1) Have you personally tried to put this idea to practice? If yes, for how long? Would you be willing to share some details? If no, why not? It doesn't take changing the entire society, you can do something like that literally now. Be creative, travel to a different random town twice a month and offer to clean toilets in a couple of buildings? Again, I don't mean to be snarky with this example, I just think working on 3D printers doesn't cut it as a type of difficult labor. Think more along the lines of going down into a mine, shoveling literal shit for 8 hours, etc.

2) Imagine, the society has actually changed such that everyone is supposed to do a couple days of difficult labor. What happens if someone refuses? A punishment? If there is no punishment, what happens if almost everyone refuses and there's not enough people to sustain this undesirable but critical jobs?