We’ve been playing around with some of the developing dual extruder modifications, and it’s been AWESOME. We’re currently working on a redesign of 1013’s excellent dual extruder mount (https://forum.lulzbot.com/t/taz-dual-extruder-mod-files/142/1). Stay tuned for a drop in dual extruder kit for your printing pleasure.
Dual extrusion lets you do all kinds of neat things; two-tone parts are just the beginning. You can print with a secondary support material like HIPS that will dissolve away cleanly. You can mount extruders with different size nozzles; allowing you to print with ultra fine detail on the surface while gobbing the infill in at high speed with a second larger diameter noz. People have even printed rudimentary circuits with dual nozzle setups (blog.reprap.org/2012/04/some-more-printed-circuitry.html).
Here are a few images of our dual extruder R&D.
What will you use dual extrusion for?