Printing Flexible TPU Without Jams: Speed, Retraction and Direct-Drive Basics

Why soft filament jams your extruder

TPU is a thermoplastic elastomer, and that's both its appeal and its problem. Polymaker's wiki says it can stretch up to 500% of its original length before breaking. That's great for a phone case or a gasket, but tough on an extruder. When the drive gears push a rigid PLA strand, the force travels straight to the nozzle. A soft TPU strand compresses instead, bends, and looks for any gap it can slip into. If there's room between the gears and the hotend, the filament snakes in, coils up, and stops the print.

Softness makes this worse. Polymaker explains that flexibility depends on Shore hardness: a lower number means a softer filament that's harder to feed. Prusa calls its Prusament TPU 95A one of the easiest flexible materials to print, so a 95A-class filament is a sensible place to start. Our breakdown of 95A vs 85A TPU covers that choice in more detail. Every setting below follows one rule: push gently and steadily on a filament that hates being pushed.

Direct drive vs Bowden: the hardware that matters most

Before you touch your slicer, look at your extruder. According to Polymaker, direct-drive systems outperform Bowden setups because they cut friction along the filament path. On a Bowden printer, TPU has to travel through a long PTFE tube before it reaches the hotend. It drags, compresses like a spring, and stops responding cleanly to extrusion commands. For softer TPU blends, Polymaker says a direct extruder is required and warns that Bowden extruders may struggle. Keep a temperature limit in mind too: above 240°C, you need an all-metal hotend.

Prusa says all of its Nextruder printers handle Prusament TPU 95A with little to no tweaking. PrusaSlicer includes profiles for the Core One, XL, MK4S, MK4 and Pro HT90. The MK3S+ and older models also work, though profiles may be missing and you might need to loosen the idler. Feeding TPU through a multi-spool unit brings its own problems, so read our guide to TPU in an AMS before you try it.

Starting values for speed, retraction and temperature

Polymaker gives a clear baseline. Print between 15 and 40 mm/s, because slower speeds keep the filament from buckling, especially with softer TPU. Keep retraction minimal, around 1 to 2 mm at 10 to 20 mm/s, to avoid clogs. A long retraction stretches the soft strand and then shoves it back, and that's exactly how it ends up wedged in the extruder.

Nozzle temperature runs from 210 to 250°C depending on the brand, and Polymaker suggests starting at 230°C. Set the bed between 40 and 60°C. A layer height of 0.2 to 0.3 mm helps the layers bond, and part cooling at 20 to 50% balances detail against layer adhesion. Treat these numbers as a starting point, not gospel. The profile your filament maker publishes for your slicer always wins, since every TPU blend behaves a little differently. For a step-by-step way to dial it in, see our retraction settings guide.

Dry filament and a clean feed path

Wet TPU prints badly. Polymaker recommends storing it in a dry box and drying it at 50°C for 24 hours before printing to prevent bubbles. Prusa is less strict about its Prusament TPU 95A, saying drying usually isn't necessary. After poor storage, though, it suggests at least 4 hours at 60°C, then keeping the spool in a dry box. Follow your filament maker's guidance, and see our filament dryer guide for your options.

The path from spool to extruder matters as much as the settings. On the Original Prusa XL, Prusa's documentation says TPU can struggle to pass through the side filament sensor. Its fix is to unplug the PTFE tube from the sensor and feed the filament straight into the tube. On the Core One, Prusa suggests unplugging the tube on the Nextruder side and pushing the filament through. Then guide it by hand through the sensor and reconnect the tube. On the MK4 and MK4S, a filament guide keeps the strand slightly taut during the print.

Bed surfaces: when TPU sticks too well

With most filaments, the worry is getting the first layer to stick. With TPU, the risk often runs the other way. Polymaker warns that over-sticking can damage build surfaces and suggests a glue stick as a release agent. PEI sheets, painter's tape and adhesive-coated glass all help first-layer grip.

Prusa goes sheet by sheet for TPU 95A. The PA Nylon sheet and the Satin sheet are its top picks: clean the first with water and the second with IPA. On Satin, larger models may need a brim plus slightly higher nozzle and bed temperatures. The PP sheet grips a bit more than Satin. The Textured sheet works, but adhesion can be too strong. In that case, Prusa suggests heating it to 40°C and lifting the part off with a spatula. Smooth PEI isn't recommended at all. Without a separation layer such as glue stick, pulling the print off will damage the sheet. Whatever surface you use, degrease it before each print the way your printer maker describes.

Fixing jams, strings and bubbles

If the filament tangles and gets stuck in the gears, Prusa recommends backing the idler screws out by 1.5 turns. For a clogged nozzle, first make sure the nozzle is clean and the filament is dry. If the clog keeps coming back, Prusa suggests loosening the idler, raising the temperature and lowering the fan speed. One easy-to-miss cause is TPU left loaded in the extruder for a long time between prints, which can deform. Simply unloading and reloading it fixes the issue. Skipped layers usually mean the nozzle clogged briefly, so treat them like any other clog.

Stringing has two likely causes. Polymaker blames TPU's elasticity and recommends less retraction and slower travel moves, while Prusa points to moisture first. Bubbles in the extruded strand usually come from moisture too, so dry the filament and check the nozzle temperature. If it's too high, lower it a little. Finally, Polymaker notes that TPU supports are often very hard to remove, so orient your part to need as few as possible.

Sources and limits

• Polymaker Wiki — TPU (the basics)
• Prusa Knowledge Base — Prusament TPU 95A material guide

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.