How is the fan speed calculated?

Let's assume a I set a layer time to start increasing cooling from the base value, and another minimum layer time at which cooling reaches the maximum I set.

How is the interpolation between the two obtained?

Background information:

In general I would expect an inversely proportional relationship, since, for example, half layer time means doubling the cooling. Is this the case, or is it a linear relationship?

If an inversely proportional formula is used, I may only need to define the layer time for the max cooling, and the software would reduce it based on layer time alone, with an additional rule about never going below a predefined amount.

• But no cooling fan cools the same, hence the flow needs to be tuned for your printer. The flow of a radial fan is generally proportional to its speed, but the exact relationship can be influenced by various factors.
– 0scar
Feb 7 at 18:17
• @0scar Ok so what is the actual formula used by slicers currently? linear? the rest was guesswork and ideas on my side
– FarO
Feb 9 at 9:45
• You could look it up in Cura slicing engine or slic3r source
– 0scar
Feb 9 at 9:58
• @0scar it's beyond my skills
– FarO
Feb 9 at 10:44
• As the ralation is sort of linear you can expect the code to linerly interlpolate in between the min. fan speed and the max. fan speed.
– 0scar
Feb 9 at 10:52