A computer printer is a computer peripheral device that produces a hard copy (permanent human-readable text and/or graphics, usually on paper) from data stored in a computer connected to it. It translates information that has been processed by the system unit and presents the information on paper.
Major types of printer
Printers can be divided into two main groups, impact printer and non-impact printer. Impact printer produces text and images when tiny wire pins on print head strike the ink ribbon by physically contacting the paper. Non-impact printer produces text and graphics on paper without actually striking the paper.
Printers can also be categorized based on the print method or print technology. The most popular ones are inkjet printer, laser printer, dot-matrix printer and thermal printer. Among these, only dot-matrix printer is impact printer and the others are non-impact printers
Some printers are named because they are designed for specific functions, such as photo printers, portable printers and all-in-one / multifunction printers. Photo printers and portable printers usually use inkjet print method whereas multifunction printers may use inkjet or laser print method
Inkjet printers and laser printers are the most popular printer types for home and business use.
The use of thermal printers is limited to ATM, cash registers and point-of-sales terminals. Some label printers and portable printers also use thermal printing.
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
DISADVANTAGES
High resolution
More expensive than inkjet printers
High print speed
Except for high end machines, laser printers are less capable of printing vivid colors and high quality images such as photos
No smearing
The cost of toner replacement and drum replacement is high
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
DISADVANTAGES
Low cost
Print head is less durable, prone to clogging and damage
High quality of output, capable of printing fine and smooth details
Expensive replacement ink cartridges
Capable of printing in vivid color, good for printing pictures
Not good for high volume printing
Easy to use
Printing speed is not as fast as laser printers
Reasonably fast
Ink bleeding, ink carried sideways causing blurred effects on some papers
Quieter than dot matrix printer
Aqueous ink is sensitive to water, even a small drop of water can cause blurring
