PID Hotend Tuning



  • Started some PID tuning on my hotend. Now I am absolutely new to programming and building printers. I am going off of the BLV MGN cube.

    I started with using M303 H1 S240, a few seconds would pass into phase 1 and the system will shut off. I noticed manually increasing temp over and at 45C prompts any shut off.

    I am using an SSR and the PS_ON.

    Here is the heaters section from config:

    ; Heaters
    M308 S0 P"bedtemp" Y"thermistor" T100000 B4725 C0 ; 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 B0 S1.00 ; disable bang-bang mode for the bed heater and set PWM limit
    M140 H0 ; map heated bed to heater 0
    M143 H0 S100 ; set temperature limit for heater 0 to 100C
    M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C0 ; configure sensor 1 as thermistor on pin e0temp
    M950 H1 C"e1heat" T1 ; create nozzle heater output on e1heat and map it to sensor 1
    M307 H1 B0 S1.00 ; disable bang-bang mode for heater and set PWM limit
    M143 H1 S260 ; set temperature limit for heater 1 to 260C

    I need some help getting past this! Managed to get this far. Thanks!


  • Moderator

    What firmware version?
    What Duet board?
    What heater and how is it wired?
    Is there an error message or just the whole thing powers off?



  • @Phaedrux

    Using version 3.1.1 firmware on the latest Duet 2 board.

    For the hotend it is a 24v 40W cartridge E3D V6.

    No error messages on power down. I discovered lowering PWM allowed temp to gain but all too slow for PID to continue. Evening after M307 H0 D30. Should I increase this D value to an outrageous amount?


  • Moderator

    Well you can increase the dead time, but I struggle to understand how the hotend isn't heating fast enough in one case, but also shutting down in the first place.

    I suspect something is wrong somewhere.

    You mention an SSR, you're not using that for the hotend though right?

    Is your PSU also 24v? Or is it 12v?

    Is something shorted at the hotend?

    When you say the system will shut off, what exactly do you mean?

    @Hellpilot said in PID Hotend Tuning:

    M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C0

    If the hotend is from E3D and you're using their thermistor, these values aren't quite right. Should be:

    M308 S1 P"e0temp" Y"thermistor" T100000 B4725 C7.06e-8 ; configure sensor 1 as thermistor on pin e0temp
    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
    M143 H1 S280                                           ; set temperature limit for heater 1 to 280C
    


  • @Phaedrux
    My SSR is used to power on my 24V PSU. Figured it would be worth mentioning.

    As far as my any shorts I checked what I could and didn't spot anything out of the ordinary. My bed heater is connected to E1 Heat, my thermistor is connected to E0 Temp. But when the system shuts off it is a hard shut off. Everything powers down but no useful error messages to read.

    *Edit

    I moved PWM down to 0.80 and added in the C7.06e-8 like you had posted. Crazy fast heat up time and no errors. What is this C value?

    *Edit Edit

    Not to mention the B coefficient in my config had 1 too many zeroes.


  • Moderator

    @Hellpilot said in PID Hotend Tuning:

    My bed heater is connected to E1 Heat, my thermistor is connected to E0 Temp.

    That's the reverse of what your gcode says. The bed should be on the bed heater and the hotend on E0.

    @Hellpilot said in PID Hotend Tuning:

    What is this C value?

    Coefficient.



  • @Phaedrux

    Right, my bed heater is connected correctly same as my bed temp. Went to run bed PID tune next. Not a complete shutdown like the hotend, but as if e-stop was pressed.
    M303 H0 S70 using values

    M308 S0 P"bedtemp" Y"thermistor" T100000 B3988 C0 ; 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 B0 S0.20 ; disable bang-bang mode for the bed heater and set PWM limit
    M140 H0


  • Moderator

    @Hellpilot said in PID Hotend Tuning:

    "bedtemp" Y"thermistor" T100000 B3988 C0

    You've got C0 there as well. What is the thermistor for the bed? Probably should remove the C0.



  • @Phaedrux

    Thank you! Both the PID tuning for the bed and hotend are complete.

    The bed is running at 40% PWM to avoid the soft shutdown. Also has some electrical noise during heating.

    I've read about thermal coupling to prevent runaway. In regarding to the warning in the console messages about potential temperature increase. How serious is this?


  • Moderator



  • @Phaedrux Yup, thats it! The console mentioned it could reach 365 something.

    There seems to be an issue running both heaters. Back to getting hard shutdowns. Will double check all my connections just to be sure...


  • Moderator

    Are you exceeding the wattage of your PSU?



  • @Phaedrux That I do not know. I am using a Meanwell 24V, 18.8A PSU.


  • Moderator

    What is the wattage of your bed heater?



  • @Phaedrux

    Culprit found. Power input voltage was set to 230V, switched to 115V. Heaters can carry full PWM now.


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