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    Help: New build homing improperly on Z axis

    Duet Hardware and wiring
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    • Holyman92
      Holyman92 last edited by

      So i just finished a build based on the HEVO using a duet 2 wifi w/ a Duex5 and triple independent Z steppers. I finally have all the motion moving the right way (bed drops away from the nozzle when homing and then moves up), the bed goes up to 0 and down to 500, the issue is when i try to home it, it tries to home at 500 (the bottom of the printer) even tho when it homes it will set that to 0.

      ; Endstops
      M574 X1 Y1 S0 ; set active low and disabled endstops
      M574 Z2 S0

      ; Drives
      M584 X0 Y1 Z2:5:6 E3:4 ; set drive mapping
      M671 X-40:440:440 Y185:325:30 S1 ; leadscrews
      M569 P0 S1 ; physical drive 0 goes forwards
      M569 P1 S1 ; physical drive 1 goes forwards
      M569 P2 S0 ; physical drive 2 goes backwards
      M569 P3 S1 ; physical drive 3 goes forwards
      M569 P4 S1 ; physical drive 4 goes forwards
      M569 P5 S0 ; physical drive 5 goes backwards
      M569 P6 S0 ; physical drive 6 goes backwards

      ; homez.g
      ; called to home the Z axis
      ;
      ; generated by RepRapFirmware Configuration Tool v2.1.8 on Wed Mar 11 2020 21:21:21 GMT-0500 (Central Daylight Time)
      G91 ; relative positioning
      G1 H2 Z5 F6000 ; lift Z relative to current position
      G1 H1 Z505 F3600 ; move Z up until the endstop is triggered
      G92 Z0 ; set Z position to axis minimum (you may want to adjust this)

      ; Uncomment the following lines to lift Z after probing
      ;G91 ; relative positioning
      ;G1 Z5 F100 ; lift Z relative to current position
      ;G90 ; absolute positioning

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      • Danal
        Danal last edited by

        @Holyman92 said in Help: New build homing improperly on Z axis:

        G1 H2 Z5 F6000 ; lift Z relative to current position

        Your homing moves are backwards. Increasing Z makes the nozzle/bed separation larger. To make that spread larger on a HEVO (and other moving bed CoreXY), the bed drops as Z increases.

        You want -5 on this move and -505 on your endstop move. Moving Z to smaller numbers (negative relative moves) moves the bed closer to the nozzle; in other words, up.

        Delta / Kossel printer fanatic

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        • Holyman92
          Holyman92 last edited by

          @Danal said in Help: New build homing improperly on Z axis:

          You want -5 on this move and -505 on your endstop move. Moving Z to smaller numbers (negative relative moves) moves the bed closer to the nozzle; in other words, up.

          now it moves up towards the nozzle when i home but when u add 5 to the z it moves up instead of down

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          • Phaedrux
            Phaedrux Moderator last edited by

            @Holyman92 said in Help: New build homing improperly on Z axis:

            Your first 5mm move is correct as positive. The 505mm move must be negative.

            Z-Bot CoreXY Build | Thingiverse Profile

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            • Danal
              Danal last edited by

              Correct. I forgot the first move is to move it away from everything.

              Also, the -505... it is sort of tradition to do -999999 or similar. This makes it very obvious that this move is a home move, and the switch will end it.

              Also, if your bed ever happened to be beyond 505 down (crammed into the bottom, for whatever reason), homing would fail with a -505, and frustratingly enough, fail JUST before it touched the switch!

              Anyway, that's the two reasons for -999999

              Delta / Kossel printer fanatic

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              • Phaedrux
                Phaedrux Moderator last edited by

                @Danal said in Help: New build homing improperly on Z axis:

                Anyway, that's the two reasons for -999999

                That's a little extreme. If the switch fails your axis will grind away for the entire duration of the move. Maybe something a little closer to the axis length but still longer. 600 maybe?

                Z-Bot CoreXY Build | Thingiverse Profile

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