How to Fix Stringing on Bambu Lab Printers

Stringing is the web of thin plastic hairs stretched between separate parts of a print, plus the little wisps that cling to towers and pins. It happens when molten plastic keeps oozing out of the nozzle during travel moves. Here is how to fix it, in the order that actually works.

Why stringing happens

Every time the printhead travels without printing, the melt inside the nozzle is under pressure and wants to leak. Three things make the leak worse: filament that has absorbed moisture (steam pushes plastic out of the nozzle), a melt that is hotter and runnier than it needs to be, and too little retraction to relieve the pressure before the move.

That order matters. Most people jump straight to retraction, but on a Bambu printer moisture and temperature cause far more stringing than retraction settings do.

Quick fixes

Advanced tuning: retraction on a direct-drive printer

All Bambu machines are direct drive — the extruder gears sit right on top of the nozzle — so they need far less retraction than the Bowden-tube printers most online advice was written for. Bambu’s filament profiles start at 0.4 mm.

• Increase retraction length in 0.2 mm steps. An extra 0.2–0.4 mm (ending around 0.8–1.0 mm) usually removes the last strings.
• Stay under 2 mm. Longer retractions pull molten plastic up into the heatbreak, where it solidifies and causes clogs.
• Verify retraction speed is around 30 mm/s (the Bambu default). Very slow retraction gives the melt time to ooze anyway.

Bambu Studio: Filament settings → Setting overrides → Retraction length / Retraction speed

Material-specific notes

• TPU always strings a little. Don’t fight it with retraction: keep it at the Bambu default of 0.8 mm and the deliberately slow 10 mm/s retraction speed. More or faster retraction buckles the soft filament and jams the extruder. Dry it and lower the temperature instead — details in our TPU printing guide.
• PC has no temperature headroom. Bambu’s PC profile already prints at the material’s allowed minimum of 260 °C, so you can’t go cooler. Attack moisture and retraction instead.
• PETG: if drying plus a 10 °C drop doesn’t do it, check our complete PETG settings guide — flow and plate choice play a part too.
• No-name/generic filament: the generic profile’s flow ratio is a guess. Run the flow ratio and pressure advance calibrations in Bambu Studio’s Calibration tab before chasing strings.

Test one change at a time

Stringing tempts people into changing temperature, retraction and z-hop in one go — and then they can’t tell which change helped. A better loop: print a small two-tower test (any “retraction test” model works, or just two 20 mm cylinders placed 50 mm apart), change exactly one value, print again. Each test takes a few minutes, and after two or three rounds you know your filament’s sweet spot instead of guessing.

And once a spool is tuned, keep it dry: an open PETG or nylon spool reabsorbs moisture within days, and the strings come back even though your settings never changed. A sealed box with silica — or an AMS with fresh desiccant — preserves the win.