Proximity switch NPN or PNP

[JAZZCNC]

How are the swithces being daisychained together?

If it's just a case of the output from one being tied to the +/- of the next, then I wouldn't of thought it would be that good a solution as I know some prox switches can take a noticeable amount of time to power down and fully kill their output.
I would of thought a better option would be to daisychain the outputs through something like an optocoupler bank.

I do it just same as Goblin explained for limits and it works fine even with cheap prox swiches. Even with one switch at each end which I rarely do as I like to keep wiring to a minimum they work fine.
For Home switches then I always wire them in parallel.