Added Marlin-compatible zero cube script

Marlin_Work_Zero_Using_Cube

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+; This script enables the automation of zeroing out new bits to a workpiece using a conductive Zeroing Cube,
+; while also automatically measuring and accounting for bit radius.
+;
+; !! Intended for Marlin 2.xx users, but may work for other firmware with slight adjustments
+;
+; Link to (3D printable) Zeroing Cube used in this script: https://www.thingiverse.com/thing:4809964
+
+; Start with end mill roughly in center of cube, with bit slightly (~3mm-10mm) above cube surface.
+; Bit must extend BELOW the top of the zero cube walls (so it touches them on a lateral move)
+
+; Wait until the planner queue is empty
+%wait
+
+; Set user-defined variables
+; !! All measurements are in mm (not in Luddite units, you savages)
+%WIDEST_BIT_YOU_OWN = 20        ; Diameter of the widest bit you'll ever use with this script
+%ZERO_CUBE_HEIGHT = 8	          ; Height of main section of Zero Cube
+%ZERO_CUBE_WALL_HEIGHT = 12	    ; How high the XY wall section extends above %ZERO_CUBE_HEIGHT (ie: NOT the total height)
+%ZERO_CUBE_WALL_THICKNESS = 5	  ; How wide (laterally thick) are the XY wall sections which extend above %ZERO_CUBE_HEIGHT
+%PROBE_XY_DISTANCE = 40         ; Max distance for a probe motion (script will fail if bit further from wall than this)
+%PROBE_FEEDRATE_FAST = 200      ; mm/min
+%PROBE_FEEDRATE_SLOW = 100      ; mm/min
+%PROBE_RETRACT = 20             ; Distance of retract before probing next axis
+%Z_FINAL = 10	                  ; Desired height of bit above ZERO_CUBE_WALL_HEIGHT after probing is finished
+
+
+%UNITS=modal.units
+%DISTANCE=modal.distance
+
+
+G91     ; Relative positioning
+G21     ; Use millimeters
+G54     ; Switch to Work Coordinate Set 1 (as opposed to Machine Coords, which should not be altered after homing)
+
+; Make sure initial coordinates remain positive for easier math
+G92 X[PROBE_XY_DISTANCE * 2 + ZERO_CUBE_WALL_THICKNESS] Y[PROBE_XY_DISTANCE * 2 + ZERO_CUBE_WALL_THICKNESS] Z[ZERO_CUBE_WALL_HEIGHT]
+
+; Probe Z
+G38.2 Z-[ZERO_CUBE_WALL_HEIGHT] F[PROBE_FEEDRATE_FAST]
+G0 Z2 ; Retract 2mm
+G38.2 Z-4 F[PROBE_FEEDRATE_SLOW] ; Slow Probe
+G92 Z[ZERO_CUBE_HEIGHT]
+G0 Z3	; Raise Z
+; A dwell time of one second to make sure the planner queue is empty
+G4 P1
+
+; Probe X to find side of bit
+G38.2 X-[PROBE_XY_DISTANCE] F[PROBE_FEEDRATE_FAST]
+G0 X2 ; Retract 2mm
+G38.2 X-4 F[PROBE_FEEDRATE_SLOW] ; Slow Probe
+%X_LEFT = posx
+G0 Z[ZERO_CUBE_WALL_HEIGHT]	; Retract Z above wall
+G0 X-[WIDEST_BIT_YOU_OWN + ZERO_CUBE_WALL_THICKNESS + 10]	; Move to other side of wall
+G0 -Z[ZERO_CUBE_WALL_HEIGHT]	; Drop Z below wall
+
+; Probe X to find other side of bit
+G38.2 X[PROBE_XY_DISTANCE] F[PROBE_FEEDRATE_FAST]
+G0 X-2 ; Retract 2mm
+G38.2 X4 F[PROBE_FEEDRATE_SLOW] ; Slow Probe
+%X_RIGHT = posx
+%X_DIFFERENCE = X_LEFT - X_RIGHT + ZERO_CUBE_WALL_THICKNESS
+G0 Z[ZERO_CUBE_WALL_HEIGHT]	; Retract Z above wall
+G0 X[X_DIFFERENCE / 2] ; Move to where the center of the bit is at zero (the right edge of the left wall)
+G92 X0
+G0 X[WIDEST_BIT_YOU_OWN] ; Position X for Y probing
+G0 -Z[ZERO_CUBE_WALL_HEIGHT]	; Drop Z below wall
+
+; A dwell time of one second to make sure the planner queue is empty
+G4 P1
+
+; Probe Y to find side of bit
+G38.2 Y-[PROBE_XY_DISTANCE] F[PROBE_FEEDRATE_FAST]
+G0 Y2 ; Retract 2mm
+G38.2 Y-4 F[PROBE_FEEDRATE_SLOW] ; Slow Probe
+%Y_TOP = posy
+G0 Z[ZERO_CUBE_WALL_HEIGHT]	; Retract Z above wall
+G0 Y-[WIDEST_BIT_YOU_OWN + ZERO_CUBE_WALL_THICKNESS + 10]	; Move to other side of wall
+G0 -Z[ZERO_CUBE_WALL_HEIGHT]	; Drop Z below wall
+
+; Probe Y to find other side of bit
+G38.2 Y[PROBE_XY_DISTANCE] F[PROBE_FEEDRATE_FAST]
+G0 Y-2 ; Retract 2mm
+G38.2 Y4 F[PROBE_FEEDRATE_SLOW] ; Slow Probe
+%Y_BOTTOM = posy
+%Y_DIFFERENCE = Y_TOP - Y_BOTTOM + ZERO_CUBE_WALL_THICKNESS
+G0 Z[ZERO_CUBE_WALL_HEIGHT]	; Retract Z above wall
+G0 Y[Y_DIFFERENCE / 2] ; Move to where the center of the bit is at zero (the top edge of the lower wall)
+G92 Y0
+
+; Place bit center at final X0 Y0
+G90	; Absolute positioning
+G0 X0 Y0 Z[ZERO_CUBE_HEIGHT + ZERO_CUBE_WALL_HEIGHT + Z_FINAL]
+
+; A dwell time of one second to make sure the planner queue is empty
+G4 P1
+
+[UNITS] [DISTANCE] ; Restore unit and distance modal state
+
+; All finished and ready to carve!