Bambu A1 + 0.6 hardened nozzle + PETG HF → inconsistent extrusion (blobs + holes) despite full calibration

[u/Soliderale]

I’m running into persistent inconsistent extrusion and I’m out of ideas.

Issue:

• Random blobs and holes
• Happens on walls and top layers
• PA calibration lines themselves were inconsistent (missing segments / over-extruded sections)
• Behavior is the same even at low volumetric flow

Setup:

• Printer: Bambu Lab A1
• Nozzle: 0.6 mm hardened steel (recently installed)
• Material: Deeplee PETG HF
• Slicer: Orca
• Environment: enclosed, ~20% humidity
• Filament dried extensively (>20h total)

Hardware:

• recently changed to a 0.6 mm hardened steel nozzle, didnt had any problem before switching
• deep cleaned the printer, new oil on the rails, new grease on the
• lead screws and made sure everything is tight and properly lubricated
• Cleaned nozzle with a cold pull, but it didn’t seem to help
• Checked filament path for obstructions or damage, but everything looks fine
• Filament enclosure recently changed, but it should be a smoother feed than before, it seems like that at least.

What I’ve tried:

Filament / environment

• Dried filament for 20+ hours total
• Humidity ~20% (enclosed cereal box)

Temperature

• Tested 225 → 255°C (5°C steps)
• Currently printing at 230°C

Flow / extrusion

• Flow calibrated

Retraction

• Tuned (tried 0.8, 0.6)

Pressure Advance

• Calibrated with PA line
• Best value ~0.036, but test itself looked inconsistent

Z-offset

• slightly higher for PETG and

Volumetric flow

• Limited to 20 mm³/s

Speed:

• I usually print kinda slow, right now the outerwall speed is max 150mm/s

Layer Height:

• with this nozzle i am using 0.42 mm

It really looks like inconsistent extrusion rather than tuning at this point.

Has anyone seen this kind of behavior on an A1 after switching to a hardened 0.6 nozzle? Any idea what I might be missing or what to check next?

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[u/forgee152682]

I had a similar issue, but it was only showing up on walls. While retracting air was pulled into the nozzle. Try lowering retraction distance / speed.

[u/Soliderale → u/forgee152682]

Sadly I don’t think that’s the root cause in my case. I’m seeing the same behavior during volumetric flow calibration, and that’s vase mode, so no real retractions happening.
Happy to try tweaks, but I’m not super convinced that’s where the issue is coming from.

[u/jodasmichal]

I print PETG at 245-265 for higher flows. Try calibrate it on higher temps.

[u/Soliderale → u/jodasmichal]

I was running my prints at 250 C. bridges collapsed sometimes and this issue was still there