Heat creep occurs when heat travels up from the hotend into the cold zone of the throat, softening filament before it reaches the melt zone. This causes the filament to swell and jam inside the heatbreak, leading to partial or complete extrusion failure — often after 30+ minutes of printing.
Common Causes
- Hotend cooling fan failure — The fan cooling the heatsink stops working or runs too slowly
- Excessive retraction length — Long retractions repeatedly drag molten filament into the cold zone
- High ambient temperature — Enclosed printers or hot rooms reduce the heatsink’s cooling efficiency
- Poor thermal break design — All-metal hotends with inadequate thermal isolation are more susceptible
- Printing too slowly at high temperatures — Extended heat exposure softens filament in the throat
Recommended Fixes
- Verify the hotend cooling fan is running at full speed — replace it immediately if faulty
- Reduce retraction distance (Direct Drive: 0.5-1mm, Bowden: 3-5mm maximum)
- Ensure the heatsink is clean and fins are not blocked by dust or filament debris
- Add or upgrade the hotend cooling fan to a higher-CFM model
- Lower the print temperature to the minimum that still produces good results
- Apply thermal compound between the heatbreak and heatsink for better heat transfer
- If using an enclosed printer, vent the electronics bay or add a small fan to circulate air around the hotend