Hi guys. I finally attempted this auto bed leveling feature. So far from my limited testing, it seems to work.
Here is a video of it in action. https://youtu.be/V33DIzl-81I
Sorry about my elementary video editing skills...
Like Joe, I had to only modify my z probe offset value. I also just moved the z endstop to the bottom of the printer, so the bed just triggers the switch lever but doesn't put any pressure on the switch body when the bed is in its resting position.
My bed is purposely not level on the x axis in the video. Notice the Z knob constantly moving when printing the layers. I am printing a scaled up version of the bed leveling probe rotated in the x axis for my first test. I printed all the probe mounts in PETG Blue and Red. Also, I usually would have my 50 mm fan going during the print, but it died a few days back, so that is why you don't see it in the video. The print still came out pretty good without it.
Things to note:
1. The probe mount blocks the filament tension screw. Maybe a easy fix would to turn the screw around so you could tighten it from the opposite side.
2. When the probe is in its locked position, it barely clears the nozzle. I probably have to fiddle more with the probe spring and the screw locking position to fix this, but for now the clearance gets me by.
3. I had to sand down the wire clip holder on the side of the extruder mount in order to get the probe mount on. Not a big deal, but something to note.
4. Having to remember to manually interact with the probe screw to move it up and down is not great, but it works for now. Like Dave said, you would probably want some sort of servo/retract in place. I was going to work on this once I get my hands on a servo this weekend. Anybody have any experience wiring up a servo to the Rambo board and controlling it with gcode?
Here is the starting gcode I used in S3D:
M108 S255 ; turn on M2 fans
M851 Z-9.4 ; set probe offset for z
G28 ; home all axes
G29 ; probe the bed
G4 S10 ; pause for 10 seconds to lift bed leveling probe screw and to lock it in place
;start the purging of the nozzle
G1 Y50 Z0.3 F9600 ; move forward to avoid binder clips
G1 X205 Z10 ; move off platform
G1 Z0.4 ; position nozzle
G92 E0 ; zero extruder
G1 E50 F225 ; purge nozzle
G92 E0 ; zero extruder
G1 X190 Z0.1 E1.0 F1200 ; slow wipe
G1 X180 Z0.25 ; lift
I would say if you are doing fine with your bed leveling and z height adjustment just stick with that, but for some reason I always have troubles leveling the bed and I hate having to adjust that z height bolt, so I will stick with this auto bed leveling for a while and see how it goes.