How Does A Laser Printer Work?

A laser printer is an essential part of a modern office. Have you ever wondered how it works? Laser beams mark targets, cut metal, and drive my cat crazy. They don’t print letters. Do they? How? Let’s look at the basic parts of a laser printer and see how they work together.

I was a kid that took things apart. Clocks, toasters, fans. I had to see how they worked. One day, I saw a laser printer. The best I was ever able to figure out on my own was that somehow the laser beams burned text onto a page. That idea failed when I considered color copies. I was stymied.

What Are The Important Parts Of A Laser Printer?

That Toner Cartridge May Have More To Do With It Than You Can See.

The first laser toner cartridge I saw escaped my understanding, too. I thought it was a big, square plastic container with printer ink in it! I grew up in the era of the inkjet cartridge.

There are several parts to the cartridge. The first is the outer housing which holds a drum within. Then, there is a wiper blade and a wiper blade housing. There is a reservoir inside containing dry powder. That one threw me for a second. Part of the powder is ink pigments, and the rest is plastic. We’ll see how they work together in a second.

What Are The Rest Of The Relevant Parts?

There is the laser, of course. Then, there is a part called a corona wire. It is a special wire about 1/50th the size of human hair. Finally, there is a fuser unit, which is two heated rollers. Oh, wait, there is one more important part. Paper. 

How Do These Parts Work Together To Print A Document? 

You want to print or copy a document. The printer gets all the information and goes to work. It activates the corona wire. The corona wire creates a visible and audible positive electrical charge that transfers to the drum within the toner cartridge and the paper.

The opposite side of the electrical charge created by the corona wire gives the toner powder a negative charge. Since opposites attract, the toner coats and adheres to the drum. 

Now the laser starts moving back and forth across the drum. The light changes the electrical charge of the powder it shines on. The powder with a positive charge falls off the drum. What remains is a reverse image of the desired document made of toner powder with a negative charge on a drum with a positive charge.

The paper is fed into the toner cartridge and pulled through the cartridge by the drum. Remember, our corona wire gave both the drum and the paper a positive charge. So as the paper pulls through, powder with a negative charge on the drum is attracted to the paper. In this way, the image on the drum is transferred to the paper.

There is only one step left before the printer spits out your document. The image is attached to the paper with positive and negative charges, but it won’t stay stuck for long unless something else happens. The powder is ink pigment and plastic. The paper feeds through the fuser, or two hot rollers, and the plastic melts. The image is now permanently fused to the paper.

And there it is! A clean, crisp copy is yours.

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