Purpose for third proximity switch

[Chuck Keysor]

When I bought my used PRT Alpha (60 x 144), it had three proximity switches! Two are as shown in the manual (one for X, one for Y). But the third proximity switch was attached to a long coil of wire, neatly rolled up and placed under the big silver control box. This extra proximity switch was/is in fact connected in parallel with the other two proximity switches, with all three being connected to the "Input #3" terminal inside the silver control box. This mystery/extra proximity switch has one end broken off. So, I simply plan to disconnect this switch and its wiring entirely.

My question is, why would there have been a third proximity switch connected on my PRT alpha? :confused: And why would it be just sitting under the machine, with its wiring all coiled up?

Thanks, Chuck

[Gary Campbell]

Chuck...
I would use it for the Z axis. I have one on my current ATC machine, as its neccessary for setting tool lengths during toolchanges. I also installed 2 on my prior dual Z PRS. Although not mainstream, I consider a prox on the Z to very useful. Even when using a single bit, the prox allows resetting the Z position similar to that of the X & Y.

[Steamplates]

Sounds like the remainder of a Z Zero plate to me?

I thought about fitting my plate's wiring to earth out at the top of Z axis travel and avoid the problem of losing the Zero I just set. Bits of red tape won out though, up to now...See my Mod.s thread for more on this. Maybe I could just fit another proximity switch as Gary suggests.

The use of the Z Zero plate is something I need to sort out, but to be fair, it belongs on a seperate thread as opposed to hi-jacking this one!

Regards

Steve

[Chuck Keysor]

Thanks Gary and Steve for your replies to my question. Since I haven't even gotten my machine completely assembled yet, and know nothing about running it, I will have to get some experience under my belt before I can look at the uses for a third proximty switch. But at least I now have some possible reasons someone had this third proximity switch. Thanks again, Chuck