CNC Z-probe Touchplate

This is a small electric touch-plate for auto-probing the Z-height for a CNC machine. It's designed for the MPCNC with a common "Chinese" spindle. I think it should work on any hobby CNC, although the spindle-mounted electrode might need replacing with a clip.

It is designed to screw down (M6 holes at 10cm spacing) onto a CNC work-bed. It uses a small piece of plain copper PCB board from Maplin (35x40mm) as the touch-plate, and a 608 bearing with a wire soldered to it as the spindle contact. This spindle has an M8 smooth shaft protruding from the top, and the bearing fits perfectly.

The design is in three parts: the base, which is normally screwed down; the top, which pins the copper board in place; and the lid, which fits on top and holds the bearing. It's designed so that the lid sits on top of the copper touch-plate to prevent dirt and dust build-up (which might affect connectivity), and to make it impossible to use without attaching the spindle electrode.

Originally, the