PETG stringing: how to fix it, step by step
Strings on PETG come from two very different places: plastic oozing out of the nozzle while it travels from one spot to another, and water vapor inside the filament. The first is fixed in the slicer; the second only by drying the spool. A close look at the part tells you which one you have, and that saves hours of fiddling with retraction for nothing.
How to tell which kind of stringing you have
- Webs between separate features, like between two towers or between the fingers of a hand: plastic oozing during travel moves. Likely causes are a high temperature or too little retraction.
- Very fine, hair-like strings all over the part, with a rough surface, bubbles or popping at the nozzle: moisture. The water turns to steam in the nozzle and the molten plastic bursts and flows out, Bambu Lab explains.
- Blobs and zits on the walls where the nozzle stopped or started: that is oozing, the same excess of plastic in the nozzle, with the same causes.
Causes, from most to least likely
- Wet filament. It is the first cause on Bambu Lab's stringing list, and no setting makes up for it.
- Nozzle temperature too high. The plastic gets runnier and flows out on its own.
- Retraction too short or too slow for the travel. Pressure is left in the nozzle when it starts moving.
- Many long travel moves. Parts spread out over the bed, or models with many separate features.
- A worn nozzle, or one larger than the profile. A 0.6 mm nozzle with a 0.4 mm profile, or a worn nozzle, lets too much plastic out. Prusa adds that PETG can leave residue inside the nozzle after long use, so it is worth cleaning.
Bambu Lab and Prusa pages checked November 2026.
The settings, in the right order
Change one at a time and print the same test after each change; touching three things at once hides which one worked.
| Order | Setting | Where to start | How to change it | Limit |
|---|---|---|---|---|
| 1 | Dry the filament | 65 °C for 6 to 8 hours | — | whatever the maker specifies |
| 2 | Nozzle temperature | the profile value | down 5 °C at a time | the bottom of the maker's range |
| 3 | Retraction distance | direct drive: about 1 mm; Bowden: about 3 mm | gradually, with the retraction test | direct drive: 2 mm; Bowden: the shortest value that gives a clean tower |
| 4 | Retraction speed | direct drive: 20 mm/s; Bowden: 40 mm/s | a little faster | when the extruder starts skipping or chewing filament |
| 5 | Nozzle path | turn on wipe and avoid crossing walls | — | — |
| 6 | Part fan (after layer 3) | 20% | gradually | half power, if strength matters |
1. Dry the spool. Polymaker gives 65 °C for 6 hours for PolyLite PETG; Bambu Lab gives 65 to 70 °C for 8 hours in a drying oven. The step-by-step is in the guide to drying wet filament. If the spool will print for many hours, keep it in a sealed box with desiccant while it prints.
2. Lower the temperature. Prusa suggests going 5 to 10 °C below the profile and checking whether the strings shrink. Stay inside the maker's range: Polymaker gives 230 to 260 °C for PolyLite PETG, and Bambu Lab gives 240 to 270 °C for its standard PETG and 230 to 260 °C for PETG HF. Below the range, layers bond poorly and the part ends up weak.
3. Set the retraction distance for your extruder type. On a direct drive, the motor sits on top of the hotend, and short retractions are enough: Polymaker gives 1 mm, and Bambu Lab and Prusa (for the MK3S and MK2.5S) recommend staying at or under 2 mm, because too long a retraction can cause clogs. On a Bowden, the motor pushes the filament through a long tube, so retraction has to be longer: Polymaker gives 3 mm, and Prusa's factory profile for the MINI uses 3.2 mm.
4. Adjust the retraction speed. Polymaker gives 20 mm/s for direct drive and 40 mm/s for Bowden. Faster helps up to the point where the motor skips steps or the drive gear chews the filament, Prusa warns.
5. Shorten and clean up the path. Turn on Avoid crossing walls in Bambu Studio and OrcaSlicer, Avoid crossing perimeters in PrusaSlicer, or Combing Mode in Cura: the nozzle travels inside the part, where any string stays hidden. Keep Wipe while retracting and retract on layer change turned on. Lower Z hop (Lift Z in PrusaSlicer), which Prusa names as a source of stringing, but don't zero it if the nozzle starts hitting the part. And keep the minimum travel for retraction low: Prusa uses 1 mm and warns that higher values increase stringing.
6. Use the part fan. Prusa says cooling PETG reduces stringing and recommends the fan off for the first layers and at half power after that; Polymaker gives 20%. More fan gives a cleaner surface but weaker bonding between layers.
The temperature tower and the retraction test
Don't guess: print the tests. In OrcaSlicer, the Calibration menu has Temperature (a tower of blocks at different temperatures, in 5 °C steps) and Retraction test (a tower that increases retraction with height). Bambu Studio has the same tests, which show up when you turn on Developer Mode in preferences and are meant for third-party printers, according to Bambu Lab's calibration guide. On the temperature tower, pick the coolest block that still has good layer bonding and a good surface. On the retraction tower, Bambu Lab's rule is the shortest length that gives the neatest tower; if the top of the tower is still full of strings, the filament needs drying. In PrusaSlicer and Cura, you can download a ready-made tower and change the temperature by height (in Cura, with the ChangeAtZ script).
Print the temperature tower before the retraction test: at the wrong temperature, the retraction test points to the wrong value.
Whatever is left: finishing with a heat gun
Thin strings disappear with a quick pass of a heat gun. Prusa suggests about 200 °C, aimed at the strings for one or two seconds and no longer, so the part doesn't deform. Thick strings come off better with a hobby knife or flush cutters before the hot air.
How to keep it from coming back
- Store PETG sealed with desiccant; for PETG HF and PETG Translucent, Bambu Lab treats this as required.
- Place parts closer together on the bed: Bambu Lab recommends reducing the spacing to shorten travel.
- Save the values that worked in the filament profile, not the printer profile. In Bambu Studio, per-filament retraction overrides (Setting Overrides) leave PLA with its own values.
- Replace the nozzle when it is worn, and check that the diameter in the slicer matches the nozzle installed.
What stringing costs
Stringing usually doesn't ruin the part: the cost shows up in your finishing time. An example, with stated assumptions: a batch of 20 PETG parts that, because of stringing, need 5 minutes of cleanup each. That is 100 minutes; at $30 an hour, the calculator's reference labor rate, it comes to $50.00 of labor that was not in the quote.
Drying the spool costs far less. Assuming a 60 W dryer running for 6 hours, it uses 0.36 kWh; at $0.17 per kWh, that is $0.06. The temperature and retraction tests are small prints, and the slicer shows the weight and time of each before you print. If you sell, put the finishing time into the price of the part: the calculator adds prep and finishing minutes into labor.
Frequently asked questions
Why does PETG string more than PLA?
Polymaker itself says PETG is more prone to stringing than PLA. It prints hotter and, in practice, molten PETG tends to stretch rather than snap when the nozzle pulls away. That is why the same profile that leaves PLA clean often leaves strings on PETG, and why PETG deserves its own retraction and temperature in its filament profile.
Does more retraction always fix it?
No. On a direct drive, Bambu Lab and Prusa recommend staying at or under 2 mm, because filament pulled back into the cold part of the hotend can cause a clog. If retraction is already at the limit and the strings remain, go back to the earlier steps: the most likely causes are wet filament or a high temperature.
Does PETG HF change anything?
Yes. In Bambu Lab's table, PETG HF prints in a lower range (230 to 260 °C against 240 to 270 °C for standard PETG), and drying before use and keeping it with desiccant during printing go from recommended to required. In other words, HF is even more sensitive to moisture.
Does printing several parts at once make stringing worse?
Yes, because the nozzle travels more between parts. Place them closer together or print them one at a time: Prusa lists sequential printing (Complete individual objects in PrusaSlicer) as a way to reduce strings between parts, as long as the nozzle can't hit the parts already finished.
Will a new nozzle help?
It can. Bambu Lab lists a worn nozzle among the causes of stringing, and Prusa notes that PETG can leave a layer of residue inside the nozzle after long use. If the strings crept in over time, with the same filament and the same profile, clean or replace the nozzle.