Introduction
You’ve waited hours for a print to finish, only to find thin threads of plastic draped between every gap, bridge and tower on the model. Stringing — also called oozing or hairy prints — doesn’t usually affect the structural strength of a print, but it ruins the surface finish and means extra post-processing work. The cause is straightforward: molten filament drips from the nozzle tip whilst the print head moves between separated sections of the model. This guide covers the specific slicer settings and hardware checks that stop it, ordered from the easiest adjustment to the most involved.
Why This Happens
Inside an FDM printer’s hot end, filament is heated to a semi-liquid state. When the print head finishes extruding in one area and travels to another, the extruder motor reverses briefly to pull filament back up the melt zone — this is called retraction. If retraction isn’t pulling back enough filament, or isn’t pulling fast enough, residual pressure in the nozzle pushes molten plastic out during the travel move. That ooze stretches into a thin string between the two points.
Several factors make stringing worse. Higher nozzle temperatures reduce the viscosity of the plastic, making it flow more freely and ooze more easily. PETG is naturally stringier than PLA because it has a wider melt zone and stays liquid longer. Wet filament — filament that has absorbed moisture from the air — produces tiny steam bubbles that increase internal pressure and push plastic out of the nozzle unpredictably. Bowden tube setups (where the extruder motor sits on the frame and pushes filament through a long tube to the hot end) are more prone to stringing than direct drive setups because the long tube introduces flex and delay in the retraction response.
The travel path also matters. If the slicer routes travel moves across open gaps rather than along the inside of the model (called “combing” or “avoid crossing perimeters”), the nozzle has more opportunity to leave strings. Travel speed plays a role too — a slow travel move gives the ooze more time to stretch into a visible string, whilst a fast move can break any ooze before it solidifies.
Step-by-Step Fix
1. Lower the Nozzle Temperature
This is the single most effective fix for stringing. Open your slicer and reduce the nozzle temperature by 5°C from your current setting. Print a test model (a stringing test tower or two small cylinders spaced apart). If stringing improves but doesn’t disappear, drop another 5°C. Keep going until you either eliminate the stringing or start seeing under-extrusion (gaps in the walls or weak layer bonding).
Typical working ranges:
- PLA: 195–210°C (most PLA strings noticeably above 210°C)
- PETG: 225–240°C (PETG is stringier by nature; aim for the lower end)
- ABS/ASA: 235–250°C
Every filament brand has slightly different temperature requirements, so treat these as starting points rather than fixed rules.
2. Tune Retraction Distance
Retraction distance controls how far the extruder motor pulls the filament back. The correct value depends on your extruder type:
- Bowden tube printers (Creality Ender 3, Anycubic Kobra): Start at 6 mm and increase in 0.5 mm steps up to 8 mm if needed. Bowden setups need more retraction because of the compliance in the tube.
- Direct drive printers (Prusa MK4, Bambu Lab A1/P1, Creality Ender 3 V3): Start at 0.8 mm and adjust in 0.2 mm steps up to 2 mm. Direct drive retraction values above 2–3 mm can cause jams because pulling filament too far back moves the cooled section into the heat break.
In Cura, the setting is under Travel > Retraction Distance. In PrusaSlicer/OrcaSlicer, it’s under Printer Settings > Extruder 1 > Retraction > Length. In Bambu Studio, it’s under Filament > Retraction > Length.
3. Increase Retraction Speed
Retraction speed determines how quickly the filament is pulled back. A faster retraction creates a cleaner break in the melt zone. Start at 40 mm/s and increase to 60 mm/s if stringing persists. Going above 70 mm/s rarely helps and can cause the extruder gear to grind the filament.
The setting is usually right next to retraction distance in your slicer.
4. Increase Travel Speed
Travel speed is how fast the print head moves when it’s not extruding. Higher travel speeds reduce the time window for ooze to stretch into strings. Set travel speed to 150–200 mm/s in your slicer. Most modern printers handle these speeds without issue on non-print moves.
In Cura, this is Speed > Travel Speed. In PrusaSlicer, it’s under Print Settings > Speed > Travel.
5. Enable Combing / Avoid Crossing Perimeters
This slicer feature routes travel moves inside the printed walls where possible, so any ooze is hidden inside the model rather than strung across open air.
- Cura: Enable Travel > Combing Mode and set it to Within Infill.
- PrusaSlicer/OrcaSlicer: Enable Print Settings > Layers and Perimeters > Avoid Crossing Perimeters.
- Bambu Studio: Enable Others > Avoid Crossing Walls.
This doesn’t stop stringing entirely, but it hides it where you can’t see it.
6. Print a Retraction Test Tower
Rather than guessing, print a retraction calibration tower that tests multiple retraction distances in a single print. These models are available on Printables and Thingiverse — search for “retraction tower test”. Some slicers (PrusaSlicer, OrcaSlicer) have built-in calibration tools that generate these automatically. The tower will show you exactly which retraction distance produces the cleanest result for your specific printer and filament combination.
7. Dry Your Filament
If you’ve optimised all the slicer settings and stringing persists — especially with PETG, Nylon, or TPU — the filament may be wet. Moisture absorbed from the air creates micro-bubbles in the melt zone that increase pressure and push plastic out. Signs of wet filament include: popping or hissing sounds from the nozzle, rough surface texture, and excessive stringing that doesn’t respond to retraction tuning.
Dry filament in a dedicated filament dryer or a conventional oven:
- PLA: 45–50°C for 4–6 hours
- PETG: 65°C for 6–8 hours
- Nylon: 70°C for 8–12 hours
After drying, store the spool in a sealed bag or dry box with silica gel desiccant packs.
Common Mistakes to Avoid
Setting retraction distance too high on a direct drive printer. Anything above 2–3 mm on a direct drive setup pulls cooled filament into the heat break, causing heat creep and eventual jams. If your Prusa or Bambu printer starts jamming mid-print after you increase retraction, this is almost certainly the cause. Reset to 1 mm and increase slowly.
Ignoring filament moisture and only adjusting slicer settings. No amount of retraction tuning will fix a spool of PETG that has been sitting open for three weeks in a humid room. If you see steam wisps, hear popping from the nozzle, or notice unusually rough surfaces alongside stringing, dry the filament first.
Lowering the temperature so much that layer adhesion fails. Chasing zero stringing by dropping the nozzle temperature too far causes weak prints that snap along layer lines. If you can break a test print apart with your fingers along a layer boundary, the temperature is too low. Accept a tiny amount of stringing over structurally compromised prints.
Using a worn or oversized nozzle without realising it. Brass nozzles wear over time, especially when printing abrasive filaments like carbon fibre or glow-in-the-dark PLA. A worn nozzle has a larger opening than its rated size, which increases ooze. If your 0.4 mm nozzle has printed several hundred hours of abrasive material, replace it — they cost less than £5.
When to Call a Professional
Stringing that refuses to go away after temperature tuning, retraction calibration and filament drying can point to a hardware fault. A partially clogged nozzle that restricts flow in one direction but not the other, a cracked or improperly seated Bowden tube coupling that introduces backlash in the filament path, or a worn extruder gear that can’t grip the filament firmly enough for reliable retraction — all of these produce stringing symptoms that software settings alone cannot fix.
On some Creality printers, the PTFE tube inside the hot end can degrade over time and create a gap between the tube and the nozzle. This gap fills with molten plastic and makes retraction almost entirely ineffective. If you suspect a hardware issue or you’ve spent more time calibrating than printing, our 3D Printer Setup & Calibration service includes a full hot end inspection, Bowden tube replacement if needed, and retraction calibration with a test print to verify the results. We cover Creality, Prusa, Bambu Lab, Anycubic and most other FDM printers across South West London.
Prevention Tips
Store all filament in sealed bags or dry boxes with desiccant. Prevention is far easier than drying. When you finish printing, put the spool back in its bag. Reusable vacuum bags with a one-way valve and rechargeable silica gel packs cost under £15 and save hours of troubleshooting.
Print a quick stringing test whenever you open a new spool. Different brands and even different colours of the same filament can need different retraction settings. A two-minute test tower saves wasting an hour on a full model that comes out hairy.
Replace brass nozzles every 500–800 print hours if you use abrasive filaments. If you only print standard PLA, a brass nozzle can last thousands of hours. But carbon fibre, wood-fill and glow-in-the-dark filaments wear the bore quickly. Keep a few spare 0.4 mm nozzles on hand.
Check the Bowden tube coupling every few months on printers that use one. Push the tube in firmly and make sure the coupling teeth grip. If the tube slides in and out freely, the coupling is worn and needs replacing — a loose tube allows filament to compress during retraction instead of pulling back cleanly.