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    Hypothetical question regarding acceleration and latency

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    • 3DPMicro
      3DPMicro last edited by

      Cartesian, Duet 2 Ethernet (or Duet 3), X axis - external driver and servo with S curve acceleration off the Expansion Breakout Board, Y axis - stepper w/ trapezoidal accel. driven by onboard driver.

      Could this scenario cause print issues because of mismatched motion profiles or latency between the two?

      o_lampe 1 Reply Last reply Reply Quote 0
      • o_lampe
        o_lampe @3DPMicro last edited by o_lampe

        @3dpmicro
        IMHO, everytime one motor runs slower than jerk setting, the mismatching ramp-up/down profiles come into play.
        Eg. at the turning point of circles
        //edit It would probably show most, when both motors run below jerk speed?

        3DPMicro 1 Reply Last reply Reply Quote 0
        • 3DPMicro
          3DPMicro @o_lampe last edited by

          @o_lampe thanks for the input. There's also potentially a speed/distance range where the move is in accel/decel for a significant amount of time that might cause issues. Outside of theory I may have to just try and see.

          o_lampe 1 Reply Last reply Reply Quote 0
          • o_lampe
            o_lampe @3DPMicro last edited by o_lampe

            @3dpmicro
            OTOH we are allowed to use different accel and jerk settings for X and Y axes. That alone would cause non-conform motion profiles.
            But I'm not aware of any complaints. Mostly because we set them identical. (and G1 always picks the slowest setting?)

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

              @o_lampe said in Hypothetical question regarding acceleration and latency:

              OTOH we are allowed to use different accel and jerk settings for X and Y axes. That alone would cause non-conform motion profiles.

              Not so. The actual acceleration and jerk used on X and Y will be in proportion to the movement distances for that move.

              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

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

                @dc42
                That's clever! So we don't have issues with linear acceleration, but external drivers with 'S' curved accel would be a problem?
                At least when they are mixed with linear acceleration drivers

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

                  @o_lampe said in Hypothetical question regarding acceleration and latency:

                  @dc42
                  That's clever! So we don't have issues with linear acceleration, but external drivers with 'S' curved accel would be a problem?
                  At least when they are mixed with linear acceleration drivers

                  External drivers that have a latency between receiving step pulses and moving to the requested position could cause mismatches in the XY tracking. If both X and U used those drivers and they had equal and constant latency then X and Y would track properly.

                  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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