Inkjet Printer Cartridges

The original inkjet printers were developed by Canon. In 1977 bubble jet technology was launched and so started a huge marker in consumables - bubblejet inkjet printer cartridges. The story goes that the technology was developed when a researcher accidentally touched an ink-filled syringe with a hot soldering iron and the heat forced a drop of ink out of the needle.

Typically inkjet printers cost less than lasers to buy but in general they are more expensive to use (cost per printed page) and maintain. Inkjet Printer Cartridges need to be changed more frequently and the special coated paper required to produce photographs can be very expensive. Inkjet printing is a non-impact process which differentiates it from earlier dot matrix type of devices. Desktop inkjet printers, as used in offices or at home, tend to use aqueous inks based on a mixture of water, glycol and dyes or pigments. These inks are inexpensive to manufacture, but are difficult to control on the surface of media, often requiring specially coated media. HP inks contain sulfonated polyazo black dye  nitrates and other compounds. Aqueous inks are mainly used in printers with thermal inkjet heads, as these heads require water to perform. In general regardless of the make, ink is emitted from nozzles while they pass over the paper. A print head scans the page in horizontal strips . Most inkjet printers including Canon, Hewlett-Packard, and Lexmark ,but not Epson, use print cartridges with a series of tiny chambers each containing a heater, all of which are constructed by photolithography. To eject a droplet 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, which causes a large pressure increase, propelling a droplet of ink onto the paper. The ink's surface tension, as well as the condensation and thus contraction of the vapour bubble, pulls a further charge of ink into the chamber through a narrow channel attached to an ink reservoir.

Epson use a piezoelectric material in an ink-filled chamber behind each nozzle instead of a heating element. When a voltage is applied, the piezoelectric material changes shape, which generates a pressure pulse in the fluid forcing a droplet of ink from the nozzle. Piezoelectric (also called Piezo) 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), but the print heads are more expensive to manufacture due to the use of piezoelectric material (usually PZT, lead zirconium titanate). A drop-on-demand process uses software that directs the heads to apply between zero to eight droplets of ink per dot, only where needed.

Piezo inkjet technology is often used on production lines to mark products - for instance the "use-before" date is often applied to products with this technique; in this application the head is stationary and the product moves past. Requirements of this application are high speed, a long service life, a relatively large gap between the print head and the substrate, and low operating cost.

A common business model for inkjet printers involves selling the actual printer at or below production cost, while dramatically marking up the price of the (proprietary) ink cartridges (a profit model called "Freebie marketing"). All current inkjet printers attempt to enforce this product tying using microchips in the cartridges to hinder the use of third-party or refilled ink cartridges. The microchips monitor usage and report the ink remaining to the printer. Some manufacturers also impose "expiration dates". When the chip reports that the cartridge is empty (or out of date) the printer stops printing. Even if the cartridge is refilled, the microchip will indicate to the printer that the cartridge is depleted. For many models (especially from Canon), the 'empty' status can be overridden by entering a 'service code' (or sometimes simply by pressing the 'start' button again). For some printers, special circuit "flashers" are available that reset the quantity of remaining ink to the maximum. Some manufacturers, most notably Epson and Hewlett Packard, have been accused of indicating that a cartridge is depleted while a substantial amount of ink remains.[ A 2007 study found that most printers waste a significant quantity of ink when they declare a cartridge to be empty. Single-ink cartridges were found to have on average 20% of their ink remaining, though actual figures range from 9% to 64% of the cartridge's total ink capacity, depending on the brand and model of printer. This problem is further compounded with the use of one-piece multi-ink cartridges, which are declared empty as soon as one colour runs low. Of great annoyance to many users are those printers that will refuse to print documents requiring only black ink, just because one or more of the colour ink cartridges is depleted.


Some printers use dye sublimation inks which contain special sublimation dyes and are used to print directly or indirectly on to fabrics which consist of a high percentage of polyester fibres. A heating step causes the dyes to sublimate into the fibers and create an image with strong colour and good durability.


The primary cause of inkjet printing problems is due to ink drying on the printhead's nozzles, causing the pigments and dyes to dry out and form a solid block of hardened mass that plugs the microscopic ink passageways. Most printers attempt to prevent this drying from occurring by covering the printhead nozzles with a rubber cap when the printer is not in use. Abrupt power losses, or unplugging the printer before it has capped the printhead, can cause the printhead to be left in an uncapped state. Even when the head is capped, this seal is not perfect, and over a period of several weeks the moisture (or other solvent) can still seep out, causing the ink to dry and harden. Once ink begins to collect and harden, the drop volume can be affected, drop trajectory can change, or the nozzle can completely fail to jet ink. To combat this drying, nearly all inkjet printers include a mechanism to reapply moisture to the printhead. Typically there is no separate supply of pure ink-free solvent available to do this job, and so instead the ink itself is used to remoisten the printhead. The printer attempts to fire all nozzles at once, and as the ink sprays out, some of it wicks across the printhead to the dry channels and partially softens the hardened ink. After spraying, a rubber wiper blade is swept across the printhead to spread the moisture evenly across the printhead, and the jets are again all fired to dislodge any ink clumps blocking the channels.
 

Because the ink used in most consumer inkjets is water-soluble, care must be taken with inkjet-printed documents to avoid even the smallest drop of water, which can cause severe "blurring" or "running." Similarly, water-based highlighter markers can blur inkjet-printed documents. The very narrow inkjet nozzles are prone to clogging. The ink consumed cleaning them - either during cleaning invoked by the user, or in many cases, performed automatically by the printer on a routine schedule - can account for a significant proportion of the ink used in the machine.

 

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