Quieting the Extruder Fan

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by Dennis Brown

I noticed that the cooling on the extruder heat sink was extreme. There was no temperature rise at all. Since it was over cooled, I figured I could slow the fan down to make the noise less annoying. I did this by experimenting with adding different current limiting resistors in series with the fan leads until it was quieter, still loud enough to be heard to know it was working, and still giving max cooling. The mod could have been made to the Extruder PCB by cutting a trace and adding the resistor to the underside, but since this was a fan specific mod (it might be different for different model fans), I thought it more appropriate to make it part of the fan. My fan consumes 90mA unmodified. I found a resistor value of 220 Ohms gave me the performance I wanted. It consumed a little over 1/2 Watt, so I used three 680 Ohm 1/4 Watt resistors in parallel (227 Ohms). A single 220 Ohm 1 Watt resister is a better choice, but I was just using what I had in my parts bin. I cut the lead near the connector and soldered the three resistors into the break. I did not completely enclose the resistor bodies, so that they could dissipate the half Watt easier. I used the finger test and also an IR heat gun to see if there was any degradation in cooling. The heat sink still stayed at ambient with the Hot end running 220C. The stepper motor housing itself was just slightly warm to the touch, as it was before.

Resistors to slow fan speed

Quieter 40 mm fans:[edit]

 25dB fan
 14dB fan