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    Synchronizing offsets for Z probe, homing, mesh compensation

    Tuning and tweaking
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    • gnydick
      gnydick last edited by

      Not sure how to most concisely ask this...

      My homing and 4 lead-screw auto-leveling works great. My current bed has a dip in the middle because I just replaced glass with a layer of PEI, so I lost the rigidity of the glass. So now, I have to run mesh compensation in order to make up for the dip.

      The mesh compensation seems to be following the surface of the bed just fine, but it's way too close to the bed, it's grinding into it.

      My question is, if the Z-home works perfectly, why does the mesh comp at the same position drive the nozzle through the bed?

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      • dc42
        dc42 administrators last edited by

        How are you homing Z: using an endstop switch, or using a Z probe? Please post your homez.g and homeall.g files.

        Please post a screen shot of your height map.

        Which firmware version are you using?

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

          @dc42

          Using a Z probe.

          0_1558546940733_eea9126b-0b98-47e8-89d1-4824d85ad161-image.png

          homez.g

          G1 X139 Y177.5
          G91                ; relative positioning
          G1 S1 Z-350 F1500  ; move quickly to Z axis endstop and stop there (first pass)
          G1 Z2 F1500        ; go back a few mm
          G1 S1 Z-3 F360      ; move slowly to Z axis endstop once more (second pass)
          G1 Z2
          G1 S1 Z-3 F60
          G1 Z1
          G1 S1 Z-2 F30
          G1 Z.5
          G1 S1 Z-1 F10
          G1 Z10 F1500
          G90
          G92 Z12.07
          

          homeall.g

          M98 Phomex.g
          M98 Phomey.g
          M98 Phomez.g
          

          0_1558546894499_88ac89c1-311d-49d1-b623-09b6a5e85409-image.png

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          • dc42
            dc42 administrators last edited by

            Your homez.g file is nowhere near correct for homing using a Z probe. Please read https://duet3d.dozuki.com/Wiki/ConfiguringRepRapFirmwareCartesianPrinter#Section_Homing_Z_using_a_Z_probe.

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

              @dc42 While unconventional, it works as it has the right offset added in, it functionally does the same thing. Does doing it this way actually cause things not to work properly?

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

                @gnydick said in Synchronizing offsets for Z probe, homing, mesh compensation:

                @dc42 While unconventional, it works as it has the right offset added in, it functionally does the same thing. Does doing it this way actually cause things not to work properly?

                The problem is that you need to keep the G92 offset in our homez.g/homeall.g files and the Z probe trigger height in your G31 command in sync. Also you need to keep your Z homing speed and Z probing zspeed in sync to ensure consistent trigger height. So I advise against it.

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                • gnydick
                  gnydick @dc42 last edited by

                  @dc42 ok. that's what I've been doing. But, I switched over to your suggestion.

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