This thing is a complete carriage assembly for the Replicator 2X (should also fit the Replicator 2 and possibly clone machines like the Creator, Duplicator, etc but this is untested).

My company has a Replicator 2 and a 2X. The 2X never worked very well due to constant nozzle jams/clogs and the lack of a nozzle area cooling fan for PLA. I designed this assembly from scratch to mount a J-head style hotend on the machine. It integrates a blower so you can print materials that need cooling (like PLA) as well as those that do not (ABS). I’ve kept the factory spring-loaded drive block assembly, since it works pretty well.

This carriage spaces the nozzle tip at the right height to use a glass plate on top of the 2X's heated platform, or skip the glass and print right on the plate. The leveling screws have enough travel to make this possible. I clamp the glass in place with binder clips right now, which isn’t the best since the clips can get in the way of the printed parts if you’re not careful with your layout. However, this makes removing your prints very easy. Just pop the glass plate in the freezer and the parts fall off within a few minutes. I plan on installing the Bottleworks aluminum arms and removable glass plate when budget allows.

I've provided Solidworks files of the entire assembly, as well as STL files. All you need to print are 4 parts: the carriage, the belt clamp, the hotend clamp bar, and the blower nozzle elbow. There are three versions of the carriage STL, two have a manually created brim and one is the original file. Use whichever one prints best on your machine, the geometry is the same on all three. The small parts probably need a raft or a brim as well.

I sized all the holes for a regular M3 or 4-40 screw to thread right into. I ream the holes with a .995 inch drill bit and the M3 screws cut their own threads on the first assembly (just be gentle). There isn't enough space for the OEM cooling fan/duct that comes with these hotends, so toss it aside and use the NMB fan listed below, which bolts right to the carriage.

The original bronze bushings snap-fit right into the carriage. LM8SUU linear bearings should also fit.

Digikey part numbers:

Cooling fan: P15610-ND NMB 40mmx15mm 24v axial fan, 6000 RPM
Connectors: 455-2266-ND Fan Connector Housing (female)
455-2879-ND Fan Connector Housing (male/header)
455-2261-1-ND Fan connector terminals
Blower fan: 1570-1034-ND Blower fan, Radial, 15x50mm, 24v

McMaster-Carr p/n 91290A171 is a nice bag of ten 30mm M3 socket head cap screws. These are the perfect length for securing the stepper motor to this assembly, and shortening a few more allows mounting of the two fans with no problem. Shorten two more and use them for the belt clamp.

Some notes & caveats:

Credit to DepthDesign3D ( http://www.thingiverse.com/DepthDesign3D/about ) who designed a carriage for a Creator Pro, which is very similar but not exactly the same as the Rep2X. I printed their carriage and was able to then make several manual changes (shims, spacers, cutting, etc) to make it work on my 2X machine. I adapted a blower into the assembly as well. The print capabilities were fantastic, no jams and really good quality prints. I wanted to take what I learned and go one step further with an all-new design specifically for the Replicator 2X.

Be aware there is a bit of additional work required to adapt a 12v hotend to the 24v machine, unless you buy the 24v specific version of the hotend. The one I bought was the [3D CAM] brand, a $20 knock-off of the E3D design, and only came in a 12v configuration. (E3D offers both 12v and 24v configurations of their V6 hotend) I had to ream the heater bore to .250", for the slightly larger Makerbot 24v heater. The 12v cooling fan goes away with my new carriage design so don't worry about that. I also added the wiring required for the nozzle blower. The blower output already exists on the Mightyboard, you just have to tap into it. If you want more info on the electrical adaptations, let me know in the comments.

I don't know how closely the knock-off hotend and the real E3D v6 will match in terms of exact feature sizes. I'm assuming they are probably the same but there could be some differences. If somebody has a genuine E3D V6 on hand and wants to test the fit, please do so and let me know the results.

With my carriage installed, you can safely generate your x3g files for a Rep2 and the 2X will behave itself with no issues (issues like slamming the carriage into the endstop, etc). 2X profiles will work also. Just remember the 2X build plate is a little smaller than the Rep2.