Magnets + Z-Probe

I'm not running the MKS Gen L v2.0 board in my printer. Mine died. I have a BTT SKR 1.4 Turbo. It's very similar to the MKS Gen L.

You can still hook up the BLTouch. There's a servo port and you can use the z-axis limit switch port to trigger it. I think, though, after looking at the board that the "AUX 1/2" would also work. The z-axis limit switch is the easier way to go but I want to say I remember that there is an advantage to using another pin.

TeachingTech did a video on this board in the Ender 3.

Also, here's the docs on the board: https://github.com/makerbase-mks/Datasheet/blob/master/English%20datasheet/MKS%20Gen_L%20DataSheet.pdf

If you need firmware compiled with it setup just let me know. I don't think this is too hard to do.

BLTouch looks promising. You seem to do your research so I assume marlin has some way to integrate the extra wire for the control signal and enable/disable it appropriately.

I'm not all that impressed with the inductive sensors. There's too many variables that can affect its accuracy.

Ok. Gotcha. I'm thinking of replacing the inductive probe. Haven't decided to make a BLTouch mount or get the 8mm one. Goal being to use a glass bed.

Exactly. You can see in my OP column 4, row 3 there's a 0.3 (mm?) difference with the magnet added directly under that probe point. And in my second set of readings you can tell where the magnets were as some points are almost identical to those in my 1st set, while others off by a deal more.

[edit]Some of that may be due to how the magnets hold the flexplate compared to the tape. But I clearly showed that magnets do affect the probe readings. With a bit more testing I could probably tell the extents of the affect.

My bed mapping is better with the magnets off; but, unfortunately, the flex plate has a little warp to it. The tape just can't hold it flat enough for a better reading. I made my own heated bed out of an 1/4 in aluminum sheet and some nichrome wire. I might try printing directly on the aluminum.

So are you saying that the magnets interfere with the probe? I'm wondering if it's the magnets pulling the flex plate to a not true plate. Flexing could be all over the place. I need to take pictures but mine changes by .75mm over the course of a cm or 2. It's ridiculous.

Oh, I also got a 310x310x3mm borosilicate glass plate to build on. The inductive probe is not able to make the difference! UGH, it's supposed to be 4mm for the trigger point.

I removed all the magnets, taped the flexplate to my bed, and ran another 3 consecutive G29 commands:

>>> g29
SENDING:G29
Bilinear Leveling Grid:
      0      1      2      3      4
 0 +0.818 +0.427 +0.365 +0.588 +1.135
 1 +0.452 +0.090 -0.025 +0.247 +0.748
 2 -0.055 -0.482 -0.555 -0.325 +0.212
 3 -0.610 -1.032 -1.152 -0.945 -0.448
>>> g28
SENDING:G28
>>> g29
SENDING:G29
Bilinear Leveling Grid:
      0      1      2      3      4
 0 +0.805 +0.413 +0.357 +0.595 +1.117
 1 +0.442 +0.080 -0.035 +0.237 +0.738
 2 -0.048 -0.473 -0.555 -0.322 +0.195
 3 -0.623 -1.035 -1.165 -0.950 -0.455
>>> g28
SENDING:G28
>>> g29
SENDING:G29
Bilinear Leveling Grid:
      0      1      2      3      4
 0 +0.805 +0.413 +0.355 +0.590 +1.112
 1 +0.438 +0.080 -0.037 +0.237 +0.738
 2 -0.045 -0.467 -0.553 -0.320 +0.202
 3 -0.623 -1.030 -1.160 -0.950 -0.450

[edit]

With these numbers saved, I think I should be alright with the magnets back in place. Just need to make sure there isn't one near the home location. ...and hope I don't need to collect new readings any time soon.