The ink jet technologies discussed in my previous articles have all employed electrical resistance to heat the ink, thereby forcing it through the printhead and onto the paper. Canon uses indirect heating by placing the heater next to a tube filled with ink. Hewlett-Packard directly heats the ink to eject it onto the paper.

Epson employs a completely different method of ink ejection called Piezo Electric. Ink ejection is accomplished through the mechanical movement of a ceramic on the print head. Ceramics have unique chemical properties that respond to electrical pulses. The atomic structure within the ceramic moves when electrical current is induced.

To print, an electrical pulse is sent from the printer to the ceramic printhead. As a result, the ceramic will expand and then contract. During expansion, the ceramic pulls ink into the firing chamber (or channel). When the ceramic contracts, the compressions causes a drop of ink to be ejected through the nozzles and onto to the paper.

The shape of the ink droplets coming from a piezo head are much smoother and more consistent than those from an HP or Canon thermal head. The compression of the piezo ceramic and the fact that the ink is not heated results in a smoother drop than the explosive departure of the ink from the nozzle of thermal cartridge.


The drop size of the ink can be controlled better with Piezo-Electric technology than with thermal. The amount of time the electrical current is applied to the ceramic directly affects drop size. The shorter the time, the smaller the drop. This contributes significantly to Epson's ability to achieve high-quality photographic prints.
The nozzles of the Epson printhead are smaller than HP's or Canon's with an average measurement of about 10 to 15 microns. The Piezo-Electric printhead fires faster than its thermal counterparts. The fastest firing rate for thermal is about 20 kHz. The Piezo can fire up to 50 kHz with expected rates of 100 kHz in the near future.


This high firing rate also brings about higher costs. In addition, the life cycle of a ceramic printhead is shorter than that of thermal printheads. The expected life of a good piezo head on today's printers is about 6 months to 2 years, depending on usage.
Troubleshooting the problem of no ink delivery from the Piezo-Electric cartridge is fairly easy. If a new tank of ink is installed and no ink flows, the nozzles or the delivery tube are usually clogged. A good cleaning with hot water will clear these orifices. If the printhead can be removed from the printer, a small amount of steam will also clean the nozzles. Back flushing with hot water will also work.
 
The ink for the Epson printers is stored in small tanks either on the carriage or within the printer housing. These "tanks" of ink are simply composed of a small plastic container, a sponge, and some ink. The tank is sealed at the tip until placed into the printer.
These tanks are rather interesting, as they seem simple and easy to refill. However, many a remanufacturer has found that these cartridges can be deceiving. Leaking can be an issue so careful refilling procedures must be followed. Selecting the correct ink is very critical as the sponge within the tank will retain some of the old ink.
As with any cartridge, the remanufacturer must thoroughly evaluate the amount of time and effort invested in the refilling process. This must be weighed against the availability of low-cost compatibles.