Technology is changing faster than we ever thought possible. Who said we couldn’t fax a part to someone. Or print it on his dorm room printer.
Some technologies completely change the operations game. It’s not like the concept is new. When I lived on the farm, there was a local blacksmith (the real thing!) who made parts out of iron for old tractors and farm machinery. That wasn’t too many years ago. In developing countries, people make parts for cars all the time, but not usually gears and the like.
There’s also a very nice article in Technology Review (from MIT) about how the 3-D printers actually work. Actually a series of articles.
Also see my post on the subject. Again from the Operations Room.