What issue am I looking at here?
Perfect adhesion on the base plate (cf second attachment). First three(ish) layers print fine. Then filament gets completely trashed around layer 5.
Nozzle is still perfectly clean, so it does not look like a delamination issue.
This started at my second print with a new roll of Yellow PETG.
The printer was previously calibrated and printing PETG (galaxy black, green) down to 0.10 mm without issues.
The printer stands in a ~16-19C hallway, no enclosure, somewhat protected against draft.
This happens for default PETG settings, default with reduced flow rate, and my own custom settings that worked well. I usually print PETG with a high retraction rate around 1-1.2mm.
At some point I switched the standard nozzle for a hardened nozzle, which might have affected heating speed. Around that time I updated to the latest firmware and ran into this issue: https://github.com/prusa3d/Prusa-Firmwa ... -455154365
I mention this because this too is a layer 3-5 problem.
From the looks, I was first thinking that the nozzle was either too close to the previous layer, or too far, resulting in a sparse layer. However I cannot see evidence of physical dragging (i.e. filament sticking to other parts of the nozzle).
The more I'm thinking about it, I wonder if heating fails around the time where I adjust temperature from previous layers. That could be either because of the fan starting (though it should start earlier), or because of a software issue when adjusting the temperature (like in the github issue). It could also be a combination of [new nozzle, high retraction, additional cooling setting in around layer 3].
I will investigate those more, I was just wondering if it looks like a known symptom or issue to you.
Thank you in advance,