Print cooling fans are a lifesaver for many 3D printing situations. They help layers solidify quickly, prevent stringing, and make overhangs cleaner. But there are times when less cooling—or even no cooling at all—is actually better.
1. Printing ABS or Other High-Temperature Plastics
ABS, ASA, and some high-temperature composites don’t like rapid cooling. When layers cool too quickly, they can shrink unevenly, leading to warping, layer splitting, or curling. For these materials, turning the fan off—or keeping it very low—allows the layers to bond properly and reduces internal stress in the part.
2. Printing Large Flat Surfaces
Even with PLA, large flat layers can sometimes warp or lift from the bed if cooled too aggressively. The sudden temperature drop causes contraction, pulling the edges upward. Slowing or stopping cooling for the first few layers of a large print can improve bed adhesion and overall stability.
3. First Layer and Initial Layers
Regardless of material, the first layer should almost always be printed without active cooling. The goal is good bed adhesion, and letting the filament stay warm ensures it sticks rather than curling or lifting. Some slicers even allow you to ramp the fan up gradually after a few layers.
4. Small or Delicate Layers
For extremely small features, thin walls, or tall fine spikes, too much cooling can cause the filament to solidify before it bonds properly, leading to weak layers, gaps, or rough surfaces. Printing slower can help, but sometimes reducing fan speed is essential for small, delicate parts.
5. Flexible Filaments (TPU, TPE)
Flexible filaments can struggle when cooled too quickly. Rapid cooling can cause poor layer adhesion, uneven extrusion, or filament snapping. Keeping the cooling fan low—or off—helps maintain smooth, continuous extrusion.
Tips for Managing Cooling
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Most slicers let you gradually increase fan speed after the first few layers. This is perfect for balancing adhesion and overhang support.
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Adjust cooling based on material and geometry. PLA usually benefits from full cooling, ABS from minimal cooling, and flexible filaments from slow or no cooling.
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Experiment with layer fan overrides for tricky parts, like bridges, overhangs, or tiny details, instead of running a fixed fan speed throughout.
Final Thoughts
Fans are great, but they’re not always your friend. Understanding when to slow them down or turn them off can prevent warping, layer separation, and adhesion problems, especially for high-temperature or flexible filaments. Knowing when not to cool is just as important as knowing when to cool—your prints will come out stronger and cleaner.
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