I am designing a fan mount for the CR-10S printer to hold the E3D All-metal v6 HotEnd and BLTouch sensor.

The CR-10S printer has two fans.

One on the front:

enter image description here

and another one on the right:

enter image description here

I need to know what the two fans are actually cooling in order to make a perfect mount.

When powered on, the front fan seems to be on 100 percent of the time. The right fan can only be on via gcode when printing.

I removed the fan mount to study it and it looks like the front fan is cooling the hotend heat sink.

enter image description here

The right fan is attached to the mount and there no hole there to let the air from the fan go through. It seems to be cooling the metal it is bolted to and that doesn't make sense.

Am I correct about the front fan? What's the right fan cooling?

  • $\begingroup$ is the part cooling fan output PWM or TTL. $\endgroup$ Sep 7, 2018 at 9:29
  • $\begingroup$ @SergioDeJesus Part cooling fans are scheduled (can run at different speeds), so PWM $\endgroup$
    – 0scar
    Sep 9, 2018 at 22:44

1 Answer 1


The function of the front fan is keeping the cold end well... cold. :) It should be spinning as long as the printer is turned on.

The right fan is known as "part fan" and its function is to cool down the plastic that has been just extruded, the idea being to solidify it as soon as possible. As you noticed it is controlled by the gcode and it can be turned on, off and even made spin at any speed in-between still and full throttle. It normally stops spinning at the end of the print (with some plastic like ABS it may be set not to spin at all even during the print).

If you take a closer look at your CR-10, you will see that the receptacle the air is blown into by the part fan has no bottom: that slit is where the air passes through, before being deflected 90° towards the nozzle.

On the CR-10 the standard deflector for the part fan does not do a good job (the air is not blown where it should) and replacing it with a custom part is one of the most common upgrades performed on the printer.

Personally on my CR-10 I used a custom mount with an integrated "fang" that blew the air from both sides and worked really well. It also had the advantage of reusing the hardware from the original assembly (= you don't need to buy anything, just print the part).

  • $\begingroup$ That makes sense. The first custom part you linked is very useful and explains the right fan well. Is the air from the right fan supposed to be blowing on the nozzle or under it where the plastic comes out to harden it? $\endgroup$
    – Programmer
    Mar 10, 2018 at 20:19
  • 2
    $\begingroup$ @Programmer - under it: you want the nozzle to stay hot! :) $\endgroup$
    – mac
    Mar 10, 2018 at 20:22
  • $\begingroup$ This hotend config is btw shared with the Ender-3. $\endgroup$
    – Trish
    Sep 4, 2018 at 10:19

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