--- In
Homebrew_PCBs@yahoogroups.com, roger lucas <ralucas4277@...> wr
wrote:
Well done Roger!
> One significant problem has emerged which Curt
> Richards did not address, (or if he did, he did not
> mention it). The wire electrode erosion is
> significant, and will require an active Z axis
> correction to maintain as consistent a spark gap
> distance as possible between the electrode and pcb
> surface.
Roger I used brass wire and distilled water and had arranged the servo
circuit to feed the wire via a pinch roller and worm screw drive. the
servo circuit is as per the NASA / Garden of EDM circuit.
>
> Curt controlled his spark discharge voltage by
> dynamically adjusting the electrode gap on the fly. I
> think that for pcb work this is not the correct
> approach because of the wire erosion problem, since
> one needs to KNOW the gap distance AND available
> discharge energy BEFORE discharge, which is why I am
> going for the touch down zeroing method, (slower but
> speed is not significant at the moment).
Roger the gap breakdown voltage controls the gap via the servo. As
the electrode ( brass wire ) advances the gap closes until the spark
after which the electrode retracts so the system is ready for he next
spark.
> The discharge
> energy will be set by presetting the voltage level
> required and capacitor selection, (simple comparator
> control integrated into the spark control). I think
> this is the secret of successful pcb edm'ing.
>
> This is really looking as if direct raw copper board
> to finished pcb is going to be possible.
>
> Roger
>
Hi Roger,
I'm glad to see someone making progress. My system is stalled at a
pulse repetition rate of 200,000 per second using IGBTs designed for
auto igniton system. That rate gives me about an hour and a quarter
pocessing time for an 8 inch by 12 inch PCB using .001 inch brass wire
as an electrode. It makes a real nice board, but I can use Toner
Transfer and CuCl2 bubble etching to make five boards in the same time!
I'll be interested in your advances to the art, but right now it looks
to me like the direct print inkjet system will replace TT and EDM for
homebrew PCB prototyping.
Curt Richards