Those guys at Metrix Create:Space think big. Really big. This time their experiment is to create the "Big Robot", a rather large HDPE-extruding 3D printer.
They're not building it from scratch, but rather they've adapted an ancient DynaCNC 1000 router table by replacing the cutter with an enormous RepRap-style extruder. This massive extruder is based on a 1 foot length of steel pipe, with heater cord wrapped around it. This thing is so big it takes an hour to warm up to HDPE operating temps!
The massive extruder is fed scraps of pre-shredded HDPE (from milk jugs, no less) by a one-horsepower auger, and it extrudes melted plastic through its 6mm nozzle at one cm per second.
The Big Robot is still an experiment, and we're not sure if this concept will ever make it into commercial space. But it is interesting. And big.