Fixing PETG & TPU Stringing on Bambu Lab 3D Printers: A Complete Guide

PETG and TPU are top filament choices for Bambu Lab users—PETG for its durability and flexibility, TPU for its elasticity—but both are notoriously prone to stringing. This guide targets Bambu Lab PETG stringing and Bambu Lab TPU stringing specifically, breaking down root causes and actionable solutions (from basic tweaks to advanced optimizations) to get clean, string-free prints every time.

PETG and TPU have unique properties that make them more susceptible to stringing than PLA, and Bambu Lab’s high-performance hardware requires targeted adjustments to mitigate this issue:

Bambu Lab printers rely on retraction to pull molten PETG/TPU back into the nozzle during non-print moves. Common mistakes:

• Retraction length too short (fails to pull filament back far enough—critical for TPU’s high flexibility).
• Retraction length too long (>2mm / 0.079in, risks clogs in Bambu Lab’s hotend).
• No "Avoid Crossing Perimeters" enabled (increases long-distance non-print moves, worsening stringing for both materials).

• Overheating:
  • PETG’s low viscosity at high temps (≥250°C / 482°F for most blends) makes it runny and prone to oozing.
  • TPU melts at lower temps (typically 210–230°C / 410–446°F) but still oozes if overheated—even 5°C / 9°F too high causes stringing.

• Line width vs. nozzle design: Bambu Lab’s standard 0.4mm / 0.016in nozzle has a "flattening ring" (outer flat surface). Setting line width >0.4mm / 0.016in forces the ring to spread PETG/TPU, causing overflow and nozzle buildup—buildup traps stringing and worsens it over time.

Start with these quick adjustments—they resolve 80% of stringing issues for both PETG and TPU on Bambu Lab printers:

For Bambu Lab X1/P1P/P1S/A1:

• PETG:
  • Retraction length: 1.0–2.0mm / 0.039–0.079in (never exceed 2mm / 0.079in to avoid hotend clogs).
  • Retraction speed: 40–60mm/s / 1.57–2.36in/s (balance speed to avoid grinding PETG).
• TPU:
  • Retraction length: 0.8–1.5mm / 0.031–0.059in (shorter than PETG to prevent stretching TPU).
  • Retraction speed: 20–40mm/s / 0.79–1.57in/s (slower to avoid snapping flexible TPU).
  • Enable "Avoid Crossing Perimeters" (under "Travel" settings).
  • Reduce spacing between multiple models to shorten non-print moves (aim for ≥5mm / 0.2in spacing to avoid collision, but keep as tight as possible).For both materials:

• PETG: Start with 230–240°C / 446–464°F (down from default 245–250°C / 473–482°F). Adjust in 5°C / 9°F increments—prioritize string reduction over layer adhesion (PETG bonds well at lower temps on Bambu Lab’s heated beds).
• TPU: Start with 215–225°C / 419–437°F (down from default 225–230°C / 437–446°F). Avoid temps over 230°C / 446°F (causes TPU to degrade and string more).

In Bambu Studio:

• Confirm "Nozzle Size" matches your installed nozzle (under "Printer" > "Hardware")—e.g., 0.4mm / 0.016in or 0.6mm / 0.024in.
• Reset flow rate to 100% (override any custom flow tweaks for testing—TPU may need 90–95% flow later, but start at 100%).

For stubborn stringing (or professional-grade results), use these Bambu Lab-specific tweaks:

• PETG: Set line width to 0.35–0.4mm / 0.014–0.016in (slightly smaller than the nozzle inner diameter).
• TPU: Set line width to 0.3–0.35mm / 0.012–0.014in (even thinner than PETG to reduce nozzle pressure on flexible filament).
• This eliminates the need for the flattening ring to spread filament—no overflow = no nozzle buildup on your Bambu Lab printer.
• Pair with Bambu Studio’s "Wipe Nozzle" feature (under "Extrusion" > "Advanced"): The nozzle wipes excess PETG/TPU on already printed lines during travel, keeping the tip clean (critical for TPU’s sticky texture).

Add a silicone sock to your Bambu Lab nozzle (sized for 0.4mm / 0.016in or 0.6mm / 0.024in nozzles)—it catches minor PETG/TPU oozing/stringing before it sticks to the nozzle, and works with the wipe feature for maximum cleanliness (especially helpful for TPU, which adheres to metal nozzles easily).

If using specialty filaments on Bambu Lab printers:

• Foamed PETG: Lower temperature by an additional 5–10°C / 9–18°F or use the Cooldry Pro system, reduce flow rate to 50–70%, and dry longer (8+ hours at 65°C / 149°F) to remove trapped gases.

• Soft TPU (Shore 95A or lower): Disable retraction entirely if stringing worsens (use "Coasting" instead in Bambu Studio), and print at 210°C / 410°F max to avoid melting too quickly.

1. Moisture is king: Dry PETG/TPU first—retraction tweaks won’t fix damp filament on Bambu Lab printers (TPU needs extra drying time).
2. Retraction limits: Stick to 1.0–2.0mm / 0.039–0.079in for PETG and 0.8–1.5mm / 0.031–0.059in for TPU to avoid clogs in Bambu Lab’s hotend.
3. Line width hack: 0.35–0.4mm / 0.014–0.016in for PETG and 0.3–0.35mm / 0.012–0.014in for TPU + wipe feature eliminates nozzle buildup (the #1 advanced fix for Bambu Lab PETG stringing and Bambu Lab TPU stringing).
4. Temperature control: Keep PETG at 230–240°C / 446–464°F and TPU below 225°C / 437°F to reduce oozing and stringing.

Have you found a winning PETG/TPU profile for your Bambu Lab printer? Share your retraction/temperature settings in the comments!