This is a video of my Makerbot printing a 15mm cube.
It take 3 try before it realy start (first 2, the extrusion stoped at the begining).
Ok, I had a problem with the raft but that dosen't change the way it works.
When carefully looking the process, I see that it pass 2 times at the same place before changing the Z.
Also, as you can see, it stop in the corner, stop the motor, restart it with a big splash of ABS before continuing the printing....