First layer test squares issues
I've been using my i3 MK3S+ for about 6 months or so now and, for the most part, things work well. However, I had a problem this week where one print was large and rectangular and one end came up off the bed enough that it warped the print. I have theories about the cause of this, but at this point, I don't want to get into that. To deal with the print issue, I recalibrated all three axes, ran it through the self-tests, then worked on adjusting the Z axis distance from the head to the bed. To do that, I used a test print I've used before: Twelve 2" squares. The slicer has the printer fill in the squares diagonally. I use 2 values per square and, since they're put down diagonally, I change the value when it prints the diagonal line from one corner to the other. Here's my latest test:
Several points about this printout:
1) The slicer did not put the squares in a clear order, so don't assume any particular square was printed before or after others.
2) As I said, each square (except one) is divided diagonally between two different bed height values.
3) I color coded the numbers to make it easy to tell at a glance which ones match. I put several numbers in red, since they seem to be outside of the "good printout" range.
4) I allowed for the possibility that when I was making adjustments to the Z Live Adjust, it might have created issues when the printer outlined the squares - or that might have lead to a stray thread falling in the square and being printed over later. (Like in row 2, column 3.) So on the top left square, for example, there is an issue along the front of the square where I had dialed in 1.260. I allow for the possibility that error could have happened while I was adjusting the value.
What concerns me is that I feel like there is an inconsistency between the different adjustments and the results. If I count the top left square as 1,1, then look at 1,3, where I use 1.265, and 3,2, where I use the same value. One looks a lot nicer than the other. Also, the 1.260 in 3,2 looks a lot cleaner than the 1.260 in 2,4. I allow that I might have been adjusting the value while the outside of the 2nd one (2,4) was being printed and the problems with the outside square could have caused the bigger issue.
When I look at these, some tests of 1.265 look notably better than the others. Also, some 1.260 tests look notably worse than some of the 1.255 and 1.250 tests.
I'm wondering if my bed could be uneven enough that a specific value on one area of the bed might be a poor choice to use on another part. While I'm wondering why there are variations in the different squares, that's my biggest concern: Could my bed be warped enough that the printer can't completely adjust for it? If not, why is there so much variation between different tests for the same value?