Fix stringing: get rid of strings in 3D printing in four steps

Stringing is the fine strings or hairs a printer leaves behind on travel moves between two parts. They look like cobwebs and are especially common with PETG and TPU. The good news: usually a single change is enough, and the right order saves you a lot of trial and error.

Typical stringing: two test towers with a web of fine strings between them.

In 30 seconds

The four most common causes, sorted by likelihood. Change only one thing at a time and print a small test afterwards.

The filament is wet. Dry it. This is the most common cause.
The nozzle is too hot. Lower it in 5 °C steps.
Retraction is too short or too slow. Increase it step by step.
Travel moves are too long. The print head should not cross over the part.

How to tell the cause

Strings plus crackling or hissing at the nozzle, a rough surface, tiny bubbles: the filament is wet.
Strings and small drops at the nozzle, a glossy surface: the temperature is too high.
Strings only on long paths between parts, not on short ones: retraction and travel moves.
Another spool of the same material prints cleanly: the problem is the spool, so moisture.

A comparison spool is the best tool you have. If a second spool prints cleanly, you do not need to touch a single setting.

Step 1: Dry the filament

Filament absorbs water from the air. When heated, it turns to steam and pushes material out of the nozzle even when the printer is not feeding.

Rules of thumb: PLA about 45 to 55 °C, PETG about 60 to 65 °C, at least 4 to 6 hours. The manufacturer's figure on the spool takes precedence.
A filament dryer is safer than a kitchen oven, whose temperature often deviates a lot.
Afterwards store it airtight or print straight from the dryer, otherwise the spool is wet again within days.

Step 2: Lower the temperature

Filament that is too hot is runny and drips. Lower the nozzle temperature in 5 °C steps. If it gets too cold, you will notice gaps in the walls and poor layer adhesion. A temperature tower prints several temperatures in one go and shows you the best value for that exact spool.

Step 3: Set up retraction

During retraction the extruder pulls the filament back briefly before the head moves.

Rules of thumb: direct drive extruders often 0.4 to 1.0 mm, Bowden 3 to 6 mm. Speed about 30 to 45 mm/s.
Increase in small steps: 0.2 mm for direct drive, 0.5 mm for Bowden.
More is not always better. Too much retraction can cause gaps or a clog.
Bambu Lab's default profiles are tuned for original filament. If only third-party filament strings, dry it and check the temperature before you change retraction.

Step 4: Shorten travel moves

Enable the option to avoid crossing walls. The head then travels inside the part instead of over the outer wall.
Lifting the nozzle on every travel move (Z hop) can encourage strings with some filaments. Try it switched off or with a small value.

Slicer settings

Names can differ depending on the program version.

Bambu Studio and OrcaSlicer

Retraction: printer settings, Extruder section, Retraction. Length and speed are there.
Z hop: in the same section (Z hop when retracting). OrcaSlicer also offers a spiral Z hop.
Avoid crossing walls: in the process profile under Quality.
If the filament profile overrides retraction, the filament profile value applies.

PrusaSlicer

Retraction: Printer Settings, Extruder 1, Retraction section. Length, Speed and Lift Z are there.
Avoid crossing perimeters: Print Settings, Layers and perimeters, Advanced.
Here too, the filament profile can override retraction.

UltiMaker Cura

Retraction: material settings, Retraction section. Enable Retraction, Retraction Distance and Retraction Speed are there.
Travel: set Combing Mode to Not in Skin.

If it still persists

Check the nozzle. A worn or dirty nozzle can drip.
Thin strings can be removed afterwards by carefully passing a heat gun over them, or by cutting them off.
Print a small test model with two towers so you can check each change on its own.