Thermoplastic Polyurethane (TPU) is a versatile flexible filament in 3D printing, favored for its ability to produce parts that are both flexible and durable. It's commonly used for applications like phone cases, wearable devices, and various industrial parts.
TPU, or Thermoplastic Polyurethane, is a highly versatile material used in 3D printing, offering a unique combination of elasticity, durability, and chemical resistance. Its properties can vary significantly based on its formulation, particularly in terms of shore hardness.
Shore hardness is a measure of a material's resistance to indentation, which in the case of TPU, correlates to its flexibility. TPU filaments are available in a range of shore hardness values, each suited to different applications:
| Shore Hardness |
Flexibility |
Real-World Examples |
Stickiness When Cold |
| 60A |
extremely Flexible |
squishy toys, grippy tires |
Very Sticky |
| 85A |
very Flexible |
Flexible tubes, gaskets, shoe insoles |
Moderately Sticky |
| 95A |
Semi-Flexible |
Rigid phone cases, industrial parts |
Less Sticky |
| 98A and above |
Least Flexible |
Mechanical parts, automotive components |
Least Sticky |
- 60A: This is among the softest TPU available, suitable for extremely flexible applications. Due to its softness, it can be very sticky when cold. It is extremely tricky to handle. The extruder tension a little to tight and it will jam. Just a little too low, and it wont be grabbed by the extruder. A Little too high friction on the spool holder, and the filament comes under tension, which makes it thinner, which makes it harder for the extruder to gra.
- 85A: A very flexible TPU, quite challenging to print! Make sure you have some experience with TPU already.
- 95A: Harder and less flexible, this type of TPU is easier to print with less deformation. It's less sticky compared to softer TPUs, making it more manageable. Still it can be painful to print with and requires some tinkering to get good quality successful prints.
- 98A and above: These are the hardest TPU types, approaching the rigidity of plastics like ABS. They exhibit the least stickiness, making them easier to handle and print but offer less flexibility. It should be printable with some adjustments in the settings. Recommended for Beginners.
¶ Flexibility and Durability
The flexibility of TPU varies inversely with its durability - softer TPUs are more flexible but may be less resistant to wear and tear, while harder TPUs, though less flexible, offer greater durability. This balance is crucial when selecting TPU for specific applications.
¶ Temperature and Chemical Resistance
TPU is generally resistant to oils, greases, and various chemicals, making it suitable for industrial applications. Its temperature resistance is good, though it can vary depending on the specific type of TPU, affecting its suitability for high-temperature environments.
TPU's stickiness when cold is an important consideration for storage and handling. Softer TPUs tend to be stickier, which can lead to issues like filament tangles and difficulties in feeding the filament into the printer. Harder TPUs are less prone to these issues.
- Flexibility and Durability: Varies based on shore hardness; softer TPUs are more flexible but less durable, and vice versa.
- Temperature and Chemical Resistance: Generally good, but varies with the specific type of TPU.
- Extruder: Direct drive is preferred. Bowden can be used with slower speeds.
- Hotend Temperature: Between 220°C and 250°C.
- Bed Temperature: Keep it below 40°C to prevent over-adhesion. Remove prints promptly after completion.
- Print Speed: Start with 10mm/s for better control.
- Cooling: Moderate cooling fan speeds are recommended.
- Bed Adhesion: Use 3DLac or similar adhesives, as TPU can be very sticky.
- Layer Height: 0.1 mm to 0.3 mm for finer details.
- Retraction: 0.5 to 1.5mm for direct drive, with slow retraction speeds (~10mm/s).
- Infill: Start with a low rate, around 15% for shore 95A TPU, to maintain flexibility.
- Supports: Avoid using supports if possible. TPU bonds insanely between layers, making support removal a very painful task.
- Pressure Advance: Use
SET_PRESSURE_ADVANCE ADVANCE=0.8 in the custom start G-code for Klipper as a starting point (direct drive). For other Printers, Try a very high value.
- Nozzle Size: A 0.6 mm nozzle can print faster and with fewer jams than a 0.4 mm nozzle.
- Retraction and Compression: Proper retraction prevents TPU from compressing and jamming in the nozzle.
- Pressure Advance: Adjusting pressure advance compensates for speed changes, improving print quality.
- Adhesion: Use specialized bed adhesives and promptly remove prints. This is not to ake the print stick better. It is to be able to remove the print due to the sticky Nature of TPU(!)
- Dry Filament: Store TPU in a dry environment. Use a filament dryer if needed.
- Least friction as possible Use a spool holder with ball bearings if possible. Dont use a revers bowden (from spool to motor). Keep the filament path as straight and short as possible.
¶ Common Issues and Solutions
- Warping or Lifting: Enhance bed adhesion and keep the bed temperature low.
- Clogging: Optimize temperature and retraction settings.
- Overhangs: Adjust cooling and speed, and avoid supports.
- Begin with Firmer TPU: Start with a relatively hard TPU (higher shore hardness) to gain experience, as it's easier to print than softer varieties.
- Consumer Products: Phone cases, shoe insoles, etc.
- Industrial Uses: Gaskets, flexible joints, etc.
TPU printing requires careful calibration and patience. Its flexibility and durability make it a highly valuable material for a wide range of applications, appealing to both hobbyists and professionals.