Firmware for the Arduino https://github.com/robottini/grbl-servo Make sure to edit the your "config.h" in the /Arduino/libraries/grbl folder to enable CoreXY. Instructions for compiling the grbl firmware https://github.com/grbl/grbl/wiki/Compiling-Grbl Use Gcode command M03 S90 to lower the pen; Use Gcode command M5 to raise the pen. NOTE: This design will also work an Arduino MEGA and RAMPS 1.4 or any other CNC/3D printer controller that supports CoreXY and servos.