Do you have problems with filament ooze on your dual extruder prints? Perhaps this idea might help you. This page describes the adaptation of a Bukobot Duo (Original 2012 Version) by Deezmaker to have two x-carriages which can be driven independently instead of the normal single x-carriage with two extruders. The change allows you to park the inactive extruder and prevent it from oozing onto the print when the other extruder is active. In addition to improving dual-extruder printing, the firmware for this design has also been extended to allow you to print two copies of the same object at once (with the heads printing at an arbitrary position and temperature offset). This doubles your printer's output in this case. (see video below) [One other technique some people have used to overcome this problem is to cool the inactive extruder below the oozing temperature at every tool head change. However this massively increases the print time as the printer must wait for the extruder to reach operating temperature at each extruder change,] Short video of operation: http://youtu.be/BHHAHQsAeuA Demo of Duplication Mode: http://youtu.be/Mdj5iZ5B2Dg Tour of printer: http://youtu.be/jAfktjeuPZ4 Picture of original Bukobot Duo here: http://bukobot.com/_detail/buildrob-wiring.jpg The above awesome dragon print model is by tbuser (here: http://www.thingiverse.com/thing:29088 ). The Ocotpus print is by moleofproduction I've also added links to other 2 color models I've printed in the comments below.The original Bukobot Duo was actually made up of two single extruder carriages held together with a linking plate and so this modification is accomplished largely by removing the linkage plate, adding additional linear bearings, stepper motor, stepper driver, idler pulleys, synchronmesh cable, end-stop and modifying the X-ends. Full build instructions can be found here: http://bukobot.com/creating-a-dual-x-carriage-bukobot The Bukobot is a fantastic printer. This is not a design fault with the printer but rather a problem common to all dual extruder printers currently out there. By the way, the latest Bukobot Duo design from Bukobot now uses a combined x-carriage which cannot be split. You would likely need to ask Diego for longer X-axis beams, rods and synchromesh cable to fit two of the current X-carriage designs (but that is one of the design features of the Bukobots, i.e., that they can be easily expanded in any direction just by lengthing some rods, beams & cables). The Marlin firmware changes I made to support the Dual X-carriage mode are now integrated into the Marlin github baseline. See Configuration_adv.h.