Stringing in 3D Printing: Avoiding Strings Between Parts
are explained briefly when you hover over or tap them.
Stringing is fine plastic strands stretched between separate parts of a print, for example between two towers. In harmless cases it is a few wisps that you can remove briefly with a hairdryer or a lighter. In bad cases the part looks as if it were covered in cobwebs.
Why do the strings form?
When the print head moves from one spot to the next without printing, the nozzle is still hot. Liquid plastic can keep running out of the nozzle and pulls a string as it moves away. The more fluid the material and the longer the travel move, the more strings.
The causes, sorted by frequency
1. Wet filament
Moisture in the filament evaporates in the hot nozzle. The steam pushes material out, even when the printer does not want to print at all. Typical signs: crackling or popping while printing, small bubbles, a rough surface.
Solution: Dry the filament. How to do that and which temperatures suit is covered in Drying and storing filament. Especially with PETG and TPU this is the most common cause.
2. Print temperature too high
The hotter it is, the thinner the plastic flows, and the more easily it runs out.
Solution: Lower the temperature in steps of 5 degrees. The quickest way to find the best value is a temperature tower. How that works is explained in Setting the print temperature correctly.
3. Too little retraction
With retraction, the printer pulls the filament back a little before every travel move so that nothing drips out. If the retraction is too short or too slow, it does not work.
Solution: Increase the retraction in small steps.
| Design | Typical retraction distance | Typical speed |
|---|---|---|
| Direct drive | 0.5 to 2 mm | 30 to 45 mm/s |
| Bowden | 4 to 7 mm | 30 to 50 mm/s |
Do not overdo it: too much retraction can pull material into cold areas and clog the nozzle.
4. Unfavourable travel moves
If the print head travels across open areas instead of over surfaces that have already been printed, more visible strings form.
Solution: In the slicer, enable the option to avoid crossing walls (“Avoid crossing walls” or similar). A somewhat higher travel speed shortens the time in which material can run out.
5. Material that naturally pulls strings
PETG and TPU are much more prone to stringing than PLA. A few fine wisps are normal with these materials.
Solution: Dry first, then adjust temperature and retraction. Whatever is left can be removed in seconds with a heat gun.
Quick checklist
- Is the filament dry? If unsure: dry it.
- Temperature at the lower end of the manufacturer’s range?
- Retraction set to suit the design?
- “Avoid crossing walls” active in the slicer?
- Print a small stringing test before you start the big part.
Always change only one setting per test print. Otherwise you will not know in the end what helped.