same switch for all 3 x axis requirements

[whitehedr]

If you use a series connection with the normally closed contact a switch that

fails open or a broken wire will cause the system to stop because it sees the
mill at a limit.  just a little bit of built in safety.

RWW

[spaceman]

After a day of diagnosing, from PC all the way to the switch.... it turns out I had a bad switch!

(paraphrasing) ARGH!

My next question about axis is this:
I hope to use Mach 3 for a 3D printer I'm making (Heated ABS plastic extrusion printing). But I'm stumped how to set up the Z axis home/limit.

For the printer to work, the head must be a very specific distance from the table for the first layer. As opposed to a milling maching, the print head will be stationary in the Z axis and the table will move up and down.  If the Mach 3 moves the table up to trip the switch during the Ref Home operation and then backs the table down until it is off the switch, during the first phase of Ref home (switch trip) the table will crash into the print heads.

Has someone out there already solved this?

My first edumacated guess would be to place a second thickness onto the first table with circular cut-outs of the print heads in the X-Y home position.  This would allow the dual thickness table to trip the switch, back off and be just the right distance for the first layer print. However, can I change the order of Ref Home axis in Mach 3.  I believe it does the Z first, which would defeat the whole idea.

[Hood]

Can you not just home the opposite way for Z and set up a Home Off value equal to the distance home is away from where you want machine zero to be?
As for your other question, yes just change the order in the RefAll button, do it from Operator menu then Edit Button Scripts, the Ref All will be flashing, Click on it and in the editor that opens put DoButton(24) to the end instead of the beginning.
Hood

[spaceman]

I'm confused then.  I thought Home Off was merely a 'DRO offset'.  As the Home switches are at 0,0,0 without Home Off.  the DRO would read the same.  If I set Home Off. to  5,5,5 the head doesn't actually move this distance, correct?  How would that help?

[Hood]

 You said if you homed the Z up it would hit the nozzle, so I said can you not home it the opposite way, ie reposition your switch so its at the other end of the axis. Then when you home you have a home off value set so the machine coords for that axis get set as you home off value.
Hood