Makerbot Operational!
First test print with the Makerbot Cupcake - still need to rig up a heated platform for full production cycle
UPDATE #1
The Makerbot has been modified with a heater bed, which prevents the "raft" from peeling off the base mid way through a build. The following video shows a project near completion.
http://youtu.be/oYlca2Pq5rM
I recycled the heating coil of an old automatic drip coffee maker, and placed beneath a 1/4 inch 4" x 4" aluminium plate. The resistance heater coil wire is about 20 Ohms, which pulls about 6 amps out of the 120 Volt wall socket (producing approximately 700 Watts). A bi-metallic thermostat shut off interrupts the circuit after approximately 30 seconds, and kicks back on when the plate cools below a certain threshold (my coffee at home stays warmed to about 140 F). It turns out that direct contact with the hot plate and the aluminium bed is way too hot to handle (more than 140 degrees!), so I introduced an 1/8" air gap with 3 small bolts sandwiched in between the hot plate and the aluminium.
Note the blue painters tape forming the grip surface for the extruded plastic. The plate now is hot to the touch, but not so much as to burn the skin. Other blog posts recommend much higher temps (almost as much as the melting temperature of the plastic, 120 C!), but this does not appear to be warranted with the "java" configuration introduced here.