By Dean Takahashi
Knight Ridder Newspapers
We take it for granted: Click an icon on your desktop computer and a document is printed in seconds. Yet there's an enormous amount of engineering and miniaturization behind today's laser and inkjet printing, much of it pioneered by Hewlett-Packard.
One of the little-known facts about a laser printer is that most of the sophistication is in the toner cartridge that gets recycled.
The cartridge contains toner ink, which is actually tiny particles of plastic. The cartridge also holds rollers that operate much like a printing press.
The rollers interact with a laser - or beam of light - which alters electrical charges on the rollers according to the pattern to be printed. When toner powder is applied, it gravitates to the altered electrical charges, thus forming the image to be produced. A heat source then melts the toner onto paper.
By contrast, a thermal inkjet printer uses liquid ink that is mostly water. Each inkjet-printer cartridge has a printer head with up to 500 nozzles on it.
Each nozzle is fed with ink by a tiny pipeline. An electrical charge heats the ink. As the ink expands upon heating up, it is forced out of the nozzle's tip and onto the page. The printer makes a variety of hues by combining tiny streams of ink in four basic colors.
© 2004, San Jose Mercury News (San Jose, Calif.).
Distributed by Knight Ridder/Tribune Information Services.