Laser Printers: Not Just Hocus Pocus
Laser printers always seemed magical to me. Other kinds of printers were easier to understand, more mechanical if you will. With laser printers, it seemed like the words and images just magically appeared.
Well, as magical as it certainly seems, the concept behind laser printers is certainly not magic. In fact, once you understand it, it’s downright simple. Ok, you got me. It’s not really that simple, but it is far from magic.
Static Electricity
Yes, it’s hard to believe, but the same principle that’s behind your socks sticking together (or to your leg) is the same thing that makes laser printers do their thing. You see, static electricity is cause by oppositely charged atoms sticking together. Who says opposites don’t attract?
Laser printers use this principle to temporarily hold things together. Let me explain.
The main component in laser printers is a photoreceptor, which is a fancy way of saying a revolving drum or cylinder that is made out of super photoconductive material and discharged by light photons.
All this really means is that this material only conducts electricity when it’s exposed to light.
The Drum
The drum, or drum assembly, is positively charged by something called the charge corona wire. The charge corona wire is simply a wire with an electrical charge running through it.
When the drum turns (remember, it only conducts electricity when exposed to light), a very tiny laser beam shines on the surface, discharging certain points, and “drawing” letters and images.
After the laser beam has finished doing its thing, the drum is coated with a fine, black powder known as toner. This toner is positively charged, so it “sticks” to the negatively charged images and letters that the laser beam has drawn on the drum.
Keep in mind that the background, thanks to the charge corona wire, is positively charged. It is for this reason that the toner does not stick to the background.
It’s kind of like making an “X” on your palm with glue, then putting your palm, face down, on some flour. When you lift it, only the glued part of your hand will contain the bulk of the flour.
While the toner is still on the drum, the drum rolls over a sheet of paper. Before this happens, the paper is given a negative charge, stronger than that of the images on the drum. This is so that when the paper comes into contact with the drum, it can pull the toner away from it.
But if the paper is negatively charged, and the drum is positively charged, why doesn’t the paper stick to the drum? Because after they connect, the paper is discharged by a little thing called the detac corona wire.
The Fuser
As the paper is released, it passes through the fuser, which is a pair of heated rollers. The fuser melts the toner and causes it to fuse with the fibers of the paper.
After the toner is put on the paper, the drum is exposed to a very bright light which discharges all the imagery from the previous printing. The charge corona wire then applies a positive charge.
1 Trackbacks/Pingbacks
- Trackback: ROGER on July 6, 2010