Heat creep happens when heat travels too far up the hot end and softens the filament before it reaches the melt zone. The softened filament swells, grips the walls, and jams, so the print slowly loses flow and may stop. Per Bambu’s heat-creep guide, the usual suspects are a weak hot-end fan, a nozzle set too hot, and retraction pulled too long.
The jam tends to build over the course of a print, so the first layers look fine and the trouble starts partway up. Clear the jam, then fix the heat path so it does not come back.
Your material sets the risk. PLA is the most prone, because it softens at a low temperature. PETG and ABS tolerate more heat before they creep.
What drives heat creep
| Likely cause | Fix | Severity |
|---|---|---|
| Hot-end fan dead or weak | Replace or fix the fan so it cools the heat break whenever the hot end is warm. | hi |
| Retraction too long | Cut retraction distance back so filament does not sit up in the heat zone. | hi |
| Nozzle temp too high | Lower the nozzle 5 to 10 C and reprint. | md |
| Blocked heat break or PTFE gap | Clean the heat break and reseat the PTFE tube flush to the nozzle. | md |
| Hot ambient or enclosure on PLA | Open the enclosure or cool the chamber when you print PLA. | lo |
Quick fixes to start with
Clear the blockage first, then cool the heat path. Reprint after each step.
Check the hot-end fan
Make sure the fan on the heat break spins at full speed whenever the hot end is warm.
Cut retraction back
Reduce retraction distance so filament does not pull up into the hot zone.
Lower the nozzle temp
Drop the nozzle 5 to 10 C and reprint to see if the jam clears.
Open the enclosure
For PLA, open the doors or cool the chamber so heat does not pool around the hot end.
When the basics are not enough
When the fan and the temps look right, the heat break and the tube are the next place to look.
Clean the heat break
Let the hot end cool, take it apart, and clear any melted residue from the heat break.
Reseat the PTFE tube
On a Bowden hot end, push the tube flush to the nozzle so there is no gap for filament to swell into.
Add a silicone sock
A hot-end sock stabilizes the temperature and blocks radiant heat from rising into the heat break.
How your material changes things
PLA softens at a low temperature, so it creeps the easiest when the heat path runs warm. PETG and ABS need higher nozzle heat and tolerate it better, but they still creep if the hot-end fan is weak. TPU resists creep but prints slow, so keep its speed low and its retraction short.
What not to do
A few common choices clear the jam but leave the cause in place.
Avoiddo not
- Only pushing fresh filament through, without fixing the fan or the retraction.
- Setting retraction long to fight stringing, which feeds the creep.
- Running PLA in a hot, closed enclosure.
- Ignoring a fan that spins but runs slow or noisy.
Key takeaways
- Heat creep softens filament too high in the hot end and jams it.
- Check the hot-end fan and cut retraction back first.
- PLA creeps easiest; cool the chamber for it.
- Fix the heat path, not just the jam.
For related problems, the clogged nozzle guide covers the blockages heat creep leaves behind, and the filament storage guide covers keeping spools dry.
Related guides
Related
More in this area
Cross-reference
Sources & methodology
2 citations · reviewed 2026-07-10- 01Bambu Lab Wiki: Heat creep (enclosure heat into the extruder)accessed 2026-07-09Tier 1
- 02All3DP: Heat creep causes and fixesaccessed 2026-07-09Tier 2