TPU flexible filament: the complete printing guide

Updated June 2026 · 14 min read

TPU — thermoplastic polyurethane — is the flexible filament that most 3D printing hobbyists eventually need. Phone cases, gaskets, wheels, grips, cable protectors, shoe insoles, and anything that needs to flex, compress, or absorb impact: TPU is the material for these applications. But TPU is also the filament that most reliably jams in Bowden setups, produces stringy blobs at high speeds, and frustrates beginners who approach it like PLA.

This guide covers everything you need to print TPU successfully: the material properties, the printer requirements, the settings that matter, and the applications where TPU genuinely outperforms every rigid filament.

What TPU actually is

TPU is a block copolymer — a polymer chain that alternates between hard segments (typically urethane) and soft segments (typically polyether or polyester). The ratio of hard to soft segments determines the Shore hardness of the final material. Most 3D printing TPU filaments fall in the 87A to 98A Shore hardness range. 87A is noticeably soft and rubbery; 95A is firm but still flexible; 98A is nearly rigid but has some give.

The most commonly available TPU for 3D printing is 95A hardness — NinjaTek Cheetah, eSUN TPU 95A, Polymaker PolyFlex TPU95, and Bambu Lab TPU 95A all fall in this range. For softer applications (phone cases, grips), 87A or 85A TPU is available from NinjaTek (NinjaFlex) and a few other brands. For near-rigid flexible applications, 98A TPU is available from several brands.

Direct drive vs Bowden: why it matters for TPU

The single most important factor in TPU printing success is the extruder setup. TPU is flexible, and flexible filament buckles under the compression forces in a Bowden tube. In a Bowden setup, the extruder pushes filament through a PTFE tube that can be 400–600mm long before it reaches the hotend. When the extruder applies pressure to advance flexible filament, the filament compresses and buckles inside the tube rather than advancing cleanly. The result is inconsistent extrusion, jams, and blobs.

Direct drive extruders — where the extruder motor sits directly on the print head — eliminate the long Bowden tube. The filament path from extruder to hotend is typically 20–40mm, which is short enough that even soft TPU can be pushed through without buckling. Prusa MK4, Bambu Lab X1C and P1S, Voron 2.4, and most modern direct drive printers handle TPU reliably. Ender 3 and other Bowden printers require a direct drive upgrade (like the Sprite or Orbiter extruder) for reliable TPU printing.

If you have a Bowden printer and cannot upgrade to direct drive, you can sometimes print very firm TPU (95A or harder) at very slow speeds (15–20mm/s) with zero retraction. This works occasionally but is not reliable enough for production use.

Print settings that actually matter

Print speed: Slow down significantly compared to PLA. 30–40mm/s is a good starting point for 95A TPU on a direct drive printer. Faster speeds cause under-extrusion as the flexible filament cannot keep up with the extruder demand. Some printers with high-torque direct drive extruders (Bambu, Prusa MK4) can push 95A TPU at 50–60mm/s, but 30–40mm/s is the reliable baseline.

Retraction: Reduce retraction significantly or disable it entirely. TPU's elasticity means that retraction pulls back more filament than expected, and the elastic rebound pushes filament forward again when retraction ends — causing blobs and inconsistent starts. For 95A TPU, start with 1–2mm retraction at 25mm/s and reduce if you see blobs. For 87A TPU, zero retraction is often the best setting.

Print temperature: 220–240°C for most 95A TPU. Higher temperatures improve layer adhesion and reduce stringing but can cause oozing. Start at 230°C and adjust based on results. Bed temperature of 30–60°C; TPU adheres well to PEI surfaces at 40–50°C.

Cooling: Moderate cooling. TPU benefits from some cooling to maintain dimensional accuracy, but excessive cooling reduces layer adhesion. 50–70% fan speed is a reasonable starting point.

Infill: For flexible parts, lower infill percentages (15–30%) allow the part to flex more. Higher infill (50–80%) produces stiffer parts. Gyroid infill is particularly good for TPU — it distributes stress evenly and allows compression in all directions.

Moisture and storage

TPU is hygroscopic — it absorbs moisture from the air, and wet TPU produces noticeably worse print quality. Symptoms of wet TPU include popping and hissing sounds during printing, excessive stringing, rough surface texture, and reduced layer adhesion. If you've stored TPU in open air for more than a week, drying before printing is worthwhile.

Dry TPU at 45–55°C for 4–6 hours. Higher temperatures can soften or deform the spool. A food dehydrator or dedicated filament dryer works well; an oven at its lowest setting (often 50–60°C) works if you can verify the actual temperature with a thermometer. Store TPU in sealed containers with desiccant between print sessions.

Applications where TPU is the right choice

Phone and tablet cases are the most common TPU application — the material's impact absorption and grip make it ideal, and the flexibility allows snap-fit installation. Cable management clips, strain relief boots for cables, and cable protectors are excellent TPU applications where the flexibility prevents cracking under repeated bending.

Wheels and rollers for robots, RC vehicles, and automation projects benefit from TPU's combination of grip, wear resistance, and shock absorption. Gaskets and seals for enclosures, pipe fittings, and mechanical assemblies are well-suited to TPU — it compresses to fill gaps and springs back reliably. Grips and handles for tools, sporting equipment, and handheld devices benefit from TPU's tactile feel and vibration damping.

Shoe insoles and orthotic inserts are a growing TPU application — custom-printed insoles with variable infill density can provide targeted support and cushioning. This is one of the more technically demanding TPU applications due to the need for precise dimensional accuracy and consistent material properties across the print.

TPU vs other flexible filaments

TPE (thermoplastic elastomer) is a broader category that includes TPU. Other TPE materials include TPC (thermoplastic copolyester, like NinjaTek Armadillo) and TPS (thermoplastic styrenic). For most 3D printing applications, TPU is the practical choice within the TPE category due to its availability, consistent quality, and well-documented print settings.

For applications requiring chemical resistance to oils and fuels, TPC materials like Armadillo provide better resistance than standard TPU. For applications requiring very soft, skin-contact materials, medical-grade TPU or silicone-like materials (Filaflex, Recreus) are available at higher cost and with more demanding print requirements.

Common TPU printing problems and fixes

Filament buckling at the extruder: The filament is bending before entering the extruder gear. This usually indicates a gap between the extruder gear and the hotend entry point. Check that the PTFE tube (if present) is fully seated against the nozzle with no gap. On direct drive setups, ensure the filament path is smooth and unobstructed.

Excessive stringing: Reduce retraction distance, lower print temperature by 5°C, and reduce travel speed. Enabling combing (printing travel moves within the part perimeter) significantly reduces stringing in TPU.

Under-extrusion: Reduce print speed. TPU cannot be pushed through the hotend as fast as rigid filaments. If under-extrusion persists at slow speeds, check for partial jams in the hotend — TPU can leave residue that builds up over time.

Poor bed adhesion: Increase bed temperature to 50–60°C. Clean the PEI surface with IPA. For very soft TPU, a thin layer of glue stick can help adhesion while also making part removal easier.