Missing top layers in Cura

8

I've just tried to make some small labels with embossed lettering. Base is 1.5 mm, with letters and a perimeter protruding by another 1 mm. After printing, I realised that Cura is not giving me a top layer, all I get is an inner and outer wall for the perimeter and the lettering:

Screenshot showing missing infill in top layer

The base is OK, with 4 layers, but there is no infill at the top. Presumably there is a setting that I've missed (I can appreciate that maybe this is a detail to the slicing which is model dependant). Layers are 0.2 mm, top and bottom set to 4 layers.

I had walls set to 1.6 mm, (4 layers) and the wall features here are 1 mm (i.e. 2.5x the nozzle). The features are solid so far as I know, not drawn as a hollow.

I found a relevant bug for Cura: https://github.com/Ultimaker/Cura/issues/1303 (and I also understand a workaround now, just need to write up an answer).

Sean Houlihane

Posted 2016-12-02T10:17:43.533

Reputation: 3 622

1Did you activate "vase mode" or something similar? – Tom van der Zanden – 2016-12-02T22:41:30.430

Not seen any options looking like that. Other prints are OK, it's just narrow walls. – Sean Houlihane – 2016-12-03T00:00:46.527

Answers

2

What is happening here is that Cura is struggling with the quantised extrusion width. This behaviour can be improved in the slicer, they have a issue tracked here https://github.com/Ultimaker/Cura/issues/1303 and 2.4 beta has improved it.

There are some pictures in this answer which show how Cura 2.3 slices a rectangle of increasing width. I got nothing at the nozzle width, then a pair of overlapping lines up to twice the width (which I assume will be over-extruded due to the overlap). For anything wider than simply two sides, the result depends on the number of walls requested.

  • One wall results in 100% infill for small regions (regardless of the infill setting). This is good, but maybe 1 wall is not apropriate for the whole model.
  • Multiple walls seem to prevent the infill untill there is space for pairs of walls. So width of 3x nozzle has a gap. Small tweeks to the nozzle size can maybe push this quantisation point about, if 1 wall is not a good workaround.

For rectangular geometry, it's worth trying to quantize small parts in 0.8mm increments. For curves, setting 1 wall shell might be better.

Sean Houlihane

Posted 2016-12-02T10:17:43.533

Reputation: 3 622

3

What is your source model? Typically this "missing layer" effect happens if the source has a wall thickness less than the size of the extruder nozzle selected. Cura will view that part of the model as non-printable.

Meshmixer and TinkerCad (among many others) will allow you to set and change thicknesses in the model.

Carl Witthoft

Posted 2016-12-02T10:17:43.533

Reputation: 2 918

1It came from TinkerCad, its just solid letters, and a solid base with a cutout (to get the perimeter wall). So I'm expecting a wall thickness of 1mm (and a 0.4mm nozzle). So, yes, I guess the question is if I want 0.8mm+0.2mm void, or a 50% over-filled centre. – Sean Houlihane – 2016-12-02T14:23:36.553

1

Try Cura 2.4.0-beta2: there is option named "Fill Gaps Between Walls" under "Shell" settings, set it to "everywhere". In stable Cura 2.3.1 this option is missing.

lz42

Posted 2016-12-02T10:17:43.533

Reputation: 76

Yes, I already noted that 2.4 beta gives some improvements in my answer... – Sean Houlihane – 2017-02-21T13:42:54.387