TPU.
THE RUBBERY ONE.
TPU (thermoplastic polyurethane) is the rubbery filament — the one that lets you print parts that actually bend. Think shoe soles, phone cases, drone propellers, gasket rings, bike grips, drawer liners. If PLA is bone, PETG is wood, and ABS is plastic, TPU is rubber.
It's also by far the trickiest of the four standard filaments to print well, because its whole point is flexibility — and flexible filament fights the extruder every step of the way. A direct-drive printer makes TPU dramatically easier than a Bowden setup. (All our Bambu Lab machines are direct-drive, which is why we offer it as a standard option.)
What it is
TPU sits between rigid thermoplastics and thermoset rubber. Chemically, it's a block copolymer of hard and soft urethane segments — the hard segments give it structural integrity, and the soft segments allow it to stretch and return. Unlike true rubber, TPU is thermoplastic, meaning it can be melted and reshaped, which is what allows it to be extruded as filament.
TPU comes in hardness grades measured on the Shore A scale — from roughly 75A (very soft, gummy) to 98A (firm, closer to hard rubber). The most common printing grade is 95A, which is firm enough to hold its shape and extrude cleanly while still flexing and bouncing back.
Technical properties
- EXTRUDER TEMP
- 220 – 240 °C
- BED TEMP
- 45 – 60 °C
- ENCLOSURE
- Not required
- GLASS TRANSITION
- ~ 80 °C (varies by grade)
- HARDNESS
- Shore 85A – 98A
- TENSILE STRENGTH
- ~ 25 – 50 MPa
- ELONGATION
- 300 – 700 % — extreme stretch
- ABRASION RESIST.
- Excellent — outlasts most plastics
- CHEMICAL RESIST.
- Good against oils, greases, fuels
- UV RESIST.
- Moderate
- WATER ABSORB.
- Hygroscopic — must be dried
- PRINT SPEED
- Slow — typically 20 – 40 mm/s
Pros
- Flexibility. This is the whole point. TPU can stretch to 5× or more its original length and snap back without permanent deformation.
- Extreme abrasion resistance. TPU outlasts almost every rigid plastic in wear-heavy applications. It is used in industrial belts, rollers, and protective coatings for exactly this reason.
- Excellent impact absorption. A TPU part absorbs dropped-object energy and spreads the shock, protecting whatever is inside it. This is why phone cases and drone frames are printed from it.
- Chemical and oil resistance. Better than PLA, comparable to PETG. Withstands motor oil, fuels, greases, and mild solvents.
- Tear resistant. Unlike rigid plastics, TPU does not crack at a stress point — it stretches and distributes the load.
- Vibration damping. TPU isolators reduce transmission of mechanical noise and vibration, which is why it's popular for machine feet, instrument mounts, and vehicle parts.
- Good layer adhesion. When printed correctly, TPU layers fuse strongly — tear strength is high.
- Wide temperature envelope for a rubber. Functional from below freezing up to about 80 °C.
Cons
- Hardest filament to print well. Flexible filament doesn't push through an extruder cleanly — it wants to buckle and bind. A direct-drive printer is essentially mandatory for reliable results. Soft grades (below 90A) are especially tricky.
- Print speed is slow. TPU cannot be pushed through a nozzle as fast as rigid filaments. Large parts take significantly longer than the equivalent in PLA.
- Stringing and oozing. The low melt viscosity makes TPU prone to drooling between features. Retraction tuning is critical.
- Hygroscopic — must be dried. TPU soaks up atmospheric moisture faster than almost any other filament. Wet TPU prints with popping, steam, and poor layer bonds. We store it in sealed drybags and dry before every batch.
- Low stiffness. TPU is the wrong material for anything that needs to resist bending under load — it is designed to flex.
- Difficult to support. Because TPU is rubbery, support material does not snap off cleanly. Design with minimal overhangs.
- Expensive. Typically 2 – 3× the cost of PLA per spool.
When to pick TPU
- Gaskets, seals, and O-ring replacements where compression and chemical resistance matter.
- Phone cases, bumper rings, protective sleeves for electronics.
- Grips and handles for tools, bike bars, steering wheels, or anything that benefits from a soft-touch surface.
- Vibration dampers and machine feet to isolate mechanical noise.
- Drawer and storage liners where a slightly tacky, non-slip surface holds contents in place.
- Wheels and tires for small RC vehicles or robots.
- Drone and FPV frame dampers where impact absorption saves hardware.
- Prosthetic and orthotic sockets that need to flex around tissue.
- Wearables — watchband straps, adjustable rings, soft-touch enclosures.
When not to pick TPU
- Anything rigid. If the part must hold its shape under load, TPU is the wrong material — even the hardest grades flex.
- Parts with lots of overhangs that would require supports — supports don't remove cleanly from TPU.
- Hot environments above 80 °C.
- Parts that need crisp, detailed surface features — TPU smooshes under its own weight as layers build.
- High-speed production runs. TPU prints slow.
- Thin-walled tall parts. They collapse under their own squish.
Design tips for TPU parts
- Choose your Shore hardness carefully. 95A is the all-around default. Drop to 85A for soft cushiony feel, bump to 98A for closer-to-plastic stiffness. Tell us what feel you want and we'll pick.
- Minimum wall thickness for structural parts is typically 1.5 – 2.0 mm.
- Design in infill percentages 15 – 100 % to tune "softness." Low infill acts like foam. High infill acts like solid rubber.
- Avoid steep overhangs. Design gentle transitions and sloped features instead of requiring support.
- For O-ring replacements, add a small dimensional allowance (+0.15 mm) to account for layer compression — a printed ring a touch oversize will compress to proper fit.
- For gaskets, account for compression set — TPU will take some permanent set over time under long-held compression. Oversized is better than undersized.
Our take
TPU is a specialty material, but when it's right, nothing else comes close. If you call us needing a rubber replacement part — a gasket, a grip, a damper, a boot, a cushion — TPU is probably the answer. It doesn't replace injection-molded rubber for industrial sealing applications, but for short-run custom work it is unmatched by any other 3D printing material.
At Spool Foundry we stock TPU 95A as our standard and can source softer or firmer grades for specific applications. Tell us the Shore hardness you've used before — or describe the feel you want — and we'll match it.
Still not sure?
Describe your part and the environment it lives in via our contact form — we'll recommend the right filament at no cost.