It makes the most sense for the OEMs to print the spare parts themselves. Because OEMs are the owners of the design of the actual parts and have complete technical specifications of the parts. They know exactly, from a technical standpoint, what can be or can’t be done and can qualify the parts as OEMs.
OEMs also have the resources (human and capital) to be able to do it. They are also the unique point of convergence for the parts demand and therefore they consolidate volumes and can better invest in the shift from traditional to additive manufacturing. For that reason, they can select the right part for 3D printing from a business standpoint and build-up viable business cases to apply the technology.
However, the problems starts here!