How to Fix Stringing in 3D Prints

Stringing is the thin web of plastic stretched across the gaps in a print, the kind that looks like a spider got loose inside the machine. It comes from one thing: molten plastic oozing out of the nozzle during travel moves. The good news is that it’s one of the most fixable problems in 3D printing, and most of it disappears once you fix the filament and the temperature.

Why stringing happens

When the hotend lifts and moves through open air between two printed areas, the plastic inside is still hot and still under pressure. Gravity and that residual pressure push a little out. When the nozzle lands again, the ooze gets dragged into a string.

Three things make it worse:

• Wet filament. Plastic that has soaked up moisture flashes to steam at print temperature. It sputters, foams, and oozes far more than dry filament. This is the cause people overlook most often.
• Temperature too high. Hotter plastic is runnier and flows more freely under its own pressure. Run the nozzle 20C above what the filament actually needs and it will string badly even when everything else is dialed in.
• Not enough retraction. Retraction pulls filament backward to relieve nozzle pressure before a travel move. Too little or too slow, and the pressure stays high.

PETG strings more than PLA, full stop. It stays stickier when molten and holds pressure longer, so a PETG profile that looks identical to a clean PLA profile will still throw strings. Nylon behaves the same way and is even thirstier for moisture.

Fix it in order

Work top to bottom, and change one setting at a time so you know what actually helped.

1. Dry the filament

Do this first, especially for PETG, Nylon, TPU, and any spool that’s been open more than a couple of weeks. A genuinely wet spool will defeat every other fix you try.

• Use a filament dryer or a food dehydrator. Common settings: PLA 45C for 4-6 hours, PETG 60-65C for 4-6 hours, TPU 50-55C for 4-6 hours, Nylon 70-80C for 8-12 hours.
• Stay well below the glass transition temperature, or you’ll soften and fuse the spool into a solid block. Keep PLA under 50C.
• An oven works but is risky. Many home ovens swing 15-20C past their setpoint, which is enough to ruin a spool. If you use one, verify the real temperature with a separate thermometer.
• Store dried spools in a sealed box with desiccant. Drying is temporary.

If drying alone clears the strings, stop here.

2. Lower the nozzle temperature

Drop it in 5-10C steps and reprint a test. Keep going down until layers stop bonding well or the extruder starts clicking, then come back up one step.

• Typical clean ranges: PLA 195-215C, PETG 230-245C, ABS 235-250C.
• A 10C drop often removes most of the stringing on its own.

Printing ABS or ASA? Run it in a ventilated space or an enclosure vented outside. The styrene fumes are an irritant you don’t want to breathe in a closed room.

3. Increase retraction distance and speed

If lower temps aren’t enough, tune retraction:

• Direct-drive extruders: start around 0.5-1.5mm. The filament path is short, so they need very little.
• Bowden extruders: start around 4-6mm, sometimes up to 7mm. The long PTFE tube needs more pull.
• Retraction speed of 30-45mm/s is a sane starting point. Raise distance in 0.5mm steps.
• More is not always better. Over-retraction causes filament grinding, clogs, and gaps at the start of each line. If you’re past about 3mm on direct drive or 8mm on Bowden and still fighting strings, the problem is somewhere else, usually moisture or temperature.

4. Enable combing

Combing (called “Avoid crossing outlines” in some slicers) keeps travel moves inside the already-printed area, so any ooze lands on infill instead of an exposed wall. Set it to avoid crossing the outer perimeters. It won’t stop the oozing, but it hides the strings where they don’t show.

5. Increase travel speed

Faster travel gives ooze less time to form a string before the nozzle reaches its destination. Push travel (non-printing) moves to 150-200mm/s if your machine handles it without ringing or skipped steps. This is separate from your print speed.

6. Add coasting and wipe

Last-resort fine-tuning once the big levers are set:

• Coasting cuts extrusion just before the end of a line and lets residual pressure finish it, so there’s less pressure left to ooze.
• Wipe drags the nozzle back over the printed line while retracting, scrubbing off ooze before travel.

Use the test prints

Two prints find the right numbers fast:

• Temperature tower: one model with blocks at descending temperatures, say 250C down to 215C in 5C steps. Print it, find the cleanest block with good bridging and no strings, and use that temperature.
• Retraction test: two posts with a gap between them. The slicer steps retraction distance or speed up the height. Pick the lowest setting that prints the gap clean.

Both take under an hour and save you days of guessing.

Practical takeaway

Print a temperature tower for each new spool and write the winning number on the spool itself. Keep PETG and Nylon in a dry box and run them through a dryer before any print that matters. When strings come back on a profile that used to be clean, suspect moisture first, before you touch a single retraction setting. That one habit clears the large majority of stringing you’ll ever see.