Laser Printer working principle depends on dry powder technology. It uses hot pressure rollers to melt and fuse the toner materials to print on the plain paper.
Laser Printer is widely used in offices, homes and cyber cafe. Because of its ability to print on plain paper and the images are permanent.
Laser printer most probably connected to single computer or to LAN to serve for single or many users. So multiple users can print documents from their machine.
Had you ever tried to under stand the beauty of laser printer working principle or steps involved in printing. Let’s understand the printing process in brief.
Main components in the printer are Toner cartridge, charge and discharge (corona) wires, transfer rollers,fusing unit, paper pick-up assembly, transport section and exit section with de-curl rollers and electro static discharge.
Laser Printer Working Principle
Receiving Data: Laser printer needs to receive the data (text or picture) from the source, this is the job of the printer controller.The printer controller is the laser printer’s main on board computer.
It talks to the host computer through parallel port or USB port or through LAN. Once the data is received and buffered the printing process starts.
Printing speed and data receiving speed are different, therefore laser printer stores received data before printing.
Charging drum: Toner cartridge consists of aluminum cylinder coated with photosensitive material, fresh toner tank and waste toner collection tank.
Once the data is received, drum is charged with high negative voltage through the charge carona wire placed at the top of the drum in toner cartridge.
Exposing drum: Received data is fed to the laser diodes or LED’s to illuminate. These light rays which is same as the received character, is written on the charged drum, there by negative charge is neutralized in the drum surface.
Exposed areas or neutralized area mostly invisible to human eyes which is exactly same as original received data. Simultaneously toner in the toner cartridge is charges negatively.
When the drum rotates and come closer to the toner container, exposed areas attracts the negatively charges toner particles thereby forming visible image in the drum surface.
Paper feed: Once the drum is ready with printable data, paper is picked up by the pick-up roller assembly. Toner cartridge is placed in the printer in such a way that the drum unit in the cartridge is in near proximity to transfer roller in the printer base.
Transfer roller is charged highly, then paper is fed in between transfer roller and drum unit. Transfer roller charge pulls the toner particle in the drum unit which sticks to the paper there by image is transferred to the paper.
This image is not permanent and it can be erased by rubbing. After transferring the data to paper any residual waste toners are cleaned by blade and collected in the waste toner container.
Fusing: Since the image or data in the paper is erasable, paper is fed in to fusing unit. Fusing unit or fuser unit has two rollers, Heat roller attains maximum temperature using halogen lamp and another roller applies pressure when the paper is fed in between them.
Due to high temperature in the heat roller toner and glue particles in the paper melts and sticks to the paper and the image becomes permanent.
Discharge: To print the next received data, drum must be cleaned to remove any traces of previous pages. Rubber blade wipes the excess toner from the drum, and then discharge lamp is used to expose and clean the drum by neutralizing residual electrical charges on it.
At the paper exit a grounded discharge material touches the paper to remove electro static charges. Paper bends because of the heat applied by the fuser unit, de-curl rollers are used to straighten the paper while exit.
This laser printer printing process was initially used in copier machines. The difference in copier machines and laser printer is the data is sent to printer in electrical form whereas the document is scanned and the image is directly sent to the drum unit in photo copier.
Some of the problems you may face in laser printer is when the charge carona wire, transfer roller, discharge wire are not functioning properly or dust accumulated, it affect the printout with vertical black lines, black background with actual data.