Is anyone else interested in this kind of thing? Looking for community.
All the "self-replicators" I've come across are either digital (e.g. Conway's Game of Life) or like the ones in this video, that is they require specialized parts as their "food." You could say they are all "carnivores" in the sense that they consume other machines. My interest is in "herbivore" self-replicators, those that reproduce by consuming raw materials and energy from their environment.
I can't help thinking about how close a water-powered lumber mill feels to full closure (i.e. it produces all the parts it uses). Humans perform the chopping, move things from station to station, and assemble the finished parts into new buildings and machines.
Usually you require a few different material "paths" for replication. You have a hard material that can be softened with chemicals for example, so it can be shaped with machinery that is softer than the end product.