Question about 2/3 stepper leveling



  • Hi,

    I read that after using G32 to invoke bed.g to auto-leveling then G30 should be used to reset the Z=0 datum as it may have changed as a result of the leveling.

    But I didn't see if G30 needed to be used BEFORE G32.

    Thanks.

    Frederick


  • Moderator

    Well if you're using bed.g to do leveling it already HAS G30 in it. But it's not really obvious what the Z0 point would be set to. I think it would be set to whatever the height was after the last point was probed.

    Normally you'd need to run G28 before that anyway otherwise you'd get an axis insufficiently homed error for the X and Y movement.



  • @Phaedrux said in Question about 2/3 stepper leveling:

    Normally you'd need to run G28 before that anyway otherwise you'd get an axis insufficiently homed error for the X and Y movement.

    homeALL.g invokes homeX.g then homeY.g then homeZ.g

    The printer is equipped with 3 Z endstops so homeZ.g first homes Z which roughly levels the bed in the process. Then it sets the nozzle position to Z=10 and executes G32 which, of course, invokes bed.g.

    When invoked bed.g currently ends with a G30 to set the Z=0 datum and I know that must be done.

    The only question in my mind is should bed.g start with a G30.

    Thanks.

    Frederick


  • Moderator

    What happens if you only home x and y and then run G32?



  • @Phaedrux said in Question about 2/3 stepper leveling:

    What happens if you only home x and y and then run G32?

    Well if the bed is too far out of level you can different errors:

    One is that the BLTouch moves to a probe point and is so close to the bed that the pin cannot drop down and the probe appears to be triggered at the start of the probe

    Another is that the auto-leveling completes but more correction was needed than allowed by the setting in the M671 command.

    There may be others that I have not seen yet.

    Frederick


  • Moderator

    Well in your case if you're running G28 before G32 you're already getting a G30 happening before the leveling takes place.

    I think it's always good idea to fully home the axis before trying to do any moves.

    @fcwilt said in Question about 2/3 stepper leveling:

    But I didn't see if G30 needed to be used BEFORE G32.

    Technically you don't NEED to have a G30 happen before since your bed.g already contains G30 in the form of G30 P0 and G30 P1, so it's going to do a probing move regardless so the question is a bit like asking if you should do a G30 before you do G30.

    Since bed.g is a macro scripted to suit your machine its up to you to decide what's the most appropriate way to achieve your goal.

    So to your question, do you need a g30 first? Well no, but you probably should home your axis first anyway.


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