10/24: output: printers types of printers: laser, inkjet, dot-matrix printers other types: plotters,...
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10/24: Output: Printers
• Types of printers: laser, inkjet, dot-matrix printers
• Other types: plotters, label printers, digital presses, photo printers, electrostatic printers, LED printers
• How color printing works
• What to look for in a printer
Printers: General
• Printers– two main groups:
impact (dot-matrix, daisy-wheel) & nonimpact (laser, inkjet, thermal)
– other types: plotters, label printers, digital presses, photo printers, large-format printers
– color printing
dot matrix printer image courtesy of epson.com, others courtesy of hp.com
Impact Printers• Dot-Matrix printers: Pins are
pushed by solenoids to hit a ribbon in front of the paper.
• Daisy-Wheel printers: Letters are pushed to hit the ribbon in front of the paper.
• Stamp ink onto the paper.• Advantages: cheap, reliable,
low CPU demand, multiple-form copying
• Disadvantages: loud, slowimages courtesy of How Computers Work and Brother.com
• The ink cartridges have tiny heating elements that cause microdrops of ink to heat up and expand, shooting out of the nozzle and onto the paper.
• Advantage: cheap color printing
images courtesy of HP.com and How Computers Work
Non-Impact: Inkjet Printers
• The ink cartridge(s)– nozzle – firing chamber– path from reservoir – thin-film resistor
Cross-section of a nozzle.
How does the ink get out? One of two ways: The Thermal method or the Piezo-Electric method.
The Ink Cartridge
Nozzle
Firing Chamber
Resistor
How the ink gets out: thermal method
• Used by Hewlett Packard & Canon
• A thin-film resistor is heated by electric current.
• The resistor heats up the ink that is next to it.
How the ink gets out: thermal method
• The ink- now gaseous - expands, forming a bubble.
• The bubble pushes out the rest of the ink in the firing chamber.
Nozzle
Firing Chamber
Resistor
How the ink gets out: thermal method
• The resistor cools, causing the bubble to shrink.
• The shrinking creates a vacuum, which draws new ink from the reservoir.
Nozzle
Firing Chamber
Resistor
• The piezo method uses a flexing, swelling crystal instead of heat to push the ink out.
Laser Printers• Deposit toner onto the paper,
then melt it to make it permanent.
• Cheaper by the day – per page printing costs are very low.
• Faster than inkjet printers.
• Very quiet.
images courtesy of How Computers Work
Laser printing
• The pattern to be printed is set up in a grid of black areas and white areas.
• The laser beams, horizontal line by horizontal line, this grid of dark areas.
Laser printing
• When the drum is hit with the laser beam, it electrically charges the coating at that spot.
• In HP & Canon printers, the coating is positively charged.
Laser printing
• As the drum rolls by, the positively charged parts of the coating on the drum attract the toner particles.
Laser printing
• The sheet of paper touches the drum coated in toner.
• The toner jumps to the paper from the drum because the paper is more strongly charged than the drum.
Laser printing
• The paper, with the toner particles, goes to the fusing rollers. The rollers use pressure and heat to bind the toner to the paper permanently.
How Color Printing Works
• subtractive color– monitors use additive
color: all colors combine to get lighter shades
• printers combine colors to get darker shades
• all colors together create black
Looking at printers in ads
• Go to http://www.buy.com
• things to note when comparison shopping:– what YOU will be using the printer for– ppm (pages per minute) in b&w, color– size limitations of paper– paper tray capacity– price (and price of ink/toner cartridges)– dpi (dots per inch) – print quality capabilities– (inkjets) type of black printing: separate cartridge?
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