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    Delta printer motor stall calibration

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    • AdrAsundefined
      AdrAs
      last edited by

      I like doing impossible things, so I wanted to give the delta calibration using motor stall detection a try.

      I started with this basic script which is supposed to just probe a single point. I'm using a small cardboard box to prevent any damage, therefore the high values for probing height etc.

      However, the issue I'm facing is that no stall gets detected at all. The head moves into the box, then the motors lose steps, and after a second I hit the emergency stop.

      Did I configure something incorrectly?

      M913 X30 Y30 Z30 ; Reduce motor currents to 30%
      M915 PX:Y:Z S-20 F0 R0 ; Configure motor stall detection on X, Y, Z axis

      M558 P10 F1000 T1000 H1000 R.5 ; Set probetype 10 (motor stall), dive height and dive speed
      M574 Z1 S4 ; Configure low z endstop??? doesn't change anything???

      G0 X16 Y-8 Z55 ; Move to center
      G30 S-1 ; Probe point

      ; Remember to set motor currents back after probing
      M913 X100 Y100 Z100

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      • Argoundefined
        Argo
        last edited by

        What board do you have?

        The Duet 2 maestro for example uses TMC2204 which don't have StallGuard.

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        • AdrAsundefined
          AdrAs
          last edited by

          I've got a Duet2 WIFI

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          • Vetiundefined
            Veti
            last edited by

            see

            https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing

            The stepper drivers only update the stall detection state every 1 or 4 full steps, depending on configuration. So the actual position of the stall is uncertain to either +/- half a full step or +/- 2 full steps. This means that when using stall detection to replace endstop switches, the position defined by the stall is much less accurate than with typical endstop switches.

            this is not accurate enough for deltas.

            here is what i use.
            https://de.aliexpress.com/item/32968709878.html
            which i put on once for calibration, and if your endstops are good enough it will last several prints before you need to recalibrate again.

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            • AdrAsundefined
              AdrAs
              last edited by

              I know that it's not accurate enough, but I wanted to give it a try anyway.

              But as mentioned above the stall detection doesn't work at all

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              • Vetiundefined
                Veti
                last edited by

                M558 configures the probe

                https://duet3d.dozuki.com/Wiki/Gcode#Section_M558_Set_Z_probe_type

                P10 is for stall detection

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                • AdrAsundefined
                  AdrAs
                  last edited by

                  That's what I'm using in my macro above, but it doesn't seem to work

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                  • Phaedruxundefined
                    Phaedrux Moderator
                    last edited by

                    The stall needs a short sharp shock to detect the back emf reliably. The squishy cardboard box may have too much give to it.

                    Z-Bot CoreXY Build | Thingiverse Profile

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                    • AdrAsundefined
                      AdrAs
                      last edited by

                      Ah, ok. I thought it's actually able to detect the restisting force. But besides of that it's also not working when I just use my print bed. The nozzle hits the bed, the motors stutter a couple of times, but no probe measurement. Just horrible noises eek

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                      • Phaedruxundefined
                        Phaedrux Moderator
                        last edited by Phaedrux

                        Well you're also trying to stall 3 motors at the same time. There's a lot of reasons it's not used with deltas. Stalling the carriages at the top of travel against the frame is one thing, but trying to probe the bed with stall is unlikely to work right.

                        Z-Bot CoreXY Build | Thingiverse Profile

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                        • AdrAsundefined
                          AdrAs
                          last edited by

                          I know, I know, that's why I mentioned I like impossible things in my initial post. It's still kinda weird that I don't get any motor stall response at all.

                          I just wanted to give it a try, because it doesn't seem like people actually tried it. Everything I found so far were some calulations which said it's not possible. Therefore I just wanted to give it a try and post some more indepth details on that.

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                          • Phaedruxundefined
                            Phaedrux Moderator
                            last edited by

                            fly.png

                            It could work....

                            Z-Bot CoreXY Build | Thingiverse Profile

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                            • AdrAsundefined
                              AdrAs
                              last edited by

                              Well, not as long the motor stall detection doesn't trigger at all. But for now I'll just play with an accelerometer, how hard can it be? xD

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