Auto Calibration: G30 ignores settings if P* parameter is used



  • Hi there,
    I just build a Delta but have problems with G30. If used with P* parameter,
    it ignores M558 (P1 I1 R0.4 F1000 X0 Y0 Z0) and crashes right into the bed with max speed.
    Without P* it uses the settings, goes down with set feed rate, stops and reports the height.

    fails:

    G30 P0 X100 Y100 S-1 H0 Z-99999

    works:

    G30 X100 Y100 S-1 H0 Z-99999

    Any ideas?

    Edit: Btw. in both cases the X/Y coords are ignored. The head always just moves down.

    Best dgrat


  • administrators

    From the wiki page on calibrating a delta printer:

    Running auto calibration for the first time

    Initially, we recommend that you set the Z probe dive height in your M558 command to a large value, in case of large errors in your M665 R and H parameters or in your endstop trigger heights, that could otherwise cause the nozzle to scrape the bed before probing starts. For example, add parameter H30 to your M558 command in config.g. This will make probing start 30mm above where the firmware thinks the bed ought to be, instead of the default 5mm.



  • I got it. There have been two problems. 1) My probe offset was just 5mm and the printer not calibrated. So it crashed into the bed, going too far to the edges, because the surface is convex (before calibration). This is more or less the case for nearly all new builds. Maybe 5mm is too optimistic as a standard. 2) G30 behaves unexpected. Without P* parameter, it just goes down slowly. With P* parameter it goes down fast, slows down when apporaching the distance from M558 (worked with 20mm for me). In my opinion a bug, G30 should behave always the same. Anyway, my printer seems calibrated now. I am impressed by how much smoother the motors run in comparison to my cheaper boards. Hope to print a test in the coming days.


  • administrators

    G30 with a P parameter is intended for auto calibration and similar operations performed when the printer has already been homed. So it starts probing from the dive height (M558 H parameter). Whereas G30 without a P parameter is intended for operations such as initial Z homing and measuring the Z probe trigger height, so it starts probing from the current height.


 

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