Printers, Laser Printers, How A Laser Printer Works

Laser Printers

Laser printers range from the small, personal desktop size to large, network printers capable of handling enormous volumes of printing on a continuous basis. Laser printers require the interaction of mechanical, electrical, and optical technologies to work.

Understanding how they work helps you to understand why safety precautions that are stated in laser printer user manuals are necessary, and is also helpful for supporting and servicing the printer.

How A Laser Printer Works?

Laser printers work by placing toner on an electrically charged rotating drum and then depositing the toner on paper as the paper moves through the system at the same speed the drum is turning. The following are the six progressive steps of laser printing. Four of these steps use components contained within the removable cartridge. The last two steps are performed outside the cartridge.

Note that only a cross-section of the drum, mechanisms, and paper. As you visualize the process, remember that the drum is as wide as a sheet of paper. The mirror, blades, and rollers are also as wide as paper. First note the location of the removable cartridge in the drawing, the photosensitive drum inside the cartridge turning in a clockwise direction, and the path of the paper, which moves from right to left.

Step 1: Cleaning

The clear view of the cleaning step:

1. A sweeper strips cleans the drum of any residual toner, which is swept away from the drum by a sweeping blade.

2. A cleaning blade completes the physical cleaning of the drum.

3. Next, erase lamps (located in the hinged top cover of the printer) light the surface of the drum to neutralize any electrical charge.

Step 2: Conditioning

The conditioning step puts a uniform electrical charge of -600V on the drive. The charge is put there by a primary corona wire, which is charged by a high-voltage power supply assembly. The primary corona in the following figure is between the primary corona wire and the drum, and regulates the charge on the drum, ensuring that it is a uniform -600 V.

Step 3: Writing

In the writing step, the uniform charge that was applied during the conditioning step is discharged only where you want the printer to print. This is done by controlling mirrors that reflect laser beams onto the drum in a pattern that recreates the desired image. This is the first step in which data from the computer must be transmitted to the printer.