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How Inkjet Printers Work
A 'very informative' and useful series of articles. Reprinted with authorization from Image Specialists.
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Origins
Thermo-Technology
Piezo-Electric Technology
Color Perception
Creating Color
Print Quality
Color Management
Ink
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Manageability & Costs |
Manageability & Costs
There's no doubt that the inkjet printer has been one of desktop computing success stories of the late 1990s. Its first phase of development was the monochrome inkjet of the late 1980s - a low-cost alternative to the laser printer. The second resulted from the advent of color and its development to the point of effective photographic quality - giving the inkjet an all-round capability unmatched by any other printer technology. However, when it comes to manageability and running costs, the inkjet trails its rival laser technology.
Hewlett-Packard's HP2000C inkjet model, launched in late 1998, signaled encouraging progress in this direction. Most inkjet printers combine the ink reservoir and the print head in one unit. When the ink runs out its necessary to replace both - even though print heads can have a lifetime many times that of ink reservoirs. The HP2000C differs radically from traditional designs, using a modular system in which the ink cartridges and print heads are kept as separate units. The printer uses four pressurized cartridges, which each hold 8cm of ink and remain static underneath a hinged cover at the front of the printer. These are connected by tubes, integrated with the standard ribbon-style cable, which run to the print head carriage. Internal smart chips monitor the supply, activating a plunger on the relevant cartridge when it requires a refill. Each ink cartridge can keep track of how much ink it has expended even if it is transferred to another printer. The print heads are also self-monitoring - triggering an alert when they need to be replaced. The whole system can also survey the requirements of a particular print job and only begin the process if it determines there is sufficient ink to complete it.
Wasted ink is also a problem that adversely affects operating costs. With printers that combine the cyan, yellow and magenta inks in a single tri-color cartridge, the emptying of one reservoir requires the replacement of the whole cartridge, regardless of how much ink is left in the other two reservoirs. The solution to this problem, already deployed by a number of printers, is to have a separate, independently replaceable, ink cartridge for each color. The downside is increased maintenance effort - an inkjet printer that uses four cartridges typically requires twice the attention of one where the three colors are combined.
In terms of manageability, the HP2000C includes another innovative feature. The incorporation of a second paper tray, which means that two paper types can be kept in the printer at once to minimize user attention.
Print capacities also have to improve. At the end of 1998 the standard output for personal laser printers was around 3,000 pages from a toner/drum cartridge. Typically the best an inkjet could manage was around 500 to 900 pages from a single black ink cartridge. Color-ink use fared even worse - supporting a capacity of only between 200 and 500 pages. Print speeds are expected to reach 10 ppm by the year 2001, and with these higher speeds there is the corresponding expectation of increased cartridge capacities. Inkjet manufacturers are already starting to introduce workgroup color printers with much larger secondary ink containers linked to small primary ink reservoirs close to or in the print head. These printers will automatically replenish the primary reservoir as needed. |
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