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    topic_unsolved Runaway motor behavior w/ 3 independent z axis steppers

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    independent z runaway
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    • jonpascoe
      jonpascoe last edited by jonpascoe

      Pressing the DWC (or PanelDue) "up 50mm" and "down 50mm" Z control buttons in succession several times results in a (repeatable) "runaway" condition. One or more of the 3 independent Z axis motors whines loudly for a few seconds, then spins rapidly up or down until I hit the power switch. This behavior has resulted in several violent head crashes. (My possibly ill-conceived reason for doing this in the first place, was to exercise or break-in the linear rails/carriages in hopes of reducing some minor Z banding.)

      Aside from this behavior, the printer will successfully home all axis, complete bed leveling, and print fine.

      I am new to 3d printing and would be grateful for help with this issue? What additional information would be helpful in troubleshooting?

      Firmware Name: RepRapFirmware for Duet 2 WiFi/Ethernet
      Firmware Electronics: Duet WiFi 1.02 or later + DueX5
      Firmware Version: 2.02(RTOS) (2018-12-24b1)
      WiFi Server Version: 1.23
      Web Interface Version: 1.22.6

      Thanks much in advance!!!

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      • Veti
        Veti last edited by

        post your config and home scripts

        jonpascoe 1 Reply Last reply Reply Quote 0
        • bot
          bot last edited by

          I suspect that there is binding in your mechanical system and one or more of the motors is stalling, but then being commanded to move again.

          Try disconnecting the motor shafts from the mechanical system and try the same moves with the motor shafts spinning freely.

          jonpascoe 1 Reply Last reply Reply Quote 1
          • jonpascoe
            jonpascoe last edited by

            Configs attached.0_1565371941476_Duet configs.txt

            1 Reply Last reply Reply Quote 0
            • jonpascoe
              jonpascoe @Veti last edited by

              @veti Done & thank you.

              1 Reply Last reply Reply Quote 0
              • Veti
                Veti last edited by

                what z motors do you have?

                jonpascoe 1 Reply Last reply Reply Quote 0
                • jonpascoe
                  jonpascoe @bot last edited by

                  @bot I’ll add this to the things-to-try list.. Thank you.

                  1 Reply Last reply Reply Quote 0
                  • jonpascoe
                    jonpascoe @Veti last edited by

                    @veti I’m almost certain I have these 1.8 degree steppers on the 3 Z lead screws:

                    STEPPERONLINE Nema 17 Stepper Motor Bipolar 39mm Body 45Ncm (63.74oz.in) 1.5A 12V ...

                    https://www.amazon.com/dp/B07LF898KN/

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                    • Veti
                      Veti last edited by

                      @jonpascoe said in Runaway motor behavior w/ 3 independent z axis steppers:

                      I’m almost certain I have these 1.8 degree steppers on the 3 Z lead screws: 1.5A 12V

                      this is important. do double check this.
                      you should normally run the steppers at 70-80% of their rated current.

                      from the config i take it you are building a RailcoreII 300ZL

                      those steppers are not the ones from the BOM.

                      from https://duet3d.dozuki.com/Wiki/Choosing_and_connecting_stepper_motors

                      Avoid motors with rated voltage (or product of rated current and phase resistance) > 4V or inductance > 4mH.

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                      • dc42
                        dc42 administrators last edited by

                        Your motor currents are all to low for those 1.5A motors. Try between 1000mA and 1300mA. The whining is almost certainly caused by binding (see the response from @bot) together with low Z motor torque.

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

                          @dc42 & @bot & @Veti I hope to give all this a go tomorrow and will report back. Thanks so much to you each!

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