TPU is the filament that makes things that flex, grip, absorb impact, and survive being dropped. Phone cases, gaskets, cosplay strap connectors, flex joints, grip handles, protective boots for functional hardware. Where PLA and PETG snap under impact, TPU deforms and bounces back. It’s the material class most makers add to their workflow after PLA and PETG, and it comes with specific printing requirements that differ meaningfully from rigid filaments.
What Is TPU and How It Differs from Rigid Filaments
TPU stands for Thermoplastic Polyurethane. It’s an elastomeric polymer that remains flexible at room temperature. Unlike PLA and PETG, which become rigid when cooled, TPU retains a rubber-like quality through its full operating temperature range.
The flexibility is characterized by Shore hardness. Consumer FDM TPU typically comes in 95A (moderately flexible, like a shoe sole), 87A (more flexible, like a soft rubber), and 83A (very flexible, almost rubbery). Higher Shore number means stiffer. 95A TPU is the most commonly printed and the easiest to work with. 83A TPU is significantly harder to print reliably.
What makes TPU different to print: TPU’s flexibility that makes it useful also makes it prone to buckling in the extruder’s feed path. The filament can compress, fold, and jam in the Bowden tube rather than feeding cleanly. This is why TPU strongly prefers direct drive extruders over Bowden setups.
Direct Drive vs Bowden: Why It Matters for TPU
Every Bambu Lab printer uses a direct drive extruder. The extruder motor sits directly on the print head, adjacent to the nozzle. The filament path from drive gear to nozzle is 2-3cm. TPU prints reliably on all Bambu Lab machines because of this.
On a Bowden setup (older Creality Ender series, some budget printers), the extruder sits on the frame and pushes filament through a long PTFE tube to the hotend. That tube can be 40-60cm long. TPU 95A can be made to work on a Bowden printer with very slow speeds, but 87A and softer variants are nearly impossible to print reliably on Bowden. If you have a Bowden printer and want to print flexible filaments, either upgrade to a direct drive extruder kit or accept significant speed limitations.
TPU Print Settings
| Setting | TPU 95A (Bambu Lab A1) | Notes |
|---|---|---|
| Nozzle temperature | 225-235°C | Slightly higher than PLA. Check brand recommendation; varies 220-240°C. |
| Bed temperature | 40-60°C | Lower end for easier removal. TPU sticks well to PEI across this range. |
| Print speed | 20-40mm/s outer wall | Slow is essential. High speed causes feeding issues even on direct drive. |
| Retraction | 0-1mm at low speed | Minimize retraction. TPU’s elasticity makes long retraction movements cause feeding issues. |
| Cooling fan | 20-50% | Some cooling helps bridges but too much reduces layer bonding. |
| Layer height | 0.2-0.3mm | Fine layers are less necessary for flexible parts. 0.2mm is a good standard choice. |
| Infill pattern | Concentric or gyroid | Grid infill creates rigid internal structure. Concentric allows more overall flexibility. |
Design Considerations for TPU Parts
Wall count controls stiffness. More walls make a TPU part stiffer. 1-2 walls for highly flexible parts (phone case flex zones, thin straps). 3-4 walls for parts that need to hold shape while still being flexible. 100% infill solid TPU is firm rather than truly flexible.
Infill affects flex behavior. Gyroid infill allows relatively even flex in all directions. Concentric infill follows the part’s perimeter and allows the most flex perpendicular to the layers. Grid infill creates stiffer internal resistance to compression. Choose based on how and where the part needs to flex.
Overhang performance. TPU handles overhangs surprisingly well because the flexible material is more tolerant of small sag than rigid filaments. Overhangs up to 45 degrees typically print cleanly. Beyond that, sag is more pronounced than PLA because the cooled material is still somewhat flexible.
Supports are harder to remove from TPU. TPU bonds to support material more aggressively than PLA. Design TPU parts to be support-free wherever possible. If supports are unavoidable, maximize the Z-gap distance (0.3-0.4mm) to allow cleaner separation.
Threads and tight tolerances. TPU’s flexibility makes it poor for threaded connections and snap-fits designed for PLA tolerances. If you’re combining TPU and PLA in an assembly, account for the slight size variation from TPU’s elasticity during printing.
Best Use Cases for TPU in Hobby FDM
- Phone cases and device protection: TPU’s impact absorption is ideal. Corner flex zones absorb drops that would crack a PLA case.
- Cosplay connectors and straps: Armor connectors, belt loops, harness attachment points that need to flex as the wearer moves. Much more comfortable to wear than rigid PLA connectors.
- Gaskets and seals: For projects that need a watertight seal, a TPU gasket compressed between two rigid PLA surfaces creates a reliable seal.
- Cable management clips: Flexible TPU clips can be pressed onto cables and released repeatedly without breaking, unlike PLA snap-fits that fatigue.
- Tires and wheels for robotics: 95A TPU provides traction and vibration absorption for wheeled projects.
- Protective feet and bumpers: Soft feet for electronics, camera sliders, tripod bases.
TPU Storage in Florida’s Humidity
TPU absorbs moisture at a rate between PLA and Nylon. In South Florida’s humidity, an open TPU spool degrades noticeably in 3-7 days. Wet TPU shows crackling during printing, increased stringing, and rough surface texture.
Store TPU sealed with desiccant immediately after opening. For active use during South Florida summer, run TPU from a dedicated filament dry box at 50-60°C. The improvement in print quality from dry TPU vs wet TPU on flexible parts is significant because any void or bubble in the material creates a structural weak point in a flexible part.
Frequently Asked Questions: TPU Flexible Filament
Can I print TPU on a Bambu Lab A1?
Yes. The A1 is a direct drive printer and handles TPU 95A well. Use the Bambu Studio TPU profile as a starting point. Print slower than PLA (outer wall 20-40mm/s) and minimize retraction. The A1 Mini is also direct drive and handles TPU similarly.
What Shore hardness TPU should I use for cosplay?
TPU 95A for straps, connectors, and flexible joints. It’s firm enough to hold shape during construction while flexible enough to be comfortable during wear. 87A is softer and more strap-like but harder to print reliably. 95A is the right starting point.
Why is my TPU stringing so much?
TPU strings more than PLA by nature. Minimize retraction (not maximize it as you would for PLA stringing), reduce print speed, and increase travel speed. Enable Combing (travel over solid print surface rather than empty space) in your slicer to eliminate stringing on travel moves that cross solid geometry.
Is TPU UV and heat resistant?
Better than PLA. TPU doesn’t have the 60°C heat deflection problem that kills PLA in Florida cars. Most 95A TPU handles temperatures up to 80-90°C before significant softening. UV resistance varies by brand; most standard TPU yellows with prolonged UV exposure but maintains its flexibility.