Learn the basics of laser printing

Most IT pros can solve simple laser printer problems, such as paper jams and low-toner alarms, but ask techs about drums and fusers and you?ll get a lot of blank looks. Set yourself apart from rest by learning the inner workings of laser printers.

While software issues cause a large number of printing problems, hardware malfunctions can be just as troublesome. If you’ve been putting off learning the nuts and bolts of laser printers, it’s time to demystify their inner workings. Here is a detailed overview of the anatomy of a laser printer and the basics behind the laser printing process. This information will give you the foundation you need to begin troubleshooting laser printer problems.

A word to the wise
Before I get started, I’d like to point out that this article is intended only to assist with basic printer repair and maintenance. If you’re unsure of your ability to perform any sort of printer repair, or if performing such repairs will void the printer's warranty, you should contact a qualified service professional or the manufacturer.

The laser printing process in a nutshell
Laser printers are surprisingly simple and contain only a few major parts. Laser printers work by receiving a document through the input port. The printer then begins to store the document in its internal memory until an entire page has been received. Once a full page exists in memory, the printer begins the printing process, which involves generating a static charge that makes toner stick in the charged areas. The paper then passes through the fuser, which melts the toner to the paper. The printed page is then ejected from the printer.

It’s all in the details
Receiving data from the computer
Now that you know the basic printing process, let's take a look at the components involved. The first thing that happens is the laser printer receives the print job from a computer and stores the print job in memory. This process is accomplished primarily by the printer’s system board (sometimes called a formatter card). The printer’s system board is connected to an input device, which is typically a parallel port, a USB port, or a network card. The system board works almost like a miniature PC. It facilitates the traffic flow through the input device and moves the data into memory. Most laser printers have some memory built into the system board but also allow external memory modules to be attached. The added memory modules allow larger print jobs to be stored in the printer’s memory.

Lasers, drums, and corona wires
Once a full print page is stored in the printer’s memory, it’s time to begin the printing process. Remember that the printing process is based on static electricity. Atoms with opposite charges are attracted to each other. If you rub a balloon against your hair for a few minutes, you can stick the balloon to a wall because the balloon has a different charge than the wall does. The same concept applies to making toner stick to the necessary components.

The printing process relies on a laser, a device called the drum (shown in Figure A), and something called the corona wire. The drum is a cylinder that’s made of very conductive material. The corona wire is nothing more than a thin wire that carries electricity. The process begins by charging the corona wire. By spinning the drum while electricity is flowing through the corona wire, the drum becomes positively charged.

Figure A
The drum is made of a conductive surface.

Next, the system board translates the print job’s language (typically PCL or Postscript) into instructions for the laser. This process directs the laser to focus on certain points of the drum. The laser is actually drawing images on the drum in the form of pixels. The points on the drum that have been hit by the laser beam become discharged. As the drum spins, toner sticks to the discharged areas. Next, the paper is passed beneath the drum and as the drum spins, the toner that is on the drum rubs off onto the paper, resulting in a printed image.

Once the toner has been applied to the paper, the paper is run through the printer’s fuser (shown in Figure B). The fuser is a series of wax rollers that get very hot. Their purpose is to melt the toner to the paper. If the paper didn’t pass through the fuser, it would actually be possible to wipe the image right off of the paper with your bare hands. The heat from the fuser is the reason that paper often feels warm when ejected from a laser printer.

Figure B
The fuser completes the job, melting the toner to the paper.

Calling all laser printer masters
Are you a laser printer whiz? Can you spot a paper jam or hear a low-toner alarm from three offices away? If so, we want to know your secrets. Post a comment to this article and share your laser printer tips.


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