Jonathan designed a great printed circuit board router, he writes – “Printed circuit boards are usually manufactured by chemical etching (with iron (III) chloride or ammonium persulfate, for example). This is not very practical if only a few boards are necessary, because these etchants are messy and somewhat dangerous. PCBs can also be manufactured by “mechanical etching,” in which a trace is “etched” by milling away the copper along its perimeter. This requires software to generate a toolpath from the layout and a small CNC mill or router. Lots of companies make routers for PCB fabrication, but they are unjustifiably expensive so I decided to build one.” Link.