I have been researching the new 3D printers for quite some time. To be able to print out the object (a tank tread or sprocket) and cast it in a simple and (relatively inexpensive*) cost effective alloy with nominal machining would be incredible.
Take a look at this link. It describes with video the complete process and outcome.
http://3dtopo.com/lostPLA/
Thanks for looking.
tjs
PS: 3D printers are now in the $500 to $600 price range with full licensing rights.