Replaces a warehouse of spare parts.
Combination 3D scanner/lathes that can create and digitally store complex mechanical schematics and then reproduce them by machining plastics, and eventually, metal alloy stock. With the capability to assemble devices made of many different materials, it would be possible to use one device to duplicate different parts, like transmissions, pumps, valves, motors etc. Just what a spacecraft would need to allow it to make almost any necessary repairs while on a long mission.