TPU Filament: Flexible Filament for 3D Printing
TPU (Thermoplastic Polyurethane) is the most popular flexible filament for FDM 3D printers. It enables printing of rubber-like, elastic parts – from phone cases to seals to shoe soles. TPU requires adapted print settings and ideally a Direct Drive extruder, but rewards with unique possibilities not achievable with rigid filaments.
What is TPU?
TPU is a thermoplastic elastomer that combines the properties of rubber with the processability of plastic. It consists of hard and soft segments that give it both elasticity and strength.
TPU is widely used in industry – from shoe soles to smartphone cases to automotive seals. In 3D printing, it opens up entirely new application areas.
TPU is characterized by the following properties:
- Flexible and elastic (depending on Shore hardness)
- Very high impact absorption
- Excellent abrasion resistance
- Chemically resistant (oils, greases, many solvents)
- Cold resistant (stays flexible even below zero)
- Little odor when printing
Understanding Shore Hardness
Shore A Scale for TPU
TPU hardness is measured in Shore A. The lower the value, the softer the material:
- Shore 85A: Very soft, like an eraser
- Shore 95A: Standard TPU, like a shoe sole
- Shore 98A: Relatively hard, but still flexible
Lower Shore hardnesses (85A and below) are significantly harder to print!
Technical Properties in Detail
| Property | Value | Meaning for Printing |
|---|---|---|
| Print Temperature (Nozzle) | 220–250 °C | Similar to PETG |
| Bed Temperature | 40–60 °C (optional) | Often possible without heated bed |
| Print Speed | 15–30 mm/s | Printing slowly is critical! |
| Shore Hardness | 85A–98A | Determines flexibility |
| Tensile Strength | 30–50 MPa | High for a flexible material |
| Elongation at Break | 400–600% | Extremely stretchable |
| Abrasion Resistance | Very high | Ideal for wear-stressed parts |
| Chemical Resistance | Good | Resistant to oils, greases, many solvents |
Pros and Cons of TPU
✅ Advantages
- Flexible and elastic
- Extremely high impact absorption
- Excellent abrasion resistance
- Chemically resistant
- Cold resistant (down to -40 °C)
- Little odor when printing
- Good layer adhesion
- No warping
❌ Disadvantages
- Slow printing required
- Direct Drive strongly recommended
- Stringing tendency
- Difficult to cut/post-process
- Not MMS compatible (AMS/CFS)
- Requires practice and patience
- More expensive than PLA/PETG
TPU is NOT compatible with automatic filament change systems like Bambu Lab AMS, Creality CFS or Anycubic ACE. The flexible material can kink in the feed mechanisms and cause jams. TPU must always be loaded manually via the main extruder.
Optimal Print Settings for TPU
| Parameter | Recommended Value | Notes |
|---|---|---|
| Nozzle Temperature | 225–235 °C | Reduce slightly if stringing occurs |
| Bed Temperature | 50 °C | Or room temperature with glue stick |
| Print Speed | 20–30 mm/s | Critical! Too fast = jam |
| Retraction | 0–2 mm (Direct Drive) | Little to no retraction |
| Fan | 50–100% | Cooling helps with details |
| Flow | 100–105% | TPU compresses slightly in the extruder |
| Infill | 10–30% | Keep low for maximum flexibility |
Direct Drive vs. Bowden
| Extruder Type | TPU Suitability | Recommendation |
|---|---|---|
| Direct Drive | ✅ Very good | Ideal for all TPU hardnesses |
| Bowden (short, <30 cm) | ⚠️ Possible | Only for TPU 95A+, print very slowly |
| Bowden (long) | ❌ Difficult | Not recommended, frequent jams |
Why Direct Drive? TPU is flexible and can kink, compress or jam in long Bowden tubes. The short, direct path to the hotend with Direct Drive extruders eliminates these problems.
Application Areas for TPU
Ideally suited for:
- Phone cases & protective covers: Shock-absorbing, grippy
- Seals & O-rings: Flexible seals
- Shock absorbers & bumpers: Vibration dampening
- Wheels & tires: RC cars, robots
- Shoe soles & insoles: Orthopedic adaptations
- Flexible hinges: Living hinges
- Grips & covers: Non-slip surfaces
- Cable guides: Flexible cable channels
- Bracelets & wearables: Comfortable on the body
Not recommended for:
- ❌ Rigid structural parts (use PLA/PETG/ABS)
- ❌ Multi-material prints with AMS/CFS
- ❌ Parts requiring precise dimensions
- ❌ Fast prototyping (slow printing)
Troubleshooting: Common Problems
Filament kinks in extruder
Solution: Reduce speed to 15–20 mm/s. With Bowden: consider Direct Drive upgrade or use harder TPU (98A).
Heavy stringing
Solution: Lower temperature by 5–10 °C. Increase travel speed. Minimal retraction (0–2 mm). Post-processing: remove stringing with heat gun.
Poor first layer
Solution: Increase Z-Offset slightly (TPU is compressible). First layer slower (15 mm/s). Glue stick on glass plate.
Under-extrusion
Solution: Increase flow to 105%. Reduce speed. Loosen filament tension on feeder.
Storage of TPU Filament
TPU is hygroscopic and absorbs moisture. Wet TPU causes bubbling and poor surface.
Proper storage:
- In sealed bags with silica gel
- Dry box during printing
- Humidity below 40% ideal
TPU Variants
TPU 95A (Standard)
Good compromise between flexibility and printability. Recommended for beginners to flexible filaments.
TPU 85A (Soft)
Very soft and elastic, like an eraser. Harder to print – only with Direct Drive and experience.
TPU 98A (Hard)
Relatively stiff, but still flexible. Easiest to print, also possible with Bowden.
TPE
General term for thermoplastic elastomers. TPU is a type of TPE. Other TPE variants can be even softer.
Our TPU Filaments in the Shop
Frequently Asked Questions (FAQ)
Can I print TPU with my printer?
Most modern 3D printers can print TPU. Direct Drive extruders (Bambu Lab, Prusa MK4, many Creality models) are ideal. Bowden printers can print TPU 95A/98A at reduced speed, but are not optimal.
Why is TPU not AMS/CFS compatible?
Multi-material systems like AMS or CFS use feed mechanisms with many deflections. Flexible TPU kinks in these systems and causes jams. TPU must always be loaded directly via the main extruder.
How do I make TPU prints waterproof?
TPU prints are already largely waterproof with sufficiently high infill (>30%) and good layer adhesion. For absolute tightness: use 100% infill or more perimeters.
Can I glue TPU?
TPU can be bonded with cyanoacrylate (super glue) or special TPU adhesive. Contact adhesive also works well. Lightly sand the surface before gluing.
How long does TPU last outdoors?
TPU has good UV resistance – better than PLA or ABS. It is well suited for durable outdoor applications, but may yellow over time (with light colors).
Related Guides
- PLA Filament: The All-Rounder
- PETG Filament: Robust and Versatile
- PA (Nylon): Extremely Durable
- The Perfect First Layer
Note: The information is based on typical properties of TPU filaments. Values vary depending on Shore hardness and manufacturer. Always consult the data sheets.