How to place dual Zmax endstop/flag accurately?

AlexLin

Hi
Currently I use the z probe to do bed leveling(and mesh comp) on my core XY. I'm thinking about installing 2 Zmax end stop and homing to max (temporarly using independend axis when homing). This would be better for power failure recovery.
However with the probe I'm sure a tilted bed or some way tilted x axis is accounted for. How do I make sure both of the Zmax endstops/flags are in exactly the right place so the bed surface is level in respect to the x/y plane? Just measuring with a tape doesn't feel accurate enough.

T3P3Tony

@alexlin one option may be to use a finely adjustable trigger mechanism (like an M3 screw). Then use the probe next to each Z axis to accurately set Z0 and move up a set distance and adjust the trigger so that is just triggers after a set move up ( on both sides)

Phaedrux

I use a macro to help me calibrate the zmax distance for my optical endstop. I think it should work just as well to adjust 2 endstops.

I use this mount for my optical endstops which uses an M3 bolt for adjustment.
https://www.thingiverse.com/thing:2070697

After mechanically level the bed, and measuring the z probe offset, I run this to calibrate zmax height.

; 0:/macros/Bed Leveling/0_Measure Zmax trigger.g
; Automates measuring the Zmax trigger for optical endstop at 300mm
;
M291 P"This will set Z0 and calibrate Zmax height to 300mm" R"Proceed?" S3
M291 P"Homing all axis" T5
G28			; Home all
G90			; Absolute positioning
M98 P"0:/macros/0_Center Nozzle.g"	; Move nozzle to bed center	
M291 P"Adjust nozzle height until it's touching bed" Z1 S3
G92 Z0 			; set Z0
M291 P"Bed will now drop to Z300" S3
G1 Z300			; Move bed down 300mm
M291 P"Adjust optical endstop flag until light just turns off" R"Set Zmax=300mm" S3
M291 P"ZMax homing will now be tested, starting with homing Zmin" S3
M291 P"Homing to Zmin" T5
G28 Z
M291 P"Ready to test Zmax homing?" R"Proceed?" S3
M291 P"Homing to Zmax" T5
M98 P"0:/macros/2_HomeZMax.g" ; Test Zmax homing
M291 P"ZMax homing test complete. Printer will now home all." R"Proceed?" S3
G28	; Home all
M291 "ZMax calibration complete." S3

AlexLin

Thanks for useful tips!

dc42

Another user with dual Y endstops splits them into Y and U for homing, then after the G1 S1 Ynn Unn move he/she sends a G1 Uxx command, where xx is a small correction to account for the two endstops not being perfectly aligned with each other. I know this because it exposed a bug! [Fixed in firmware 2.01beta2].