Important: Preheat both nozzles before starting print. Modified GCode doesn't wait for second nozzle to heat. Minor fixup of http://www.thingiverse.com/thing:24195 to dual extrude G1 commands with A|B feed commands, which seems to come out of the latest MakerWare. Original from http://www.thingiverse.com/thing:23792 I've also put this up on GitHub to show the diff's of what I modified from Joe's original: https://github.com/simon-clay/3dprinting-gcode-dualextruder-processorYou will need to compile this into an executable using Xcode, gcc or Visual Studio Express, I'm afraid the time is long past for downloading random .exe's from the internet and running them on your computer, so I am not providing built binaries here, please don't ask for them - sorry!