I don't think you're arguing against what I actually said. I said in 20 years it might be possible to replicate a printer using nothing but raw materials and a lot of work, but it wouldn't make sense economically. That's very different than saying you'll be able to print all the parts you need in one go, or that you would want to, which obviously isn't viable without molecular-level assembly. That's a holy grail in the distant future. But making PCBs is already possible without specialized equipment, metal sintering gets you pretty far on components needed for things like steppers and threaded rods, etc. If you follow the research being done (ex. [1,2]) it's pretty clear that the boundaries of what's currently possible are being pushed in interesting directions.
To me the biggest hurdle is the electronics, which currently do require special tooling to even produce basic components. You're probably right that we're more than 20 years from self-replication ability (again, not practicality), but I'd be surprised if it's more than 50 years out.
To me the biggest hurdle is the electronics, which currently do require special tooling to even produce basic components. You're probably right that we're more than 20 years from self-replication ability (again, not practicality), but I'd be surprised if it's more than 50 years out.
[1] https://arc.aiaa.org/doi/abs/10.2514/1.A33409 [2] https://3dprintingindustry.com/research/