by cvoinescu » Wed Oct 23, 2013 8:50 am
Three homing switches are enough, but you need six limit switches, aka endstops. Of course, in the ORD Bot and most other printers and small CNC machines, three of the limit switches are also used as homing switches, but that is not necessarily true in general. At any rate, it makes no sense to have only three endstops. That's like locking only the doors on the left side of your car.
That said, I think you're actually questioning the usefulness of having the limit feature at all, vs. homing only. Limit switches are not a must-have, but they are nice because they detect some types of mistake early. Also, some firmwares can use the limit switches to auto-detect the size of the machine and self-configure (which is not a terribly important feature in my book, but it's an example of their use).