TPU has a reputation for being difficult that it mostly does not deserve. Nearly every jam comes from one of three causes, and all three are fixable before you start the print.
Pick the right hardness first
Shore hardness decides how hard the filament is to push:
- 95A is the standard choice. Firm enough to feed like a stiff filament, flexible enough for phone cases, gaskets, and bumpers. Start here.
- 85A is properly rubbery and much harder to feed. Worth it only when the part needs to squash rather than bend.
- Above 95A starts behaving like a hard plastic with a bit of give.
Most disappointment with TPU comes from buying something softer than the job needs.
Extruder and filament path
A direct drive extruder makes life much easier. Bowden setups can print 95A if the tube is short and well constrained, but every millimetre of unsupported filament is somewhere soft plastic can buckle.
Look for gaps. The classic failure is a small void between the drive gears and the hotend inlet, where soft filament curls sideways instead of going down. Removing that gap fixes more TPU jams than any slicer setting.
Check spool drag too. TPU cannot pull hard against a stiff spool holder, so a holder with a bearing beats a fixed rod.
Speed is the setting people ignore
TPU needs time for the melt to keep up with the extruder. Typical guidance:
- Standard TPU: 20 to 30 mm/s on walls
- High flow TPU: up to 80 mm/s, sometimes more
Almost every “my TPU jammed” story starts with someone printing at PLA speeds. If a print is failing and you change one thing, halve the speed.
Retraction and stringing
Keep retraction very low, half a millimetre to one millimetre on direct drive, and near zero on Bowden. Soft filament stretches rather than retracting cleanly, so a big retraction just stores tension that releases in the wrong place.
The cost is stringing. Accept it, reduce travel moves where you can, and clean the finished part with a heat gun or a quick pass with a lighter held well back.
Temperature
Most 95A TPU prints between 210 and 240 °C. The manufacturer’s range is a better starting point than a generic profile, because formulations vary more than they do in PLA. Bed temperature between 30 and 60 °C is plenty, and TPU sticks to textured PEI without adhesive, often enthusiastically.
Cooling around 40 to 50% keeps overhangs tidy without hurting layer bonding, which is exceptional in TPU regardless.
Drying matters more than you think
TPU is hygroscopic. A spool that printed well last month can crackle and foam after a humid fortnight in the open. Dry at 55 to 70 °C for four to eight hours depending on the manufacturer’s guidance, and store it sealed with desiccant.
Wet TPU is the second most common cause of “this spool is faulty” after printing too fast.
Design for the material
- Oversize press fit holes by about 0.2 mm; soft filament squashes under the nozzle and holes come out tight.
- Avoid tall thin towers with lots of travel; the stringing shows.
- Use more perimeters and less infill. Wall count drives flexibility and strength in TPU far more than infill percentage does.
- Vase mode works beautifully for gaskets and bellows.
A working first profile
Nozzle at the middle of the manufacturer’s range, bed 50 °C, walls at 25 mm/s, retraction 0.8 mm, cooling 40%, direct drive, dried spool. Print a 40 mm square gasket. If that comes out clean, raise speed in steps until quality drops and settle just below it.