Part four of the troubleshooting series: stringing, sometimes called oozing or “hairy” prints. It’s when thin strands of plastic stretch between separate parts of a model wherever the nozzle travels over open space.
What’s actually happening
Between moves, a small amount of molten plastic keeps oozing out of the nozzle tip under pressure, even when it’s not supposed to be extruding. Retraction is the slicer pulling filament backward slightly before each travel move to relieve that pressure. When retraction isn’t tuned correctly for your setup, oozing during travel moves shows up as strings.
The settings I tuned, in order
- Retraction distance — I started low and increased it in small steps until stringing mostly stopped. Direct-drive extruders typically need far less retraction than Bowden setups, so I didn’t just copy a number from a random guide.
- Retraction speed — faster retraction pulls the filament back before it has time to ooze further, but too fast can grind the filament on some extruders. I tested a range and picked the fastest speed that didn’t cause grinding.
- Nozzle temperature — running a few degrees hotter than necessary makes the plastic thinner and more prone to oozing. Dropping temperature slightly (while staying above where extrusion gets unreliable) reduced stringing noticeably for me.
- Travel speed — faster travel moves mean less time for plastic to ooze out mid-move. I bumped this up once retraction was dialed in.
Retraction distance and nozzle temperature did most of the work. Travel speed was a smaller improvement on top.
A simple test I use
Most slicers have a “temperature tower” or retraction test model built in or freely available — printing one gives a direct visual comparison of stringing at different settings in a single print, which is far faster than testing one variable across many full prints.
Don’t forget the cleanup
A little leftover stringing on an otherwise good print can usually be cleaned off with a heat gun on low, held a few inches away, or just picked off carefully once cooled.
Stringing is one of the most satisfying problems to fix because the improvement is so visible — one good settings change can take a print from hairy to nearly clean.
