Doing Filament Change Command (M600) using limit switches

[Roxy]

My ramps had no pins so I had to add them for the ABL but what a PITA getting all of those wires back on for the motors etc... I never added the ones that didn't have anything to do with the servo. Every time I take that off I always end up missing a wire when I put it back together.

Every picture of RAMPS boards I've seen have lots of GPIO pins sticking up to put other boards on. If you don't have dual extruders, I would think there should be extra GPIO pins on the Arduino board that would handle that if it was plugged in. In that case, you just plug a wire like here and run it to a switch:

http://www.ebay.com/itm/10pcs-Female...item4d1baa25fc

Why do I need to wire something else up to get M600 to work?

Because the Arduino can't read your mind and know when the filament change is completed. It needs you to tell it that everything is done and it can continue. If you wanted to be really lame, you could look at one of your limit switches for one of the axis instead of a new switch. But connecting up a switch is really pretty simple and a better way to go.