At the limit

Had a good old look at the limit and dead stop switches the other night. I need to figure out what's already in place and if it will do for my needs. I may need to reconfigure them or run some additional wires etc.

For the X and Y axes, each has a rather proper looking 4-position limit switch assembly from Omron. These contain 4 microswitches, each with NO and NC contacts. There are corresponding ramps fitted to the underside of the tables to operate them. They are screwed in place, so if necessary I could move the ones that are there or add some more of my own. They look almost IP68 in terms of sealing, although the cable entry is not sealed in this machine. So the Y axis switch was full of oil that had dribbled in from above. This was most likely (neat) cutting oil. It's handy that the previous owner never used water-miscible coolant otherwise the switch would have died long ago.

In fact, they have only connected up 2 of the switches in each module. One is a NC "dead stop" switch wired into the e-stop circuit that kills the drives if the table ever reaches that far. Both ramps operate the same switch, so it doesn't matter which direction it's going in, although of course the controller should know. The other is a "limit" or home switch and presumably signals that the controller shouldn't think of going any further - and for homing. Again, the limit ramps at each end share the same switch.

So I pretty much have what I need already. I also have the old chestnut to contend with - do I want my home switch right at the very end of travel? That would require a lengthy and possibly awkward move right to the end of X and Y travel each time I home the machine. On the other hand, if you switch the machine off when the table is "past" the home switch, it will end up hitting the dead stop switch without encountering the home switch.

The whole Z axis assembly is enclosed within the head anyway, so no need for any fancy IP68 industrial switches. There are 3 microswitches at the top of travel and one at the bottom. I assume the top ones comprise (from the top) dead stop, home/limit and tool change positions, while the bottom is dead stop. I probably only need 3 of them - dead stop at top and bottom and home switch near the top.