Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Bengt" <tecnoconsult@t...> wrote:
> 
> Hi Curt,
> Do you have more detailed info on EDM how it is done and with *home* 
> built gear, I am interested in learning how to build and use EDM for 
> PCB. Happy to receive info offline if not on list.
> Bengt

Hi Bengt,

Basically I used a modified HP Deskjet 500 to "print" my artwork onto
the board.  My thinking was that I could easily transfer any image
that could be scanned or generated by any Windoze program.  I mounted
a plastic tray in place of the paper magazine into which the board was
placed and covered with distilled water.  The tool was the carbide
point from a hand scriber which was carried in place of the ink
cartridge.  The tray was supported by ball bearings in vee groves such
that the friction wheels moved it instead of the paper.  ( This worked
better than I thought it might needing only to aligned properly during
setup and then kept CLEAN. )  I used a lower power version of the
sparker outlined at:  

http://cscott.net/Projects/FabClass/final/edsign1.html


  And it worked as far as it went, since I could use PCL commands to
control everything, but.....   ( you knew there was a but! ) It is
very slow.  It takes seven hours to do a single side, 4 inch by eight
inch board.  The problem is that for good resolution you are stuck
with a very small spot which is also the increment you move the head
between sparks.  

All in all it's not ready for prime time, since you can use TT and
CuCl etch and have a finished board in a fraction of the time it takes
to EDM one.  

What might be a useful line of investigation would be to convert a
plotter.  That way you could control line width by choosing a
different "pen" ( electrode ) instead of making multiple passes.  Also
vector graphics should allow for speedier positioning.

If there is interest I'll take some photographs of the beast and work
my notes into readable form after the holidays.

Merry Christmas one and all

Curt