Only because I wondered what the first standard should be for fully printing 3D printers and other cool stuff and looked up “earliest microprocessor”.
Intel 4004: Min. feature size 10 µm
N2 FF 3D Printer, Up to 10 micron Z resolution and 12.5 micron X/Y step size.
Since it only produces plastic we can at least make a prototype that’s up to scale.