Auto_Bed_Leveling: Enhanced G29 command

[DarkAlchemist]

I didn't see anything wrong with that gcode, but it didn't include any movements other than that last extruder move, so we can't see if it will crash the nozzle into the bed or not.

Didn't think you needed that but I have uploaded it now.
What good is the gcode because it isn't adding the offsets from the G29 and that is what will possibly crash the head.

[Roxy]

What good is the gcode because it isn't adding the offsets from the G29 and that is what will possibly crash the head.

The Auto Bed Level Correction is done entirely on the Printer side of things. The G29 will tell you the 3x3 Bed Level Correction matrix that it generates. Once it has that, any coordinate it gets from the GCODE is multiplied by that matrix to 'correct' it for your printer.

I have my bed on springs so if a mistake happens, I usually have time to press the reset button. But one thing you can do is add a little more offset from your Z_PROBE_OFFSET number and verify things make sense by just printing in the air and see if the gap look reasonable. And then maybe cut the extra gap in half and try again and verify everything is reasonable. And cut in half again... It is extra time and effort, but if you are worried about destroying things, it is a way to get there safely.

Alternatively... What I did the first time was I had Safe Z Homing turned on so it would do the G28 in the center of the bed. I did the G29 and moved back to the center of the bed. I moved the nozzle to about 1 or 2mm from the bed and then started moving to each corner. The nozzle should stay the same height from the bed at each corner (because the bed leveling will be active after the G29). If you confirm that, you should have some level of confidence things are going to behave correctly.

[DarkAlchemist]

The Auto Bed Level Correction is done entirely on the Printer side of things. The G29 will tell you the 3x3 Bed Level Correction matrix that it generates. Once it has that, any coordinate it gets from the GCODE is multiplied by that matrix to 'correct' it for your printer.

Which is exactly what I was saying because my uploaded gcode means absolutely nothing in the end.

I have my bed on springs so if a mistake happens, I usually have time to press the reset button. But one thing you can do is add a little more offset from your Z_PROBE_OFFSET number and verify things make sense by just printing in the air and see if the gap look reasonable. And then maybe cut the extra gap in half and try again and verify everything is reasonable. And cut in half again... It is extra time and effort, but if you are worried about destroying things, it is a way to get there safely.

Not sure I would see a change as it glided into position though.

Alternatively... What I did the first time was I had Safe Z Homing turned on so it would do the G28 in the center of the bed. I did the G29 and moved back to the center of the bed. I moved the nozzle to about 1 or 2mm from the bed and then started moving to each corner. The nozzle should stay the same height from the bed at each corner (because the bed leveling will be active after the G29). If you confirm that, you should have some level of confidence things are going to behave correctly.

When I do a G28 my head moves to the middle of the bed as well.

I like that last part but how would I measure it? Just do the M114 G92 tricks and see if it stays -2.1?

[Roxy]

Which is exactly what I was saying because my uploaded gcode means absolutely nothing in the end.
Not sure I would see a change as it glided into position though.
When I do a G28 my head moves to the middle of the bed as well.

I like that last part but how would I measure it? Just do the M114 G92 tricks and see if it stays -2.1?

I would probably move to a corner, and use some feeler gauges to find the distance. Or, find something else the right size. And then use that to compare the next and the next corner. At all times, there would be enough of a gap you could move safely to check things out. And I would be double checking things with the M114 command.