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How do Laser Printers Work
laser printer

In an ideal office world, paper would be a thing of the past. Many companies have attempted the ”paperless office”  However, the concept appears to still be a myth and printers are still out there doing their job spitting out sheet after sheet of paper. Among the many type of printers on the market that need a computer technician’s love and care is the laser printer. Naturally, a computer tech will want to become familiar with how do laser printers work. 

The Basics

The primary principle at work in a laser printer is static electricity. Yes, it is that thing that happens when you walk across a room on a carpet floor and receive a nice electrifying, gigantic shock as soon as you touch the doorknob. Or maybe when you rubbed a balloon in your hair and laughed as it stood straight up. A laser printer uses this exact phenomenon to transfer a dry ink powder called toner. The mechanism used is called electro-photographic imaging. The laser printers rely on the photoconductive properties of certain organic compounds. Photoconductive means that the particles, when exposed to light will conduct electricity.

The Parts
inside laser printer
Toner Cartridge

Toner cartridges holds toner powder, a fine, dry mixture of plastic particles, carbon, and black or other coloring agents that make the real image on the paper. Fortunately many of the parts that take the most wear and tear are contained inside the toner cartridge.

 

Photosensitive Drum

This is an aluminum or metal cylinder coated with particles of a photoconductive coating which allows it to hold an electrostatic charge. The quality of the output depends highly on your drum.

Erase Lamp

The erase lamp exposes the photosensitive drum to the light to neutralize the electrical charges, allowing any remaining particles to be removed before the next print.

Primary corona/charge roller

The primary corona negatively charges (~600 to ~1000 volts) the photosensitive particles on the surface of the drum.

Laser

The laser acts as the writing mechanism of the printer, when particles are struck by the laser, they are discharged and left with negative ~100 volts.

Toner

Toner with a negative charge is placed on the drum and transferred to the paper.

Transfer corona/transfer roller

The transfer corona positively charges the paper to attract the particles off the drum and on to the paper. The transfer roller is used on newer laser printers.

Fuser assembly

The fuser assemble melts the toner permanently to the paper using a pressure roller and heated roller.

Power supplies

There is two types of power supplies. You have the primary power supply that provides power to the motors that move the paper, system electronics, and transfer corona. The high voltage power supply provides power to the primary corona/charge roller.

Gear System

All the mechanical functions of a laser printer are served by complex gear systems. These gear systems are generally packed together in what is called gear boxes.

System board 

The system board of a laser printer contains the main processor, ROM, and RAM.

Sensors and switches

The sensors detect paper jams, empty paper trays, low toner levels, etc.

Drivers and Software

Most laser printers ship with software that includes the basic drivers that communicate with the operating system, diagnostic programs, and advanced programs that allow full control of all the printer’s options.

Resolution

When it comes to quality output, a laser printer can print at different resolutions. The resolution is expressed in dots per inch (dpi)—for example, 300 × 300 or 1200 × 1200 dpi. The first number is the horizontal resolution—how fine a focus can be achieved by the laser. The second number is the vertical resolution—the smallest increment by which the drum can be turned.

Printer Speed

In printing, PPM is an abbreviation that stands for “pages per minute.” If a vendor advertises a speed of 25 PPM, the vendor is saying that the printer will print 25 test pages in one minute. Beware as the vendor can decide about what content is on that ”test page”  Therefore these numbers are sometimes slightly exaggerated.

Now that you are familiar with how a laser printer works,  you should be less intimidated to attempt and repair one. Although, the price of a replacement printer is usually cheaper than the cost of a repair job , there is still certain instances where it could be more advantageous to repair the printer instead of  replacing it. Not to mention you will look like a real I.T pro in front of your colleagues. We will touch on trouble shooting laser printers in an upcoming article.