How do Laser Printers Work?

- Feb 25, 2018-

Laser printers are ubiquitous in offices and in copy environments. The first was developed by Xerox Corporation in 1971 and entered the commercial market in 1977. Although the printer's internal work remains mysterious to many, fast, clear printing quickly makes these printers a popular choice for many consumers. Due to the name, some consumers think that these devices will somehow actively use lasers on paper. In fact, they actually use electrostatic for printing, although lasers do play a role in the printing process.

When the printer receives data from the computer, the print job starts and the printer sends data through the central controller (a small computer in the printer). Many laser printers have a controller that can handle multiple jobs at the same time, put them in a queue and print them out. This ability to handle multiple sets of data makes this printer very popular. After the controller determines what to print, the process begins.

The inside of the printer has a charge-holding drum. Next to the drum is a transfer corona roller that charges the drum negative or positive as needed, as well as a toner cell. In most laser printers, the toner cartridge starts to be positively charged, although this process can also work in reverse. The controller manipulates a small laser to "write" the negative charge on the drum to produce an electrostatic image.

The drum is then wound with positively charged toner so that it fits snugly against the negative charge area on the drum. The printer feeds a sheet of paper that is given a stronger negative charge by the transfer corona wire before it rolls over the cylinder. The electrostatic image on the drum is transferred to the paper and then discharged to prevent the drum from sticking to the drum. Then conveyed through a fuser that heats the toner and binds it to the fibers in the paper.

At the same time, the drum passes the discharge lamp, which exposes the entire surface of the drum and erases the electrostatic image. The transfer corona wire applies another positive charge, and the printer is ready for the next page or job.

Color laser printers perform multiple passes of work. In addition to black, most printers have blue, red, and yellow inks that can be combined to create any color. Some printers gradually put ink on the drum so that the image can be printed as the paper passes, while other printers can cycle through the paper multiple times to apply a progressive color layer. Large color printers sometimes have separate drum and toner assemblies for each color, with the paper passing through each drum separately.


Editor’s Note: This post was Updated by Proffisy on 25 Feb,2018.