A PETG blob on the nozzle is a ball of plastic that grows on the tip as you print, then drags across the model and smears it. PETG oozes more than PLA at print temperature, so a little extra pressure or a damp spool turns into a blob fast. Bambu’s PETG guide ties most nozzle blobs to wet filament, low retraction, and a nozzle that runs a little hot.
The blob is annoying but easy to chase down, because PETG behaves the same way for everyone. Dry it, set the retraction, and clean the tip, in that order.
Wet PETG is the lead cause. Per Bambu’s PETG page, dry the spool at 60 to 65 C before you blame the slicer.
What causes it
| Likely cause | Fix | Severity |
|---|---|---|
| Wet PETG oozing | Dry the spool at 60 to 65 C for 4 to 8 hours, then reprint. | hi |
| Retraction too low | Raise retraction for the Bowden tube so less PETG sits in the nozzle. | hi |
| Nozzle too hot | Drop the nozzle toward 230 C, the low end of the PETG range. | md |
| No z-hop or wipe | Enable wipe while retracting, and keep z-hop low so the tip clears the part. | md |
| Buildup not wiped | Clean the nozzle tip with brass tweezers or a wire brush while warm. | lo |
Try these first
Print a small PETG part and watch the nozzle tip, then work top to bottom and reprint after each step.
Dry the PETG
Run the spool at 60 to 65 C for 4 to 8 hours in a dryer, then reprint.
Raise retraction
Step the retraction up for your Bowden setup and reprint, until the ooze stops.
Drop the nozzle temp
Lower the nozzle toward 230 C and reprint, since cooler PETG oozes less.
Clean the tip
While the nozzle is warm, wipe the buildup off with brass tweezers or a brass brush.
Deeper fixes to try next
When drying and retraction do not stop the blob, the travel settings are next.
Turn on wipe
Enable wipe while retracting in PrusaSlicer or Bambu Studio to clear the tip on each move.
Cut z-hop
Lower or turn off z-hop, since a hopping nozzle can pick up a blob on the way down.
Print from the dryer
Run the PETG straight from a filament dryer so it stays dry through a long print.
How PETG differs
PETG oozes more than PLA because it runs hotter and stays runnier at the nozzle, so it builds a blob faster when the pressure is off or the spool is wet. PLA rarely blobs at its lower temperature, and nylon oozes even more than PETG. A wet PETG spool makes every one of these worse, since the boiling moisture pushes extra plastic out the tip.
Mistakes that keep the blob growing
A few choices fight the symptom and leave the cause.
Avoiddo not
- Tuning retraction before you dry the PETG.
- Running the nozzle at the top of the PETG range all the time.
- Wiping the tip cold, which smears instead of clearing.
- Changing retraction, temp, and wipe in one pass.
Key takeaways
- A PETG blob on the nozzle comes from wet filament, low retraction, and a hot tip.
- Dry the PETG at 60 to 65 C first, then raise retraction.
- Drop the nozzle toward 230 C and clean the warm tip.
- PETG oozes more than PLA, so it blobs faster.
For the surface version, the blobs and zits guide covers blobs on the print, and the filament storage guide covers keeping PETG dry.
Related guides
Related
More in this area
Cross-reference
Sources & methodology
4 citations · reviewed 2026-07-10- 01Bambu Lab PETG Usage Guide (wiki): PETG flow and oozingaccessed 2026-06-29Tier 1
- 02Bambu Lab Wiki: Printing wet or undried PETG (oozing and drying)accessed 2026-07-09Tier 1
- 03Prusa Knowledge Base: PETG (cooling, stringing, buildup)accessed 2026-07-09Tier 1
- 04All3DP: PETG stringing, three ways to prevent itaccessed 2026-07-09Tier 2