Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, roger lucas <ralucas4277@y...> 
wrote:
>>snip<<

 
> My own experiments had showed that circuit board
> copper ablation was definitely possible, and Carl has
> confirmed this. I personally think the success of this
> project is in controlling the wire drive, for which I
> have already constructed a miniature geared drive,
> which will track the set peak discharge voltage.
> 
> You are welcome to my schematic in a few days on the
> basis that it is purely experimental, but it would be
> nice to collaborate with someone who also has a desire
> to see trhis thing cutting track. I will attach the
> pic asm code when i have got it working. Do you do
> PIC's?
> 
> Both the IPS5451 and the IPS5751 are listed by Farnell
> UK as high side drivers, and the 5751 seems quite
> suitable. 
> 
> I really want this m/c to be sitting on the bench
> turning out PCB's ready for roller tinning while I do
> other useful things.
> 
> Roger
>

Roger,

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