Around 30 mm/s for TPU 95A. Softer grades want less; the harder 98A will take more.
The cost of that is substantial. A phone case that prints in 1.02 hours in PLA at 100 mm/s takes 3.36 hours in TPU at 30 mm/s — the same 25 cm³ of plastic, three times the machine time.
The limit is mechanical, not thermal
TPU melts perfectly well at speed. The problem is upstream: flexible filament behaves like a rope, and pushing it hard makes it buckle in any unconstrained gap between the drive gear and the melt zone.
Once it buckles, it coils inside the extruder, jams, and usually needs the hotend stripping. That is why the speed limit is really a limit on how fast the extruder can push without losing control of the filament.
Which means the number depends on your machine more than on the spool:
- Direct drive with a short, constrained path — the best case, and where 30 mm/s or a little more is realistic
- Bowden — much worse, because the whole tube is unconstrained. Some Bowden machines never print soft TPU acceptably at any speed
- Geared extruders with a light spring tension — better, because grip is achieved without crushing the filament
Hardness changes the answer
- TPU 85A is a difficulty-5 material and the slowest of the three; treat 30 mm/s as an upper bound rather than a target
- TPU 95A is the mainstream compromise and where most published settings apply
- TPU 98A is nearly rigid, rated difficulty-2, and prints close to normal speeds
If a flexible part does not actually need to be very soft, printing 98A instead of 85A is the cheapest speed improvement available.
The other settings that go with it
Retraction as short as you can get away with, or none at all — retracting flexible filament is what pulls it into a coil. Acceleration and jerk turned down, so the extruder is never asked for a sudden change. And a spool holder that unwinds with almost no resistance, because TPU stretches rather than dragging the reel round.
Set the speed field to whatever your extruder tolerates in the print time estimator and the cost in hours appears immediately. Hardness, density and drying for each Shore grade are listed on the TPU 95A page, and the same job at PLA speeds is compared in how long to print a phone case.