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Unanswered why do none of my PID values match after 7 successive iterations

Discussion in 'Troubleshooting' started by SC_MudDuck, Mar 29, 2021.

  1. SC_MudDuck

    SC_MudDuck New Member

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    Trying to solve my dreaded E1 Thermal Runaway issue by doing a PID Tune. After running the tune 7 back to back times, I do not see any consistency within the tune. Is this normal? The values below are the results of each tune after cycling 10 times each go at it.

    Robo 3D r1+
    Dual fan 40x40x20 @ 100%
    Factory enclosure
    24C start temp
    Marlin 1.1.9

    M303S220C10

    The values aren't even close. Can someone help me make sense of these values?

    PID1 33.57, 2.30, 122.37
    PID2 30.60, 2.32, 100.91
    PID3 19.91, 1.07, 92.95
    PID4 17.65, 0.71, 109.91
    PID5 25.34, 1.15, 139.06
    PID6 26.19, 1.13, 151.77
    PID7 18.06, 0.98, 83.23
     
    #1 SC_MudDuck, Mar 29, 2021
    Last edited: Mar 29, 2021
  2. SC_MudDuck

    SC_MudDuck New Member

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    So does no one know what I am asking? Help me help you understand my question.

    If no one can help, is there anywhere else I can look for this answer?
     
  3. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Thermal Runaway is likely to be a failing thermistor if it is not actually overheating.

    The firmware will tell the heater core to add heat until it gets within the tolerance specified by the PID tune or the setpoint in a non-PID config. You will in the non-PID get overshoot and then it will maintain.

    If the thermistor is failing it will usually take one of two approaches.
    It will totally fail and not respond to heat at all or it will internally crack and generate spurious readings as the internal resistance jumps around.

    You might want to replace the thermistor and/or the heater core. I always use 40w ceramic cores on my FDM printers since those are capable of getting to temperature faster and being mush more stable at maintaining.
     
  4. SC_MudDuck

    SC_MudDuck New Member

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    Thanks for the reply Mark, it was very helpful. I will search for the necessary parts for the repair/upgrade.

    Should I see similar values upon successive PIDs, if the start temp is the same every time?
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    It is likely they will be different since you need to change the thermistor.
     
  6. SC_MudDuck

    SC_MudDuck New Member

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    Replaced the heater cartridge to 40W, still waiting on the thermistor. I have observed where it still has a difficult time overcoming the fans @ ~205 close to the bed. I just I need to calibrate the temp:fan fan speed with a fan tower. This could tell me the height or layer where it can overcome the fan speed, right?
     
  7. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yes. I normally do not even have the cooling fan running for the first few layers.
     
  8. BrooklynBay

    BrooklynBay Active Member

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    Check the voltage of the power supply to see if it's low. Low voltage will cause similar issues since the heater will be running with minimal power. Power supplies have a set screw adjustment. Sometimes they might be a little off after a lot of use, and need an adjustment. Connect a voltmeter to the power supply then on the wiring at the place where the heater is connected. Your wiring might be bad if you see that the voltage is a lot lower than at the power supply.
     

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