How to fix stringing and oozing in 3D prints
Stringing is plastic leaking from the nozzle as it travels between parts of a print, leaving thin hairs or cobwebs behind. Fix it in this order: dry the filament, lower the nozzle temperature 5–10 °C within the filament's range, then tune retraction. Most "retraction problems" turn out to be wet filament or a nozzle that's too hot.
- Dry the filament, especially PETG, TPU and nylon (or any spool that pops and hisses).
- Drop the nozzle 5–10 °C, staying inside the filament's range.
- Tune retraction: 0.5–1 mm on direct drive, 2–6 mm on Bowden.
- Turn on wipe and "avoid crossing walls" in your slicer.
- Keep Z-hop at 0.2 mm or less, or turn it off.
What causes stringing in 3D printing?
Whenever the nozzle stops extruding and moves to another spot, molten plastic inside the hot end keeps trying to drip out. Retraction pulls the filament back to relieve that pressure. Stringing happens when something makes the plastic runnier, adds pressure, or gives it more time to leak.
| Cause | Clues | Fix |
|---|---|---|
| Wet filament | Popping or hissing at the nozzle, bubbles or pits on walls, fuzzy strings that get worse over days | Dry the spool |
| Nozzle too hot | Thick strings, drooping overhangs, glossy surfaces | Run a temperature tower |
| Retraction too short or slow | Strings on every travel, even with dry filament | Run a retraction test |
| Long or slow travel moves over open air | Strings only between separate parts or towers | Change travel settings |
| Dirty nozzle or worn hardware | Blobs and drips, plastic coating the nozzle, sudden change after maintenance | Clean and check the hot end |
Stringing has two close cousins. Oozing that leaves dots where a wall starts and stops is covered in blobs and zits. General excess plastic everywhere, not just on travels, is over-extrusion.
1. Dry wet filament
Most filaments slowly absorb moisture from the air. In the hot end that water turns to steam, which pushes plastic out when it shouldn't and breaks the strings into fuzz. No retraction setting fixes wet filament, and even a freshly opened spool can be damp.
| Filament | Drying temperature | Time | Moisture sensitivity |
|---|---|---|---|
| PLA | 40–50 °C | 4–6 h | Low to moderate |
| PETG | 60–70 °C | 4–6 h | Moderate; a common stringing culprit |
| ABS | 65–80 °C | 2–4 h | Moderate |
| TPU 95A | 50–60 °C | 6–12 h | High |
| Nylon | 70–90 °C | 12–16 h | Very high; can be wet within hours |
| Polycarbonate (PC) | 80 °C | 6–8 h | High |
Check your brand: some manufacturers recommend longer cycles. Bambu Lab, for example, lists around 8 hours for PLA, PETG and TPU. If a spool still strings after a short cycle, give it longer. Never exceed the filament's softening point, or the spool will fuse together.
After drying, store spools sealed with desiccant, or print straight from a dry box. More detail in the filament drying guide.
Free PrintPal toolFilament Drying GuideLook up drying temperature and time for your exact filament and dryerOpen tool2. Lower the nozzle temperature with a temperature tower
Hotter plastic is runnier and leaks more. A temperature tower prints the same small test block at a range of temperatures so you can see where stringing, bridging and layer bonding are best.
- Generate a tower. OrcaSlicer has one built in under Calibration → Temperature. In other slicers, download a tower model and add a temperature change at each block height.
- Cover the filament's range in 5 °C steps (for PLA, 200–220 °C; for PETG, 225–245 °C).
- Pick the coolest block that still looks good: fewest strings, clean bridges, and layers that don't snap apart when you flex the tower. OrcaSlicer's guide suggests choosing from the middle of the good range rather than the very edge.
- Save that value in your filament profile.
Two related tips: going below the filament's range causes under-extrusion and weak layers, and fast printers need hotter plastic to keep up. Bambu Lab ties the two together: if you print slowly, use a lower temperature.
3. Tune retraction distance and speed
Only tune retraction after the filament is dry and the temperature is set, or you'll chase the wrong problem. Retraction needs differ hugely between extruder types, because a Bowden tube adds slack that the extruder has to take up first.
| Setup | Retraction distance | Retraction speed | Notes |
|---|---|---|---|
| Direct drive (Bambu Lab, Prusa MK4S/CORE One, Creality K-series, most 2026 printers) | Start at 0.5 mm; usually 0.4–1.0 mm | 30–45 mm/s | Stay under 1 mm if you can; above 2 mm risks clogs |
| Bowden (Prusa MINI+, older Ender 3 and similar) | Start around 2–3 mm; test up to about 6 mm | 30–70 mm/s | Prusa's MINI+ default is 3.2 mm at 70 mm/s |
| TPU and other flexibles | Short, or off | Slow | Flexible filament compresses instead of pulling back; dry it and tune temperature first |
- Calibrate pressure advance first if your printer supports it (see the tip below). It changes how much retraction you need.
- Print a retraction test. OrcaSlicer's built-in test steps from 0 to 2 mm in 0.1 mm increments for direct drive, or 1 to 6 mm in 0.2 mm increments for Bowden.
- Find the height where strings stop and read off the matching retraction value.
- Use the shortest value that works. Extra retraction just adds wear and grinding. OrcaSlicer notes some PLA and ABS setups need only 0.2–0.4 mm.
- Only then try retraction speed, in 5 mm/s steps.
Pressure advance first: pressure advance (Klipper), Linear Advance (Marlin) and Flow Dynamics calibration (Bambu Lab) all manage nozzle pressure at the start and end of every line. With it tuned, the nozzle is already at low pressure before a travel move, so short retractions work. Ellis' tuning guide recommends calibrating it before retraction.
More is not better: long retractions on direct drive pull molten plastic up into the cold part of the hot end, where it can solidify and cause a jam. See heat creep. Bambu Lab recommends keeping retraction at 2 mm or less.
4. Change travel and wipe settings
The less time the nozzle spends over open air, the fewer strings. Each slicer has its own names for the same ideas:
| Setting | What it does | Where to find it |
|---|---|---|
| Avoid crossing walls / perimeters | Routes travel moves inside the part instead of over gaps | Bambu Studio and OrcaSlicer: "Avoid crossing wall"; PrusaSlicer: "Avoid crossing perimeters"; Cura: "Combing mode" |
| Wipe while retracting | Drags the nozzle along the wall during retraction to leave the drip there | PrusaSlicer, OrcaSlicer and Bambu Studio: "Wipe while retracting", in the printer or filament retraction settings |
| Coasting | Stops extruding just before the end of a line, using up the pressure in the nozzle | Cura: "Enable coasting" (Experimental). Not needed if pressure advance is tuned |
| Z-hop (lift Z) | Raises the nozzle on travel to avoid hitting the part | Keep it at 0.2 mm or less; higher lifts add strings |
| Travel speed | Faster travel gives less time to leak | Raise it if your printer's default is slow |
Layout matters too. Bambu Lab suggests placing small parts closer together so the nozzle has shorter jumps between them.
Free PrintPal toolG-code ViewerTurn on travel moves to see where the nozzle crosses open air and where retractions happenOpen tool5. Clean and check the hot end
- Clean the nozzle tip. Old plastic stuck to the outside drips onto the print and drags strings. Prusa notes that a film of PETG on the nozzle is a common cause of PETG stringing.
- Check for a partial clog. Inconsistent flow causes pressure spikes. See clogged nozzle.
- Bowden printers: check the tube. A loose coupler or a gap at the nozzle end adds slack and makes retraction less effective.
- Check the extruder tension and gears. Slipping or chewed filament means retraction isn't actually happening.
A month-old spool of PETG has started stringing badly, and you can hear faint popping from the nozzle. What's the most likely fix?
Popping is steam escaping from wet filament. Drying PETG at 60–70 °C for 4–6 hours (or longer) is the fix. Extra retraction won't help and can cause jams, and a hotter nozzle makes stringing worse.
Stringing tips for PLA, PETG, TPU and nylon
- PLA (200–220 °C): usually the easiest. If it strings, it's typically too hot or too wet. Keep the fan at 100%.
- PETG (225–245 °C): naturally stringier, and a few fine wisps are normal. Dry it, print toward the cool end, keep the nozzle clean and use wipe. See the PETG guide.
- TPU (215–230 °C): very moisture-hungry. Dry it, print slowly and keep retraction minimal. See the TPU and flexibles guide.
- Nylon (250–280 °C): almost always strings because it's wet. Print from a dry box.
How to clean up strings after printing
Fine wisps peel or brush off. For thicker strings, snip them with flush cutters, or pass a heat gun over the part briefly on a low setting, keeping it moving so the part doesn't soften. A few seconds is plenty; the strings shrink back before the part warms through. It beats a lighter, which leaves soot.
Frequently asked questions
What causes stringing in 3D printing?
Stringing happens when molten plastic leaks from the nozzle while it travels between parts of the print. The three main causes are wet filament, a nozzle temperature that is too high, and retraction that is too short or too slow (or pressure advance that hasn't been calibrated).
What retraction settings should I use?
On a direct drive extruder, start at about 0.5 mm at 35 mm/s and stay under 1 mm if you can; 2 mm is a practical maximum. On a Bowden setup, start around 2–3 mm and test up to about 6 mm, at 30–70 mm/s. Run a retraction test in your slicer to find the shortest value that stops strings.
Why does PETG string so much?
PETG is stickier and more prone to oozing than PLA, so a few fine wisps are normal. Dry it, print near the low end of its 225–245 °C range, keep the nozzle clean of PETG residue, and turn on wipe and avoid-crossing-walls travel settings.
Can wet filament cause stringing?
Yes. Water absorbed by the filament turns to steam in the hot end, which pushes extra plastic out during travel moves and causes popping, bubbles and fuzzy strings. Drying the spool, for example PLA at 40–50 °C or PETG at 60–70 °C for 4–6 hours, often fixes stringing that no setting change could.
Related articles
Sources & further reading
- Prusa Knowledge Base — Stringing and oozing
- Bambu Lab Wiki — Stringing and oozing
- Bambu Lab Wiki — Drying filament
- Ellis' Print Tuning Guide — Retraction
- OrcaSlicer Wiki — Retraction calibration
- OrcaSlicer Wiki — Temperature calibration
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