Slow down before you touch retraction
TPU does not string like PETG or PLA: the hairs are thick and stretchy, and the usual retraction fix can kink the soft filament. The first thing to change on a TPU stringing problem is speed, because printing too fast is what makes the flexible filament ooze.
Why speed matters most
TPU is flexible, so printing too fast and too hot makes it ooze and string. Polymaker's TPU printing guide recommends slowing down and keeping the temperature in a tight range. Damp TPU strings far more than dry filament, so drying comes first.
Recommended settings
Each value below is quoted from the Polymaker TPU material guide.
- Print speed — slow down to 15–40 mm/s for standard TPU; slower speeds prevent the filament from buckling, and too fast is a main cause of stringing. (Polymaker TPU)
- Nozzle temperature — use 210–250 °C (varies by brand; start around 230 °C) and lower it if stringing continues. (Polymaker TPU)
- Bed temperature — 40–60 °C; a heated bed improves adhesion. (Polymaker TPU)
- Dry the filament — TPU is hygroscopic; pre-dry at 50 °C for 24 hours before printing if it has absorbed moisture. (Polymaker TPU)
Confirming the fix
Slow the print first, then run a small block or a short flexible hinge. When the strings disappear and the side walls stay smooth, the speed and temperature are right. If hairs remain, lower the temperature in small steps rather than adding retraction — on TPU, aggressive retraction kinks or strips the filament faster than it helps.