EDIT: Solved this - read the fifth post below for a method to determine if your bed is physically out-of-level (mine was >0.5mm off, more than auto-leveling could address), and a technique to get your automatic bed leveling to within 0.01mm at each corner.
I am having problems with automatic bed leveling. The result after leveling is the front-left corner and the back-right corners are a >0.5mm different than the other two corners.
I have done the following…
- With automatic leveling off (M420 S0), I’ve manually leveled Z to ensure the physical system is level (note: if I leave automatic leveling off, it is better than turning it on)
- Verified that the washer thickness is the consistent between the corners (it is within .01mm)
- Verified that the distance from the bottom of the aluminum bed to the top of the washer is the consistent (it is within .02mm)
- Verified that the distance from the bottom of the aluminum bed to the top of the heated bed is the consistent (it is also within .02mm)
- Swapped washers, standoffs and flexible corners between the sides (no change), and cleaned under and around all of them.
- I have verified that leveling is “working” by placing a thick washer on top of one corner washer and the resulting Z position is correctly offset on future moves
- Measured the deflection on the X bar to ensure that wasn’t adding to the problem (it isn’t, and the problem is opposite corners not side-to-side)
- I have changed firmware to latest release, and then back to 1.1.5 and no change.
- I am not using any software, just manual G-code commands (M420 S0, G28, G29, G1 in that order)
- I have done a “Restore failsafe” on the firmware with no change in behavior
- I am able to get great small-to-medium prints at the center of the bed when I adjust z-offset correctly, but large prints consistently are a problem as I can’t offset sufficiently for this.
- I have tried adding spacers to raise the back-left and front-right washers above the heated bed (increasing the measured gap by about .6mm) and then leveling gets very close, but I’m unable to adjust Z-offset sufficiently (I have to now offset more than -2mm, which is the maximum of Z-offset).
I’m quite lost here - since the measurements from the aluminum bed to washer/heated bed are within .02, and I’ve verified leveling is working - so I don’t see why the resulting automatic leveling is off by more than 0.5mm.
Any help would be appreciated,