enabling Thin Walls causes lumpy curves

[seancmonahan]

What happened?

I started noticing a lot of my prints coming out with "lumpy" perimeters on their curved exteriors. I've narrowed it down, I think, to enabling "Thin walls" (thin_walls). The lumps are present even in models where the g-code preview shows no "thin wall" features.

Actually, looking at the g-code itself right now, there are extremely short G1's emitted with no extrusions. This is from slicing a solid, built-in cylinder with "thin_walls: true" and "thin_walls_merge: false". The zero-extrusions seem to only be on the external perimeter. Similar zero-extrusions are present when "thin_walls_merge" is enabled. They are not present when "thin_walls" is disabled.

G1 X117.737872 Y106.088192 E0.006251
G1 X117.737873 Y106.088193 E0
G1 X118.13324 Y106.397085 E0.016983
G1 X118.434695 Y106.683154 E0.014067
G1 X118.434699 Y106.683159 E0
G1 X118.710056 Y106.994394 E0.014066
G1 X118.710061 Y106.994401 E0
G1 X118.710062 Y106.994402 E0
G1 X119.004386 Y107.399503 E0.016949

SuperSlicer version is 2.4.58.2, AppImage release.

Project file & How to reproduce

thin-walls-lumpy-curves.zip

Version

2.4.58.2

Operating system

AppImage release on Manjaro Linux, Plasma Edition (KDE)

Printer model

Ender 3 V2, Klipper firmware

[seancmonahan]

This appears to be a regression. The same .3mf from above when opened and sliced in 2.48.1 does not emit any G1 ... E0s in the perimeters.

❯ grep -c '^G1 .* E0$' ./*.gcode
./2.48.1-thin-walls-lumpy-curves_26m_0.2mm_215C_PLA_1_ENDER3V2.gcode:0
./2.48.2-thin-walls-lumpy-curves_26m_0.2mm_215C_PLA_1_ENDER3V2.gcode:2379

sliced gcodes from 2.48.1 and 2.48.2: thin-walls-regression.zip