Thats what I thought, no motors no pumps everything nicely contained in the box, just a source of compressed air from the outside going into the box.
But I am not sure if enough etchant can be moved with this method, too much air pressure or volume would be needed and theres still the fact you loose heat when making a fine spray. Its just a wild Idea at the moment and I am exploring its possibilities.
Irregular spray pattern can be compensated by moving the PCB instead. pinned on a slowly rotating disk or if you want double sided etching fixed into a slowly rotating ring.
The disk or ring could be moved by magnetic coupling from the outside. So still no motor inside of the box. The magnets needed on the ring and its stand can be sealed with a bit of epoxy ot silicone. Small neodynium magnets are dirt cheap nowadays.
--- In Homebrew_PCBs@yahoogroups.com, Stefan Trethan <stefan_trethan@...> wrote:
>
> I don't think you understand the bernoulli pump, the fluid is not
> pressurized, it is "pulled along" by the airstream.
> So it can recirculate just fine.
>
> However I suspect there might be trouble with etching uniformity.
>
> ST
>
> On Fri, Dec 14, 2012 at 5:15 PM, <psykhon@...> wrote:
> > Its not viable becasuse etchant does not recirculate, you just pump it out of the vessel and to the board but if you try to put it back in, it will loose presure and stops spraying.
> > To put it back in without pressure loss, it will need a pump capable of more pressure thats in the chamber, so the whole thing becames ilogicall.
> >
> > Another way is to have LOTS of etchant and a very powerfull air pump to compensate for the volume, Raising cost to an unpractically level
> >
> > However this is the kind of ideas that migth contribute to something in the future so I dont consider it a waste of time to give it a thougth or two.
> >
> >
>