How to Print TPU: Shop-Tested Settings for Soft Filament That Won't Jam

TPU is the filament that makes people give up on flexible printing. It buckles in the extruder, comes out with a beard of strings, and the first layer looks like it was laid by a caterpillar. Then someone online tells you to buy a direct-drive extruder. It is usually not the hardware. Nine times out of ten it is four settings, and you can fix them at the slicer in ten minutes.

Why TPU Jams (And Why It Is Rarely the Filament)

Flexible filament has nothing to push against. The drive gears shove it toward the melt zone, but the nozzle can only swallow it as fast as it melts. Feed faster than the melt can keep up and the filament kinks sideways, wraps the gear, and you are pulling the hotend apart. Two things cause that: too much speed, and back pressure from too much retraction or too little heat. Get those right and a $22 spool prints like a $45 one.

Temps and Speeds That Actually Work

95A, the standard flexible spool, runs 225-235°C on a 0.4mm nozzle. Softer 85A likes 215-225°C. Bed at 45-55°C.

Cap wall speed at 20-30mm/s and infill at 30-40mm/s, and keep volumetric flow under about 5mm³/s. A 0.6mm nozzle at 15-20mm/s is a strong combo for chunky parts that need toughness more than detail. Turn on wipe-on-retract and run outer walls a notch slower than inner walls. It costs nothing and kills most of the blobbing.

Retraction and Part Cooling

Direct drive: 0.5-1mm at 20-25mm/s. Bowden: 3-5mm, and expect to tune it per spool. More retraction is not better with TPU. Past roughly 1mm on a direct-drive setup the filament stretches thin, and the next extrusion comes out starved.

Part cooling is the opposite of nylon. Run the fan at 60-100% and leave the door open. Soft filament does not want a hot chamber; heat makes it sag, stick to itself, and turn a clean print into a lump.

Drying and Bed Adhesion

TPU takes on water like everything else. If a fresh spool pops and hisses at the nozzle, or the surface comes out cloudy instead of glossy, dry it at 50°C for 4-6 hours. Do not push past that. Most spools deform around 60°C, and a warped spool will not feed.

Textured PEI holds TPU hard, which is great on the first layer and annoying at part removal. On a smooth plate, soft filament can bond so well it tears the sheet. A thin wipe of bed adhesive gives you a release barrier that keeps the bottom face flat instead of squashed and shiny.

What We Use

For plate prep we keep Nano Polymer Adhesive on the bench. On smooth PEI it acts as the release barrier, and on textured plates it is cheap insurance when a tall TPU part starts lifting a corner at hour three.

For the plate itself we run a BIQU Cryogrip Pro on the machine that does most of our soft-filament work. The textured side grabs the first layer, and once the plate cools the part pops off with a flex instead of a scraper blade under the corner.

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