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    Calibrating steps/mm

    Tuning and tweaking
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    • Jddt
      Jddt last edited by

      When I completed the steps/mm calibration and I run code, like the homing code, then the distance is completely wrong.

      Any advice.
      Thanks

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      • mrehorstdmd
        mrehorstdmd last edited by

        What type of mechanism? What distance is "wrong" when homing?

        Steps per mm is normally a simple function of the pulley teeth, belt pitch, and steps/rev of the motor.

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        • Jddt
          Jddt last edited by

          I am using external drivers. All my final drive pulleys are HTD5 20 tooth. I do not get any consistency with the distance the axis move.

          See calculations below.0_1529519753000_04bdb18e-452c-4e57-9863-3e6df798767c-image.png

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

            If you are using external drivers then you will need to use a T parameter on the M569 commands for those drivers, because the default width of the step pulses generated is fine for the built-in TMC2660 drivers but too short for almost all external drivers. See https://duet3d.dozuki.com/Wiki/Using_external_stepper_motor_drivers#Section_Configuring_the_Enable_polarity_and_step_timing.

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            • Jddt
              Jddt last edited by

              Settings I am using now. Can the T setting influence the accuracy of my steps?

              M569 P0 S1 ; Drive 0 goes forwards
              M569 P1 S1 ; Drive 1 goes forwards
              M569 P2 S1 ; Drive 2 goes forwards
              M569 P3 S1 ; Drive 3 goes forwards
              M569 P5 S1 R1 T2.5:2.5:5:2.5
              M569 P6 S1 R1 T2.5:2.5:5:2.5
              M569 P7 S0 R1 T2.5:2.5:5:2.5
              M569 P8 S0 R1 T2.5:2.5:5:2.5
              M584 X5 Y6 Z7 E8

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              • dc42
                dc42 administrators last edited by

                If the T values are too small then you can miss steps.

                Jddt 1 Reply Last reply Reply Quote 0
                • nz_andy
                  nz_andy last edited by

                  What is the external drive micro step set at? you have 10,000 miro-steps per revolution listed in you post, so micro step setting is 50?

                  deckingman 1 Reply Last reply Reply Quote 0
                  • Jddt
                    Jddt last edited by

                    0_1529529121089_101629b9-b45f-49e9-b784-5c2885a5e270-image.png

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                    • nz_andy
                      nz_andy last edited by

                      Have you tried using 1/16 micro-stepping instead of 1/50th? if that works that may tell you there is an issue with the signal frequency / pulse width.

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                      • deckingman
                        deckingman @nz_andy last edited by

                        @nz_andy said in Calibrating steps/mm:

                        What is the external drive micro step set at? you have 10,000 miro-steps per revolution listed in you post, so micro step setting is 50?

                        Good spot. That could well be the OP's problem as 50x micro stepping isn't a supported mode - see documentation here https://duet3d.dozuki.com/Wiki/GCode#Section_M350_Set_microstepping_mode.

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                        • Jddt
                          Jddt last edited by

                          Thanks for noticing the error in my calculation. I am using external drivers and are not using the M350 command.

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                          • Jddt
                            Jddt @Jddt last edited by

                            @jddt Changed to 128 Micro Steps
                            0_1529533726144_0e3b9ecf-03e0-4ad5-9459-69e0547a993c-image.png

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                            • Jddt
                              Jddt @dc42 last edited by

                              What is the max T values you suggest to be safe?

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

                                @jddt said in Calibrating steps/mm:

                                What is the max T values you suggest to be safe?

                                High T values will limit the maximum step pulse frequency. I doubt that any stepper drivers need greater than T10.

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                                • Jddt
                                  Jddt last edited by Jddt

                                  The motors started to work properly with a value of T5

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                                  • dc42
                                    dc42 administrators last edited by

                                    According to the datasheet, T2.5:2.5:5:0 should work.

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