Stringing means thin hairs of plastic stretched between the features of your print — as if a spider had wrapped the model in silk. It appears when molten filament oozes out of the nozzle during travel moves, i.e. when the printhead moves without extruding. The three most common causes are poorly calibrated retraction, a nozzle temperature that is too high, and moist filament — and that is exactly the order in which you should check them.
Where do the strings come from?
Molten plastic in the melt zone behaves a bit like honey on a spoon: even when you stop feeding it, a little will still flow out. When the printhead finishes one wall and travels across a gap to the next one, residual pressure in the nozzle pushes out a small amount of material. That material trails behind the head and solidifies in mid-air as a thin string.
The printer tries to prevent this with retraction — just before a travel move, the extruder pulls the filament back a few millimetres to “suck” the molten material out of the nozzle. If retraction is too short or too slow, or the temperature is so high that the plastic becomes too runny, strings will form anyway. That is why fighting stringing is always a battle on several fronts at once.
Step 1 — calibrate retraction
Retraction is described by two parameters: distance (how many millimetres the filament is pulled back) and speed (how fast it happens). Sensible values depend mainly on the extruder type:
- Direct drive (extruder on the printhead) — the path from the drive gears to the nozzle is short, so 0.5–2.0 mm is usually enough.
- Bowden (extruder on the frame, filament running through a PTFE tube) — the slack and springiness of the tube must be compensated with distance, typically 3–6 mm.
Start in the middle of the range and print a stringing test tower (e.g. two slim pillars side by side — you will find such models in any model library under “retraction test”). Change one parameter at a time: distance in 0.2 mm steps for direct drive or 0.5 mm steps for Bowden. Careful: too much retraction is harmful too — it can pull molten material up into the heatsink and end in a clog.
Step 2 — lower the nozzle temperature
The hotter the nozzle, the runnier the plastic and the more eagerly it oozes on its own. If retraction is already set sensibly and strings still appear, lower the temperature in 5 °C steps and compare the results. The quickest way is to print a temperature tower — a tower whose consecutive segments print at progressively lower temperatures.
You will find approximate ranges for popular materials in our temperature table, and a detailed discussion for PLA in our guide on PLA printing temperature. Do not go below the manufacturer's lower limit though: printing too cold means weaker layer bonding.
Step 3 — check whether your filament is moist
This is the most commonly overlooked cause of stringing. Water absorbed by the filament from the air flashes into steam inside the nozzle. The steam increases pressure in the melt zone and literally pushes the plastic out — your retraction can be perfect and you will still get strings.
Typical symptoms of moisture: hissing and popping while printing, a dull, rough surface, tiny bubbles, and stringing that appeared “out of nowhere” on a proven profile. PETG, TPU and nylon absorb moisture fastest; PLA is more resistant, but after months in open air it can surprise you too. We described the remedies step by step in our guide on storing and drying filament.
Step 4 — fine-tune travel moves in the slicer
- Travel speed — the faster the head crosses the gaps, the less time there is for oozing. Values around 150–200 mm/s are safe for most machines.
- Combing / “avoid crossing walls” — the slicer will route travel moves over infill instead of over empty space, so any ooze stays inside the model.
- Z-hop — lifting the nozzle during travel moves protects the print from scratches, but often makes stringing worse, because it lengthens the path and detaches the nozzle from the material. Enable it only when you really need it.
- Wipe — a short “wipe” of the nozzle against the freshly printed wall before a travel move collects the leftover material and helps noticeably with PETG.
Starting settings against stringing
| Material | Nozzle temperature | Retraction (direct drive) | Retraction (Bowden) | Retraction speed |
|---|---|---|---|---|
| PLA | 190–210 °C | 0.5–1.0 mm | 3–5 mm | 35–45 mm/s |
| PETG | 220–240 °C | 1.0–2.0 mm | 4–6 mm | 25–35 mm/s |
| TPU | 210–230 °C | 0.5–1.0 mm (or none) | as short as possible | 15–25 mm/s |
Treat the table as a starting point, not gospel — every combination of printer, nozzle and filament behaves slightly differently. With PETG, slower retraction plus wipe works better; with TPU, keep retraction to a minimum, because flexible filament tangles easily in the extruder.
Most common mistakes
- Changing several parameters at once — after the print you do not know what actually helped. One test, one change.
- Cranking retraction up endlessly — beyond sensible values the strings do not disappear, but the risk of clogs and ground-down filament grows.
- Ignoring moisture — calibrating retraction on wet filament is a waste of time; dry first, test later.
- Testing on large models — a test tower prints in fifteen-odd minutes, a large model takes hours. Calibrate on small samples.
- Z-hop left on “because it was in the profile” — check whether your prints really need it.
Frequently asked questions
Does stringing always mean bad settings?
No. Very often the culprit is moisture in the filament or simply a worn-out nozzle. If a proven profile suddenly started stringing, dry the filament first and only then touch the settings.
What is a good starting retraction for PLA?
For a direct drive extruder a good starting point is 0.8 mm at around 40 mm/s; for Bowden — 4–5 mm at 35–45 mm/s. Then fine-tune in small steps on a test tower.
Does Z-hop help with stringing?
Usually not — more often it makes it worse, because it lengthens travel moves and detaches the nozzle from the fresh material. Z-hop is mainly there to protect delicate prints from nozzle strikes, not to fight strings.
How do I remove strings from a finished print?
A quick sweep of the model with hot air from a heat gun works best — the strings shrink and vanish in a fraction of a second. Keep the heat source moving and at a safe distance so you do not melt the walls. Cut off thicker leftovers with a hobby knife and sand gently.
Summary
Stringing is not a printer defect — it is a signal that one piece of the puzzle (retraction, temperature, moisture or travel routing) needs attention. Go through the four steps above in order, change one parameter at a time, and the strings will disappear from your prints for good.
The material itself matters a lot too: a consistent, well-packaged filament is simply easier to calibrate. If you are looking for a predictable everyday material, have a look at our PLA filament collection — for example Porima PLA ships vacuum-sealed, so you start calibrating with dry, fresh material.