Quote Originally Posted by Roxy View Post
Code:
Recv: -0.24115 -0.06140 +0.05835 +0.12860 +0.13910
Recv: -0.20715 -0.00765 +0.10510 +0.17160 +0.15835
Recv: -0.27265 -0.02565 +0.08585 +0.16560 +0.20235
Recv: -0.34990 -0.09965 +0.03785 +0.13285 +0.15435
Recv: -0.39390 -0.15590 +0.00960 +0.11010 +0.15535
That's interesting... I didn't know there was a Corrected Bed Height vs. Bed Topology:
section to the report. That is new. I'll have to look at the code to see what that is doing. But if the report is orientated correctly for your bed it is saying the front left is almost .4mm below the mean and the front right is .15mm above the mean. Going diagonally, you have .5mm of difference from front left to back right. And .4mm difference from back left to front right. That is a lot. The Auto Bed Leveling should be able to adjust for that, but you will get better prints if you physically adjust out some of that error.

At this point if you manually adjust your bed to bring all those numbers closer to zero, you will be able to see if there is a warp or a bulge in the bed. What will happen in the case of a warp or bulge is you will see a row or column start off +, go to - and then flip back to +. (or start -, goto +, and then back to -) If you see that on any column or row, you have a non-flat bed and there is some kind of warp. If you see that happen in both a row and a column, it will be likely the intersection of the two is the location of the bulge. But that will only show up on the Topological Map if you have it adjusted closer to level.
Just realized I never came back with an update. I eventually got the bed shimmed to within .06mm of flat and it's good enough if I split the difference on the Z height.

After talking with a mechanical engineer at work, it seems that this is typical. Flat glass really isn't very rigid. It tends to take a bow, usually across the diagonal. Once it takes this bow, it becomes very rigid and stable, but it's very tricky to keep it entirely flat.