Just completed Auto Tune



  • Auto Tune says my hotend heater is overpowered....
    Do I really care? How accurate is auto tune and its estimation the hotend can reach 533C?

    Warning: Heater 1 appears to be over-powered. If left on at full power, its temperature is predicted to reach 533C.
    Auto tune heater 1 completed in 438 sec
    Use M307 H1 to see the result, or M500 to save the result in config-override.g



  • Same here. I reduced the max. PWM and ran auto tune again: warning gone. This is my config for the heater:

    M305 P1 T100000 B4725 C7.060000e-8 ; set thermistor + ADC parameters
    M307 H1 A512.1 C269.5 D3.8 B0 S0.7 ; set tuning parameters

    When I cut the max. PWM at 0.7, the heater overshoots much less, which translates to a smooth temperature curve.

    Depending on your heater, try your own PWM values and run auto tune on them. Fortunately, M307 H1 reports the overshoot temperature - among other values.


  • Moderator

    Reducing the PWM value won't help for what the warning is talking about. It means that if something were to go wrong and the heater was faulted on without any firmware control it could reach those temps based on the model used during tuning.

    Reducing the PWM won't help because the PWM is controlled by the firmware and in a fault condition, the firmware is out of the equation. So you've really only slowed your heatup time.

    The warning is there to let you know that leaving your printer unattended is not recommended basically. Take precautions for the worst case scenarios. Smoke detector. Fire extinguisher. Don't leave it unattended. Consider using a lower wattage heater cartridge. Consider adding a thermal fuse to the hotend to cut power if case of a thermal excursion.



  • @Phaedrux Right. I share your safety concerns, but at least, I wanted to reduce the stress for the heater cartridge under working conditions - clipping the max. power consumption is a way to achieve this goal. And, talking about safety, this is definitely better than to manipulate the heater fault tolerance (with M570).



  • @Phaedrux said in Just completed Auto Tune:

    Consider adding a thermal fuse to the hotend to cut power if case of a thermal excursion.

    Can you provide a link to an example of this type of device?

    Thanks.

    Frederick


  • Moderator

    @fcwilt Something like this: https://www.be-electronics.com/searchresults.asp?Search=thermal+cut+off&Submit=

    http://www.be-electronics.com/v/vspfiles/datasheet/nte/thermalCutoff.pdf

    Non-resettable. Come in a wide range of set temps. For the bed heater it would be trivial to add. For the hotend you'd likely have to attach to the heatsink due to the temp limit of the devices. So you'd have to do some figuring to decide how hot the heatsink would get in a fault condition.



  • @Phaedrux said in Just completed Auto Tune:

    Non-resettable. Come in a wide range of set temps. For the bed heater it would be trivial to add. For the hotend you'd likely have to attach to the heatsink due to the temp limit of the devices. So you'd have to do some figuring to decide how hot the heatsink would get in a fault condition.

    Thanks much. I have not seen that type of device before.

    Frederick


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