Laser printers are the printer of choice for most office environments, because the print is letter quality, the print mechanism is fast, and the cost per page is low. Laser printers work in the same way as photocopiers - a laser beam is fired at a photo-sensitive drum. Where the beam strikes, print will appear on the page.

Operation and Architecture

Laser printers use a toner cartridge containing a powder made of plastic and iron particles that is bonded to the paper to create an image. The paper feed mechanism is similar to the paper feed in an inkjet printer in that it uses pickup rollers to push the paper into the print mechanism.

A laser print engine is made up of several components - there are only a few print engines are used in all the major brands of laser printers available today, and most work in a similar manner. The major components in a laser printer and the role of each is explained below.

Cleaning stage — A photosensitive drum known as an Environmental Photocell (EP) cartridge is exposed to an erasure lamp to evenly charge the drum and prepare it to accept data.

Writing stage — The data received from the PC fires a laser into a mirror, which reflects the beam to a photosensitive drum. The the image that will be transferred to the paper is drawn on the photosensitive drum.

Developing stage — Toner is attracted to the areas of the photosensitive drum that have been struck by the laser.

Transferring stage — Paper running through the print mechanism is charged to a greater potential than the photosensitive drum by a transfer corona wire. As the paper passes near the photosensitive drum, the toner is transferred to the paper.

Fusing stage — The paper is fed into a fuser assembly that is heated to more than 600 degrees, which melts or “fuses� the toner to the paper.

Final stage — Export rollers receive the paper from the fuser assembly and push the paper out of the printer.

The drum is made of a fragile material that can be damaged by light or dirt, so you should never touch the photosensitive drum or expose it to light for extended periods of time. Some laser printers, such as Hewlett-Packard printers, have an enclosed combination toner reservoir/photosensitive drum, while other manufacturers, such as Okidata, separate these components.

Troubleshooting

Laser printers normally have two problems — poor print quality or paper jams. Listed below are a few of the causes for each:

Poor print quality — The most common cause of poor print quality is the toner cartridge. If possible, replace the toner cartridge and print several test pages. Rebuilt toner cartridges can be newly installed and still print poor-quality pages. Look at the fuser and make sure the roller is free of dirt and is not marred. Look at the mirror in the lid and make sure it is free of oil, dirt, and debris.

Paper jams — First, you need to determine whether the paper is jamming at the entrance or while exiting. The fuser assembly can be considered the midway point. Make sure the pickup rollers are free of dirt or oil and are not worn or cracked. Make sure the paper path is free of paper and debris. If the paper is jamming during exit, make sure the gears on the fuser assembly aren’t damaged.