13.3.1 Laser Printers

Learn about how to troubleshoot and maintain laser printers.

Laser printers are fast, produce high quality printouts, and reasonably inexpensive to use and implement in an enterprise setting, which is why they're highly used. Laser printers use a process and melting and cooling plastic in order to produce a high quality image on a piece of paper.

Component List

• Laser
• Toner
• Developer Roller
• Image Drum
• Charge Roller
• Transfer Roller
• Fuser
• Oscillating Mirror

Printing Process

Processing

The document is sent to laser printer.

• The laser printer receives a document from the connected computer.
• The document passes through the raster image process (RIP), which divides it into horizontal raster lines of organized dots as characters words, and graphic images.
• The document is stored in the printer's memory.

Charging

The imaging drum is prepared to receive the image.

• The imaging drum is a rotating cylinder covered with a special photoconductive (green) coating.
• A primary charge roller (PCR), or a corona wire in some older printers, passes a high-powered negative charge to the surface of the imaging drum.
• The drum can be built into the toner cartridge rather than a standalone unit, depending on the printer manufacturer.

Exposing

The laser writes the image on to the drum.

• A highly focused laser light and scanning mirrors are used to shine across the surface of the imaging drum and write or expose the rasterized image onto the drum.
• The laser removes the charge causing a neutralized electrical charge wherever the light has written.
• The neutralized areas are ready for the toner particles to adhere

Developing

The toner is applied to the imaging drum.

• The toner cartridge hopper releases electrically charged carbon toner particles onto the drum as it turns.
• Because it is electrically charged, the toner is attracted to the imaging drum only where the laser wrote the image.

Transferring

The image is transferred to paper.

• Pickup rollers on top of the paper tray pick up paper and begin feeding it through the printer.
• Separation pads under the paper spin in the opposite direction and push extra paper back. These pads help prevent more than one piece of paper from being sent through the printer at a time.
• The transfer roller (or transfer corona in some older printers) applies a charge to the paper to attract the toner.
• As the drum turns and the paper is moved through the printer, the charged paper attracts the toner away from the drum.
• After the toner is transferred from the drum onto the paper, it is held with an electrostatic charge.
• In some color laser printers, a rotating belt or transfer belt is used to transfer colored toner to the paper. Different color toners require a separate step for each color.

Fusing

The toner is bonded to the paper.

• The fuser assembly uses a combination of friction and heat to melt the toner onto the paper. The fuser can get as hot as 356 degrees Fahrenheit.
• The toner is sealed to the page, so it's no longer in powder form. If the toner smudges or wipes off the printed page, it's because of a faulty fuser assembly.
• A static eliminator strip removes the charge from the paper.

Cleaning

The roller is cleaned for the next image.c

• Cleaning is a physical and electrical process to remove the previous image from the drum.
• An electrostatic erase lamp neutralizes the charges on the drum from the previous printed image.
• The scraper works like a windshield wiper to remove excess toner from the drum.
• If a print job shows a ghost image of a previous page, the erase lamp or scraper might be the problem.

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