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Stringing and oozing: how to get rid of filament strings and blobs

Assessed from documentation · Content verified on October 6, 2026

Where to start

  1. Check dry filament and clean the nozzle before increasing retraction.
  2. Repeat a small two-tower test: change temperature or retraction, one at a time.
  3. Use your machine’s profile: settings for a Bowden extruder do not automatically apply to direct drive.
Stringing and oozing: how to get rid of filament strings and blobs
Illustration of the defect, not a test photograph. Shapes are simplified.

How to recognise it

Stringing shows up as thin, cobweb-like strands stretched between two parts of the model or between different models on the same plate: molten material keeps leaking from the nozzle while the toolhead travels without extruding. Oozing is the same phenomenon seen up close: drips and blobs that build up on the nozzle or in specific spots on the surface.

Bambu Lab describes the two defects as closely related and attributes most cases to three factors: excessive extrusion, wet filament and incorrect retraction settings. Prusa lists a printing temperature that is too high and badly configured retraction as the main causes, plus material residue left on the nozzle after long print sessions (for example with PETG).

Checks to do, in order

Change only one parameter at a time and print a small stringing test (two towers spaced apart) after each change: that way you know which adjustment worked. Before any work on the nozzle, remember that the hotend and nozzle are very hot.

  1. Check that the material profile, printer profile and nozzle diameter in the slicer match what is installed. If possible, start again from the manufacturer's official profile.
  2. Try another spool, or dry the one in use and store it in a sealed container with desiccant (see the filament drying guide).
  3. Clean old material residue off the nozzle while hot and wearing insulated gloves: for some models (e.g. Neptune 4) Elegoo says to switch off the printer and wait for it to cool before removing the toolhead.
  4. Lower the nozzle temperature: Prusa suggests trying 5–10 °C less, while staying within the range printed on the spool.
  5. Adjust retraction: increase length or speed slightly. Excessive retraction can cause clogs, under-extrusion and gaps between layers; a speed that is too high can make the extruder motor skip steps.
  6. Lower the minimum travel distance that triggers retraction: according to Prusa a higher value shortens print time but increases oozing and stringing; Bambu Lab shows how lowering it removes strings across small gaps.
  7. Enable "wipe while retracting", retract on layer change and the option that avoids crossing perimeters/walls; place models closer together on the plate or consider sequential printing.
  8. If strings remain after all this, check nozzle wear, the PTFE tube and the extruder gears.

Notes from manufacturer documentation

Prusa (PrusaSlicer): the settings are under Printer Settings → Extruder 1. On the direct-drive MK2.5/MK3 the stated maximum retraction length is 2 mm, while the MINI profiles with a Bowden extruder use longer values. Prusa recommends leaving wipe while retracting enabled and notes that a lower Z lift (Z hop) reduces strings, but disabling it completely may let the nozzle hit the part. Flexible filaments usually need longer retractions and dedicated tuning.

Bambu Lab (Bambu Studio): generally recommends not exceeding 2 mm of retraction to avoid clogs, reducing the spacing between models and enabling "Avoid crossing wall". The "Slope", "Spiral" and "Auto" Z hop types help reduce oozing and strings. With flexible materials such as TPU, retraction can worsen extrusion. A visibly worn nozzle should be replaced.

Creality and Elegoo: for the Ender-3 V3 Plus, Creality says to use a generic profile if the filament is not the one the profile was made for, and to check the PTFE tube and extruder gears. Elegoo also lists a clogged or worn nozzle and excessive print speed among the causes of oozing, and describes hot nozzle cleaning, recommending insulated gloves.

When replacing a part is justified

In most cases there is nothing to buy: dry filament, a correct profile and suitable temperature and retraction solve the problem. Replacing the nozzle is justified when it is visibly worn or deformed (Bambu Lab says so explicitly) or when a clog cannot be removed by cleaning. A deformed PTFE tube or worn extruder gears should be replaced if the inspection finds them damaged. A filament dryer is useful if you often print moisture-absorbing materials, but the drying guide also explains how to check first whether the filament is really wet.

How to verify the result

Record the model and variant, material, slicer profile and change made. Repeat the same test and compare the result with a photo taken before the adjustment. Keep the change only if it improves the defect without introducing others. Use your model’s instructions for temperatures, calibration and disassembly; this guide is not based on our own hands-on tests.

The most common causes

Wet filament: moisture absorbed by the filament turns into steam in the nozzle and pushes material out even when the extruder is stopped. Bambu Lab stresses that in this case adjusting retraction alone usually is not enough: the filament must be dried first. For the full procedure, see the site's guide on drying wet filament.

Temperature too high: the material becomes more fluid and drips more easily. Insufficient retraction or long travel moves: if the toolhead travels long distances without printing and retraction is too short, the material has time to leak out. Wrong profile: Creality notes that using a profile designed for a different material (for example a "Hyper PLA" profile with another kind of PLA) causes stringing and other defects; Bambu Lab also mentions a nozzle diameter set in the slicer that differs from the one installed.

Nozzle and feeding: a worn or partly clogged nozzle, a deformed PTFE tube or worn extruder gears make the flow irregular (Creality, Elegoo). Finally, low-density lightweight filaments expand a lot while printing: for these materials Bambu Lab recommends lower temperature and flow, following the values in its own guide.

What users report in the forums

Users in the forums often report that even PETG fresh out of its vacuum-sealed bag can already be wet: in a Bambu Lab forum thread about a P1P, several users pointed to drying as the main fix. The same thread notes that slowing the print down too much does not help, because it gives the material more time to drip during travel moves.

In another long thread about PLA stringing on an A1, some users only solved it by replacing the nozzle after trying temperature, retraction and drying without success: this is individual experience, not official guidance, but it confirms that the nozzle should be checked once everything else has been ruled out. For strings already on the part, Prusa suggests a brief pass with a heat gun, without lingering so the part does not deform.

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