Stringing and oozing diagnosis
Stringing is when filament oozes between separate parts of your model during travel moves, leaving fine threads. Oozing also shows up as blobs on top surfaces or unexpected smears.
Read the symptoms first
Different patterns point to different fixes:
| Symptom | Most likely cause |
|---|---|
| Fine, sparse strings between parts | Slightly under-retracted |
| Heavy "spiderweb" stringing | Wet filament |
| Blobs on top of model | Z-seam alignment / pressure advance |
| Strings that look melted/dripped | Nozzle too hot |
| Strings only on tall narrow towers | Travel speed too slow |
1. Dry your filament
PETG, TPU, and nylon are all hygroscopic and will absorb moisture from the air in 1-3 days of open exposure. Wet filament makes microscopic steam bubbles in the melt zone that translate into stringing on every travel.
If your stringing is fluffy/spiderwebby, dry the spool before tuning anything else. See the drying schedule guide.
2. Retraction calibration
Print a retraction tower or temperature/retraction calibration print:
- Direct-drive extruder (Bambu, Prusa MK4, K1): 0.4-1.0 mm retraction is normal
- Bowden extruder (older Ender, Mini+): 3-6 mm retraction is normal
Most slicers can auto-test a retraction range. Use those tools rather than guessing.
3. Print temperature
Print a temperature tower for every new filament. Move down 5 C at a time from the manufacturer's max. The lowest temperature that still gives you good layer adhesion is the right one for stringing.
Generic ranges:
- PLA: 190-220 C
- PETG: 230-250 C
- TPU: 220-240 C
- ABS: 230-260 C
4. Travel speed
Faster travels mean less time for the nozzle to ooze. Try 200-300 mm/s on travel moves if your printer can handle it (most modern printers can). Stock travel speed on older printers is often too slow.
5. Coasting and wipe
In your slicer, enable "Coasting" (stops extrusion just before the end of a wall) and "Wipe" (drags the nozzle back across the just-printed line to clean it). Both reduce blob formation at the end of perimeters.
6. Pressure advance / linear advance
Bambu, Klipper, and Marlin-with-LA can calibrate pressure advance. This compensates for the pressure built up in the nozzle and produces cleaner corners + less oozing. Run the calibration once per filament; it's a real difference-maker.
7. Nozzle condition
A partially-clogged or warn brass nozzle will dribble more than a clean one. If you've been printing CF filaments through a non-hardened nozzle, it's probably worn out.
What NOT to do
- Don't crank retraction to 8mm on a direct-drive printer. It causes clicking, under-extrusion, and tip cooling that creates clogs.
- Don't drop temperature 30 C below recommended just to fight stringing. You'll lose layer adhesion and parts will snap.
- Don't ignore a wet filament problem by tuning around it. The strings will come back the moment you cross 50% humidity.