Homebrew PCBs

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
>