3D Printer Cooling Calculator
Recommends a cooling fan speed percentage for FDM 3D printing based on material type, layer time, nozzle temperature, and ambient conditions. Use it to dial in cooling settings for overhangs and bridging.
About this calculator
Optimal cooling fan speed is a balance between solidifying extruded plastic fast enough to hold shape and keeping the material warm enough to bond to the previous layer. The formula computes a recommended fan percentage: Fan% = min(100, max(0, materialFactor × 100 × (30 / max(layerTime, 5)) × (1 + (nozzleTemperature − 200) / 100) × (1 + bridgeDistance / 20) × (1 − (max(ambientTemperature, 20) − 20) / 50))). The material factor encodes how cooling-tolerant a material is (PLA ≈ 1.0, PETG ≈ 0.5, ABS ≈ 0.0). The layer-time term increases cooling for fast layers that don't have time to solidify naturally. The nozzle-temperature term compensates for hotter extrusion needing more cooling. Bridge distance increases cooling demand, while higher ambient temperature reduces the need for active fan cooling. The result is clamped between 0% and 100%.
How to use
Printing PETG (materialFactor = 0.5) with a 15-second layer time, 240 °C nozzle, 25 °C ambient temperature, and a 10 mm bridge distance. Step 1: layer-time factor = 30 / max(15, 5) = 2.0. Step 2: nozzle factor = 1 + (240 − 200) / 100 = 1.4. Step 3: bridge factor = 1 + 10 / 20 = 1.5. Step 4: ambient factor = 1 − (25 − 20) / 50 = 0.9. Step 5: Fan% = 0.5 × 100 × 2.0 × 1.4 × 1.5 × 0.9 = 189, clamped to 100%. Use 100% fan speed for this bridge on PETG at these conditions.
Frequently asked questions
Why should I use less cooling fan speed when printing ABS or ASA compared to PLA?
ABS and ASA are prone to warping and layer delamination caused by rapid thermal contraction between layers. Aggressive fan cooling accelerates this temperature drop, creating internal stresses that cause corners to lift off the bed and layers to crack apart. These materials are best printed with the fan at 0–20% or completely off, relying on a heated enclosure to maintain ambient temperature above 40 °C instead. PLA, by contrast, benefits from maximum cooling because it has a much lower glass transition temperature and needs active cooling to solidify before the next layer is deposited.
How does layer time affect cooling fan speed in FDM 3D printing?
Short layer times mean each new layer of molten plastic is deposited before the previous layer has had time to cool on its own, which can cause heat buildup, drooping, and poor surface finish — especially on small features. The calculator increases fan speed when layer time drops below 30 seconds to compensate. Many slicers have a 'minimum layer time' setting that slows the print to allow natural cooling; the cooling fan recommendation here works in conjunction with that feature rather than replacing it.
What fan speed setting should I use for printing overhangs and bridges?
Bridges and overhangs are the most demanding cooling scenarios in FDM printing because the plastic must solidify mid-air before sagging under gravity. For PLA, maximum fan speed (100%) is recommended for bridges longer than 30–40 mm. PETG tolerates bridging better than its reputation suggests but still benefits from 50–80% fan speed for spans over 20 mm. ABS bridges best in an enclosed printer where gentle airflow from a low fan setting (10–20%) or no fan at all is combined with slow bridge speed settings in your slicer. The bridge distance input in this calculator directly increases the recommended fan percentage to reflect these demands.