How to Prevent Stringing in 3D Prints
Contents
If there are thin cobweb-like strands between two pillars of the part you take off the bed, the nozzle is oozing plastic as it moves through empty space. This is called stringing. Insufficient retraction, high nozzle temperature or wet filament is usually responsible. PETG and TPU are more trouble than PLA in this respect.
Symptoms
- Thin strands like hairs between two pillars or parts.
- Small plastic beads and "hair"-like protrusions on the part surface.
- Sometimes the strands thicken into blobs that stick to the part.
Stringing does not usually affect the strength of a part, but it spoils its look and needs cleanup.
What causes it?
There is always some melted plastic inside the nozzle, and it is under pressure. When the nozzle moves without printing, that pressure pushes plastic out. Retraction reduces the pressure by pulling the filament back a short distance. If this setting is insufficient, the temperature is high or the filament is wet, the leak gets worse.
1. Adjust the retraction settings
This is the first place to look. Retraction must be enabled in the slicer. Starting values:
| Extruder type | Retraction distance | Retraction speed |
|---|---|---|
| Direct drive | 0.5–2 mm | 25–45 mm/s |
| Bowden | 4–6 mm | 35–50 mm/s |
Test by raising the distance in steps of 0.5 mm (1 mm for Bowden). Too much retraction can wear the filament at the gear and lead to a clogged nozzle. So do not go above the recommended range.
We cover the retraction test and other related settings in detail in Retraction settings.
2. Lower the nozzle temperature
Hot plastic is more fluid and leaks more easily. Lower the temperature in 5 °C steps. If you lower it too far, layer bonding weakens and under-extrusion starts.
The best way to find the right temperature is to print a temperature tower. Compare the amount of stringing in each section of the tower and choose the lowest temperature with good layer bonding.
3. Dry the filament
When wet filament is heated, the water inside turns to steam, the plastic foams and it leaks uncontrollably from the nozzle. Signs of moisture:
- Popping and cracking sounds during printing.
- Bubbles and roughness on the surface.
- Heavy stringing that does not go away whatever the retraction setting.
PETG, TPU and nylon absorb moisture quickly. You can find how to dry it in the How to dry filament guide.
4. Use the travel settings
Slicers have extra settings that reduce stringing:
- Travel speed: The faster the nozzle crosses empty space, the less it leaks. 150 mm/s and above usually gives good results.
- Combing / Avoid crossing walls: Makes the nozzle pass through the inside of the part as much as possible. Leaked plastic stays on the inside, not outside.
- Wipe: During retraction, the nozzle moves a short distance along the wall to wipe its tip.
- Minimum travel / retraction distance: Prevents unnecessary retraction on very short moves.
- Z hop: Lifts the nozzle during travel. It prevents collisions but sometimes increases stringing. Try turning it off when you have a stringing problem.
5. Tips by material
- PLA: Retraction and temperature settings are usually enough.
- PETG: It oozes by nature. Some stringing is normal. Instead of raising retraction a lot, lower the temperature, raise travel speed and dry the filament.
- TPU: Because it is flexible, it does not respond well to retraction. Reduce or turn off retraction and slow the print. See the TPU printing guide.
Cleaning remaining strands
A small amount of thin strands can be removed by a quick, short blast of hot air from a heat gun or hair dryer. If you hold the heat on one spot, the part softens and loses its shape. For thick strands use a fine-tipped hobby knife.
Frequently asked questions
How much retraction will end stringing?
Beyond a certain point retraction does no good and does harm. Before going above the recommended range, check the temperature and filament moisture.
Why does PETG string more than PLA?
When melted, PETG stays stickier and fluid for longer. A little stringing is normal with PETG. Drying and a lower temperature usually give enough improvement.
Are stringing and ghosting the same thing?
No. Stringing is thin plastic strands. Ghosting is a vibration mark that shows up as ripples on the surface. See Ghosting and ringing.