Archive of the former Yahoo!Groups mailing list: Homebrew PCBs

--- Andrew Mawson <andrew@...> wrote:



I'm a 'Johnny come lately' both on this board and on
this thread so
I've probably missed something vital but something
puzzles me about
this process:

Presumably the 3 thou brass wire is one electrode of
the discharge,
and the copper board target forms the other. This
being the case, as
the cut progresses to the point where one section of
copper is
totally isolated the cut will cease. The implication
being that the
motion driving software (presumably G code?) must have
knowledge of
this limitation and forward plan accordingly. I assume
then that this
rules out off the shelf packages intended for
isolation milling like
PlatinCNC ( http://www.platincnc.com/ )

I'm currently using PlatinCNC on my Bridgeport
Interact 1 CNC mill
but really only for hole drilling as it's quicker to
etch the boards
than mill them as I have the luxuary of a set of Mega
tanks set up.

The concept of EDM'ing a board is attractive - I have
an EDM
diesinking machine in my workshop so am familiar with
the process. A
big contributor to the speed of the process is the
operating fluid
used, as each micro discharge vaporises the fluid
carrying away the
metal fragments into the bulk of the liquid, and as
the vapour
condenses the rush back of liquid into the void
ensures fresh
dielectric. I'm using "Ionoplus" from Oel-Held (
http://www.oel-
held.de/ )which unlike paraffin based conventional
ones isn't
inflamable and doesn't stink - it also has the side
benefit of being
a lurid fluorescent green which entertains visitors
<G>

AWEM



Andrew,

The pcb must be edm'ed in a raster fashion, ie
consecutive passes with the electrode so that the
electrode always approaches fresh copper, analagous to
the old dot matrix printers.

However, I have no knowledge of an off the shelf
package to convert pcb layout to raster scan format.
At the moment I am converting to bitmap and cobbling
from there. The resulting file needs to be edited for
spark on/off to pass over copper that has to remain.
Maybe someone can help here, by suggesting a better
process!

For further enlightenment see the following messages
on the Homebrew_PCB forum,

9593, 9594, 9602, 9604, 9614, 9805, 10006, 10024,
10096,

I am interested in the dielectric fluid you mention,
and will try to obtain some for trials.

Roger



Be sure to visit the group home and check for new
Links, Files, and Photos:
http://groups.yahoo.com/group/Homebrew_PCBs

If Files or Photos are running short of space, post
them here:
http://groups.yahoo.com/group/Homebrew_PCBs_Archives/



---------------------------------
YAHOO! GROUPS LINKS


Visit your group "Homebrew_PCBs" on the web.

To unsubscribe from this group, send an email to:
Homebrew_PCBs-unsubscribe@yahoogroups.com

Your use of Yahoo! Groups is subject to the Yahoo!
Terms of Service.


---------------------------------






___________________________________________________________
To help you stay safe and secure online, we've developed the all new Yahoo! Security Centre. http://uk.security.yahoo.com