How to print TPU without stringing or jams
TL;DR
- Dry the spool at 55 °C for 4 hours if it has been open.
- 220–240 °C nozzle, 30–60 °C bed, no glue on textured PEI.
- Direct drive: 1–2 mm retraction at 20–30 mm/s. Bowden: 4–6 mm or turn it off and use wipe.
- Slow down: 30 mm/s for 85A, up to 80 mm/s for 95A on a direct-drive high-speed printer.
Why TPU behaves differently
TPU is an elastomer: push on it and it compresses rather than sliding. Anywhere the filament path has slack, the filament buckles instead of feeding. Every setting below exists to remove slack, reduce pressure or slow things down.
Direct drive vs Bowden
A direct-drive extruder sits on the hotend, so there is almost no path for the filament to buckle in. That is why 85A and 90A are direct-drive only, and why 95A prints two to three times faster on direct drive.
On a Bowden machine keep the tube short, tighten couplers, and print 95A or harder at 20–30 mm/s with retraction reduced or disabled.
Settings that matter
Start from the slicer profile on the product page, then adjust in this order.
| Setting | Direct drive | Bowden |
|---|---|---|
| Nozzle | 220–235 °C | 225–240 °C |
| Bed | 30–50 °C | 30–50 °C |
| Speed | 30–80 mm/s by grade | 20–30 mm/s |
| Retraction | 1–2 mm at 20–30 mm/s | 4–6 mm or off, wipe on |
| Cooling | 50–100 % | 50–100 % |
| Flow | 95–100 % | 95–100 % |
How to print TPU, step by step
- Dry the spoolDry at 55 °C for 4 hours in a filament dryer or oven with a thermometer. Wet TPU pops, strings and jams.
- Load the profileImport the FilamentBay TPU profile for your slicer from the product page. It sets temperature, speed and retraction for the grade.
- Loosen the extruder tensionBack the idler off until the filament feeds without being flattened. Over-tension is the most common cause of grinding.
- Print slow for the first layerFirst layer at 15–20 mm/s on a clean textured PEI sheet at 30–50 °C. No glue; TPU sticks hard to smooth PEI.
- Tune retractionPrint a retraction tower. Raise retraction distance in 0.5 mm steps until stringing stops, never above 2 mm on direct drive.
