I finished this design several months ago but never got around to posting the results. Having used Chase Wichert's brilliant Dual Titan carriage for a couple years I felt I could see how to improve it slightly. My goals were pretty simple: Capable of accessing the entire 300x200 build area with both nozzles Modular carriage and extruders. Everything connectorized and easy to take apart Better cooling than the original Dual Titan carriage. This drove me to use a Titan and a Mirrored Titan Easier belt installation, tensioning, and removal without damaging the belts Improved wire routing The picture above shows how the fan wires disappear into the X-carriage. All X-Carriage utility wiring (end stop switch, part cooling fan, and infrared Z-sensor) is routed through internal conduits in the printed carriage. They exit through the top center of the carriage and terminate in a connectorized central yoke or tower. The next photo with the extruder sleds removed show the fan wires disappearing and reappearing at the yoke. Looking at it from the left side you can see the limit switch wiring going into the internal conduit. From the back you can see the Z-sensor cabling going into another internal cable path. The extruder sleds are very similar to Chase' original but with Molex Microfit 3.0 connectors and of course the left and right are mirror images. One thing I'm particularly proud of is the X-belt tensioner. It uses a sort of screw driven rack that can capture the end of the belts and drag it to tension the system. The tricky part is the tiny printed part that grabs the belt. It's shown below on top of USA penny to show scale. The X-motor mount and X-idler (Y-carriages) were both redesigned to maximize clearances so the entire 300 mm wide build area was available to both extruders. So that's my version of the dual direct BigBox carriages.