Most consumer inkjet printers, such as those made by Canon, HP, and Lexmark (but not Epson) use a thermal inkjet; inside each partition of the ink reservoir is a heating element with a tiny metal plate or resistor. In response to a signal given by the printer, a tiny current flows through the metal or resistor making it warm, and the ink in contact with the heated resistor is vaporized into a tiny steam bubble inside the nozzle. As a consequence, an ink droplet is forced out of the cartridge nozzle onto the paper. This process takes a fraction of a millisecond.
The printing depends on the smooth flow of ink, which can be hindered if the ink begins to dry at the print head, as can happen when an ink level becomes low. Dried ink can be cleaned from a cartridge print head using isopropyl alcohol or water. Isopropyl alcohol will damage the printing head, melting the plastic at the connections and rubber gaskets. Tap water contains contaminants that may clog the print head, so distilled water and a lint-free cloth is recommended.
The ink also acts as a coolant to protect the metal-plate heating elements − when the ink supply is depleted, and printing is attempted, the heating elements in thermal cartridges often burn out, permanently damaging the print head. When the ink first begins to run low, the cartridge should be refilled or replaced, to avoid overheating damage to the print head.
All Epson printers use a piezoelectric crystal in each nozzle instead of a heating element. When current is applied, the crystal changes shape or size, increasing the pressure in the ink channel and thus forcing a droplet of ink from the nozzle.
There are two types of crystals used: those that elongate when subjected to electricity or bi-morphs which bend. The ink channels in a piezoelectric ink jet print head can be formed using a variety of techniques, but one common method is lamination of a stack of metal plates, each of which includes precision micro-fabricated features of various shapes (i.e. containing an ink channel, orifice, reservoir and crystal). This cool environment allows use of inks which react badly when heated. For example, roughly 1/1000 of every ink jet is vaporised due to the intense heat, and ink must be designed not the clog the printer with the products of thermal decomposition. It also can make a smaller ink drop in some situations than thermal inkjet schemes.
Color inkjets use the CMYK color model: cyan, magenta, yellow, and the key, black. Over the years, two distinct forms of black have become available: one that blends readily with other colors for graphical printing, and a near-waterproof variant for text.
Most modern inkjets carry a black cartridge for text, and either a single CMYK combined or a discrete cartridge for each color; while keeping colors separate was initially rare, it has become common in more recent years. Some higher-end inkjets offer cartridges for extra colors.
Some cartridges contain ink specially formulated for printing photographs.
All printer suppliers produce their own type of ink cartridges. Cartridges for different printers may be incompatible — either physically or electrically.
Some manufacturers incorporate the printer's head into the cartridge (examples include HP, Dell, and Lexmark), while others such as Epson keep the print head a part of the printer itself. Both sides make claims regarding their approach leading to lower costs for the consumer.
Ink cartridges are typically priced at $13 to $75 per ounce ($1,664 to $9,600 per gallon) of ink, meaning that refill cartridges sometimes cost a substantial fraction of the cost of the printer. To save money, many people use compatible ink cartridges from a vendor other than the printer manufacturer. Others use aftermarket inks, refilling their own ink cartridges using a kit that includes bulk ink. The high cost of cartridges has also provided an incentive for counterfeiters to supply cartridges falsely claiming to be made by the original manufacturer. The print cartridge industry lost an estimated $3 billion in 2009 due to this, according to an International Data Corporation estimate.
Another alternative involves modifications of an original cartridge allowing use of continuous ink systems with external ink tanks. Some manufacturers, including Canon, have introduced new models featuring in-built continuous ink systems. This was seen as a welcome move by users, especially small business owners who rely on bulk-printing solutions, like Internet cafes and small-scale print shops.
Some printer manufacturers set up their cartridges to interact with the printer, preventing operation when the ink level is low, or when the cartridge has been refilled. One researcher with the magazine Which? over-rode such an interlocked system and found that in one case he could print up to 38% more good quality pages, after the chip stated that the cartridge was empty. In the United Kingdom, in 2003, the cost of ink has been the subject of an Office of Fair Trading investigation, as Which? magazine has accused manufacturers of a lack of transparency about the price of ink and called for an industry standard for measuring ink cartridge performance. Which? stated that color HP cartridges cost over seven times more per milliliter than 1985 Dom Perignon.
It can sometimes be cheaper to buy a new printer than to replace the set of ink cartridges supplied with the printer. The major printer manufacturers − Hewlett Packard, Lexmark, Dell, Canon, Epson and Brother − use a "razor and blades" business model, often breaking even or losing money selling printers while expecting to make a profit by selling cartridges over the life of the printer. Since much of the printer manufacturers' profits are from ink and toner cartridge sales, some of these companies have taken various actions against aftermarket cartridges.
Refills and third party replacements
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Infusing an inkjet printer
Because printer cartridges from the original manufacturer are often expensive, demand exists for cheaper third party options. These include ink sold in bulk, cartridge refill kits, machines in stores that automatically refill cartridges, remanufactured cartridges, and cartridges made by an entity other than the original manufacturer.
Consumers can refill ink cartridges themselves with a kit, or they can take the cartridge to a refiller or remanufacturer where ink is pumped back into cartridges made up of components from previously used cartridge products. PC World reports that refilled cartridges have higher failure rates, print fewer pages than new cartridges, and demonstrate more on-page problems like streaking, curling, and color bleed.
Another option is for the consumer to purchase "bulk ink" (in pints, quarts, or gallons) and refill the cartridges themselves. This can be extremely cost-effective if the consumer is a heavy user of cartridges, although care is required while refilling to avoid ink stains on hands, clothes, or surroundings. One US pint (437 ml) is sufficient to fill about 15 to 17 large-capacity cartridges (or 34 to 39 per liter of ink).
Generally speaking, Canon, Dell, HP, and Lexmark cartridges are not difficult to refill, though some Lexmark cartridges employ a built-in counter chip that can't be reset; Epson cartridges and some newer Brother cartridges also have a built-in counter chip, however it is possible to purchase a chip resetter for these models. Since older Brother cartridges generally lack any chip and consist of merely a sack of ink, they can be readily refilled.
Some third party manufacturers have been offering refillable cartridges with an auto reset chip to simplify the refilling process. These refillable cartridges are less harmful to the environment and often easy to further refill.
Perhaps the easiest, most trouble-free method of refilling ink cartridges is through the use of a CISS (Continuous Ink Supply System). A CISS consists of a set of cartridges that have tubes connected to them, through which the ink continuously flows from ink reservoirs on the outside of the printer. Instead of refilling the cartridges themselves, the user simply refills the bottles on the outside of the printer. Early CIS systems were composed of OEM cartridges that had been drilled and outfitted with fittings to accept the ink delivery tubes, a set of 'ribbon' tubes, and plastic bottles with holes drilled in the caps for the tubes and the vents. Today's CIS systems are mass-produced in China, often incorporating all ink bottles into one partitioned container. They typically utilize auto-reset chips, which means the cartridges rarely have to be removed from the printer.
Resetting an Epson ink cartridge using a resetter tool
Laser toner or inkjet cartridges sold as remanufactured are cartridges that have been reassembled with parts already in production, and refilled with new ink. Many third party newly manufactured cartridges exist, these are named compatible cartridges and refer to any cartridge that is not made by the original manufacturer of the printer. Inkjet cartridges sold as "compatible" are typically newly manufactured cartridges. Compatible and OEM cartridges can be remanufactured and refilled. Inkjet cartridges sold as "remanufactured" are cartridges that have been used at least once by a consumer and then refilled by a third party.
The legality of this industry was brought to the United States Court of Appeals for the Sixth Circuit in the case of Lexmark Int'l v. Static Control Components. The Court ruled that reverse-engineering the handshaking procedure to enable compatibility did not violate the Digital Millennium Copyright Act.
HP has fiercely defended its printing interests from the refill industry, including filing patent complaints and false advertising lawsuits which allege that inferior ink is not properly differentiated from the original HP ink.