Types of printers

• Dot-matrix printers

  Are impact printers, which use a matrix of pins. A print head containing tiny pins strikes an inked ribbon to make letters or graphics. The ribbon impregnated with ink transfers the image or text on paper. The ribbon needs changing when the ink is used up or dries out.

• Ink-jet printers

  Operate by spraying small ink droplets onto paper to form the required image. A standard ink-jet has a three colour cartridge and a black cartridge. Professional ink-jets have five-colour cartridges plus black. They work well on ordinary paper. They are suitable for small quantities or home use.

  Advantages/disadvantages

  • The printers themselves are relatively cheap to buy
  • They produce images that are almost as good as photographs if they are printed on high quality paper
  • They take up less space than laser printers
  • They are almost silent in operation
  • The wet ink droplets tend to spread before they dry
  • Are slower than laser printers
  • Running costs are usually higher than for lasers because inkjet cartridges do not last long and have to be replaced. For a high quality printout special paper is required.

• Laser printers

  Scan the image with a laser beam and transfer it to paper with a special ink powder called toner. The toner is attracted to paper by an electrostatic charge and then fixed by a hot roller. Lasers use a Page Description Language (PDL) which describes how to print the text and draw images on the page. The most common languages are Adobe PostScript and HP Printer Control Language.

  
  

  Laser printers are fast and produce a high resolution, so they are ideal for businesses and professional graphics work.

  Advantages/disadvantages

  • They are fast
  • They have high resolution
  • They are expensive, particularly colour laser printers
  • They are quite cheap to run because toner cartridges don´t have to be replaced so often

• Thermal transfer printers

  Produce colour images by transferring a wax-based ink onto the paper. They are used for printing bar codes, labels and medium-resolution graphics.

• Multi-function printers

  Are devices that can work as a printer, scanner, photocopier and a fax. Some of them accept memory cards and print photos directly from the camera using the PictBridge technology.

• Imagesetters and platesetters

  Imagesetters produce very high resolution output on paper or microfilm. They are most often used in desktop publishing (DTP). They produce the highest quality output, but are very expensive

  
  

  In modern lithographic printing, images are created on a DTP computer and then output directly to the printing plates, without a film as an intermediate step. This technology is called computer to plate – CTP, and the machine is called platesetter.

• Plotters

  Are devices for producing high quality graphical output on paper. They can produce construction plans, engineering drawings, maps, diagrams and three dimensional drawings. There two main types of plotters – pen plotters and penless plotters. Pen plotters use pens containing different colour inks to produce images. The pens can reach any point on the piece of paper. The lines drawn are continuous, not made of dots and the drawing is very accurate. Penless plotters use various technologies. High quality output is produced by electrostatic plotters. Plotters are slow but very accurate.