CuraEngine Fan Speed Trouble

I do not understand the fan speed control in CuraEngine. Is this a bug?

In the "Filament" tab I have set the minimum fan speed to 10% and the max 30%.
In the "Extrusion" tab I set "fan max at height" to 3mm.
Cooling is enabled on the slicing tab. I am slicing using the correct profile with these settings.

However, when I slice with Cura, the resulting gcode does not scale the fan speed correctly at the layers. By the time my Z-axis reaches 7.5mm high the fan is only at 9%, too low to even start spinning. At layer 2, the fan was set to 1%, far below the minimum of 10%.

Why is Cura not recognizing the minimum fans speed setting and not correctly ramping the fan speed linearly as it should?


  • I'm having much the same problems with fan control.  I'm having over-extrusion problems with my first few layers and I wanted to try running the fan to see if that helped.  In Print/Extrusion settings, I set 'Fan Full at Height' to 0.5 mm, and I'm using 0.3 mm per layer. This should cause the fan to run 'Full' from layer 2 onwards, but it never runs at all.
    What gives?


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