All laser printers run in a very different manner to inkjet printers and dot matrix printers. An inkjet printer will get information from the computer directly and print the results as soon as they are received. Due to the way a laser printer works a very different approach is required.
Laser printers require a more complete picture of how a page will appear before they set out on the page printing process. To do this a laser printer pulls together and stashes away the needed information about a page locally inside its memory before it begins to print. This is why there are usually bigger delays in commencing printing between inkjet printers and lasers.
The main component of a laser printer is a drum unit that will roll over the page to print the image. A common inkjet printer will print each letter when it gets it, but because a laser printer uses a drum to roll across the page a more complete picture of the final page is needed before the printing begins. A laser is used to project the image of the pages directly on to the drum. That drum is covered in a substance known as selenium. The parts of the selenium that have been hit by the laser beam lose their electrostatic charge. This process is known as exposing.
The toner in the printer, which is dry ink, is attracted to the charged areas on the drum and repelled from the uncharged areas producing a full picture on the drum. Coating the drum with the dry toner is known as developing. The drum in the laser printer is run across the paper to transpose the picture to the page.
The part of the process that involves the most power is known as Fusing. In order to get the dry toner particles to adhere to the page a combination of heat and pressure is essential. To attain this, the paper is put through a fuser unit. Typically a fuser unit applies a heated roller that runs over the page followed by a rubber roller that tightly compresses the warm toner to the page.
The drum does not need to have a complete picture of the page exposed upon it before the printing starts, rather it has to have a total width of a picture for a predefined depth. When enough information is assembled the laser printing action starts in a continuous manner.
Laser printing is not as new of a technology as many people think with its origins dating back to the late 1960’s. It was however to take until 1984 before commercial mass market laser printers became available.