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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).

1 Answer 1

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.