A clogged nozzle is a partial or full blockage in the hot end that chokes the filament path. You see it as under-extrusion, gaps in the print, or filament that stops coming out altogether, often with a clicking extruder. Per Bambu’s print-quality catalogue, most clogs trace to burnt residue, a nozzle that ran too cold, or heat creep.
The first move is almost always a cold pull, which clears the blockage without taking the hot end apart. Work the causes in order so the clog does not come straight back.
Your material changes the odds. PETG and flexible TPU clog more than PLA, and any wet filament can swell and jam.
Likely causes, ranked
| Likely cause | Fix | Severity |
|---|---|---|
| Burnt or residue clog | Run a cold pull to drag the blockage out, then push fresh filament through. | hi |
| Nozzle too cold | Raise the nozzle 5 to 10 C so the filament melts fully. | hi |
| Heat creep | Check the hot-end fan runs, and cut retraction back so filament does not soften high in the heat break. | md |
| Debris in the nozzle | Remove and clean the nozzle, or fit a new one. | md |
| Wet filament swelling | Dry the spool, then reprint. Wet filament can swell and jam. | lo |
Try these first
Clear the blockage first, then remove the cause. Reprint the same test after each step.
Run a cold pull
Heat the hot end, let it cool partway, then pull the filament out fast to drag the clog with it.
Raise the nozzle temp
Set the nozzle 5 to 10 C higher and push filament through by hand to confirm clear flow.
Check the hot-end fan
Make sure the hot-end fan spins whenever the hot end is warm, so filament does not soften high in the heat break.
Dry the filament
If the jam came with popping or bubbles, dry the spool and reprint.
Deeper fixes to try next
When a cold pull does not hold, the hardware and the path are the next place to look.
Remove and clean the nozzle
Unscrew the nozzle while warm, poke or soak it clear, or fit a new one.
Reduce retraction
If heat creep keeps coming back, cut retraction back so filament does not sit too long in the melt zone.
Check the PTFE tube
On a Bowden hot end, look for a gap or a melted tube end under the fitting, and reseat it.
How the material differs
PLA clogs least, because it melts clean at a low temperature. PETG and flexible TPU clog more, since they run hotter and ooze, and TPU can fold inside the extruder path. Any wet filament can swell and jam, so dry the spool first when clogs repeat.
Pitfalls to avoid
A few common habits make the next clog worse or hide the cause.
Avoiddo not
- Forcing a needle or Allen key through a cold nozzle. It can damage the inside.
- Running the nozzle far above the filament range to push a clog through. It burns the filament and worsens the next clog.
- Ignoring a dead hot-end fan. Heat creep will keep clogging the nozzle.
- Skipping the dry step. Wet filament swells and jams again.
Key takeaways
- A clog chokes flow and shows up as under-extrusion or a clicking extruder.
- A cold pull clears most clogs without taking the hot end apart.
- Check the hot-end fan and retraction if clogs come back from heat creep.
- Dry PETG and TPU first. Wet filament swells and jams.
For related problems, the extruder clicking guide covers the sound that often comes with a clog, and the filament storage guide covers keeping spools dry.
Related guides
Related
More in this area
Cross-reference
Sources & methodology
3 citations · reviewed 2026-07-10- 01Bambu Lab Wiki: Common print quality problems (clogs, elephant foot, extrusion)accessed 2026-07-09Tier 1
- 02All3DP: Clogged nozzle, cold or atomic pull methodaccessed 2026-07-09Tier 2
- 03Anycubic Wiki: printer manuals and troubleshootingaccessed 2026-06-29Tier 1