I am making my first foray into CNC machining with an old Amdek plotter and running GRBL on an Arduino Uno. So far everything works great and I can plot perfectly! The last bug is getting the plotter to go through the homing cycle. If I click the "Home Machine" on the Universal GCode sender, the plotter barely blips and just sits there. I suspect it is looking for the Z limit switch which I don't have and don't need. (I do a raise and lower pen with a solenoid). I have run the setup wizard and it does recognize the +/- X and +/- Y switches. Should I just put a jumper across the +/-Z pins on the control board (protoneer CNC shield) to fool GRBL? My switches are wired Normally Open.