Cooling / Fan Speed
Part cooling fan speed — controls how fast extruded plastic solidifies, affecting overhang quality, bridging, and layer bonding.
Medium priority
Filament-Specific
What It Is
Part cooling fan speed controls how quickly the just-deposited plastic solidifies. More cooling = better overhangs and bridges (plastic freezes in place before drooping), but too much cooling = poor layer adhesion (layers don’t bond if they cool too fast).
What It Controls
- Overhang quality (cooling prevents droop)
- Bridge performance (cooling freezes spans)
- Layer adhesion strength (too much cooling weakens bonds)
- Small feature quality (thin features need cooling to hold shape)
- Curling on overhangs
Why It Varies
- Material type (PLA loves cooling, ABS hates it, PETG is in between)
- Layer height (thinner layers cool faster, may need less fan)
- Print speed (faster = less time per layer = may need more cooling)
- Part geometry (small layers need more cooling time)
- Fan duct design affects actual airflow vs. percentage
How to Calibrate (Manual)
- Print an overhang test at different fan speeds (0%, 25%, 50%, 75%, 100%)
- Evaluate: overhang quality vs. layer adhesion
- Some slicers allow per-feature fan speeds (bridges: 100%, perimeters: 50%)
- Set minimum layer time to ensure small layers have enough cooling
How the Auto-Tuner Calibrates It
- Camera + overhang droop analysis — evaluates overhang quality at different fan speeds
- Measures droop angle vs. fan speed to find optimal cooling
- Can be combined with speed profile tuning for per-feature optimization
Related Anomalies
- Rough Overhangs — insufficient cooling
- Bridge Sag — insufficient cooling during bridges
- Delamination — too much cooling weakens layer bonds
- Warping — uneven cooling causes thermal stress