Stringing and Oozing: How to Eliminate Fine Hairs Between Features
The three causes of stringing are: print temperature too high, retraction too short or too slow, and travel speed too slow. Lower temperature first (2–3°C at a time), then increase retraction distance by 0.5mm increments, then increase travel speed.
Stringing occurs when molten filament oozes from the nozzle during travel moves — the rapid movements between features where no material is being deposited. As the nozzle travels, it leaves a thin string behind. In severe cases this produces cobweb-like artefacts; in mild cases a few fine hairs that are easy to remove.
The Three Causes
Excessive temperature: Hotter melt is less viscous and oozes more freely. Lowering print temperature by 5–10°C (in 2–3°C steps, checking results between each) is often the quickest fix.
Insufficient retraction: Retraction pulls filament back into the nozzle during travel moves, reducing the pressure in the melt zone and stopping it from oozing. Too little retraction (distance or speed) leaves the nozzle pressurised during travel.
Slow travel speed: The longer the nozzle spends crossing a gap, the more time ooze has to accumulate into a string. Faster travel means less ooze per crossing.
Retraction Settings Reference
| Printer Type | Retraction Distance | Retraction Speed |
|---|---|---|
| Direct drive (Bambu, Voron) | 0.5–1.5mm | 25–45mm/s |
| Bowden (Ender, standard) | 4–7mm | 40–60mm/s |
| Direct drive, flexible filament | 0.2–0.8mm | 20–30mm/s |
Excessive retraction causes grinding marks on the filament and, in Bowden systems, air gaps at the start of extrusion (under-extrusion following retraction). Start conservatively and increase by 0.5mm at a time.
Material-Specific Notes
PETG is notoriously prone to stringing. Its tacky melt adheres to surfaces and pulls strings easily. Lower temperature (to the minimum that still produces good layer adhesion) and fast travel (150–200mm/s) are more effective than aggressive retraction for PETG.
TPU cannot be retracted normally — aggressive retraction causes it to buckle in the extruder. For TPU, rely on very slow print speeds and reduce temperature rather than retraction.
PLA strings are usually easy to remove with a heat gun (brief pass, 150–200°C) which melts the strings without damaging the part.
The Combing / No-Travel-Perimeters Setting
Modern slicers include a "combing" or "avoid crossing perimeters" setting that routes travel moves within the infill area, crossing as few boundaries as possible. This significantly reduces visible stringing on external surfaces even if some stringing still occurs internally. Enable this setting as a first measure while tuning retraction.
Cleaning Strings After Printing
Fine strings on a finished print can be removed with:
- A brief pass with a heat gun (hold 15–20cm away, keep moving)
- A lit lighter moved quickly under the strings (more aggressive, avoid on thin features)
- Tweezers for individual hairs
- Fine brush for soft material strings
Related materials
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