Inkjets create images by squirting minuscule drops of ink onto paper or fabric. The ink is stored in cartridges and delivered through nozzles in the printhead, the main ink-delivery component.
Redesigned printheads account for this year's primary advancement in inkjet technology, as companies have created smaller and more accurate nozzles as well as electronics that control the ink flow. The Hewlett-Packard HP 2000C's printhead is a four-piece modular system with 1,216 nozzles; it allows parts of the printhead to be individually replaced when worn out, instead of the complete unit, as in the past. A memory chip indicates when to replace the 2000C's printhead entirely. Consistent drop size and placement are the two key factors that affect print quality.
Hewlett-Packard's singles cost about $40 apiece, while standard printhead replacement units can cost between $200 and $300. However, many printheads last two to four years. Okidata projects the life span of its Okijet 2500's printhead at up to three years. Epson's printheads are permanent, on the other hand, so replacement costs are not a consideration.
The two most popular methods of inkjet printing are the traditional "hot" (thermal) and the new "cold" (piezo). Thermal technology usually takes longer because it uses heat to boil the ink. The resulting bubbles push the ink through nozzles in the printhead. Piezo technology forms droplets through a vibration that squirts the ink through the nozzles.
Compaq uses a tiny heater in its thermal technology and says speed is no problem; the heat/jet cycle occurs hundreds of thousands of times per second. Speed is often relative, however, when comparing inkjet printers because density, detail and a wide variety of colors in an image can sometimes slow down production.
Other new developments in inkjet printing technology include seven-color printing processes, printheads that dramatically improve resolution, extra cartridges that can be added to increase color options, separate black and color ink cartridges, denser black inks, and specialty inks. Canon has pioneered a handful of inkjet innovations with its patented Bubble Jet system, seven-color ink system and microscopically fine ink drop system.