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(From: Tony Hardman (AHED_CIJ@f54x19.demon.co.uk).)
There is a US publication called 'The Hard Copy
OBSERVER' from Lyra Research Inc. Tel: (617) 322-0708.
This discusses the latest technologies and who
does what. It may not cover the print head technology very much
but is a good read if you are into print technology in general.
There are many companies that sell variable print
processes. One I have heard of is RALFLATAC. They do a brochure
that does an excellent brief of most technologies available for
printing. They have UK (and many other sites in europe) and US sites.
UK Tel 01732-583661, US Tel (704) 684-3931.
I have no idea if you can easily get copies of
either publication from them so here goes a very very brief description.
Ink jet printing has two main types, continuous
ink jet (CIJ) and impulse printing (DOD) (drop on demand). Each
of these can be a single jet, or an array of jets.
- CIJ as a single jet is used on product identification (sell
by dates, serial numbers) on high speed industrial applications.
CIJ is a continuous jet of ink cycling round a system and
occasionally (when required) a drop is deflected out of the
stream onto the paper. The stream is modulated to break it into
a consistent drop size. The deflection works like the beam on
an oscilloscope. If you charge 1 drop and pass it between two
high voltage plates it is deflected. This system also requires
cunning mechanics, but the support electronics is much more
complex, and probably one of the reasons for its performance
limitations being not up to what you might expect. The calculations
of the aerodynamics of drops being deflected is no small task,
even if look up tables are used.
- DOD is often an array of small jets used on desk top printers.
DOD works in principal like an old Dot Matrix pin printer.
Instead of firing a pin at a ribbon, a drop of ink is fired
at the paper. The drop is fired by either a piezo crystal squeezing
the ink out of a small tube, or by boiling the ink and the vapor
forces the ink out of the chamber. The key to both of these
processes is in the mechanical design of very small components
if 300 dpi is required. The control electronics is a bit cunning,
but I figure it is the easy bit.
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