PT100 Autotune…. not so auto :(



  • Trying to wrap my head around this whole autotune thing…. I have a E3D 12v/40w: 3-4 ohms - I checked the resistance at the terminals on the duetwifi for the heater: 4 Ohms. I also have the PT100 with the E3D copper heat block (Better temp regulation).

    I am trying to autotune so I can print materials like this:
    http://www.3dxtech.com/firewire-psu-3d-printing-filament/
    Extruder Temp: 350 - 380°C (all-metal extruder)

    I tried even lower temps like 320C still can't get the autotune to work, It either overshoots the temp or it says it doesnt reach the temp even when it does (watching the readout on the screen)

    This was my last attempt:
    M303 H1 P0.733 S320

    says it doesnt reach it… but this says overshoot:
    M303 H1 P0.735 S320

    This is what I currently have for M143
    ; Heaters
    M143 S321 ; Set maximum heater temperature to 321C


  • administrators

    Auto tune in 1.18 will always overshoot the target temperature. You need a larger difference between the target temperature you use in M303 and the temperature limit set in M143. You should use the default P1.0 in M303.



  • @dc42:

    Auto tune in 1.18 will always overshoot the target temperature. You need a larger difference between the target temperature you use in M303 and the temperature limit set in M143. You should use the default P1.0 in M303.

    Thank you!

    I set the temp limit to 400C (the limit of the PT100)

    ; Heaters
    M143 S400 ; Set maximum heater temperature to 400C
    
    

    Then set the target to the highest temp of filament I plan to use

    M303 H1 P1.0 S380
    
    

    This was the console message:

    Warning: Heater 1 appears to be over-powered and a fire risk! If left on at full power, its temperature is predicted to reach 609C.
    Auto tune heater 1 completed in 545 sec
    
    

    M307 H1 result:

    Heater 1 model: gain 589.9, time constant 284.6, dead time 5.0, max PWM 1.00, mode: PID
    Computed PID parameters for setpoint change: P17.2, I0.061, D60.3
    Computed PID parameters for load change: P17.2, I1.100, D60.3
    
    

    Any Suggestions or is it safe to leave like this? Not sure if the parameters adjust for the over powered message automatically.


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