Inkjet Printer Imaging Process

Inkjet printers are often used for good-quality color output
- E.g., photo printing
- cheap to buy but expensive to run
  - costly consumables such as ink cartridges and high-grade paper
Compared to laser printers:
- are slower and often noisier
  - less popular in office environments
Good for:
- low-volume, good-quality color printing

work by firing microscopic droplets of ink at the paper
- creates high-quality images, especially when specially treated paper is used
- prone to smearing and fading
two main types of inkjet print head:
- charge (or piezoelectric) method
  - used by Epson printers
  - nozzle contains a piezoelectric element
    - changes shape when a voltage is applied
  - This acts like a small pump, pushing ink through the nozzle and drawing ink from the reservoir
- thermal method
  - used by HP, Canon, and Lexmark
  - the ink at each nozzle in the print head is heated, creating a bubble
  - When the bubble bursts, it sprays ink through the nozzle and draws more ink from the reservoir
  - cheaper and simpler to produce
  - but heating elements have a relatively short life
  - use a combined print head and ink reservoir
    - When the ink runs out, the print head is also replaced

Carriage System

inkjet printers build up the image line by line
print head is moved back and forth over the paper by a carriage system
- two ways:
  - one-directional
    - ink is applied when the print head moves in one direction only
  - bidirectional
    - apply ink on both the outward and return passes over the page
carriage system uses:
- a stepper motor, pulley, and belt to move the print head
- guide shaft to keep the print head stable
- sensors to detect the position of the print head
flat ribbon data cable connects the print head to the printer’s circuit board
When a line has been completed
- another stepper motor advances the page a little bit
- next line or row is printed
may also be a lever used to set the platen gap or the printer may adjust this automatically depending on driver settings
- is the distance between the print head and the paper
- Having an adjustable platen gap allows the printer to use thicker media