Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, "Stefan Trethan" 
<stefan_trethan@g...> wrote:
> On Thu, 29 Sep 2005 17:37:32 +0200, Andrew Mawson <andrew@m...>  
> wrote:
> 
> >
> > Yep - I had to buy two of those drums - nearly £270 including
the
> > VAT ! But at least the workshop doesn't stink of paraffin and so
far
> > hasn't burnt down <G>
> > AWEM
> 
> 
> Would not water be sufficient for PCBs?
> 
> A ion exchanger would not be expensive. Rainwater would be even 
cheaper.
> 
> How do you maintain the expensive EDM fluid in working order?
> 
> ST

Stefan,

This is a 'Die Sinker' edm m/c - the fluid is constantly pumped
through 
two big cylindrical filters the size of lorry (truck?) air filters.

The true edm process (as opposed to spark ablation)controls the 
discharge very carefully to create the explosive expansion and
collapse 
to keep the discharge channel free of debris. This expansion and 
collapse is very much affected by the dielectric properties. I'm not 
saying deionised or distilled water won't work in your application as 
the conditions are very different. The depth of fluid is quite 
important as if too shallow the vaporised bits leave the surface and 
give a fog in the room. If deep enough they re-condense within the 
body of the fluid.

AWEM