well thanks for your interest on the EDM.
no i wasn't aware of any published books on the
idea use of EDM on clad boards., i got the idea back
when i use to service some machine shop equipment. there
they had 2 EDM's, one for rough cut and one for the fine
they would make carbit dyes use in various operations like
stamping out revits, nuts etc..
because the material is very hard it makes it difficult to
use common milling processes..
so what they did was make for example Hex brass stock and use that
for the quill (neg side) the stock material was placed in a holder at
the base of the tank and then the tank was filled with insolating oil.
after a short period of the brass probe inserting it self against the
stock material with regulated currents and servo's on the drive you
would have a nice near perfect hex hole of about 1 " in depth.
this unit simply used rectified DC at around 400 volts low current.
the second unit for the final was polishing used 400 cycles of
pulsed Dc on the probe. the unit had 4 banks of Push-Pull 3-400Z tubes
the whole theory is simply a plasma burn much like used today in
plasma cutters etc..
using the insolated oils it cuts down alot on the splatter and
i call it plasma, some simply call it electro discharge burn.
i maybe miss using the terms but i think i get my point accross.
any ways i use 1 stepper motors to drive the X scan in bidirection
scans to speed things up and the Y motor to move down the clad board.
the head is a retractable hard point tip that is pulled in via a
electromagnet to skip over the area's not required to be removed..
i use a current shunt circuit so that i know when the copper is
fully removed. if a short out takes place the tip is retracted and
when the area is complete the X scan moves to the next possition.
this works well because low side of the board is clamped into the table
for the current path.
i need to remove the pin now an then and clean it up for better edges..
my use of the blue dye actually works quite well too.
how ever that means i need to use etching.
Allan Adler wrote: