Your idea is interesting.
I use to service gestetner products in my hay-days. They had a machine which used a 24 inch long rotating aluminum drum. A paper copy on the left side was read by a photomultiplier/microscope assembly and the signal was used to drive a high freq power osc. This signal went to a tiny stylus (think it was tungsten) in contact with a stencil. The sparks burned holes through the stencil to make an image silkscreen for a duplicator ( a thingy with 2 4inch rollers that squeezed ink through the stencil and onto the paper)for the youngsters. Sparks (high frequency only) actually do a nice job but
the mechanics to do this on a flat pwb I think isn't worth the effort considering the cheap imaging devices that can be hacked to do the same.
--- In Homebrew_PCBs@yahoogroups.com, "Jeff" <jeff.heiss@...> wrote:
>
> I have an idea for making boards using Electrical Discharge Machining (EDM) that I would like to bounce off you guys.
>
> The idea is to use a needle on a CNC x-y table (picture pen plotter with the pen replaced with the needle). The needle hovers just above the copper board a few thousandths, maybe .003" .006". Paint the copper with automotive spray paint. Apply a high-voltage/high-current to the needle and ground the board. The spark between the needle and copper will burn and evaporate away the paint. The board could be submerged in oil or some dielectric to keep oxygen out. The artwork drawn would be like that of a milled board where the copper around the traces is removed or all copper could be removed with multiple back and forth scans over the whole board.
>
> What do you guys think? Would acceptable trace spacing and widths be achievable?
>