X42 reference switch

this is not a reference switch... it is not accurate to be any sort of reference.

this switch is for CHECKING if mastering or mechanical position of robot joints are reasonably ok... (close enough to expected to not pose hidden danger to humans).

where possible, it could be also used to confirm that robot tooling is also ok. because if any of those are too far out of spec, that could bring robot or tooling on a collision path with some oblivious human...

for example if robot thinks that everything is ok when really some axis is slipped somehow, or ware moved without power, or was dial mastered in wrong position or if long tooling was bent and now gets closer to operator. normally robot can detect if axis is moved without power, (and this works most of the time) but... it is not entirely bullet proof... not when human life is at stake.

in an odd chance that motor was turned exactly 90deg (if 4-pole motor) or exactly 120deg (3-pole motor), robot would think that everything is fine and would not un-master that axis. but this is motor angle... if you divide this value by axis gear ratio you get axis movement in degrees... suppose some axis has 100:1 gearbox, then this 90deg turn on motor would mean axis position changed 0.90deg.

and if robot was hit in transport or during maintenance for example, and the axis moved any multiple of that angle (+/-0.9, 1.8, 2.7, 3.6, 4.5, etc degrees), you have a problem... 360deg/0.9deg = 400 possible undetected points. but each robot system will have more axes, and there are many robots.... so the "unlikely" event is not that unlikely.