TPU Printing Guide: How to Print Flexible Filament
Contents
With TPU you can print parts that flex like rubber: phone cases, gaskets, vibration pads, non-slip feet. But its flexibility causes trouble during printing. TPU pushed too fast bends and jams between the extruder and the nozzle. The fix fits in three phrases: print slowly, reduce retraction and leave no gap where the filament can buckle.
What is Shore hardness?
TPUs are classified by hardness on the Shore A scale. The lower the number, the softer the material and the harder it is to print.
| Hardness | Trait | Printing difficulty |
|---|---|---|
| 98A | Firm, slightly flexible | Easy to medium |
| 95A | The most common, a good balance | Medium |
| 85A–90A | Clearly soft | Hard |
| Below 85A | Very soft | Very hard, direct drive a must |
If you are new, start with 95A.
Extruder type matters
Because TPU is flexible, it tends to buckle when pushed. The longer the path the filament travels between the extruder gear and the nozzle, the higher the risk of jamming.
- Direct drive: The best system for TPU. The short, enclosed path between the gear and nozzle prevents the filament from buckling.
- Bowden: TPU of 95A and harder can be printed at very slow speeds. Softer TPU usually fails on a Bowden.
If there is a gap in the extruder between the gear and the hotend entrance, TPU escapes through the gap and wraps around the gear. Extruders with a filament guide that closes this gap are ideal for TPU.
Recommended settings (starting point for 95A)
| Setting | Value |
|---|---|
| Nozzle temperature | 220–240 °C |
| Bed temperature | 40–60 °C |
| Print speed | 15–30 mm/s (Bowden), 20–40 mm/s (direct drive) |
| Retraction | Off, or 0.5–1 mm at low speed (on direct drive) |
| Part cooling fan | 50–100% |
| Volumetric flow | Keep low, about 3–5 mm³/s |
These values are for a start. Fine-tune for your own filament by printing a temperature tower.
Step-by-step tips
1. Print slowly
In fast printing the extruder pushes TPU quickly, but the nozzle cannot melt the flexible plastic at the same rate. The filament caught in between buckles. Lowering speed is the most important rule with TPU. Travel speed can stay high; just lower the speeds at which extrusion happens.
2. Reduce or turn off retraction
During retraction flexible filament is stretched, and when it is pushed back it buckles. This leads to under-extrusion and jams.
- First try with retraction turned off entirely.
- If stringing is too much, try 0.5–1 mm at low speed (20–25 mm/s) on direct drive.
- Having the nozzle travel through the inside of the part (combing) makes stringing invisible.
- Detailed explanation: Retraction settings.
3. Loosen the extruder tension
If the extruder arm holds TPU too tight, it squashes the filament and deforms it. Loosen the tension a little from the PLA setting.
4. Dry the filament
TPU absorbs moisture very quickly. Wet TPU foams, strings and has a rough surface. Dry it at 45–55 °C for a few hours before printing. See How to dry filament.
5. Let the spool run free
If the spool catches, flexible filament stretches and extrusion becomes uneven. Make sure the spool turns freely. Feed the filament to the printer from above, along a short, straight path.
6. Bed adhesion
TPU usually sticks well to the bed. It can stick too much to smooth PEI; a glue stick as a release agent makes removal easier. A glass bed is also a good surface for TPU.
Design tips
- Wall count and infill determine a part's flexibility. Low infill and few walls make the part softer. Dense infill gives a stiffer part. See Infill settings.
- Gyroid infill is a good choice for TPU parts because it gives even flexibility in every direction.
- Fine details and sharp overhangs are hard in TPU. Reduce regions that need support; supports are hard to separate from a flexible material.
Common problems
| Problem | Cause | Fix |
|---|---|---|
| Filament wrapped around the gear | High speed, gap in the extruder | Lower the speed, use an extruder with a guide |
| Under-extrusion | Retraction, tension, speed | Turn off retraction, loosen the tension, slow down |
| Heavy stringing | Moisture, high temperature | Dry it, lower the temperature by 5 °C |
| Rough surface | Moisture | Dry the filament |
Frequently asked questions
Can TPU be printed on a Bowden printer?
TPU of 95A and harder can be printed at very slow speeds (15–25 mm/s) with retraction off. Softer TPU needs direct drive.
How durable is a TPU part?
TPU is very resistant to wear and impact, and the bond between layers is strong too. This makes it very suitable for parts that take constant impacts, such as foot bumpers and protective cases.