Homebrew PCBs

--- In Homebrew_PCBs@yahoogroups.com, Matthew Smith <matt@...> wrote:
> You want either a magnetic drive pump (polypropylene would probably
be a 
> suitable material) or a peristaltic pump (actually a positive 
> displacement pump - a set of lobes on a rotor squeeze a plastic tube to 
> push the fluid along.)
I used a magnetic drive pump on an etcher some years ago.  The etchant
slowly ate the magnet material, eventually ruining the pump.  I made a
pump out of Plexiglas that ran at a low speed, and was driven by a
long Plexiglas vertical shaft that ran down through the fluid sump to
the pump.  This was seal-less.  The impeller bearing was a piece of
Plexi bar stock in a piece of Plexi tube, with a spiral groove on the
bar to work fluid through the bearing, to prevent heat buildup.  It
actually worked quite well.  I held the pump pieces together with a
bunch of nylon screws and was astonished that the FeCl2 etchant would
turn the nylon brittle and the screws would pop their heads in a
couple minutes.
These weren't "in the soup" but just got drips and splashes on them,
but that's all it took.

I eventually got a discarded Kepro "bench top" etcher which uses two
Little Giant brand pumps.  I suspect these pumps have titanium shafts,
and the rest of the lower section (impeller, impeller housing) are
some blue plastic that seems to hold up remarkably.

Jon