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printers
Posted Date: 05 Apr 2008 Resource Type: Articles/Knowledge Sharing Category: Education
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Posted By: sharu Member Level: Gold
Rating:  Points: 2
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Inkjet Printers
Inkjet printers are non-impact printers which print text and images by spraying tiny droplets of liquid ink onto paper. They are the most popular printers for home use.
Currently, most inkjet printers use either thermal inkjet or piezoelectric inkjet technology. Thermal inkjet printer uses heating element to heat liquid ink to form vapor bubble, which forces the ink droplets onto the paper through the nozzle. Most inkjet manufacturers use this technology in consumer inkjet printers.Piezoelectric inkjet technology is used on all Epson printers and industrial inkjet printers. Instead of using heating element, these printers use a piezoelectric crystal in each nozzle. The piezoelectric crystal changes shape and size based on the electric current received, and forces tiny droplets of ink onto the paper from the nozzle.
Thermal inkjet printers use aqueous ink which is a mixture of water, glycol and dyes. These inks are inexpensive but they can only be used on paper or specially coated materials. Piezoelectric inkjet printers allow the use of a wider range of inks, such as solvent inks, UV-curable inks, dye sublimation inks, and can print text and graphics on different uncoated materials.
The inkjet head design is also divided into two main groups: fixed-head and disposable head. Fixed-head is built into the printer and should last for the whole life of the printer. It produces more accurate output than cheap disposable head. The ink cartridges for fixed head printers are also cheaper as the print head does not need to be replaced. However, if the head is damaged, the entire printer has to be replaced.
Disposable head is included in replacement ink cartridge. It is replaced each time an ink cartridge runs out of ink. This increases the cost of ink cartridges and also limits the use of high quality print head in these cartridges. However, a damaged print head is not a problem as one can easily replace it with a new ink cartridge.
Some printer manufacturers use disposable ink and disposable print head separately. The print head can last much longer than cheap disposable head and is suitable for high volume printing. However, it can also be replaced easily if the head is clogged or damaged.
Although inkjet printers are generally used in home and small businesses, some manufacturers, such as Hewlett Packard, have produced high end inkjet printers for industrial use. These professional inkjet printers are usually used to print advertising graphics or technical drawings.
Advantages of inkjet printers:
1) Low cost2)High quality of output, capable of printing fine and smooth details
4) Easy to use5) Reasonably fast
7) No warm up time
Disadvantages of inkjet printers:
1) Print head is less durable, prone to clogging and damage
2) Expensive replacement ink cartridges
3) Not good for high volume printing
4) Printing speed is not as fast as laser printers
5) Ink bleeding, ink carried sideways causing blurred effects on some papers
6) Aqueous ink is sensitive to water, even a small drop of water can cause blurring
7) Cannot use highlighter marker on inkjet printouts
Obsolete and special-purpose printing technologies
The following technologies are either obsolete, or limited to special applications though most were, at one time, in widespread use. Among these types are impact printers and pen-based plotters.
Thermal printers work by selectively heating regions of special heat-sensitive paper. These printers are limited to special-purpose applications such as cash registers and theprinters in ATMs and gasoline dispensers. They are also used in some older inexpensive fax machines.
Impact printers rely on a forcible impact to transfer ink to the media, similar to the action of a typewriter. All but the dot matrix printer rely on the use of formed characters, letterforms that represent each of the characters that the printer was capable of printing. In addition, most of these printers were limited to monochrome printing in a single typeface at one time, although bolding and underlining of text could be done by overstriking, that is, printing two or more impressions in the same character position. Impact printers varieties include, Typewriter-derived printers, Teletypewriter-derived printers, Daisy wheel printers, Dot matrix printers and Line printers
.
Laser Printers
Laser printers are non-impact printers which can print text and images in high speed and high quality resolution, ranging from 600 to 1200 dpi.
Unlike inkjet printers, laser printer use toner (black or colored powder) instead of liquid inks. A laser printer consists of these major components: drum cartridge, rotating mirror, toner cartridge and roller. The drum cartridge rotates as the paper is fed through. The mirror deflects laser beam across the surface of the drum. Laser beam creates charge that causes the toner to stick to the drum. As the drum rotates and presses on paper, toner is transferred from the drum to paper, creating images. Rollers then use heat and pressure to fuse toner to paper. Colored laser printers add colored toner in three additional passes.
Advantages of laser printers:
1) High resolution
2) High print speed
3) No smearing
4) Low cost per page (compared to inkjet printers)
5) Printout is not sensitive to water
6) Good for high volume printing
Disadvantages of laser printers:
1) More expensive than inkjet printers
2) Except for high end machines, laser printers are less capable of printing vivid colors and high quality images such as photos.
3) The cost of toner replacement and drum replacement is high
4) Bulkier than inkjet printers
5) Warm up time needed
Less Popular Printers
Dot-matrix printer
Dot-matrix printer is an impact printer that produces text and graphics when tiny wire pins on the print head strike the ink ribbon. The print head runs back and forth on the paper like a typewriter. When the ink ribbon presses on the paper, it creates dots that form text and images. Higher number of pins means that the printer prints more dots per character, thus resulting in higher print quality.
Dot-matrix printers were very popular and the most common type of printer for personal computer in 70’s to 80’s. However, their use was gradually replaced by inkjet printers in 90’s. As of today, dot matrix printers are only used in some point-of-sales terminals, or businesses where printing of carbon copy multi-part forms or data logging are needed.
Advantages of dot matrix printer:
1) Can print on multi-part forms or carbon copies
2) Low printing cost per page
3) Can be used on continuous form paper, useful for data logging
4) Reliable, durable
Disadvantages of dot matrix printer:
1) Noisy
2) Limited print quality
3) Low printing speed
4) Limited color printing
Thermal printers
Thermal printers use two types of printing technologies: direct thermal and thermal transfer printing. Traditional thermal printers use direct thermal method by pushing electrically heated pins against heat-sensitive paper (thermal paper). The coating on the thermal paper turns black in the areas where it is heated, producing characters or images. Direct thermal printers have no ink, toner or ribbon. These printers are durable, easy to use and cost less to print than other printers. However, the thermal paper is sensitive to heat, light, water, and abrasion and the text and images may fade over time.
In thermal transfer printing, a thermal print head applies heat to a heat-sensitive ribbon, which melts ink onto paper and a wide range of materials to form text and images. The printouts can be extremely durable and can be stored over long period of time.
Thermal printers are often used in cash registers, ATM and point-of-sales terminals. Direct thermal printing was used in some older fax machines before the 21st century. However, these old models are now replaced by new machines which use laser and inkjet printing. Thermal printing is still considered as the best technology for bar code printing because it produces accurate, high quality images with exact bar widths. Some portable printers and most label printers still use thermal printing method.
Thermal printer is not the same as thermal inkjet printer. The latter uses inkjet print technology by heating liquid ink to form vapor bubble, which forces the ink droplet onto the paper from the nozzle.
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