How Does a Laser Printer Work, Anyway?

This is a great question. After all, how can a laser write on paper? The answer, of course, is that it doesn’t. It writes on an electrically charged drum, and uses the differences in electric potential to coat the drum with toner, and place the toner on the paper.

OK, that sounds like a mouthful, and it is, so we’ll look at it step-by-step.

The Drum

When a laser printer starts a print job, the first thing it does is apply a positive electrical charge to the drum unit. Afterwards, the laser system ‘writes’ the page image onto the drum with a negative charge, creating an electric “virtual negative” of the image.

The Toner

The drum unit rotates, and as the image is written on it, it picks up toner, the laser printer equivalent of ink. The toner is positively charged, and so it sticks to the image that the laser drew. The paper presses against the drum, and receives the toner image.

The Fuser

When the paper first picks up the toner, the image is not set. Toner is a dry, dusty material, and it the electric charge cannot hold it strongly to the paper. In order to make the image permanent, the paper runs through the fuser, which heats it, and melts the toner onto the page. The paper exits the printer, and that’s that.

See? That wasn’t too hard to follow…