Auto bed compensation questions and issues



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    Bed compensation in use: mesh



  • @veti said in Auto bed compensation questions and issues:

    However if you connect 4 motors in parallel you run them at 1/4 the current.

    From the description above it seems that the steppers are connected as 2P2S and thus each sees 1/2 of the current.



  • @phaedrux said in Auto bed compensation questions and issues:

    M122

    I started from scratch and now the compensation is working...

    Regarding G31 command... What is the difference between the P and the Z? How do I work with those values for an inductive sensor?

    How do I set the offset values of the probe relative to the nozzle? Do I use minus values? I know I use G31 with X and Y values but how to set them relative to my nozzle?


  • administrators

    @gaz6 said in Auto bed compensation questions and issues:

    Regarding G31 command... What is the difference between the P and the Z? How do I work with those values for an inductive sensor?

    Z is the trigger height. For an inductive sensor it should be positive (sensor triggers before the nozzle touches the bed).

    P is trigger level, and only makes much difference if you are using a sensor with an analog output.

    How do I set the offset values of the probe relative to the nozzle? Do I use minus values? I know I use G31 with X and Y values but how to set them relative to my nozzle?

    The X and Y parameters in G31 are the offsets of the probe from the head reference point (HRP). In single-extrusion printers, the HRP is normally the nozzle. So use positive values if the probe offsets are in the +X and +Y directions from the nozzle.



  • Ok, thank you.

    When I add the probe offset the printer won't probe a lot of points that my probe can reach. My inductive sensor is located inside the bed during all movement of the printer.
    My last probing point is the bed size minus the probe offset values. I would like to be able to probe from edge to edge. Is it possible?

    In Marlin, you have an interpolation command to estimate the points the probe can't reach. Does duet have it as well?

    Thank you for all the help!



  • @gaz6 RRF will automatically interpolate for the area it can't reach.


  • administrators

    @gaz6 said in Auto bed compensation questions and issues:

    My last probing point is the bed size minus the probe offset values. I would like to be able to probe from edge to edge. Is it possible?

    In your M557 command, specify the coordinates that you want to probe. Do not correct them for probe offset. The firmware will place the nozzle at the correct point so that the probe is where you asked to probe, allowing for the nozzle offset. So you can probe anywhere that the probe can reach, assuming you have set the M208 limits correctly. For example, if your probe is offset by +30mm in the X direction, and the lowest X coordinate you want to probe is X10, then the firmware will move the head to X-20 to do that - assuming that the lower X limit set by M208 is -20 or lower.



  • Thank you.
    I have just done that.
    I had to add G92 X0 to my homeall and xhome files after homing is finished so I won't have -30 in my X position after homing. Any other solution to that?



  • Well you may actually want to have that -30 in your X position if the nozzle is actually 30mm away from the edge of the bed.


  • administrators

    @gaz6 said in Auto bed compensation questions and issues:

    I had to add G92 X0 to my homeall and xhome files after homing is finished so I won't have -30 in my X position after homing. Any other solution to that?

    If your printer homes X with the nozzle 30mm off the left edge of the bed, then it's right that the X position is -30 immediately after homing X, assuming that you want X=0 to correspond to the left edge of the bed. [Another common choice is to make X=0 Y=0 the centre of the bed.]


 

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