Filament Guide
TPU Filament Guide
The flexible material. Rubber-like, impact-absorbing, durable.
Last updated: May 2026
TL;DR
- Flexible, rubber-like material, great for phone cases, gaskets, vibration dampeners, and grips
- Needs a direct drive extruder, since Bowden tubes let the filament buckle and jam
- Print slow: 20-40mm/s at 220-250°C, no retraction or minimal retraction
- Shore 95A is the standard hardness, where lower A = more flexible, higher = stiffer
TPU
Thermoplastic Polyurethane
The flexible material. Rubber-like, impact-absorbing, durable.
Intermediate
Flexible
TPU bends, stretches, bounces back, and handles impacts that would shatter PLA or PETG. It's rubber-like but melt-processable: the hard urethane segments give it shape, the soft polyol segments give it flex. That structure is what lets you print phone cases that actually compress, gaskets that seal, vibration dampers that damp, and grips that feel like rubber rather than plastic.
The trade-off is printability. TPU's flexibility makes it buckle in the extruder, especially on Bowden setups where the long PTFE tube gives the filament room to compress and kink. Direct drive is strongly recommended for any serious TPU work. Expect to print standard TPU at 20-40mm/s; high-flow TPU variants from Bambu, Polymaker, and SUNLU handle 60-80mm/s on tuned direct-drive extruders. The speed limit isn't the hotend or the part-cooling; it's the extruder's ability to push flexible filament without the filament collapsing inside its own path.
Hardness is measured in Shore A, and consumer TPU filaments range from ~70A (Recreus FilaFlex, very flexible, almost silicone-like) to ~98A (semi-rigid, barely flexible). Most general-purpose TPU sits around 95A: firm enough to print reliably on most direct-drive printers, flexible enough for cases, gaskets, and grips. As you go softer (90A → 85A → 70A) the material becomes more useful for elastomer applications but progressively harder to print, and sub-85A really wants a Voron-class direct-drive setup with very short filament path.
TPU is also one of the most chemically resistant common filaments. It shrugs off oils, fuels, and most solvents, making it a workhorse for automotive gaskets, fuel system components (where chemistry permits), and industrial seals. Combined with its abrasion resistance (TPU is used commercially in shoe soles and tyre-contact surfaces), it's the right pick for any flexible part that lives in a hostile environment. The notable exception is UV: most consumer TPU yellows and embrittles within 1-2 years of direct sun, so for outdoor flexible parts you want either a UV-stable TPU variant (Recreus, specific Polymaker grades) or to combine TPU with a UV-stable rigid carrier like ASA.
Chemistry
Block copolymer: hard urethane segments + soft polyether or polyester segments
Print Temp
Hardness Range
87A-98A Shore - lower = softer. Most common: 95A[2]
Heat Resistance
Softens at ~80-120°C depending on formulation
Abrasion Resistance
Excellent - used for wear pads, seals, and tyre-contact surfaces
Extruder Type
Direct drive strongly preferred.[1] Bowden: use only 95A+ and go very slow.
Pros
- Flexible, elastic - returns to shape after deformation
- Exceptional impact and abrasion resistance
- Good chemical resistance (oils, fuels)
- Usable in low temperatures (stays flexible at −40°C)
- Soft surface feel - ideal for grips and wearables
Cons
- Difficult to print - requires slow speeds
- Bowden setups struggle or fail
- Highly hygroscopic - must be dried before printing
- Strings and oozes easily
- Cannot be printed with rigid part infill strategies
- Hard to support and remove supports cleanly
Best Used For
Phone cases
Gaskets & seals
Grip surfaces
RC tyre inserts
Vibration dampeners
Wearables & straps
Bump stops
Cable strain relief
Flexible hinges
Niche Tips
Drying is non-negotiable. Wet TPU pops, bubbles, and produces weak, rough prints. Dry at 50-60°C for 4-8 hours before every print session if stored open.
Disable retraction or use very minimal retraction (0.5-1mm direct drive). High retraction causes filament to coil inside the extruder.
Infill pattern matters: Gyroid or honeycomb infill produces better elastic behavior than grid. For very flexible parts, use 10-20% gyroid.
TPU bonds to itself chemically - multi-layer welds are strong. However it barely bonds to PLA/PETG, which is useful for printing sacrificial rigid supports that peel cleanly.
Storage & Humidity
Target: below 20% RH. TPU absorbs way more moisture than PETG or ABS. Wet TPU bubbles, loses layer adhesion, and strings everywhere. Store sealed with fresh desiccant, always.
Drying: 65-75°C for 8 hours. TPU is temperature-sensitive - don't exceed 75°C or the filament can soften and tangle on the spool.
TPU is one of the materials most worth running from a drybox during printing, especially in humid climates. The quality difference between dry and wet TPU is dramatic.
Bed Adhesion
Best surfaces: PEI (smooth or textured), blue painter's tape. TPU adheres well to most surfaces without adhesion aids.
Recommended bed temp: 30-60°C. Higher end of this range improves adhesion for flexible prints that can peel during printing. TPU doesn't warp, so bed temp is less critical than for rigid materials.
Release: Simply flex the build plate. Flexible TPU prints pop off textured PEI with very little force. Avoid using adhesion aids that make release harder - TPU can tear if over-adhered.
Variants & Special Types
TPU 95AStandard shore hardness - flexible but firm. The most common TPU variant and the best starting point. Good balance of flexibility and printability.
TPU 90ASofter than 95A. More flexible, but harder to print - more prone to buckling in Bowden tube setups. Direct drive extruders strongly recommended.
TPU-CFTPU with carbon fiber. Increased stiffness while maintaining some flexibility. Niche use for semi-rigid seals and vibration dampeners that need structure.
TPU ESDElectrostatic dissipative TPU for flexible ESD-safe parts. Used in electronics manufacturing for protective covers and grips.
TPU RapidFaster-printing TPU variant with modified flow. Reduces the speed penalty that makes TPU slow to print.
Brand Picks for TPU
Best budget 95A: SUNLU TPU (~$22/kg). Vacuum-sealed with desiccant, prints with stock TPU profiles, well-tolerated diameter for direct-drive setups. The most-named entry-level pick on r/3Dprinting. Good for phone cases, simple gaskets, basic flexible parts. More SUNLU options.
Best premium 95A: Polymaker PolyFlex (~$32/kg). Documented chemistry, ±0.03mm diameter tolerance, prints faster than budget TPU thanks to a higher-flow formulation. Worth the upgrade when stringing or under-extrusion is hurting your prints. Polymaker also publishes a Shore-A reference card across their flexible range.
Best high-flow: Bambu TPU 95A HF (~$35/kg). Tuned for X1C / P1S / H2D, it runs at 60-80mm/s where standard TPU caps at 30-40mm/s. Bambu Studio profile works first try. Premium pricing reflects the high-flow chemistry and Bambu-tuning, not chemistry novelty. SUNLU and Polymaker both have similar HF variants now too.
Best soft TPU (sub-85A): Recreus FilaFlex 70A (~$55/kg). Real elastomer territory. Phone cases that compress like rubber, drone bumpers that absorb crash impact, vibration dampers that actually dampen. Direct-drive only, very slow (15-20mm/s), and don't bother with a Bowden setup at all. NinjaFlex Cheetah sits in the same tier with slightly easier printability.
Best for stiffness: TPU-CF (~$45-60/kg). Carbon-fibre-filled TPU for parts that need flex plus structural support. Niche but useful for semi-rigid seals, vibration dampers that need shape retention, RC body components. Wears brass nozzles slightly, so hardened steel is preferred for long-term use.
Avoid: No-name AliExpress TPU. Diameter consistency is often poor (±0.10mm not uncommon), and that's exactly the variable that breaks Bowden setups and causes mid-print buckling on direct drive too. The $5/kg saving isn't worth the failed-print rate.
Printer-Specific TPU Tips
Bambu Lab X1C / P1S / H2D. Direct-drive extruder handles 95A TPU well at 30-50mm/s; with TPU 95A HF, push to 60-80mm/s. Skip the AMS, because Bambu officially doesn't support TPU in it since PTFE-tube friction causes binding. Use the external spool holder with a direct path to the extruder. The Bambu filament guide covers AMS workarounds for users who want to try anyway.
Bambu Lab A1 / A1 Mini. Direct-drive, no enclosure needed for TPU (it doesn't warp). 95A works first-try with the bundled TPU profile at 25-35mm/s. AMS Lite has the same PTFE-friction issue as the full AMS, so feed externally. Soft TPU (below 85A) is borderline on the A1's stock extruder; Recreus FilaFlex prints but very slowly.
Prusa MK4S / MK3S+. Native TPU support with bundled PrusaSlicer profile. MK4S handles 95A at 30-40mm/s reliably; the extruder gear pattern is designed to grip flexibles without buckling. For soft TPU (70-85A), reduce speed to 15-20mm/s and disable retraction entirely. Prusa's flexible-print guide has tuning for sub-85A.
Voron / Stealthburner / CW2. The natural habitat for TPU. Direct-drive with very short filament path, geared extruder grips flexible material reliably, and the chamber heat (40°C+ ambient) helps adhesion without affecting TPU since TPU doesn't warp. Soft TPU prints reliably here when other printers fail. Print profiles for 95A and softer all exist in Voron's community config repos.
Ender 3 (stock Bowden). 95A TPU works at 15-25mm/s with patience and minimal retraction (1mm max). Soft TPU (below 90A) is impractical without a direct-drive upgrade, because the Bowden tube allows the filament to compress and buckle inside the path. Microswiss direct-drive conversion or BMG-style geared extruder is the standard upgrade for serious TPU work on Ender 3.
Common TPU Pitfalls
Filament buckling at the extruder. Cause: filament path has too much room for compression. On Bowden, this is structural, and direct drive is the fix. On direct drive, check that the filament path is constrained from spool entry through to the hotend, with no gaps. A short PTFE liner in the extruder helps. Symptom: print stops mid-job with no extrusion despite the spool still moving.
Stringing between perimeters. Three causes: (1) wet filament, so re-dry at 65-75°C for 8h; (2) retraction too high, so drop direct-drive retraction to 0-1mm; (3) print temp too high, so try 5°C lower. Some stringing is unavoidable with TPU; cleanup with a heat gun on low temp removes what's left.
Bubbly surfaces and popping at the nozzle. Wet TPU. TPU absorbs more moisture than PETG. Dry at 65-75°C for 8 hours, print from a sealed drybox. Don't dry above 75°C, since TPU softens and the spool can deform.
Layer separation on tall prints. Print speed too high or part fan too aggressive. Drop speed to 20-25mm/s, reduce part fan to 30-50%. TPU layers don't fuse well when the previous layer cools too fast. Higher hotend temp (5-10°C up) also helps if speed and fan adjustments aren't enough.
Print won't release from the bed without tearing. TPU bonds strongly to PEI and most adhesives, often too strongly. Skip glue stick and adhesion aids; flexible TPU pops off textured PEI easily once the bed cools. If parts still tear, lower bed temp 5-10°C or print thicker first layers (0.3mm).
When TPU Isn't the Right Answer
Need rigid parts → PETG or ABS. TPU is the wrong tool when stiffness matters. PETG handles most rigid functional parts; ABS adds heat resistance. For brackets, jigs, and structural prints, even the stiffest TPU (98A) flexes too much.
Need extreme flexibility → silicone (not 3D printable easily). If you need true rubber-like behavior (below 60 Shore A), TPU isn't soft enough. Cast silicone with a 3D-printed mould is the standard approach for that range. Some specialty SLA resins reach down to 50 Shore A but require very different print hardware.
Need outdoor UV stability → check brand specifically. Most TPU has limited UV resistance and yellows and embrittles in 1-2 years of direct sun. Recreus FilaFlex and a few specific Polymaker variants have documented UV stability. For outdoor flexible parts, ASA-rigid + TPU-gasket assemblies usually outlast all-TPU prints.
Need food-contact flexible parts → cast silicone. Even food-rated TPU loses its rating after FDM printing because layer lines harbour bacteria. For food-contact gaskets, seals, or moulds, cast food-grade silicone in a 3D-printed master.
Need high heat resistance → PA6 or PC. TPU softens at 80-120°C depending on formulation. For heat-tolerant flexible parts, there isn't really a great option. PA6 (rigid but tough) or PC (semi-rigid, 145°C Tg) cover the heat side; flexible-plus-heat-resistant is a specialty silicone job, not an FDM filament job.
References
- Prusa Knowledge Base - Flexible Materials (TPU/TPE). Print temperatures, direct drive requirements, and speed recommendations. help.prusa3d.com/article/flexible-materials-tpu-tpe_2057
- Bambu Lab Wiki - Filament Guide Material Table. Shore hardness scale and printing parameters for flexible filaments. wiki.bambulab.com/en/general/filament-guide-material-table
Frequently Asked Questions
Does TPU work with Bowden extruders?
Soft TPU (below 90A Shore hardness) is very difficult to print reliably with a Bowden setup because the long PTFE tube allows the flexible filament to compress, buckle, and jam. Harder TPU (95A) can work with Bowden if you print slowly (15-25mm/s) and use a constrained filament path. Direct drive extruders are strongly recommended for all TPU printing.
What Shore hardness should I start with?
Start with 95A TPU. It is the most common hardness, the easiest to print, and works for most flexible applications like phone cases, bumpers, and grips. 85A is noticeably softer (similar to a rubber band) but much harder to print. Only go below 90A once you are comfortable with 95A and have a direct drive extruder.
Why is my TPU stringing?
TPU strings easily because it is elastic and does not retract cleanly like rigid filaments. Reduce stringing by disabling or minimising retraction (0-2mm for direct drive), lowering print temperature by 5°C increments, increasing travel speed, and enabling wipe/coasting. Some stringing is normal with TPU and can be cleaned up with a heat gun on low.
Is TPU waterproof?
TPU is highly water-resistant and does not absorb water significantly in use. Printed TPU parts work well as seals, gaskets, and waterproof enclosures. However, FDM layer lines may allow water to seep through at high pressure. For fully watertight prints, use more walls (4+), higher infill, and consider coating the part.
Which TPU brand should I buy?
For 95A TPU starting out, SUNLU TPU and Polymaker PolyFlex are the most-recommended budget and premium picks respectively. Bambu's TPU 95A HF is the named pick for X1C / P1S / H2D users (faster than standard TPU). For very soft TPU (sub-85A), Recreus FilaFlex 70A and NinjaFlex Cheetah are the specialist picks. Avoid no-name AliExpress TPU, because diameter consistency is often poor and that's the variable that breaks Bowden setups.
How much does TPU cost?
Budget TPU 95A runs $20-28/kg from SUNLU, Elegoo, and Sainsmart. Premium TPU from Polymaker (PolyFlex) or Bambu costs $30-40/kg. Specialist soft TPU (70-85A) and TPU-CF can hit $50-70/kg from Recreus FilaFlex or NinjaFlex. TPU is consistently more expensive than PETG or ABS, because manufacturing tolerance for flexible material is harder to hold. See live TPU prices.
Does TPU work in the Bambu AMS?
Officially no. Bambu does not support TPU in the AMS because PTFE-tube friction can cause the flexible filament to bind or jam mid-print. Many users do feed 95A TPU through the AMS successfully but slowly (15-20mm/s) and with a single spool only (no multi-color swaps). For reliable TPU printing on Bambu, use the external spool holder with a direct path to the extruder.
Does TPU need drying?
Yes. TPU is highly hygroscopic, more so than PETG. Wet TPU pops at the nozzle, produces bubbly surfaces, and prints with weak layer adhesion. Dry at 65-75°C for 8 hours before printing. Don't exceed 75°C, since TPU softens above that and can deform on the spool. Print from a sealed drybox in humid climates; the quality difference between dry and wet TPU is dramatic.
Can I print TPU faster than 30mm/s?
Standard TPU caps at ~30-40mm/s before the extruder loses control of the flexible filament. High-Flow TPU variants (Bambu TPU 95A HF, Polymaker PolyFlex) can hit 60-80mm/s on a tuned direct-drive extruder. Push past those limits and you get under-extrusion, stringing, and layer separation. For volume TPU work, the high-flow variants pay back their price premium in print time.
Is TPU food-safe?
Some TPU is food-contact rated; most consumer TPU is not. Recreus FilaFlex 82A and a few specific NinjaFlex variants carry food-contact certifications. For most TPU, assume not food-safe. Even certified-safe TPU loses its food-contact rating once printed via FDM because layer lines harbour bacteria and can't be properly cleaned. For food-contact flexible parts, use injection-moulded silicone instead.
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