@Laurensvdg said in Ender3 + Duet Wifi,Dual Z, E3D Hemera, BLTouch. Need Advice:

As a part cooling fan i used a 6000 rpm 5015 12v sunon fan which is actually pretty nice, but does not like to be run with less than 12v and i can't figure out how to control the speed on it...

Try adjusting the PWM frequency using the M106 F parameter. Values from 10 to 30000 hz are valid. The Sunon blower I'm using is not super powerful so it basically needs to be at 100% at all times anyway, but changing the frequency can often help adjust for sound level as well.