PID Autotune... with or without plastic?



  • As the title would suggest... should the PID autotune be done with or without plastic in the hot end? I seem to be leaning towards yes as I'm sure it will have an effect on the system response... what do you guys do?



  • @doublec4

    I've never given it any thought.

    However since I tune when the hotend is first installed it likely has never been used and is free of filament.

    Frederick



  • Digging a little deeper in the guides...

    https://duet3d.dozuki.com/Guide/Ender+3+Pro+and+Duet+Maestro+Guide+Part+4:+Calibration/40#s161

    It says ideally without filament. Seems a little counter intuitive to me as I thought the filament acts like a heat sink but I guess not?


  • Moderator

    There's a very small volume of plastic in the hotend when loaded so it's not going to have a huge effect. It's not like you're extruding at the time. (Though I suppose you could manually push some through.)

    The reason for suggesting you remove it is just to keep it from oozing out or potentially cooking and getting clogged.

    It's also suggested to have the cooling fan on at a normal print speed so that the algorithm can take some of that additional cooling into account.



  • @Phaedrux There is a caveat to that advice, which is regarding mixing hot ends such as the Diamond. In such cases, the volume of plastic in the melt chamber is very much greater and can have a significant effect. So my advice for mixing hot ends is to always run the PID tuning with filament loaded. BUT, as you rightly point, this will "cook" any loaded filament, so it is important to purge that out at the end of the the tuning process.


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