TPU (Thermoplastic Polyurethane) is one of the most exciting 3D printing materials—strong, flexible, durable, and perfect for making phone cases, seals, gaskets, wheels, and wearable parts.
However, stringing is a common problem when printing TPU, often leaving thin, messy webs of filament between parts or infill lines.
In this guide, you’ll learn why TPU stringing happens, and how to tune your settings and techniques to achieve clean, smooth, professional-quality TPU prints—without endless cleanup.
Why TPU Prints String More Than PLA or PETG
| Reason | Explanation |
|---|---|
| High elasticity | TPU stretches instead of snapping cleanly at retraction |
| Low stiffness | Difficult for extruder to fully control flow stop/start |
| Slow flow behavior | TPU tends to ooze out even when extrusion stops |
| Moisture sensitivity | Wet TPU strings much more easily |
Because of these physical properties, TPU demands different settings and handling compared to rigid filaments.
How to Stop TPU Stringing: Step-by-Step
1. Dry Your TPU Thoroughly
Wet TPU = terrible stringing.
| Drying Recommendation | Details |
|---|---|
| Temperature | 45–55°C (113–131°F) |
| Time | 4–6 hours minimum |
| Storage | Airtight container with silica gel |
📌 Tip: You can use a filament dryer or a food dehydrator to dry TPU safely.
2. Lower Printing Temperature Slightly
- Printing too hot makes TPU more liquid and oozy.
- Find the balance between good flow and minimum stringing.
| Material | Typical Print Temperature |
|---|---|
| Soft TPU (85–90A) | 210–225°C |
| Stiffer TPU (95A+) | 220–240°C |
Tip:
If you see heavy stringing, lower your nozzle temp by 5–10°C and test again.
3. Reduce Retraction Distance and Speed
Retraction settings for TPU are very different from PLA or PETG.
| Setting | Suggested Value |
|---|---|
| Retraction Distance | 1.0–2.0 mm (Direct Drive) / 3.0–5.0 mm (Bowden) |
| Retraction Speed | 15–30 mm/s |
📌 Slow retraction speed is critical because TPU can’t retract quickly without causing jams.
For Direct Drive:
- Retraction Distance: 1.0–1.5 mm
- Retraction Speed: 20–25 mm/s
For Bowden setups:
- Retraction Distance: 4.0–5.0 mm
- Retraction Speed: 20 mm/s
4. Use Z-Hop (Lift During Travel)
Enable Z-Hop to lift the nozzle slightly during travel moves:
- Z-hop height: 0.3–0.5 mm
This helps avoid dragging melted TPU across your prints.
5. Lower Print Speed
TPU prints best at slow speeds to maintain clean extrusion control.
| Setting | Suggested Value |
|---|---|
| Outer Walls | 20–30 mm/s |
| Infill | 30–40 mm/s |
| Travel Moves | 100–150 mm/s |
📌 Faster travel helps minimize stringing without affecting printed paths.
6. Enable Coasting (If Available)
Coasting turns off extrusion slightly before the end of a path, allowing residual pressure to finish the line naturally.
- Enable coasting in your slicer (Cura, PrusaSlicer, etc.)
- Start with a small coasting volume (e.g., 0.05–0.1 mm³)
📌 Coasting significantly reduces the pressure buildup that causes stringing in TPU prints.
7. Minimize Cooling
Too much cooling causes filament to solidify on the nozzle tip, leading to strings.
| Cooling Fan | Suggested Setting |
|---|---|
| 20–40% fan speed | Enough to cool, but not too much |
Some TPU prints benefit from fan off for the first layers and low fan for the rest.
8. Tune Your Travel Paths
- Enable Combing Mode: Within Infill (Cura) or Avoid Crossing Perimeters (PrusaSlicer).
- This keeps travel moves inside already-printed areas to avoid external stringing.
Quick Troubleshooting Table for TPU Stringing
| Problem | Likely Cause | Solution |
|---|---|---|
| Fine webs between parts | Wet filament | Dry TPU thoroughly |
| Thick strings at nozzle tips | High print temp | Lower nozzle temp by 5–10°C |
| Excessive wisps during travel | Retraction too fast or too far | Slow down and reduce retraction distance |
| Tiny hairs across part | Cooling too high | Reduce cooling fan speed |
| Sticking during travel | Z-hop not enabled | Enable Z-hop during travels |
Best Slicer Settings for TPU to Minimize Stringing (Summary)
| Setting | Value |
|---|---|
| Nozzle Temp | 220–230°C (adjust per filament) |
| Bed Temp | 40–60°C |
| Retraction Distance | 1–2 mm (Direct Drive) / 4–5 mm (Bowden) |
| Retraction Speed | 20–30 mm/s |
| Travel Speed | 120–150 mm/s |
| Cooling | 20–40% |
| Z-Hop | 0.4 mm |
| Coasting | Enabled |
Top Tips for Best TPU Print Quality
- Keep filament dry at all times—moisture ruins TPU prints fast.
- Use a direct drive extruder if possible—better flow control than Bowden setups.
- Print slow and steady—rushing TPU causes blobs, stringing, and poor adhesion.
- Use PEI sheets, textured plates, or glue stick for excellent TPU bed adhesion.
FAQs
Q1: Can TPU be printed without stringing at all?
Mostly, yes. With proper drying, tuning, and slow settings, you can get nearly string-free TPU prints.
Q2: Is Bowden printing TPU impossible?
Not impossible, but trickier. Use a tight PTFE tube (like Capricorn tubing), low retraction speed, and slow print speeds for best results.
Q3: Does TPU require special nozzles?
Not necessarily, but a clean, wide-diameter nozzle (0.4–0.6 mm) works better to avoid pressure buildup.
Q4: Why does my dried TPU still string?
It may still need slightly lower temperatures, better retraction settings, or less cooling to optimize string reduction.
Conclusion
Printing flexible TPU can be one of the most rewarding 3D printing experiences—but it requires patience and proper tuning.
By drying your filament, adjusting retraction and temperature settings, reducing cooling, and slowing down your print speeds, you can produce clean, strong, flexible TPU prints with minimal or zero stringing.
Mastering TPU unlocks a whole new world of functional, durable, flexible parts that regular filaments can’t match.