TPU 3D printing: the settings that stop stringing and jams

Why TPU fights back

TPU, or thermoplastic polyurethane, is the go-to filament when you need a part that bends instead of breaks. Phone cases, gaskets, drone bumpers, and wearable gear all start with it. The trouble is that TPU is soft and springy on the spool, and that same flexibility makes it buckle, ooze, and string if your printer treats it like PLA.

Start with a dry, warm setup

Flexible filament drinks moisture from the air, and wet TPU prints like a bubbling mess. Dry it at 45 to 50 degrees C for several hours before you print, and keep it in a dry box if your room is humid. Sovol's own guide puts the nozzle at 220 to 235 degrees C and the bed at 40 to 60 degrees C, which is a solid baseline for most 95A spools.

Slow down and let it breathe

Speed is where most TPU failures begin. Drop to 20 to 40 millimeters per second. Fast moves stretch the filament and cause jams in the Bowden tube. If your printer uses a Bowden setup, consider a direct drive upgrade or at least short, tight filament paths. Direct drive printers handle TPU far better because the extruder grips the filament right at the hot end.

Retraction is a trap

The instinct with stringing is to crank retraction. With TPU that backfires. High retraction pulls the soft filament into a knot inside the extruder. On a direct drive, try 1 to 2 millimeters at low speed. On a Bowden, you may need a little more, but keep it as low as you can. Some makers run zero retraction and just accept tiny zits at the cost of cleaner travel moves.

Cooling and geometry

Use part cooling, but not so much that layers fail to bond. Around 30 to 50 percent fan is a good start. Watch your model too: thin towers and sharp overhangs fight flexible filament. Wider bases and gentle overhangs print far more reliably.

The payoff

TPU asks for patience, then pays you back with parts that survive being stepped on, stretched, and dropped. Once you tune temperature, speed, and retraction for your machine, flexible printing stops being a chore and becomes one of the most useful things your printer can do.