James Cox (Chris & Joan's son) had some 3D printed line spools for sale at our last contest, and I was gifted a couple of them by Tim Just. I thought the design and detail was pretty interesting with all the small holes being hexagonal...why? Probably because he could?
Anyway, James had two sizes, matching the size of (big) Brodak and (small) Pylon/SIG spools. It turns out that some guys hate the small spools, and I am a fan of the small spools, and don't care for the large spools. But we all have our reasons. I am attaching a picture of one of the small spools. They are made in two pieces, and it has occurred to me that perhaps a coil spring could be sandwiched between the two halves to make them self-tightening. Otherwise, I guess it might be desireable to glue the two halves together, though it doesn't seem like they'll come apart.
IMO, a 3D printer could be useful, but it also seems like another hobby, and I don't need another hobby!

Steve