Homebrew PCBs

I worked on a project for a company that makes CIJ (Continuous Ink Jet)
print heads like you are talking about here. I'm not sure I'd call it
archaic, in that it is the technology behind all of the date codes on
your pop bottles, etc. CIJ printers are used in packaging and printed
material production facilities because they can be run very fast, from a
pretty high distance above the material they're printing on. With the
right ink, they can print on just about anything. The actual print heads
are simply amazing pieces of technology - they set up an acoustic
standing wave inside the little ink tank at the bottom of the head,
which guarantees very precise droplet sizes at very precise times (a
constant stream of drops from each hole in the head - in the KHz range
if I remember correctly). The electrostatic forces are applied by tiny
fingers that fit between the droplet streams and deflect individual
droplets. Each droplet goes in one of two places - if the electricity is
on, it goes at a slight angle (onto the pop can or magazine, etc.). If
the electricity is off, it goes straight down into a little collector
thing which sucks the ink back up into the main reservoir for recycling
and printing again. 

How is this on topic? It's not I guess, but I know that the inks they
used are _very_ resistant to everything. (Try etching the date code off
of your Coke can.) So they'd probably be great for making PCBs. You can
line up four or eight print heads to cover an 8" swath of conveyor belt,
so you could print whole boards in one swipe. If you had to make many
boards rapidly, with each one being slightly different, this might work
great. Except that the printer heads are super expensive, and it takes
about 30 minutes to get the printer running in the first place (once it
runs you don't shut it down) and involves a LOT of spraying MEK around
until it starts printing right.

*Brian

-----Original Message-----
From: Homebrew_PCBs@yahoogroups.com
[mailto:Homebrew_PCBs@yahoogroups.com] On Behalf Of Andrew
Sent: Wednesday, May 31, 2006 4:07 PM
To: Homebrew_PCBs@yahoogroups.com
Subject: [Homebrew_PCBs] Drop on Demand - was - Re: Unblocking epsons

In archaic inkjet printers the print head would
fire out a constant stream of drops.  It would
then use an electrostatic charge to either direct
these drops out to the paper or back into an
ink collection system for re-use.  The print
heads did not have any tiny tiny little elements
in them - they where just a nozzel being fed by
a pump.