Hotend fan speed - how to change?  

RE: Hotend fan speed - how to change?

Posted by: @peter-habermehl

Hi all,

I would like to raise the speed of the hotend fan. M106 as GCode does only affect the print fan. I played around with the fan index, but no effect at all.

So how could I raise the fan speed (or PWM ratio) for the hotend fan? I'm willing to build a custom firmware, but I need to know where to modify.

Thanks and kind regards

Peter

You can set the nozzle fan speed in the slicer (binary value from 0 to 255). You can also specify these values in %, e.g.: 50% = 255/100*55 = 127 binary or vice versa 127 binary = 127/255*100 = 50%.
You can also send the commands via a terminal (Pronterface, Octoprint) with M106 Sxx (xx = value between 0 and 255).

The Noctua heatsink fan cannot be controlled. It is controlled by the firmware. Here I would strongly recommend not to change it.

RE: Hotend fan speed - how to change?

Posted by: @karl-herbert

Posted by: @peter-habermehl

So how could I raise the fan speed (or PWM ratio) for the hotend fan? I'm willing to build a custom firmware, but I need to know where to modify.

The Noctua heatsink fan cannot be controlled. It is controlled by the firmware. Here I would strongly recommend not to change it.

Thanks for your post but:

1. The hotend fan is not a Noctua. It's a Delta. https://github.com/prusa3d/Original-Prusa-MINI/blob/master/DOCUMENTATION/ELECTRONICS/mini-extruder-fan-DS.pdf

2. I was precisely asking for the hotend fan. Of course I know how to set the print fan speed. I cited M106. But since I've designed a whole new x carriage with a completely different fan, I need to adapt the fan speed or voltage in the firmware.

So if anyone could indicate how to change the hotend fan speed, please let me know.

Thank you

Peter

RE: Hotend fan speed - how to change?

@peter-habermehl

You can change fan speed in the firmware in Configuration_A3ides_2209_MINI_adv.h

// @section extruder

/**
* Extruder cooling fans
*
* Extruder auto fans automatically turn on when their extruders'
* temperatures go above EXTRUDER_AUTO_FAN_TEMPERATURE.
*
* Your board's pins file specifies the recommended pins. Override those here
* or set to -1 to disable completely.
*
* Multiple extruders can be assigned to the same pin in which case
* the fan will turn on when any selected extruder is above the threshold.
*/
#define E0_AUTO_FAN_PIN -1
#define E1_AUTO_FAN_PIN -1
#define E2_AUTO_FAN_PIN -1
#define E3_AUTO_FAN_PIN -1
#define E4_AUTO_FAN_PIN -1
#define E5_AUTO_FAN_PIN -1
#define CHAMBER_AUTO_FAN_PIN -1
#define EXTRUDER_AUTO_FAN_TEMPERATURE 50
#define EXTRUDER_AUTO_FAN_SPEED 255 // 255 == full speed

I assume that it is known that after firmware changes the buddy board has to be modified to flash it:

https://hackaday.com/2019/12/16/prusa-dares-you-to-break-their-latest-printer/

RE: Hotend fan speed - how to change?

@karl-herbert

Sorry if I seem to be a little annoying, but... the auto fan pins are all disabled in that piece of code you cited. And since EXTRUDER_AUTO_FAN_SPEED is set to 255, which is still valid for the most recent version of this file, this would mean that the fan already would run at max speed, which is not the case.

So the actual extruder fan setpoint must be defined somewhere else.

But thanks for trying again.

Peter

RE: Hotend fan speed - how to change?

@peter-habermehl

I took some time and tested this (original Mini extruder fan) -> working!
I measured the speed of the fan with a laser measuring device (fan starts rotating from 50 degrees):

EXTRUDER_AUTO_FAN_SPEED is set to 30:

EXTRUDER_AUTO_FAN_SPEED is set to 255:

fanspeed after reset (fullspeed):

changing the variable (EXTRUDER_AUTO_FAN_SPEED) has an influence on the fan speed, but i have to say that i have already made some changes in the firmware and unlocked the board.

added src/common/Marlin_eeprom.cpp in CMakeLists.txt

added #include "wdt.h" in Marlin_eeprom.cpp

Of course i leave the original equipment with the value 255. I can't say what will happen with fans with other technical parameters.

RE: Hotend fan speed - how to change?

@karl-herbert

Thank you for your efforts. The firmware seems to be full of surprises. I will try this out as soon as I've received the fan I ordered.

Kind regards

Peter

RE: Hotend fan speed - how to change?

So how does one change the fan speed to a higher rpm?

The too low cooling performance of the MINI+ hotend fan seems to be the biggest bottleneck of the whole printer and the only thing keeping me from a near perfect experience. The heat creep really gets on my nerves right now with an e3d V6 "upgrade".

Did somebody check if it's the fan itself which limits the flow? Did someone try a different one?

RE: Hotend fan speed - how to change?

Hola perdonar mi ignorancia, tengo la misma necesidad, subir las rpm del ventilador.

Mi pregunta es, ¿se puede modificar el firmware 4.4.1 original y cargar en la impresora? 

Gracias y un saludo.

Hardware fix for 100% hotend fan speed

howdy folks. I had this issue last night with a new hotend fan I purchased that has 2x CFM and 2x static pressure over the stock fan on my MK3S. The approach was to just do a straight swap of the fan, but after a lot of troubleshooting I realized the fan was only running at 3000 rpm when it should be maxing out at 7000 rpm according to the datasheet. 

after some research, I learned the hotend fan is pwm controlled in the firmware, and the pwm control is on the ground (black) pin of the fan header it’s plugged into.

also, the research claims the set point for the hotend fan is 255 which “should” be 100% fan speed according to the firmware code. Yes, you might be able to change your settings via firmware and have a special custom firmware loaded to the printer, but this kinda makes updating the printer with new firmware difficult.

I decided to do some experimentation and removed the ground pin from the fan header connector (this can be done by pushing on the visible detent for the pin you want to remove on the side of the connector, and then pulling the pin out). 

I installed the removed black wire from fan connector onto a nearby unused pin that I assumed was ground (should be verified, but it was late and I was willing to take the risk of blowing up my fan). Turns out it was indeed ground, and I now have a pure 5V supply, and stable ground connection to the fan. 

this indeed did increase my fan’s rpm to 7000+ per the data sheet which completely solved my heat creep issues. 

something worth noting is that this completely removes all features of the hotend cooling fan built into the firmware. The moment the printer is turned on, the cooling fan is running at 100% capacity and will continue to run until the printer is completely turned off. 

I personally prefer this, the gimmicky 50C threshold that prusa uses to turn on and off the fan does not really do anything other than maybe save on some noise when the printer isn’t running. I keep the printer off if I’m not using it anyway, so this is not an issue for me. 

happy printing folks!