Note: Installing homing and limit switches will slightly reduce the overall maximum travel of your machine (Roughly by 12mm per axis for every installed switch – thus a homing and limit switch on the x-axis will reduce total machine travel by ~24mm on the x-axis). While it is common to install a homing and limit switches on all three axis, many 3018 users do not install (or remove) the limit switch on the Z axis as the machine is already somewhat “Z-travel Challenged”.
This included switch is delivered with Ground (black) and Signal (white) wired normally closed (NC). Some machines are delivered with normally open (NO) switches which are far more susceptible to signal noise and false triggers than a machine wired with a NC switch arrangement. NC works better as the ground reference of the board and DC power supply are used to sink any electrical noise that the limit switch wires may pickup.
When using a NC switch with homing enabled on your grbl based machine, you’ll need to set $5=1 in your grbl settings, to invert the limit lines for homing.