A Z=0 endstop for fans of old-school printers
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This may be of interest to those who still use endstop switches to set Z=0 in their printer. I was using a lever/cam with a clicky microswitch to set the Z=0 position in my printer, but it developed a problem so I decided to work on a replacement. I changed to an opto endstop that has an LED that lights when the beam is broken. But that's not the interesting part. I made a differential screw driven adjuster for the flag that breaks the light beam. The differential screw moves the flag 100 um per rev so it is very easy to make small adjustments without over adjusting. The differential screw assembly mounts on the bed support that moves up and down and the opto endstop mounts of the printer's frame:
The screw was made by turning the end of an M5x0.8 screw down to 4 mm on a lathe and then threading it for M4x0.7. When you turn the screw 1 rev, it moves 0.8 mm up, while the M4 nut (and the flag) move up 0.1 mm. It has about 2mm of adjustment range, so you get it close by moving the opto endstop on the frame, and make fine adjustment with the screw.
More: https://drmrehorst.blogspot.com/2020/03/a-new-z-axis-optical-endstop-design-for.html
