G29's parameters not working correctly

[yonkiman]

I'm able to perform a bed calibration on my delta with a simple G29 and I get a mesh report at the end. Everything seems to be working perfectly.

But if I try G29 with any of the switches (G29 S0 or G29 S4 Z0.05 or G29 S1), the motors start singing and the carriage starts moving across the Z plane incredibly slowly until I reset the CPU. Am I perhaps misunderstanding G29 usage?

[yonkiman]

OK, I have a little more clarity on this. In the ~2-3 year old version of Marlin I had been using, I would adjust Z offset with "G29 R0.05", "G29 R-0.05", etc. That doesn't work with Marlin 1.1.0. The only Z offset adjustment I could find in 1.1.0 was "G29 S4 xxx", which doesn't work - just sends the carriage slowly off into the sunset (that's the bug).

Is there a different command I should be using to adjust Z offset?

EDIT: Duh, it's M851.

There's still a bug with M29, though: My delta, with AUTO_BED_LEVELING_BILINEAR enabled and apparently working, responds incorrectly to an "M29 Sx" command. I believe that command should be ignored if MESH_BED_LEVELING is not enabled.

[fiveangle]

G29 when ABL enabled is:

[S<rate>] - Set the XY travel speed between probe points

http://marlinfw.org/docs/gcode/G29.html

[fiveangle]

If you submit G29 Sn where n=XY_PROBE_SPEED in your Configuration.h, does it work correctly ? (also, I assumed you didn't mean "M29 - Stop SD write."

[yonkiman]

Thanks for the pointer to the more complete documentation. And the laugh: I was setting movement speed to 1mm/min and it was doing exactly what I asked it to do!

So there's no ABL equivalent of MBL's G29 S4? I was expecting to be able to do an ABL and then do a single "Adjust Z so a piece of paper can just pass under the nozzle" (from the MBL docs) to account for any variation in probe-to-nozzle distance. Is the assumption with ABL that the probe-to-nozzle distance will be perfect in Configuration.h and never change over time? Not sure how ABL is supposed to get that right...

Nomenclature-wise, I think it's a little confusing that the choices are Auto BL or Mesh BL, yet ABL_BILINEAR produces a mesh. Also is there a difference between Manual Bed Leveling and Mesh Bed Leveling (they seem a little conflated in http://marlinfw.org/docs/gcode/G29-mbl.html), and does the MBL acronym apply consistently to one or the other?

If you submit G29 Sn where n=XY_PROBE_SPEED in your Configuration.h, does it work correctly?

Will try tomorrow. But ABL seems to work perfectly (at what seems like XY_PROBE_SPEED) when I submit G29 with no arguments, so I suspect G29 Sn where n=XY_PROBE_SPEED will work the same.

[yonkiman]

Yes, G29 S4000 started a normal ABL. So there's no apparent issues with the code, just my understanding of the G29 command and exactly how ABL is supposed to be set up...

[fiveangle]

I suspect once UBL gets fleshed out, code will collapse to UBL with an auto and manual method for inputs. All in good time…

To answer your nozzle height question: review M851

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