Most complex machines are assembled from parts, which are themselves assembled from other parts, often several levels deep until you get to the individual component made of one type of material. All these sub-units are composed of several different types of material, glass, rubber, plastic, fabric, metals, etc. Its like organic beings, who follow a similar hierarchy: solvent, protein, organelle, cell, tissue, organ, system, organism. I can't see how any one machine could handle all of these levels.

Of course, the printer would not make the whole product at once, it would be used to make the individual parts, which would then be assembled by hand or by robot on a conventional assembly line.

Still, the economy of printer assembly would tempt engineers to design machines so they could be easily and cheaply printed, rather than emphasize safety, performance, durability, or other characteristics. Can you imagine a part like a water pump or alternator designed so it could be manufactured out of a minimum of printable materials, instead of choosing the optimum material for each component and application?

I think this is a great idea, but its going to have to be monitored. This won't be like the transition from hand assembly to assembly line mass production. It takes the opportunity to cut corners a lot further down into the structure.