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    Sensorless homing for Deltas

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    • MarioZundefined
      MarioZ
      last edited by

      I looked to all documentation and discussions about sensorless homing and I didn't find any specific topic related to sensorless homing for delta printers. So I have a question:

      1. Does make sense to implement it on delta printer?

      If yes, than I would need some help to understand how it should be implemented.

      The documentation (https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing) is from my opinion a little bit confused. In the Configuring Stall Detection the M915 command should be used, but in the "Testing it using Macro" there is no M915 command. So I assume that testing macro should be used for testing, before re-configuring the printer to use sensorless homing and stall detection.

      If my thinking is correct, the M915 command should go in the config.g and rest in homedelta.g?

      An example of config.g and homedelta.g would be helpfull.

      Thank you.

      PS: The RepRapFirmware configuration tool when selecting sensorless homing doesn't do anything. So the sensorless is not configured.

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      • DjDemonDundefined
        DjDemonD
        last edited by

        I have it on a delta but I'm away from home right now but I can supply sample homing file unless someone does it sooner. It works well. But you have to calibrate after homing everytime as the accuracy of endstop position is not repeatable enough to skip G32 before printing. I'd recommend a reliable accurate probe. (smart effector/piezo probe).

        Simon. Precision Piezo Z-Probe Technology
        www.precisionpiezo.co.uk
        PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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        • dc42undefined
          dc42 administrators
          last edited by

          https://duet3d.dozuki.com/Wiki/Stall_detection_and_sensorless_homing#Section_Limitations says a little about sensorless homing on deltas. As a minimum, you should do 3-point auto calibration after homing, so allow for inaccuracies in the endstop position when using stall detection in place of real endstops.

          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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          • DjDemonDundefined
            DjDemonD
            last edited by

            Here's my homedelta you'll need to adjust the m915 S parameter to get it to stall with as little impact with whatever physical endstop you have (suggest replaceable printed blocks), but minimise false detects.

            M80					;PSU ON
            ; Homing file for RepRapFirmware on Large Kossel
            ; Sensorless Homing test file for RepRapFirmware on Kossel
            M915 X Y Z S2 F1 R0    ;set stall detect drives, S-threshold (-64 to 63), F1 filtered, R-log only
            M400					; make sure everything has stopped before we make changes
            M574 X2 Y2 Z2 S3			; set endstops to use motor stall
            M913 X30 Y30 Z30			; reduce motor current to 50% to prevent belts slipping
            G91					; use relative positioning
            G1 S1 X700 Y700 Z700 F2000		; move all carriages up 700mm, stopping at the endstops
            G1 Z-5 F2000				; down a few mm so that we can centre the head
            G90					; back to absolute positioning
            M400					; make sure everything has stopped before we reset the motor currents
            M913 X100 Y100 Z100			; motor currents back to normal
            G1 X0 Y0 F2000				; centre the head and set a reasonable feed rate
            ;M574 X2 Y2 Z2 S1			; set endstops back to normal so that homedelta.g works
            

            Simon. Precision Piezo Z-Probe Technology
            www.precisionpiezo.co.uk
            PT1000 cartridge sensors NOW IN, just attach to your Duet board directly!

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            • MarioZundefined
              MarioZ
              last edited by

              Thank you. I will try following your instructions…

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