Practical PETG Extrusion Guide

Why PETG needs different settings

PETG is stronger than PLA but more challenging to dial in. It's sensitive to extrusion rate and hotend temperature. Push too hard (too much flow), and the nozzle jams. Too soft, and layers don't bond. This guide covers the safe flow rates and line widths that work across different printers, so you can print functional PETG parts without failure.

Safe flow rate ranges for PETG

Formula: Flow (mm³/s) = Nozzle diameter (mm) — Layer height (mm) — Print speed (mm/s). Calculate your flow before printing using the volumetric flow calculator.

Bambu Lab P1S PETG profiles

Profile: Balanced (default starting point)

• Nozzle temperature: 245°C (Bambu default) or 250°C (safer for first print)
• Bed temperature: 80°C
• Line width: 0.5mm (1.25× nozzle)
• Print speed: 150 mm/s (Bambu standard) but reduce to 100 mm/s for first PETG job
• Layer height: 0.2mm
• Cooling: 0% (PETG needs minimal cooling; turn off part cooling fan)
• Flow rate: ~8 mm³/s (at 100 mm/s with 0.4 nozzle)
• Expected result: Strong layer adhesion, acceptable surface quality, reliable prints

Profile: Quality (slower, stronger layer bonds)

• Nozzle temperature: 250°C
• Bed temperature: 80°C
• Line width: 0.48mm
• Print speed: 60–80 mm/s
• Layer height: 0.12mm
• Cooling: 0% (keep fan off for first 5 layers, then 5% if needed)
• Flow rate: ~3–4 mm³/s (very safe, excellent bonding)
• Expected result: Smooth surfaces, perfect layer adhesion, functional parts, 2–3× print time vs balanced

Prusa i3 MK4 PETG profiles

Profile: Standard (Prusa's optimized setting)

• Nozzle temperature: 240°C (Prusa PETG default)
• Bed temperature: 85°C (Prusa PEI sheet handling)
• Line width: 0.5mm
• Print speed: 120 mm/s (Prusa optimized)
• Layer height: 0.2mm
• Cooling: 5% (light cooling only)
• Flow rate: ~9.6 mm³/s (safe, reliable)
• First layer: 100 mm/s at 245°C, 0% cooling
• Expected result: Prusa's tested profile, strong prints, good speed/quality balance

Profile: High-strength functional parts

• Nozzle temperature: 245°C
• Bed temperature: 85°C
• Line width: 0.52mm (1.3× nozzle for thick walls)
• Print speed: 80 mm/s
• Layer height: 0.2mm
• Infill: 20–30% (brackets/holders need structure)
• Cooling: 0% (no cooling = maximum bonding)
• Flow rate: ~8.3 mm³/s (safe and strong)
• Expected result: Strongest layer adhesion, excellent for mechanical parts

Common PETG printing problems and solutions

Problem: Nozzle jam after 30 minutes

Likely cause: Flow rate too high (>12 mm³/s). PETG viscosity is high; excessive speed pushes too much plastic through.
Solution: Reduce print speed by 20%, lower nozzle temp to 245°C, or increase line width. Check flow rate with volumetric flow calculator. If flow >12 mm³/s, reduce it to 8–10.

Problem: Weak layer adhesion (layers separate easily)

Likely cause: Cooling fan too high or nozzle temperature too low.
Solution: Turn off part cooling fan (PETG needs heat, not cooling). Increase nozzle to 245–250°C. Increase print speed slightly (better extrusion consistency). Reduce line width to force more overlap.

Problem: Ooze and poor surface finish

Likely cause: Nozzle temperature too high (>250°C) or retraction too weak for PETG's viscosity.
Solution: Lower nozzle to 245°C. Enable retraction: 4–5mm at 40 mm/s (PETG needs aggressive retraction). Add small coasting distance (0.5mm) to reduce pressure at layer changes.

Problem: Warping at corners (especially on large flat parts)

Likely cause: Bed temperature too low or cooling fan on too early.
Solution: Maintain bed at 85°C minimum. Turn off cooling completely. Print first 5 layers slowly (50 mm/s). Add a larger brim or skirt for adhesion insurance.

Problem: Rapid plugging (jam after many prints)

Likely cause: Moisture in PETG (hygroscopic, absorbs water). Degraded material in nozzle.
Solution: Dry PETG in oven at 70–75°C for 4 hours before printing. Store in sealed container with desiccant. Clean nozzle monthly with cold pull method (print in ABS/nylon, then pull while hot).

PETG vs PLA: Quick comparison