Flexible TPU keeps getting jammed and prints poorly
TPU doesn't fail because it's difficult, but because it's printed using PLA settings. It's soft, so pushing it fast is like pushing a piece of string.
What the failure looks like
The filament bends inside the extruder and slips out the sides, the part comes out stringy all over, or extrusion stops completely.
Causes, most likely first
- 01
Excessive speed
Above 30 mm/s the filament compresses instead of feeding through.
- 02
Gaps in the filament path
In bowden setups or extruders with a gap between the drive gear and heatbreak, the TPU bends and pops out.
- 03
High retraction
It stretches the material and disrupts the flow for seconds.
- 04
Moist filament
TPU absorbs a massive amount of moisture.
Step-by-step fix
1. Reduce the speed to 15-25 mm/s
And keep a constant speed, without sharp accelerations.
2. Reduce retraction almost to zero
0-0.5 mm on direct drive. On bowden, 1-2 mm and accept some stringing.
3. Adjust temperature to 215-230 °C
Bed 50-60 °C. Fan at 40-60%.
4. Loosen the extruder tension slightly
Tightening it more doesn't help: it deforms the filament.
5. Dry it first
50-55 °C, 6-8 hours.
6. Choose the right hardness
95A is the easiest and sufficient for most cases and stoppers. 85A is softer and much harder to print.
So it doesn't happen again
- Always store TPU in an airtight bag.
- Use specific TPU profiles, not modified PLA profiles.
Related questions
Can TPU be printed on a bowden setup?
Yes, with 95A, low speed and patience. It is much more forgiving with a direct drive extruder.
Does it hold up outdoors?
Reasonably well, better than PLA. For permanent outdoor use, ASA is still better if the part doesn't need to flex.
Keep reading
What if it isn't worth your time?
Sometimes the part is more urgent than the learning curve. We're a workshop in Viladecavalls: send us the file and we'll print it with the right material and settings.
Still not working?
Tell Marco which printer and material you use and he'll tell you what to change.
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