Stringing Is a Retraction Problem
Stringing — those fine wisps between towers and walls — happens when molten filament oozes from the nozzle during travel moves. The primary fix is retraction: pulling filament back up the hotend so it cannot drip. Getting retraction right is the single most visible quality win for a new printer owner.
How Retraction Works
A direct-drive extruder needs a short, fast retraction because the filament path is short. A Bowden extruder needs a longer retraction to take up slack in the PTFE tube. Get the geometry wrong and you trade stringing for under-extrusion and clogged nozzles.
Filament-Specific Starting Points
| Material | Direct Drive | Bowden | Retraction Speed |
|---|---|---|---|
| PLA | 0.5–1.2 mm | 4–6 mm | 40–60 mm/s |
| PETG | 0.8–1.5 mm | 4–7 mm | 30–45 mm/s |
| ABS | 0.7–1.3 mm | 4–6 mm | 35–50 mm/s |
| TPU | 0.3–0.6 mm | Avoid Bowden | 15–25 mm/s |
The Tuning Procedure
- Print a two-tower retraction test (25 mm apart, 20 mm tall).
- Start with the median value in the table and note stringing at each end of the travel.
- Increase retraction distance by 0.2 mm steps (direct drive) or 0.5 mm (Bowden) until strings disappear.
- Stop the moment stringing clears — too much retraction causes gaps at the start of each wall.
Keep Moisture in Mind
Even perfect retraction cannot fix a wet spool. PETG, ABS and TPU all absorb water aggressively, and wet material strings no matter what you do. PLA+ is more forgiving but still benefits from dry storage.
Beyond Retraction
If stringing persists, check nozzle temperature (hotter = more drip), travel speed and a clean nozzle tip. Lowering temperature by 5 –10 °C, raising travel speed to 150 mm/s and using 'avoid crossing perimeters' all help on top of retraction.