Incorrect probe grid locations?

I have a cartesian printer running version 92.8 firmware configured with the online tool.  I am not sure what I have wrong in my config and need some help.

What is happening:  The printer successfully homes to X-min, Y-min, and Z-max.  After homing, M114 correctly reports the expected, homed location.  I then drop the Z axis closer to the nozzle and start G32 - all values of S show the same behavior.  On G32, the probe switch (which is on a servo next to the nozzle) is lowered into position, and the nozzle moves to the first probe point (25,25).  It then lowers and probes the bed.  I have it doing multiple probes, so it rises a little and probes again a few times.  This is repeated in 5 locations in Y up to the intended 185 Y point.  This is repeated in 5 locations in X up to the intended 185 X point. I would say the grid is complete and correct.  After the last point, the print head moves an amount in X and Y that appears to be equal to the offset of the probe and the nozzle.

What is wrong with it:  Everything is good except the probes should be done with the probe at the various points rather than with the nozzle at that point.  The final move where the printhead indicates that it is undoing a shift that never happened.  That is after the nozzle moves to (25,25) I would expect it to then shift before probing by the offset so that the probe is at (25,25).  That first shift never happens even though the recovery from it happens at the end.  From that point on, the reported location value is wrong by that offset value.

It I home all axis, move the printhead someplace on the bed, and execute G30, it does exactly what I would expect.  It shifts position to put the probe where the nozzle was, probes, and then shifts to put the nozzle back to the original location.

Any idea what is going on here?  I would be happy to provide the config file, but I do not see an option to attach one.  If it would help for me to paste some sections into a post, let me know.




  • I figured it out.  After homing, the printhead is sitting at (0,0).  Apparently, the grid probe was trying to move to compensate for the offset, but was hitting the X min and Y min in the process.  I added GCode to the slicer start script to move the printhead to the middle of the bed after homing but before G23.  After that, it works perfectly.
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