Advanced 3D Printing

Those fine wispy threads stretched between the parts of your print — stringing (or oozing) — are one of the most common and most fixable 3D printing problems. They happen when molten plastic leaks from the nozzle while it travels across open space. The good news: it's almost always solved by tuning a handful of settings. Here's how to fix it, in the order that actually works. Why Stringing Happens Inside a hot nozzle, filament is molten and under slight pressure. When the print head moves between two points without printing (a 'travel move'), that pressure can push a little plastic out — it cools mid-air into a thin string. The fix is about controlling that leakage: pulling filament back before travel (retraction), not running hotter than necessary, and keeping moisture out of the filament. Fix It in This Order Work through these in sequence — each step removes a cause, and doing them in order stops you chasing the wrong fix. 1. Dry Your Filament First This is the most overlooked cause, and on PETG, TPU, and nylon it's often the whole problem. These materials absorb moisture from the air; when that water hits the hot nozzle it turns to steam, spitting and oozing plastic everywhere. If your filament has been open for weeks and you're getting sudden stringing with little popping sounds, dry it (a filament dryer or a low oven, 45–55 °C for several hours) before changing any other setting. Storing filament sealed with desiccant prevents the problem returning. 2. Lower the Nozzle Temperature Hotter plastic is runnier and oozes more. Drop your nozzle temperature in 5 °C steps and watch the strings shrink. The cleanest way to find the sweet spot is a temperature tower, which prints the same shape at several temperatures so you can see exactly where stringing stops without sacrificing layer strength. 3. Tune Retraction Retraction pulls filament back before a travel move, relieving nozzle pressure. The two settings are distance (how far) and speed (how fast): Direct-drive extruders: 1–2 mm distance, 25–45 mm/s speed. Bowden extruders: 4–6 mm distance (the long tube needs more), similar speeds. Increase distance gradually until strings disappear — too much causes jams and gaps. A retraction test print dials this in fast. 4. Enable Travel Optimisation In your slicer, turn on options like 'combing' / 'avoid crossing perimeters' (keeps travel moves inside the model so any ooze is hidden) and 'wipe before retract'. 'Z-hop' lifts the nozzle during travel and can help, though it slightly slows printing. 5. Increase Travel Speed The faster the head crosses open space, the less time plastic has to ooze and the less the string can form. Raising travel speed to 150–200 mm/s often visibly reduces fine stringing. Material-Specific Notes PETG is the classic stringer — it's naturally prone to it and very moisture-sensitive. Expect to dry it, run slightly cooler, and tune retraction carefully. See our PETG/TPU/ASA settings guide. TPU strings because it's flexible and hard to retract. Minimise retraction, print slow, and keep it dry — long retractions just snarl flexible filament. PLA rarely strings badly; if it does, it's usually temperature or moisture. ASA/ABS ooze less than PETG but still benefit from drying and tuned retraction. Quick Diagnostic Symptom Most likely cause First fix Sudden stringing on filament that printed fine before Moisture Dry the filament Popping/crackling sounds while printing Moisture Dry the filament Fine consistent strings everywhere Temperature too high / retraction too low Lower temp, tune retraction Blobs and zits on surface Retraction / coasting / wipe Enable wipe, tune retraction Strings only on flexible filament Over-retraction of TPU Reduce retraction, slow down Consistent Filament Makes This Easier A lot of "random" stringing is really moisture or inconsistent diameter. Our filament is made in Spain to tight ISO/REACH tolerances and sealed with desiccant, so it arrives dry and prints consistently. Once you've dialled in your settings on a good spool, they'll keep working. Still fighting strings after all this? Tell us your material and printer and we'll help you troubleshoot.