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The Basic Engine

Laser Printers are really very simple devices. The technology came from the copier industry. Infact, Canon was one of the first to be sucessful at marketing a laser copier called the PC20. The early HP original laser printer is based on this copier. The steps of a laser engine is really easy to follow.

Paper Feed

In the picture above, the paper enters the laser engine. It is pushed through the engine with a paper feed assembly. Depending on the model this feed can be a simple one drive system like the picture above, or a more complex one with many rollers. The main point is to push the paper along, under the drum, to the fuser assembly.

Image Process

The paper is pushed along into the image area. Depending on the model, the process can vary. The image above is based on the Canon, HP, Apple, Minolta, and other models like them. A single unit cartridge contains the drum, toner, and waste hoppers all in one. We'll explain each part of the process.

The first thing that happens is your computer sends a line of data to the laser printer. It's stored and then formated. Once enough data has arrived to complete a page, the laser printer starts a series of things. First, it starts to send the page to the drum, line by line. A laser beam is modulated to place dots on a rotating drum, one line at a time. Above in our graphic, you'll see the laser hitting a mirror that directs the beam onto the drum surface. Several laser printers use different types of drums. The laser beam causes the drum to become negative orpositive in the places the beam hits. As the drum rotates it touches a roller called the developer roller or the Mag rollers.

The purpose of the roller is to pick up toner from the toner chamber, then with an even layer of it, roll on to the drum. The roller is charged with either positive or negative voltage. Again, this depends on the printer. When the drum, with a lack of voltage meets the toner with the excess voltage, the toner is pulled into the places the laser has touched. The next step is to move the toner from the drum to the paper. In the picture above, there is a item called a Corona. This is a thin wire that sits under the drum and is charged with a very high voltage. As the drum turns, the paper passes over the corona and is between the corona and the drum. The paper is touching the drum a slight bit. The high voltage running through the corona wire creates a pull to attract the toner from the drum onto the paper. As the paper moves on, it takes this image to the next section of the printer (the fuser).

Before we hit the fuser, the drum continues to rotate. As it does hit with a special light that erases or returns the drum back to its state of discharge. The image is removed with a blade near the erase lamp and you now have a clean drum. As it continues to rotate, it is charged up for the next image with a second corona wire. In some printers they use a charge roller. In any case, the drum is recharged to positive or negative forces and the image process starts all over.

The final step before you can use the paper is to fuse the toner to the paper. As the paper with the toner image is moving out of the image area. It moves into the fuser section. This is a device that looks sort of like an old time washing machine. These two rollers touch with a great deal of force between them. One of the rollers is heated up to 200 degrees or more. The paper is fed into the fuser. The pressure rollers heat up and fuse the toner to the fibers on the paper. The fuser then pusheds the paper out of the printer into the waiting hands of the user.



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