This project prints four 10 mm cubes near the outer edges and one in the center. Once printed, you can measure the height of each cube. I used the stock settings with PLA. I have the Funssor build plate with almost no adjustments. Here’s what I got:

Left-Rear: 10.58 mm

Right-Rear: 10.08 mm

Center: 10.08 mm

Left-Front: 10.09 mm

Right Front: 9.93 mm

So the accuracy on my Kobra S1 printer is great from right-rear to left-front, but not so great in the left-rear. I had not run this test with the original bed, so I don't know how far it was out. Some manual adjustments should improve this, but for now, it's good enough for the work I do.

Part 2: I decided to see if I could improve it. I adjusted the Left-Rear spring down 1/4 turn and re-ran the same file and settings:

Left-Rear: 10.57 mm

Right-Rear: 10.02 mm

Center: 10.06 mm

Left-Front: 9.97 mm

Right Front: 9.81 mm

So it didn't help at all and made the Right Front worse. I'm not quite sure what to make of that. In every run, there is a slight mushrooming of the bottom layers on the Left-Rear cube that does not appear on any other cubes. Perhaps the gentry is flexing when probing.

To check consistency, I returned the Left Rear spring to my original position (1/4 turn clockwise) and then re-ran the test a third time.

Left-Rear: 10.56 mm

Right-Rear: 9.99 mm

Center: 10.08 mm

Left-Front: 10.05 mm

Right Front: 9.88 mm

So one takeaway is the automatic bed leveling sort of hides what adjustments you do (as far as layer hieght). It also seems like you may get a +/- 0.05 mm varanice from run to run. My micrometer is seeing less than +/- 0.02 mm varience on reading the same part over time and multiple times.