple different ways to close this gap.

When using a .44mm extrusion width and 2 perimeters you will be left with .28mm of space in the middle of your 2mm wide part. This is too small to be filled with your current infill overlap setting. It would need to be a larger number to allow the software to fill in this section.

If, alternatively, you wanted this filled with Single Extrusion Fill then you would have to use 3 perimeters in this case. Single Extrusion Fill does not replace Infill or Solid Layers but replaces perimeters. With no perimeter to replace there will be no single extrusion.

[dkightley]

It looks to me that the "Thin wall" behaviour is not being triggered because the shape is not being identified as being "thin" as the maximum number of shells (in your case, two) can be placed....and what you're getting is the normal infill behaviour.

Upping the number of shells to three invokes the "Thin wall" behaviour as the third shell cannot be placed.

You're bound to now say that this is a bug....but look it logically. What is the difference between a "thin wall" and "not a thin wall"? There has to be something that delineates between the two. In this case, S3D have chosen not reaching the maximum number of shells as the defining factor....which makes sense to me.

EDIT....just beaten to it by Alex effectively saying the same thing, but more of a "customer" explanation than my programmer's view!

[blackbird2016]

Thank you both S3D-Alex and dkightley.
You are certainly right, I couldn´t explain how I missed the outline overlap as reason for this.
Increasing the overlap certainly solved this problem for me.
Just an idea...
Why not making this a feature?
Where there is need for 40%-50% outline overlap for infill why not just give the option to use single extrusion instead.
Should be "easy" to programm, single extrusion already exists, where there is a gap, say nozzle zize or smaller,
let the software treat the number of walls where there are solid layers determined as "infinite" and force single extrusion fill.
Makes a nice surface and faster printing speed...

EDIT

If, alternatively, you wanted this filled with Single Extrusion Fill then you would have to use 3 perimeters in this case. Single Extrusion Fill does not replace Infill or Solid Layers but replaces perimeters. With no perimeter to replace there will be no single extrusion.

That obviously isn´t quite right..

Take the factory file from above and increase infill overlap from 20% up to 25% and..... Voila!
S3D is exactly doing that! Closing the top layers with single extrusion.
Easy solution to play with the infill overlap, but that a setting I hadn´t had to mess around until now...
Thank you both for leading me the right way.

[dkightley]

Take the factory file from above and increase infill overlap from 20% up to 25% and..... Voila!
S3D is exactly doing that! Closing the top layers with single extrusion.

Just for correctness......do that and you get a very shallow zig-zag infill created by the infill generator...NOT a straight single line created by the "thin wall" behaviour.

[blackbird2016]

Aaaawwwww.
You got me. Zooming in it indeed is a zig-ag line.
No matter what, problem solved by increasing the outline overlap. (and that not by much)
Suggestion for improvement made.
Thanks again for all your help.

[PaV]

I'm very confused, and I think you can work over the problem. With an outer layer, the dynamic fill is correct, but when there are two layers there is no fill and there are serious gaps. Increasing overlap does not affect print well. The material is a lot and the print is ugly.
Give me advice, what settings should I use to fix the problem?

https://youtu.be/KCf4TW_r7sg