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(From: Tony Hardman (AHED_CIJ@f54×19.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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