UPDATED - new source file that guarantees no over-hang issues (by cutting off the top section and joining it to the H-carriage so the print is still only three parts.

My own model of the MakerBot Replicator 5th Generation. The smart extruder and carriage are separate pieces, Simply glue the smart extrude to the flat side of the carriage and slot the carriage on the top of the main body. I don't own a MakerBot and therefore not tested the print. Apologies for any inaccuracys of the model as I made it by eye.

Google SketchUp with 'solid inspecor' and 'STL exporter' plugin.