>
> Hi Curt,
>
> After your previously posted details of your system, I carried out some
> more tests on pcb spark erosion. What became immediately clear was the
> requirement for an accurate wire feed for the electrode.
>
> I put together a mall stepper driven wire roller feed mechanism, using
> a gearbox and a butchered capstan mechanism from an old tape recorder,
> with fixed orifices above and below the vertical roller wire drive,
> thus giving the step in/out for the spark initiation. This worked using
> 10 mil wire, (smaller dia wires are more difficult to source easily in
> small quantities in the UK, if anyone knows better, please let me
> know), but the need for a more precision unit was needed, and other
> things intervened. I bought a micro lathe intending to put together a
> higher precision unit. A servo motor rather than a stepper may give a
> speed increase.
>
> The reason that I still intend to develop this system, is that direct
> printing is, as far as I can tell, still a bit of a black art, (and I
> never really got toner transfer to work reliably 100% of the time), the
> inks are expensive to import to the UK, you still need to etch, and you
> have to modify a printer anyway.
>
> PCB EDM can eliminate these costs at the expense of speed, whilst
> simultaneously using a mini cnc for drilling and etching.
>
> If the feed wire mechanism can be made to work at reasonable speed, I
> think that the next bottleneck would be the turn on/off times of the
> spark controlling mosfets. I thought that this could be overcome by
> using multiple spark generators sequentially fired, if necessary.
>
> Of course, the whole thing may be constrained by the speed of the cnc
> machine used, but then this whole approach is not really a problem when
> the machine could run in the background unattended. Speed is as
> Einstein pointed out relative anyway.
>
> I intend to do some more development this summer. Is anyone else
> interested in this approach, do you think?
>
> Good to hear you still have an interest in the method.
>
> Roger
>
>
>
>
>
>
> --- In Homebrew_PCBs@yahoogroups.com, "curt_rxr" <curt_rxr@> wrote:
> >
> > Hi all,
> >
> > When this list first started, I posted about my attempts to turn an HP
> > Deskjet into an EDM machine for PCBs, but I abandoned the project
> > after Stefan and others developed toner transfer into a reliable
> > system. The EDM was just too slow compared to TT. I've moved on to a
> > modified Xerox Phaser printer that puts wax directly on a thin sheets
> > of epoxy PCB and allows me to 'print' my board and etch it rapidly.
> >
> > I know that Graham and others kept up the work on EDM and I was
> > wondering if anyone on the list had made any breakthroughs? I still
> > think that there must be a way to reliably generate pulses fast enough
> > to create a PCB in a reasonable time, especially if a drill head was
> > incorporated to allow drilling and 'etching' with one setup.
> >
> > Curt
> >
>