Hotend heatsink cooling fan wont run at full speed



  • Hot end heat sink fan wont spool up to full speed on thermostatic control until i send a manual M106 S255 P0. Any ideas?

    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4138 ; configure sensor 0 as thermistor on pin bedtemp
    M950 H0 C"bedheat" T0 ; create bed heater output on bedheat and map it to sensor 0
    M307 H0 B1 S1.00 ; enable bang-bang mode for the bed heater and set PWM limit
    M140 H0 ; map heated bed to heater 0
    M143 H0 S115 ; set temperature limit for heater 0 to 115C
    M308 S1 P"spi.cs1" Y"rtd-max31865" ; configure sensor 1 as thermocouple via CS pin spi.cs1
    M950 H1 C"e0heat" T1 ; create nozzle heater output on e0heat and map it to sensor 1
    M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
    M308 S2 P"e1temp" Y"thermistor" T100000 B4138 ; configure sensor 2 as thermistor on pin e1temp
    M950 H2 C"e1heat" T2 ; create chamber heater output on e1heat and map it to sensor 2
    M307 H2 B1 S1.00 ; enable bang-bang mode for the chamber heater and set PWM limit
    M141 H2 ; map chamber to heater 2
    M143 H2 S75 ; set temperature limit for Chamber to 75C

    ; Fans
    M950 F0 C"fan0" Q500 ; create fan 0 on pin fan0 and set its frequency
    M106 P0 S1 H1 T45 ; set fan 0 value. Thermostatic control is turned on
    M950 F1 C"fan1" Q500 ; create fan 1 on pin fan1 and set its frequency
    M106 P1 S0 H-1 ; set fan 1 value. Thermostatic control is turned off
    M950 F2 C"fan2" Q500 ; create fan 2 on pin fan2 and set its frequency
    M106 P2 S0 H-1 ; set fan 2 value. Thermostatic control is turned off


  • Moderator

    How do you have your tools defined?

    What happens if you change M106 P0 S1 H1 T45 to M106 P0 S255 H1 T45 ?

    What firmware version? Should be 3.1.1



  • yea im on 3.11. ok ill try it thanks. Dont know how i missed that lol.



  • This post is deleted!


  • funny it still seems slow down but at the end of the print, full speed during the print. Is that normal?


  • Moderator

    Do you have any other M106 commands elsewhere?

    There should be no difference between S1 and S255. They both say the same thing. S0 to S1 can be used as a decimal representation of a percentage. S0.5 would be 50%. Or you can use S0 to S255 to set it as an 8bit value (at least I think that's the origin of that).

    your command is otherwise correct. H1 attaches it to heater 1 and T45 sets the temp to 45c. So when heater 1 reaches 45c it should turn on fan 0 to full power.

    Perhaps the fan is failing? Or perhaps it doesn't like the PWM frequency.

    Try changing the M950 Q parameter to change the frequency. 500hz is the default, but you can try as low as 10 or up to 30000.


  • administrators

    I suggest you swap fans numbers 0 and 1 over so that Fan 0 is the print cooling fan and Fan 1 is the thermostatic heatsink fan. This is what we recommend, see https://duet3d.dozuki.com/Wiki/Connecting_and_configuring_fans.

    The reason is that fan 0 is the one that slicers use by default. What I think is happening is that the slicer has put a M106 S0 or M107 command in the GCode file before a tool is selected, which tells RRF to turn off the thermostatic fan. But RRF allows a minimum 50% speed for thermostatic fans when they are supposed to be on.



  • Ok ill try it out tonight, Thanks.


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