Bottom line: TPU stringing is rarely caused by one setting. Moisture, nozzle temperature, travel path, retraction and nozzle condition all interact. Dry the material and check the nozzle first, then tune temperature and travel speed, and adjust retraction last. Flexible filament responds poorly to large retraction, so more retraction usually makes feeding worse rather than cleaner.
Five common causes
| Cause | What you see | First action |
|---|---|---|
| Wet filament | Bubbles, crackling, unstable flow | Dry per TDS |
| High nozzle temperature | Oozing, long strings | Lower 5–10 °C |
| Poor travel path | Strings across open areas | Enable combing |
| Wrong retraction | Grinding, gaps, worse feeding | Reduce or disable |
| Nozzle wear or debris | Uneven extrusion | Clean or replace |
Recommended order
- Dry the spool and print from a dry box.
- Inspect and clean the nozzle; check the feeder tension.
- Lower the nozzle temperature within the material window.
- Raise travel speed and enable combing.
- Reduce retraction distance, or disable it on Bowden setups.
- Confirm the result on at least two parts.
Costly mistakes
- Increasing retraction first — flexible filament absorbs it.
- Using PLA settings on TPU.
- Ignoring moisture because the spool looks dry.
- Changing temperature, speed and retraction at once.
- Judging the fix from a single small test print.
Buyer / engineer checklist
- Is the filament dried and kept dry during printing?
- Is the nozzle clean and unworn?
- Is the nozzle temperature at the low end of the window?
- Is the travel path optimized?
- Is retraction kept small or disabled?
Send us your printer setup, TPU hardness and current settings and we can narrow the adjustment range.Get TPU support