No, it's not magic.
If someone said that there was a device in your office capable of firing a laser, would this be exciting or startling news? Well, if you have a laser printer in your office as most do, this laser is a major component in your average toner-based printer. While it doesn’t sound very exciting once you learn that this “laser ray” is mostly used to produce printed versions of spreadsheets and company memos, there is some seriously impressive science happening in that machine that you may take for granted. In this article, we’re going to look at how toner-based printers use lasers to print your organization’s documents and photos. It may sound overly complicated at first, but we’ll make sure to simplify each step with an example you're sure to understand.
1. "The Paint Roller Sleeve"
Laser printing, or “the electro-photographic process”, first begins typically with a Primary Charge Roller (PCR) applying a negative charge (or sometimes positive charge depending on the printer) to an Organic Photo Conductor (OPC) drum — something that looks like a big metal rolling pin. The OPC drum usually has an aluminum substrate that allows it to hold the PCR’s applied charge. This charge allows the toner to stick to OPC drum.
Simplified explanation: Think of the PCR applying a negative charge to OPC drum like your hand applying the brush sleeve to a paint roller handle so the paint can stick to it.
2. “Begin (air quotes)‘laser’ ignition sequence.” — Dr. Evil, Austin Powers: International Man of Mystery
Now that the drum is good and “sticky” with a negative charge, a laser unit fires the image onto the OPC drum, usually through a mirror. The laser beam in combination with the mirror generates a negative image on the OPC drum. The OPC drum then rotates past what is called a “toner hopper” — a toner receptacle containing the powdery substance you may have seen within a laser printer. The toner hopper applies a thin layer of the toner powder to the laser-blasted OPC drum.
Simplified explanation: Now that the paint roller sleeve has been applied to the paint roller handle, think of the toner-coated OPC drum (your paint roller) now as being pre-painted with the picture you wish to apply elsewhere...only instead of a paintbrush creating the picture, this image is created with a laser!
3. Mmm, Melted Toner
As the OPC drum picks up toner from the toner hopper, paper rolls under the OPC drum to receive the toner-covered image applied to the drum from the laser like a big elaborate stamp or paint roller. Though the image is applied to the paper, the toner at this stage is still pretty much like sticky powder and needs a more permanent application to the paper, much like a balloon statically stuck to your sweater would still need to be glued to your sweater if you wanted it to remain attached to your sweater (we make no judgment on your fashion sense). On its way to greet you on the other end, the paper with the laser-drawn toner image passes through a hot, ceramic-fusing element that melts the powdery toner into the desired image. If you’ve ever felt a sheet of paper fresh out of the printer, you’ll notice that it’s very warm and may even have a slightly burnt of melted smell to it. That’s freshly cooked toner on the page ready for your next conference room meeting!
Simplified explanation: If your OPC drum is like a paint roller with a picture already painted on the roller itself, imagine rolling this pre-made painting onto a t-shirt. While the painted image is on a t-shirt, it’s not quite ready to wear out on the town because the paint is still wet! The ceramic element toner-heating process would be like helping your t-shirt painting dry with the help of hairdryers. After the blasted heat does its job, your image is safely applied and ready for the world.
And that’s about it! While most of us take it for granted, there is a lot of genius engineering packed into every laser printer on the market.