Holes at Z-Seam with large nozzle

V-Core 3 500 with Orbiter 2.0, Rapido UHF and a Bondtech CHT 1.2mm nozzle. RatOS 2.0.2. PrusaSlicer 2.7.4 Printing with any filament results in pretty severe underextrusion at Z-seam. Layer Heights between 0.2 and 0.6, layer widths between 1.2 and 1.6 mm. I have ran the Tuning Tower with inconclusive results; based on the printed tuning tower, a PA of 0.005 should be used. Still, even at 0.005 PA and smooth time of 0.01, there are holes at the Z-Seam, and underextrusion immediately after them. Retraction is set to 0.5mm distance and 40 mm/s speed. Depending on filament type and brand, I can see stringing and symptoms of low retraction, but still Z-seam has holes throughout the print. Volumetric Flow Rate is capped at 25 mm^3/s, I have tried values between 10 and 40 mm^3/s with no changes in behavior. Images attached, white and black PETG printed at 245 degrees. I'm not sure how to troubleshoot further. The only thing I haven't tried yet is the "Deretraction extra length" setting in PrusaSlicer, which pushes extra filament after retraction. Maybe someone who also uses a large nozzle could point me to the right direction.
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Solution:
FWIW: I solved it using a „Deretraction extra length” setting of 0.4mm.
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2 Replies
war4peace
war4peaceOP7mo ago
Update: I have disabled both Pressure Advance as well as retraction, and there are still gaps in walls where layer starts (after Z-seam). Then, I have changed the nozzle to a brand-new, identical one, printed the same G-Code file, and there was no change in behavior, therefore we can rule out a bad nozzle. Right now I have switched from PrusaSlicer to Cura, currently printing the same model again, sliced with Cura, just to make sure it's not a slicer issue. Update #2: The issue persists across slicers (Pressure Advance and retraction disabled). It seems to be something mechanical is causing this.
Solution
war4peace
war4peace7mo ago
FWIW: I solved it using a „Deretraction extra length” setting of 0.4mm.
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