Self-replication has always been a pipe dream of futurists and technologists. Why should we have to waste time and resources making new parts for a broken down machine when the machine can just make the replacement parts itself? It's not exactly feasible in most industries as of yet, but it is entirely possible in the 3D printing industry.
Objet recently showed off how its researchers experiment with minor design changes to its 3D printers. The team will create multiple "ABS-like parts that are drilled, assembled and then used as short run end-parts in an Objet Desktop 3D printer to test a new design tweak."
For printers from a professional design 3D printer company like Objet, 3D printed parts can only do so much. The smaller companies like MakerBot, however, have already created 3D printers that can make be made almost entirely by another 3D printer. There are other "indie" 3D printers that have found success on Kickstarter based on the promise of an open source design that can be created by other 3D printers.
All that being said, it probably won't be long before industrial 3D printers can replace their own parts. We might even be able to upgrade older printers with newer 3D printed parts in the near future. The constantly evolving nature of 3D printing technology makes everyday an adventure in innovation.