TPU calibration: temperature tower and flow test
Two tests turn a TPU preset into settings that work on your machine: a temperature tower for bonding and surface, then a flow test for exact extrusion.
Flexible, rubber-like filament. Prints slowly and needs a direct-drive extruder or a well-tuned Bowden setup. Great for phone cases, gaskets, and wearables.
Starting point
| Nozzle | 220–240 °C |
|---|---|
| Bed | 40–60 °C |
| Drying | 50 °C × 6 h |
| Enclosure | Not required |
Temperature tower
Print a tower with five bands across the range, keeping flow at 1.00 and cooling fixed.
Five bands: 220 · 225 · 230 · 235 · 240 °C
Dry the filament at 50 °C for 6 h first. Moisture shows up as stringing and a rough surface and will make the tower misleading. This material strings easily, so judge the bands on stringing as well as strength.
Read the tower in this order:
- Layer adhesion — snap each band. A clean, strong break above the band is good; a brittle, flaky break means too cold.
- Stringing — look at the gaps between features. The cooler bands should have less.
- Surface and bridging — glossy, blobby or drooping bands are too hot.
Pick the lowest band that still gives strong layer adhesion and a clean surface. Lower is better for stringing and overhangs, as long as the part is not brittle.
Flow test
Print a single-wall cube with two perimeters, no top or bottom layers, and your normal line width. Measure the wall in several places with calipers.
extrusion multiplier = target wall width ÷ measured wall width
For a 0.45 mm line width, a measured 0.48 mm wall means 0.45 ÷ 0.48 = 0.94. Set the multiplier to 0.94 and print the cube again to confirm.
Change only the multiplier between tests. If the wall varies by more than 0.03 mm, fix mechanical issues (loose belts, a worn nozzle, inconsistent filament diameter) before tuning further.
Retraction starting points
Print a retraction test with two towers 30 mm apart. Increase the retraction distance in 0.2 mm steps until stringing stops, then back off one step to protect layer adhesion.
- Direct drive: 0.6 mm at 30 mm/s.
- Bowden: 5 mm at 40 mm/s.
- Flexible filament: about 0.4 mm on direct drive or 1.5 mm on Bowden, at 20 mm/s.
Then print a 20 mm calibration cube and a 10 mm hole. FDM holes usually come out small; add 0.05–0.15 mm of hole compensation rather than scaling the whole part.
When is it good enough?
- The temperature band snaps cleanly and has no stringing.
- The measured wall is within 0.02 mm of the line width.
- Two towers 30 mm apart print with no visible strings.
- A 20 mm cube measures 20.0 ± 0.1 mm.
Tools that help
Volumetric flow calculator
Check whether your speed exceeds what the hotend can melt.
Print cost calculator
Price the part once the profile is dialled in.
FAQ
What temperature should I print TPU at?
The usual range is 220–240 °C. Start in the middle and pick the final value from a temperature tower.
How do I calibrate flow for TPU?
Print a single-wall cube, measure the wall with calipers, and set the extrusion multiplier to target width ÷ measured width.
Do I need to dry TPU before printing?
Yes. Dry it at 50 °C for 6 h — this material absorbs moisture.