We are currently developing a highly unusual 3D printing system built around industrial robot arms, one of which holds the build tray while the other holds the material extruder. The system uses the Fused Filament Fabrication approach (like most desktop 3D printers), in which a thermoplastic material is melted and extruded from a small nozzle. In contrast to a normal printer which has 3 degrees of freedom, this system has 12 degrees of freedom, which brings a number of potentially significant advantages. Firstly, it means that different parts of an object can be printed in different orientations, largely eliminating the need for support material underneath overhangs. Secondly, it allows us to print with curved layers conforming to the shape of load-bearing structures. Most significantly, it makes it possible to print material onto and around pre-existing components, typically unprintable things like sensors, actuators, batteries and circuit boards. Ultimately we aim to create a system that can print fully-functional robots that require no further assembly. The approach could also allow parts to be printed in and around larger structures, possibly for purposes such as temporary repairs.