This idea is based on Gav's Z-Probe, but this version is mounted outside of the build area and does not require running the axis so far past the point where it would normally collide with the platform. Instead of icky glue and scrap acrylic, it uses a smaller board-mount microswitch mounted to the z-guide screws with a bit of perf board and some left-over standoffs. This version makes it possible to home all three axes without X/Y endstops (though they are recommended, and it makes terrible noises without them).Here's my homing gcode:( 3-axis homing with a z probe on the back-right leadscrew nut ) G91 (relative Positioning) G0 Z10 (raise Z stage to clear the switch) G0 X0 Y150 (move Y axis to the back) G0 X150 Y0 (move X axis to the far right) G0 Z-50 (lower Z until hits limit) G92 Z0 (Set current point as Z-origin) G0 Z6.5 (raise Z to clear screws) G0 X-66.5 Y-50 (move build platform to middle of table, use X-63.5 with ABP) G0 Z-10 (touch the table) G92 X0 Y0 Z0 (Set current point as origin) G90 (switch back to absolute positioning) ( Honey! I'm home! )