Auto tune cancelled - timeout and underpowered



  • So I know the heater is under powered, question is it better to let ut autotune at a lower temperature, or allow a longer timeout?
    (This is the stock PCB heater in a Up! Mini 2. About 14 ohm and 140x140mm, running it at 24V instead stock 19V helps a lot, but its still quite weak)

    It can reach some 60-70C in 20 minutes depending on ambient. Ideally it should go to 90 but it takes longer than 20 minutes.

    Would having the timeout as a parameter to M303 be a thing to consider?


  • Moderator

    The PID parameters are still valid for a fairly wide range, so if you can get a successful tune at a lower temp I'd start there.

    Do you have any insulation on the bottom? That can make a huge difference.



  • No insulation on the bottom, only room to insulate part of the bed anyway. Very small enclosed build volume 120x120x120 and tight for space in some areas like under the bed.


  • Moderator

    Even a thin sheet of cork works wonders.



  • I did actually try a two thin sheet of woven fiberglass, which was about all i could fit, and taped it down with some kapton and teflon tape (tried both to see which held up better).

    Need to run the test again because it seemed to reduce the max temperature?!

    Does PCB heaters have PTC characteristics? I would swear it was about 14 ohm at 20c and 18.5 ohm at 75C before I tried the insulation.


  • administrators

    @bearer said in Auto tune cancelled - timeout and underpowered:

    Does PCB heaters have PTC characteristics? I would swear it was about 14 ohm at 20c and 18.5 ohm at 75C before I tried the insulation.

    Yes they are slightly PTC because the heating element comprises the copper traces on the PCB, and copper has a positive temperature coefficient of resistance.



  • Should have thought about that, but yeah, thanks. 0.393% pr 1C is almost a perfect fit. Which means that thing will never overheat, which is a nice feature, it it only could get to the proper temperature in the first place.

    But back to the question at hand; making the 15 minutes configurable is not something that is worth considering to allow even the lower powered setups to get as hot as they can possible get?


  • administrators

    @bearer said in Auto tune cancelled - timeout and underpowered:

    But back to the question at hand; making the 15 minutes configurable is not something that is worth considering to allow even the lower powered setups to get as hot as they can possible get?

    The timeout is 20 minutes for bed and chamber heaters. I will increase it to 30 minutes in the next build.



  • My bad, but thanks!

    I will replace the bed at some point, but I know others with the same printer will just replace the board so it should benefit them in the long run 👍


  • administrators

    Meanwhile, try using a lower target temperature when tuning the bed.



  • I did tune it to 55 or so, thanks!


  • administrators

    Btw if your PSU has a voltage adjustment pot and a high enough power rating, you can increase the bed power by turning up the voltage. A 20% increase in voltage will increase the heating power by 44%. Don't forget to retune all heaters if you do this.



  • Already at 25V Vin (and it only adjusts to 27 so not going to add external FET until I replace the bed and use 230V)


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