Inkjet Printing Technology Overview

For the “boffins” amongst you who wonder how a sheet of paper we sell is compatible with such a huge range of printers, here is a short history and overview of inkjet printing technology.  We are concentrating on the part of the process that sprays the ink onto the paper.

Inkjet printing technology was invented in the late 70’s. Hewlett Packard (HP) launched their first commercial inkjet printer in the late 80’s. It is rumoured that the first home inkjet printing technology was in fact developed by Canon, who called it Bubble Jet and HP have licensed it from them ever since.

There are two main types of Inkjet printing technology

•    Thermal (used by HP, Lexmark, Canon)
•    Cold Piezoelectric (Mainly Epson)

Thermal inkjet technology:

A series of tiny chambers each containing a heater are instructed by digital command (computer) to eject a droplet of ink from each chamber. A pulse of current is passed through the heating element causing a rapid vaporisation of the ink in the chamber to form a bubble, causing a pressure increase and propelling the droplet of ink onto the paper (hence Canon’s trade name of Bubble Jet).

Piezoelectric (Also known as Piezo):

This technology was developed by Epson and is used in most of the inkjet printer range. Some printer manufacturers also bought the licence for it making it the most common technology for the commercial and industrial machines in the market. Piezoelectric consists of an ink filled chamber behind each nozzle instead of a heating element. When voltage is applied, the piezoelectric substance changes shape, generating a pressure pulse in the fluid, forcing a droplet of ink from the nozzle. Piezoelectric inkjet allows a wider variety of inks than thermal inkjet as there is no requirement for a volatile component, and no issue with kogation (build up of ink residue).  On the other hand the print heads are more expensive to manufacture due to the use of piezoelectric material.
Subsequently, when making paper for inkjet printing, a manufacturer only needs to make it compatible with only two types of technologies, used by a wide variety of printer manufacturers and their different models.

Ink Cartridge Replacement:

There is a fundamental difference between the two technologies in the way the ink cartridges are constructed and setup.

Thermal printer system (HP, Lexmark) the print head is integral with the ink reservoir meaning that when the old cartridge is removed and replaced, the print head is replaced as well.  It also means that if there is damage to the print head, the cost of repair is essentially the cost of a new cartridge and does not require specialised care.

The reason the head is replaced with every cartridge change the deterioration it experiences due to the constant heat pulses in the printing process.

In the Piezoelectric system (Epson), the heads are fixed and are separate from the cartridge which is essentially an ink reservoir.  Each time a cartridge is replaced, the head stays behind and is expected stay there for the lifetime of the printer.

Although the Piezo printheads are considered long lasting, constant flow of ink through the same head can clog the print head with a deposit left along the time it is used.

To prevent clogging, ink manufacturer add glycol to the ink to ensure the print heads remain clear.

Compatible Cartridges:

Compatible cartridges made by third parties are more likely (although getting better all the time) to cause clogging in the print heads than if only originals are used. When buying a compatible cartridge for Epson therefore, it is very important to buy from a well accredited manufacturer which in some cases may even produce ink that is as good or better than the original.

Due to the high cost of replacement of the Piezo printhead of the Epson desktop printer, in many cases when the heads are clogged it worth to buy a new printer rather than sending it to a technician to be fixed.

Consequently, when buying compatible cartridges for thermal printers (HP), the risk to the printer is minimal because a duff cartridge is unlikely to cause damage to the printer.  Once it is removed and replaced, clogged head is discarded and a fresh one installed.

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