First post on here...
I've built a "plug-and-play" belt-driven 3mm dual extruder that uses pretty standard Greg's parts, adapts onto the i3v X carriage, and plugs directly into the RAMPS 1.4 without any extra mods. Been printing at normal speeds for the makerfarm i3v without an issue. Figured out all of the necessary changes to the firmware thanks to this forum and others. Here's a video from early on in the testing:



Nozzle offset is ~33mm, so not much taken away from the build envelope. The dual hexagons run great with the right slic3r settings to cut down on the ooze (not the ooze prevention settings, but the retraction settings when tool is disabled).

All in all, I'm really happy with having dual extrusion on the 8" i3v that can use 3mm filament and that has plenty of torque on the hobbed bolts to keep the speed up. More pics to come soon.
Photo Oct 04, 8 01 04 PM.jpgPhoto Sep 30, 6 51 12 PM.jpgPhoto Oct 04, 8 03 36 PM.jpg