15m Industrial Plasma Cutter

Every machine will be different depending on how you lay it out. My limit switches are within 2-3mm of the hard endstops.

A good length might be 1600mm rail with a 1400mm rack. On my Y axis, this gave me 1264mm of travel but my carriages are further apart there than on my X.

I have never even seen a plasma cutter, so take this idea as purely theoretical.

But I think this could make a good floating mount:
uk.rs-online.com/web/p/slide-unit-actuators/1244615/
The idea being that after the probe the air pressure can be increased to lock the head down to avoid false-tripping by vibration.

we use a SBR free float system to get Touch off and safe
i added the FC file

There are definitely cheaper ways than the pneumatic cylinder. I only really proposed that as an off-the-shelf unit to save time.
The cylinders also have provision for mounting solid state switches in a range of styles and types: uk.rs-online.com/web/c/?sra=oss&r=t&searchTerm=D-M9

Ok, I am thinking of using a Nema 23 for my z axis, as used in this design.

www.veloxcncrouters.com/xz-za-series

Does LinuxCNC and 7i67E interface well with hybrid steppers? Do you guys using steppers have rotary encoders?

Yes. I think normally, the closed loop steppers are closed on the stepper driver so Mesa and Linuxcnc don't care. Wait for others to respond because I think feedback can be closed in Linuxcnc but it may not be worth the complexity.

Nema 23 is fine. I use 269 Oz/in Nema23 on mine