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Heater Control

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Tuning and tweaking
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  • undefined
    dc42 administrators
    last edited by 19 Sept 2016, 18:20

    Those results don't sound right. What M307 parameters did it return? Can you measure the resistance of the heater cartridge? Do you have any thermal insulation on your hot end?

    I believe E3D changed the power of the heaters they ship from 40W to 25W some time ago.

    Duet WiFi hardware designer and firmware engineer
    Please do not ask me for Duet support via PM or email, use the forum
    http://www.escher3d.com, https://miscsolutions.wordpress.com

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    • undefined
      mhackney
      last edited by 19 Sept 2016, 18:25

      This is a 40W cartridge that measures 3.6Ω, no insulation. Unfortunately, I did not check M307.

      I just reran it after waiting for it to cool to room temperature as:
      M303 H1 P0.25 S250

      Temperature increased gradually (I have a screen shot) and then get this message:
      Auto tune of heater 1 with P=0.25 S=250.0 cancelled because temperature limit exceeded. Use lower P or higher S in m303 command.

      I did an M307 H1:
      Heater 1 model: gain 862.3, time constant 296.2, dead time 6.9, max PWM 1.00, in use: yes, mode: PID
      Setpoint change: P8.9, I0.03, D42.9
      Load change: P8.9, I0.65, D42.9

      I'll rerun the P0.2 S240 and do an M307 this time.

      My 3D Printing blog: http://www.sublimelayers.com
      Coming this summer: "3D Printing Strategies - the art of perfecting your designs and prints"

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      • undefined
        dc42 administrators
        last edited by 19 Sept 2016, 18:40

        So that's 43W at 12.45V. Your time constant found by tuning is about double the value I get, which suggests to me that either your hot end is better insulated than mine or your hot end heatsink cooling fan is not very effective. The combination of high heater power and long time constant explains the high gain and hence the warning message.

        Duet WiFi hardware designer and firmware engineer
        Please do not ask me for Duet support via PM or email, use the forum
        http://www.escher3d.com, https://miscsolutions.wordpress.com

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        • undefined
          mhackney
          last edited by 19 Sept 2016, 18:47

          It's a stock E3D V6 with standard cooling fan and shroud. I've measured the top of the cold zone and it is fine and I never get plugging with PLA. The parameters I use with the M301 are:

          M301 H1 P20 I0.27 D100 T1.1 S1 W300 B30

          (this is with 1.15-beta3) and worked fine. Hot end heated up quickly and stabilized. I have other printers I can update to the 1.15c firmware but they are Duet .85 controllers. Not sure what to do here with this one though.

          I did rerun the P0.2 S240 and got the same overpower warning and this time I dd the M307:

          M307 H1
          Heater 1 model: gain 884.2, time constant 296.0, dead time 6.8, max PWM 1.00, in use: yes, mode: PID
          Setpoint change: P8.7, I0.03, D41.8
          Load change: P8.7, I0.64, D41.8

          My 3D Printing blog: http://www.sublimelayers.com
          Coming this summer: "3D Printing Strategies - the art of perfecting your designs and prints"

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          • undefined
            dc42 administrators
            last edited by 19 Sept 2016, 18:53

            The warning is genuine then, although it may be exaggerating somewhat because it assumes that the heat loss is linear with temperature, which is not exactly true.

            I suggest you plug the M307 parameters into config.g. If they don't give you good temperature control, you can put your M301 command back after the M307 if you double and halve the I and D parameters as per the 1.15 release notes.

            Duet WiFi hardware designer and firmware engineer
            Please do not ask me for Duet support via PM or email, use the forum
            http://www.escher3d.com, https://miscsolutions.wordpress.com

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            • undefined
              mhackney
              last edited by 19 Sept 2016, 19:04

              Thanks David.

              But this begs the question - what's the "right" thing to do from a heater perspective? Is this legitimately a safety concern and if so, what should be done to rectify it? Is this unique to my E3D V6 or all of them?

              My 3D Printing blog: http://www.sublimelayers.com
              Coming this summer: "3D Printing Strategies - the art of perfecting your designs and prints"

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              • undefined
                mhackney
                last edited by 19 Sept 2016, 19:18

                Ok, I plugged the parameters into M307:
                M307 H1 A884.2 C296.0 D6.8 B0 S0.8

                I did leave S0.8 for no good reason. It is working perfectly - climbs steadily up to my target (190°C) and then levels with no overshooting and stabilizes much faster with less than +/-.1°C variation. Much better than what I had before.

                My 3D Printing blog: http://www.sublimelayers.com
                Coming this summer: "3D Printing Strategies - the art of perfecting your designs and prints"

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                • undefined
                  dc42 administrators
                  last edited by 19 Sept 2016, 19:18

                  @mhackney:

                  Thanks David.

                  But this begs the question - what's the "right" thing to do from a heater perspective? Is this legitimately a safety concern and if so, what should be done to rectify it? Is this unique to my E3D V6 or all of them?

                  You might want to consider replacing your 40W heater cartridge by a 25W one, which I understand is what E3D ships as standard these days. Otherwise you might suffer a heater block meltdown if the heater ever got stuck at full power.

                  Duet WiFi hardware designer and firmware engineer
                  Please do not ask me for Duet support via PM or email, use the forum
                  http://www.escher3d.com, https://miscsolutions.wordpress.com

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                  • undefined
                    elmoret
                    last edited by 19 Sept 2016, 19:25

                    30w is now standard, which tops out at ~330C without heater block insulation or a fan blowing on the heater block.

                    40w will get hot enough to melt the aluminum in the event of a firmware/FET failure.

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                    • undefined
                      mhackney
                      last edited by 19 Sept 2016, 19:28

                      Ok, this is good to know! I will check and update the cartridges in all of my printers. No need playing with fire!

                      My 3D Printing blog: http://www.sublimelayers.com
                      Coming this summer: "3D Printing Strategies - the art of perfecting your designs and prints"

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