Monday, September 24, 2001		On Hardware

Inkjet printers for home users
Jasjot Singh Narula

PRINTED things always fascinate the humans either in the form of photograph, text or graphics. The journey of reproducing text on paper through machine started with the typewriter. With the advent of computer, printers came into being which gave a new dimension to the printing technology. Today printers like Dot matrix, Inkjet and Laser jet faithfully replicate what is input in a computer.

Printers are extensively used in every sphere like business houses, corporate houses and home users. These are widely accepted because of their quality and ease-of-use. Every segment has its own needs and selects the printer accordingly. Accountants and banks use dot-matrix printers or line printers for maximum output at lesser price, the advertisement companies or corporate houses uses laser printer for quality and efficiency whereas the home segment generally uses the inkjet printers because these are inexpensive and provide quality.

Inkjet printers trace their origin to ‘Bubble Jet technology,’ which was accidentally discovered by the Canon researchers in1979. The researchers unintentionally touched the ink-filled syringe with hot soldering iron, which causes the air bubble to form and spray out from the syringe.

Since, their introduction in the late ’80s, inkjet printers have grown immensely in popularity and performance while nose-diving significantly in price.

Inkjet printer is any printer that places extremely small droplets of ink onto paper to create an image. There are two different types of Inkjet technology used like thermal or piezo-electric technology.

Thermal inkjet printers use heat to fire ink. When the controller sends the signal to the printer head, the heating element that are tiny resistors in the printer head warms the ink until it forms a bubble, which further sprays out from the print cartridge to the paper till the image is formed. These types of printers are called Bubble Jet printers or Inkjet printers and manufactured by the Canon, Hewlett Packard, and Lexmark companies.

Piezo-electric printers work through piezo crystals. These crystals change shape when an electrical current passes through them. As a crystal changes shape, it squeezes ink out of the nozzle. Epson manufactures these kinds of printers.

The inkjet printer has Print-head assembly and Paper-feed assembly. The Print-head assembly consists of ink cartridge, print head, print head stepper motor and belt.Ink cartridge comes in various combinations and models like in separate black or colour cartridges or different colours in a single cartridge. The cartridges of some inkjet printers include the print head itself. The drawback of the ink cartridges is that they work only on the specific printer model. For example, HP’s cartridges won’t work on Epson printer.

Print head is the integral part of the inkjet printer, has 300 or 600 tiny nozzles and all of them can fire droplets simultaneously. Print head stepper motor moves the print head assembly back and forth across the paper. Some printers have another stepper motor to park the print head assembly when the paper is not in use. Belt is used to attach print head assembly to the stepper motor.

Paper feed assembly consists of paper feeder or tray, rollers, paper-feed stepper motor, power supply, controller board and interface ports.

Paper feeder or tray is used for loading the paper. Rollers pull the paper from the tray or feeder and advance the paper into the printer for further printing. Paper feed stepper motor powers the rollers to move the paper. Controller board is the sophisticated circuit board, which consists of microprocessor and memory and controls all the mechanical aspects of operation, as well as decipher the information sent to the printer from the computer.

Most of the printers come with parallel port but these days Universal Serial Bus (USB) port is widely accepted.

First of all, the printer must be communicating with the computer system, which should be further compatible with software as well as hardware. The computer sends the signals through the interface i.e. from Parallel port (LPT port) or USB port in binary form. When data is frequently sent to the printer the printer stores that information into the buffer memory, which ranges from 512 KB to 16 MB depending on the model. Buffers are useful because they allow the computer to finish with the printing process quickly, instead of having to wait for the actual page to print. When the paper is fed into the tray, the rollers pull the paper under the print head and the print head stepper motor uses the belt to move the print head assembly across the page. The motor takes a pause for a fraction of a second and the print head sprays dots of ink on the page and this is a continuous motion till the process is not complete. Multiple dots are made at each stop. It sprays the CMYK (Cyan, Magenta, Yellow, Black) colour in precise amount to make any other colour imaginable.

Inkjet printers are rough to use but require servicing on time and users always use the good quality paper for printing. Usually users use refilled cartridges that may damage the printer or print head assembly.