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    Z-motors moving out of sync

    Duet Hardware and wiring
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    • jckray
      jckray last edited by

      Hi,

      I have been running into an issue with the printer I am developing where the z motors move out of sync (see linked video). This only seems to happen after a print has been completed. Power cycling fixes the issue every time.

      Any ideas? Let me know if you need more info.

      https://photos.app.goo.gl/pPb8hjugwmhxfNAT8

      John
      Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
      https://www.hydraresearch3d.com/

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      • gtj0
        gtj0 last edited by

        That's funny! OK, not really.

        Exactly what gcode is the printer trying to execute? Some kind of a home to Z max?
        Have you separated the Z motors into separate axis letters at that point or are they still combined to Z?
        When the one of the motors stops is it skipping/binding?
        Are you using stall detection for anything?

        jckray 1 Reply Last reply Reply Quote 0
        • jckray
          jckray @gtj0 last edited by

          @gtj0

          Haha yeah, it's pretty weird.

          The z motors are connected to the default z inputs, so both are driven by the same driver. The connector wires the motors in series, so one motor should not be able to move without the other...

          At the end of a print, a home to z max is triggered using sensorless homing. After a print has finished even regular z movement happens like this, not just the homing. Sensorless z homing is also used at the beginning of a print and during startup when the printer is powered on. There is no issue then, everything works fine.

          As far as I can tell there is no skipping/binging. My only theory was that is had something to do with idle currents and that for some reason the motor current wasn't at full during these moves. This doesn't really seem possible, but I changed my idle current setting to set 100% current to all motors at all times. This did not fix it.

          John
          Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
          https://www.hydraresearch3d.com/

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          • Phaedrux
            Phaedrux Moderator last edited by

            The sensitivity of the stall detection will vary with motor temperature. That may explain why it works fine at the start, but doesn't work right after a print.

            Z-Bot CoreXY Build | Thingiverse Profile

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            • dc42
              dc42 administrators last edited by

              What is the specification of the Z motors, what current are you running them at, which Duet are you using, and what supply voltage?

              Please post the homing file (homez.g or homeall.g?) that it executes at the end of the print.

              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

              wilriker jckray 2 Replies Last reply Reply Quote 0
              • wilriker
                wilriker Moderator @dc42 last edited by

                @dc42 said in Z-motors moving out of sync:

                What is the specification of the Z motors, what current are you running them at, which Duet are you using, and what supply voltage?

                Please post the homing file (homez.g or homeall.g?) that it executes at the end of the print.

                And also end gcodes of the print might be interesting as well.

                This looks to me like something I had when I switched the Duet and had my steps/mm wrong (much too high). IIRC it moved in a similar pattern. Do you by any chance modify the steps/mm anywhere outside your config.g?

                Manuel
                Duet 3 6HC (v0.6) with RPi 4B on a custom Cartesian
                with probably always latest firmware/DWC (incl. betas or self-compiled)
                My Tool Collection

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                • jckray
                  jckray @dc42 last edited by jckray

                  @dc42

                  I'm aware of the motor temp affecting stall detection, which is why I switch to limit switches for the x and y. This could be causing the issue for z, I will investigate this further.

                  Z motor currents and steps per mm are not modified anywhere other than in config.g

                  Z Motors

                  • 0.4A
                  • 1.8deg,
                  • 320mA (80% of rated current)
                  • StallGaurd is set at 21
                  • Microstepping 128
                  • Stepps per mm 3200

                  Supply voltage = 24V
                  Duet 2 WiFi v1.04

                  himez.g
                  M400 ; make sure everything has stopped before we make changes
                  M574 Z2 S3 ; set endstops to use motor stall
                  G91 ; use relative positioning
                  G1 S1 Z240 F1200 ; home z
                  G90 ; back to absolute positioning
                  M400 ; make sure everything has stopped before we reset the motor currents

                  John
                  Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
                  https://www.hydraresearch3d.com/

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                  • dc42
                    dc42 administrators last edited by

                    Low current motors like those will work better if you connect them in parallel instead of in series. Alternatively, if the E1 motor output is free, connect one Z motor to Za, put 2 jumpers in Zb, and connect the other Z motor to E1. Put this command in config.g, before you set motor currents or microstepping:

                    M584 Z2:4 E3

                    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

                    jckray 1 Reply Last reply Reply Quote 0
                    • jckray
                      jckray @dc42 last edited by

                      @dc42

                      All drivers are currently in use. I have parallel splitter pcbs that connect to the KK type terminals, so I'll give that a go as well.

                      John
                      Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
                      https://www.hydraresearch3d.com/

                      dc42 1 Reply Last reply Reply Quote 0
                      • dc42
                        dc42 administrators @jckray last edited by

                        @jckray, you will probably need to adjust the stall detection settings. Getting stall detection working with two motors connected in either series or parallel is likely to be tricky anyway, because the signal from one motor gets attenuated by the other, unless both of them stall at the same time.

                        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

                        jckray 1 Reply Last reply Reply Quote 0
                        • jckray
                          jckray @dc42 last edited by

                          @dc42

                          Yes, I'm all too aware of the finikyness of stall detection. I'll update this topic once I have had a chance to test some of these things. Thanks for your help.

                          John
                          Founder of Hydra Research LLC, developers of the open-source 3D printers and providers of 3D printing services.
                          https://www.hydraresearch3d.com/

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