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    BLTouch Offset Changes After A Print

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    • biradamundefined
      biradam
      last edited by

      Hi,

      I'm having issues with the Z Offset of the BLTouch. Everytime I print something, I have to re-calibrate the Z offet of the BLTouch and the difference is about (+ or -) 0.15mm each time. That's a huge difference for the first layer and due to this issue sometimes I have issues with first layer (too low or high).

      I'm sure that wiring is correct and cables are good. Also it is mounted well and it doesn't wobble on the mount.

      config file is as following:
      M574 Z1 S2 ; Set endstops controlled by probe
      M307 H3 A-1 C-1 D-1 ; Disable heater on PWM channel for BLTouch
      M558 P9 H5 T5000 A2 F120 ; Set Z probe type to bltouch and the dive height + speeds
      G31 P25 X25 Y35 Z0.88 ; Set Z probe trigger value, offset and trigger height
      M557 X25:275 Y35:240 S20 ; Define mesh grid

      Any idea why would this happen and how to avoid?

      Thanks!
      M

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      • Phaedruxundefined
        Phaedrux Moderator
        last edited by Phaedrux

        If you grab the heat block (while it's cold) and wiggle it, do you feel any movement? Are you sure there is no play in the print head and mount?

        Is the base of the BLTouch 8mm vertically from the nozzle tip?

        What is your bed surface like? Is it spring mounted?

        Try this for your M558

        M558 P9 H5 F100 T4000 A5 R0.3 S0.005 B1

        A little slower on the probe and travel move, and will pause for 0.3 seconds after travel to let the head settle before starting to probe. A5 will attempt to probe up to 5 times until 2 consecutive results are within 0.005mm of the trigger height. A2 won't actually work for that because the minimum and maximum number of probe attempts are the same, so if your probe is getting inconsistent results you won't be able to tell. And finally, B1 will disable the heaters during probing to eliminate any possible interference.

        Z-Bot CoreXY Build | Thingiverse Profile

        biradamundefined 1 Reply Last reply Reply Quote 0
        • biradamundefined
          biradam
          last edited by

          Thanks Phaedrux!

          I will be trying in 5 minutes when I cool the nozzle and let you know.

          I know that there is a movement when I wiggle the extruder mount but it's the whole carriage and rods, not only the mount.

          My surface is FilaPrint from Filafarm and yes I have Ultimaker springs.

          In the meantime I've changed the homeall to something you mentioned in one of your other posts.

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          • biradamundefined
            biradam @Phaedrux
            last edited by

            @Phaedrux

            So, the base of the BLTouch is 10mm from tip of BLTouch when it's deployed and 6mm when retracted.

            Also, with the cold heat block, there is no play at all. It's the whole carriage that moves when wiggled.

            Phaedruxundefined 1 Reply Last reply Reply Quote 0
            • Phaedruxundefined
              Phaedrux Moderator @biradam
              last edited by Phaedrux

              @biradam 0_1540071882675_BLTouchZHeight.png

              8mm from the plastic base to the nozzle tip

              Z-Bot CoreXY Build | Thingiverse Profile

              biradamundefined 1 Reply Last reply Reply Quote 0
              • biradamundefined
                biradam @Phaedrux
                last edited by

                @phaedrux

                Oops, sorry.

                It's around 8.4mm from base to nozzle tip.

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                • dc42undefined
                  dc42 administrators
                  last edited by

                  Which firmware version are you using? Some older firmware versions could cause a Z shift if you used a Z probe to re-home the printer while you had bed compensation enabled. The workaround was to cancel bed compensation before homing Z.

                  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

                  biradamundefined 1 Reply Last reply Reply Quote 0
                  • SputnikOC3dundefined
                    SputnikOC3d
                    last edited by

                    Ive reported this issue in other threads - knew something was wrong but couldnt get me head round how or why it was happening !

                    What firmware do I need to be on to avoid this issue ?

                    Since day 1 Ive been a Baby Stepping fool between every print ...

                    My Custom Start Gcode in slicer - rehomes between prints - but also disables [ once ] the mesh grid comp before it homes - yet I still get this issue can be off as much as .22 ....

                    dc42undefined 1 Reply Last reply Reply Quote 0
                    • dc42undefined
                      dc42 administrators @SputnikOC3d
                      last edited by

                      @sputnikoc3d said in BLTouch Offset Changes After A Print:

                      What firmware do I need to be on to avoid this issue ?

                      See https://github.com/dc42/RepRapFirmware/blob/dev/WHATS_NEW.md for the firmware revision log.

                      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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                      • biradamundefined
                        biradam @dc42
                        last edited by

                        @dc42

                        I'm on the 2.02 RC3 already. I've just ordered IR Probe. Once I receive it, I hope the problem will be eliminated.

                        I also realized that the offset changes when I switch the power off and on.

                        Once I power on and set the offset, I can print with that offset a thousand times and the offset will stay same if the power was not switched off.

                        While setting the offset, G30 S-1 would return the same number even if I retry for 10 times but after a power-off, the number changes.

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