The first RepRap we built using the standard Prusa I3 design with a Wades extruder. In true RepRap fashion the majority of the parts were 3D printed from another RepRap. The X and Y axis are belt driven and the Z axis are driven by a threaded rod.
The MadCat II is the second RepRap which was built with a custom design and used primarily aluminum for it's structure. Not old is the MadCat a 3D Printer but can also be converted to a CNC machine using a interchangable extruder/drill bracket.