Impact Printers

• An impact printer prints by hitting an ink-saturated ribbon with a striker within the printer. Mechanically, impact printers operate on principles similar typewriters: Rollers grab the paper and advance it through the printer, white output is printed a line at a time by way of the printer ribbon. Dot matrix printers strike the printer ribbon with a head that leaves a series of dots in a grid, and those dots form the letters or other output on the page. Daisy wheel printers contain all the letters, numbers, and symbols of your keyboard as individual strikers in a radial configuration, like the petals of a flower. The wheel rotates to place the appropriate striker against the ribbon for each character, and each character is printed individually and in sequence.
  
  

Inkjet Printers

• Inkjet printers place ink on the page via the series of tiny nozzles, or jets, that give this type of printer its name. Consumer inkjet printers are generally thermal. The print head contains tiny heating elements which propel individual bubbles of ink onto the paper.
  
  The print head in an inkjet printer may either be part of the printer or part of the ink cartridge. If it's part of the ink cartridge, the print head itself is designed to be disposable, and you may experience problems with refilled cartridges as the print head simply wears out. An inkjet printer print by moving the print head in lines back and forth across the page as rollers advance the paper.
  
  

Laser Printers

• Unlike inkjet or impact printers, laser printers print with toner, not ink. This may result in sharper printing, and a laser-printed page is not subject to smearing in the same way an inkjet- or impact-printed page is. As with most other printers, a series of rollers guide and advance the paper through your printer. An electrostatic charge is projected onto the print drum. The laser inside the printer passes across the print drum in a series of dots corresponding to the text or image you're printing. The laser reverses the electrostatic charge on the drum in those dots where it's applied.
  
  The drum is exposed to negatively-charged toner, which adheres to the charged portions of the drum in a fine dust. The printer advances your paper over the drum to acquire the toner. The paper may be backed by a positively-charged roller to assist in the transfer of toner. Then the paper passes through the fuser, where heat and pressure melt the toner "dust" into a smooth substance and bond it to the page.