JohnSL FSR board and z probe setup

  • Hello,

    This question regarding z probing using JohnSL FSR board. That board has 3 FSR connection. My printer will have dual extruder with its own x and z axes. For setting bed mesh levelling, Do I need two of JohnSL board or 1 is sufficient?

    I'd like to use only 1 FSR board and use that same FSR to probe both head independently. Is this doable? If so then I think this would automatically took care of the offset between the two hotends in the event of changing nozzles


  • administrators

    On a standard IDEX machine with independent X carriages but a common Z axis, I think you could run G29 bed probing separately for each head, storing the resulting height maps using different filenames. Then in the tpost#.g tool change files, load the height map for the incoming tool.

    If you have a separate Z axis for each head, one option might be to use the FSRs to Z home each head independently, switching the Z axis to the appropriate motor driver using M584. After homing both, use M584 to assign both drivers to Z.

    Either way, only one FSR interface board needed.

  • thank you 42 I do have separate Z axis and got the duex5 as well

    I'm not sure what you mean by "use M584 to assign both drivers to Z."

    I was about to use
    M584 X0 Y1 Z2 U3 V4 E5:6 ; U for the other x axis and V for the other z axis and basically the two extruder motor will connect to Duex5

  • administrators

    The current firmware doesn't support remapping the Z axis in the way that it supports remapping X and Y, so you can't use V as a substitute Z axis. That's why you will need to use M584 to change the Z driver mapping if you want to perform G29 mesh bed probing separately for each head. If you are happy with both Z motors moving together most of the time, then Z2:4 can be the normal mapping in M584 and you can change it to Z2 or Z4 just when you want to probe the bed.

  • Will that be implemented in future firmware? I think it would continue to build upon the idea of U map to X and V map to Z


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