1. 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

2. 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

3. 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, slow
images courtesy of How Computers Work and Brother.com

4. Non-Impact: Inkjet Printers
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

5. The Ink Cartridge 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.

6. 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.
Nozzle
Firing
Chamber
Resistor

7. 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

8. 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.

9. 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

10. 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.

11. 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.

12. Laser printing
As the drum rolls by, the positively charged parts of the coating on the drum attract the toner particles.

13. 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.

14. 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.

15. 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

16. Looking at printers in ads
Go to
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?