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    Auto-tune heater

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    • fmaundefined
      fma
      last edited by

      I just launched a M303 auto-tune command. Here is the M307 resulting params:

      M307 H3 A748.3 C962.6 D4.5 B0

      It improved a lot the over-shoot, but now, the temperature is not very stable: it oscillates +-1.7°C; was only +-0.2°C without the tuning…

      Which param can I tune to reduce this oscillation?

      Frédéric

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      • dc42undefined
        dc42 administrators
        last edited by

        To reduce the oscillation, increase D.

        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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        • fmaundefined
          fma
          last edited by

          Thanks.

          I had to increase D up to 10 to keep oscillations below +-0.2°C. But now, it takes muuuuch longer to reach the setpoint; Is there another param I can change to fix that?

          Frédéric

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          • deckingmanundefined
            deckingman
            last edited by

            Assuming H3 is a hot end (as H0 is normally the bed, then your M307 shows a gain of 748.3 which means that if left unattended it could potentially reach a temperature of around 750 deg C! That would mean a massively powerful heater of around 80Watts plus. Is that what you have? If not, then another explanation could be that you have a 12V heater running on 24V.

            You ought to check that out but one way to "tame it" would be to tune it with a PWM of 0.5 or so.

            Ian
            https://somei3deas.wordpress.com/
            https://www.youtube.com/@deckingman

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            • fmaundefined
              fma
              last edited by

              Yes, I saw the warning. As I was running at 12V, and now switched to 24V, I checked if I didn't forget to switch the cartridge, but no: 14.5 Ohm -> 41W…

              It's a E3D Lite6, with the silicone insulator. How could it reach 750°C? Is it really possible with 40W?

              Frédéric

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              • fmaundefined
                fma
                last edited by

                I just make a new auto-tune cycle, with PWM 0.5. Now params are:

                M307 H3 A352.5 C275.7 D3.2 B0 S0.5

                It takes longer to reach the setpoint, and I still have a huge oscillation (+-1.4°C)!

                Frédéric

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                • fmaundefined
                  fma
                  last edited by

                  I checked, and default params are:

                  M307 H3
                  Heater 3 model: gain 340.0, time constant 140.0, dead time 5.5, max PWM 1.00, mode: PID

                  It overshoots 2°C, then takes 15s to get back to the setpoint, and stay there within 0/-0.2°C…

                  Should I let the default values?

                  Frédéric

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                  • deckingmanundefined
                    deckingman
                    last edited by

                    It will take longer to reach the set point using 50% PWM because it's running at half power (more or less). I know that the silicone sock makes a difference but I'm surprised it makes that much difference. I guess you could try tuning without the sock, just to see. TBH 2 degrees overshoot but recovering within 15sec isn't too bad and is unlikely to result in huge problems I would have thought.

                    I'm still very surprised that the sock makes that much difference so maybe try tuning without the sock but with PWM of 1.0 just to check. If you still get a warning and up with a high gain, then it has to be the heater cartridge that is too powerful.

                    Ian
                    https://somei3deas.wordpress.com/
                    https://www.youtube.com/@deckingman

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                    • dc42undefined
                      dc42 administrators
                      last edited by

                      If it overshoots the set point, increase the A parameter in the M307 command.

                      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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                      • fmaundefined
                        fma
                        last edited by

                        I will try to tune without the silicone sock, to see its effect…

                        And I will test with different values for A.

                        Thanks.

                        Frédéric

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                        • fmaundefined
                          fma
                          last edited by

                          Here are the results without sock:

                          Heater 3 model: gain 878.2, time constant 287.3, dead time 4.9, max PWM 1.00, mode: PID

                          BTW, as I mostly run around 190-200°C, should I use 200 for S param in the auto-tune sequence, instead of 240°C?

                          Frédéric

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                          • deckingmanundefined
                            deckingman
                            last edited by

                            @fma. For info, I know I have a different hot end to you (Diamond 3 and 5 colour) but I get the following with the 3 colour version

                            40 Watt cartridge without Silicone sock, A349.7 C233.5 D7.0
                            40 Watt cartridge with home made silicone sock A 360.6 C213.5 D6.0

                            So it makes a bit of difference but not much.

                            Now, the Diamond 5 colour comes with an 80Watt cartridge (I don't understand why) but tuning that with PWM of 1.0 I get:

                            A647.7 C190.4 D6.4 so the gain doubled and was similar to yours which is why I thought your heater must be very powerful.

                            with PWM of 0.6 I get A350.4 C194.8 D5.2.

                            HTH

                            Edit. Just seen you last post - that gain is higher than my 80Watt cartridge!

                            Ian
                            https://somei3deas.wordpress.com/
                            https://www.youtube.com/@deckingman

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                            • fmaundefined
                              fma
                              last edited by

                              Strange! As said, my cartridge has a resistance of 15 Ohm, which gives 40W under 24V…

                              I will monitor current and voltage during heat up to see if there is not a problem (short circuit inside the cartridge, lowering the resistance when heated up... Not convinced, as I would have seen a change in heating curve).

                              Frédéric

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                              • deckingmanundefined
                                deckingman
                                last edited by

                                I had a cartridge fail once. Measured the resistance and it was fine but it wouldn't heat up at all. Double checked the resistance, treble checked it, wiggled the wires around, checked the connector. No problem but it still wouldn't heat up. Fitted new cartridge and all was fine. Weird…......

                                Ian
                                https://somei3deas.wordpress.com/
                                https://www.youtube.com/@deckingman

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                                • fmaundefined
                                  fma
                                  last edited by

                                  Well, my cartridge is OK: I measured a current of 1.6A during all the heating… So, 40W. And 0.38A to maintain 190°C (~9W).

                                  It is normal that it heats up much faster than the Diamond, as the E3D is smaller. But why such a difference with a standard E3D? I don't know.

                                  I'm using a Lite6, with the last heater block...

                                  Frédéric

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                                  • fmaundefined
                                    fma
                                    last edited by

                                    FYI, it takes 77s to reach 190°C on my E3D Lite6. Is it something similar to you?

                                    Frédéric

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                                    • deckingmanundefined
                                      deckingman
                                      last edited by

                                      @fma:

                                      FYI, it takes 77s to reach 190°C on my E3D Lite6. Is it something similar to you?

                                      No nothing like, but then my 5 colour Diamond hot end is great big lump of brass with 5 heat sinks screwed into it and a high flow (20cfm) fan blowing over them. Currently with the 80Watt heater running at 60% PWM it takes around 120 seconds to reach 190deg C but then it overshoots by around 3 degrees and takes about 20 seconds to stabilise. This is about the same time it used to take the 3 colour Diamond with a 40 Watt heater but I only used to get about 1 degree overshoot. When I get time, I'm going to ignore what RepRap.me say and fit a 40 Watt heater cartridge instead of the 80Watt that they recommend.

                                      Ian
                                      https://somei3deas.wordpress.com/
                                      https://www.youtube.com/@deckingman

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                                      • dc42undefined
                                        dc42 administrators
                                        last edited by

                                        Ian, I presume you tuned the new heater? You can increase the A parameter to reduce overshoot.

                                        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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