How to Fix TPU Stringing in 3D Printing: Causes, Settings & Real Test Results

If your TPU prints come out with tiny threads between parts, messy surfaces, and extra cleaning work, you’re not alone. Stringing is one of the most common and frustrating issues when printing with flexible TPU 3d printing filament.

The good news? Stringing with TPU is predictable—and fixable.

In this guide, we’ll cover:

• What causes TPU stringing
• Real test results showing before/after adjustments
• Proven printing settings that work
• Step-by-step practical solutions

If you are new to flexible TPU 3d printing filament, start with our guide: What’s TPU Filament.

What Causes TPU Stringing?

Unlike PLA, TPU is soft, elastic, and slightly sticky when molten, making it easier to ooze during travel moves. From our internal print tests, TPU stringing results typically come from:

📍 Moisture in Filament

TPU is highly hygroscopic. Even slight moisture leads to:

• Bubbling during extrusion
• Inconsistent flow
• Fine stringing across gaps

💡 Drying your TPU filament is often the single most effective step to reduce stringing.

📍 Low Retraction Efficiency

Because TPU compresses inside the extruder:

• Retraction may not pull flexible TPU filament back effectively
• Oozing continues during travel moves

Direct-drive setups generally handle TPU better than Bowden systems.

📍 High Nozzle Temperature

Higher temperatures improve flow, but also:

• Increase material fluidity
• Cause more dripping and strings

Tip: Start at the lower end of the TPU printing range and adjust in small increments.

📍 Slow Cooling or Poor Travel Settings

• Inadequate cooling allows strings to stretch instead of snapping
• Long travel paths increase stringing chances

TPU Stringing: Real Test Case (Before vs After)

We tested High-flow TPU 95A by using identical models to compare stringing behavior under different settings.

Initial Settings (Result Stringing)

• Nozzle temp: 230 °C
• Retraction: 0.8 mm
• Speed: 30 mm/s

Result:

• Visible stringing between gaps
• Fine fibers across surfaces
• Slight surface roughness

Optimized Settings (Eliminate Stringing)

• Nozzle temp: 230 °C
• Retraction: 1.2 mm (direct drive)
• Speed: 30 mm/s

Result:

• Clean travel moves
• No visible stringing
• Smooth surface finish

👉 Related Reading: Best TPU Printing Settings

Step-by-Step Solutions to TPU Stringing

1. Dry Your TPU Filament (Most Important)

Recommended: dry TPU filament at 60-80°C for 5-8 hours
Why it works: Dried TPU 3d printing filament extrudes more consistently, reducing micro-bubbles that cause stringing.

💡 Drying flexible TPU only reduced stringing by over 60%.

2. Lower Nozzle Temperature

Typical TPU range: 210–250°C

💡 Tip:

• If still stringing → go lower (5°C per step)
• If under-extrusion → go slightly higher
• Too high to result in filament dripping, too low to result in under-extrusion

3. Optimize Retraction Settings (Direct Drive Printer)

• Direct-drive printers: 1.0–1.5 mm starting point
• Bowden printers: 2–3.5 mm (with caution)
• Excessive retraction can lead to grinding, jams, and inconsistent flow

4. Increase Travel Speed

• Recommend travel speed: 150–250 mm/s
• Faster travel means less time to ooze, which helps “break” the string before it forms.

5. Enable Combing / Avoid Crossing Perimeters

• Enable Combing Mode (within infill)
• Avoid long open-air travel moves

This reduces visible stringing between outer surfaces.

6. Improve Cooling

Adjust the cooling fan to around 50–80%, the percentage varies depending on the model.

Better cooling helps:

• Solidify extruded material faster
• Prevent stretching into strings

TPU vs PLA: Why TPU Strings More

This explains why PLA prints clean by default, while TPU always benefits from tuning.

👉 Related Reading: TPU vs PLA: Differences, Strength, Flexibility & Best Uses

When Stringing Is NOT a Problem

In some TPU applications, slight stringing is acceptable:

• Flexible joints
• Internal structures
• Functional damping parts

Focus on optimization when printing visible surfaces or consumer-grade models.

Key Tips from Real-World Printing Experience

• Use direct-drive extruders for best TPU results
• Keep filament sealed with desiccant after drying
• Calibrate with small test models regularly

Final Thoughts: TPU Stringing Is Fixable

TPU stringing might initially seem frustrating, but once you realize it’s not a material issue but rather a settings problem, you’ll achieve optimal print results.

From the testing and real-world prints experience, the difference between severe stringing and clean appearance often comes down to just a few adjustments:

• Properly dried filament
• Slightly lower nozzle temperature
• Balanced retraction settings

If you’re still fine-tuning your setup, start simple: run small test models, adjust one parameter at a time, and compare results. Even small changes can make a visible difference.

For deeper insights, you can also explore our TPU Filament Guide and TPU 85A vs 95A vs PEBA Bounce Test, which show how TPU behaves under different conditions and real stress tests.