I know, weird right? Its true though. If you run “cheap” letter head or envelopes through a laser printer… there is a chance that your fantastic logo and beautiful information on your stationary will MELT! The streaking and lines and “fuzz” you sometimes seem when running your letterhead through your copier isn’t always a dirty roller or dust …. I called William Shatner to do a “Weird or What?” segment on this, but it appears I am on my own.
Lets do some science ….
The toner cartridge contains a rotating, magnetic, metal-developing cylinder, a toner reservoir, and a height control mechanism that limits the amount of toner the cylinder can pick up at a time. Toner consists of plastic resin particles (the particles that melt to produce the image on paper) and iron oxide (the particles that are affected by magnetic attraction and electrical charges). The toner’s metal particles adhere to the magnetic cylinder, and the cylinder presents the toner to the drum as it passes by. The developing cylinder is charged to -600v, like the blank portions of the photosensitive drum, and the toner adhering to the cylinder also takes on that same charge.
If you ever get toner on fabric accidentally, you can get it off with a magnet, since the toner is about 50 percent iron oxide.
As the drum passes by the cylinder, the toner ignores all the areas charged to -600v because that’s the same charge as itself. It jumps off and clings to the areas with the lesser charge (-100v), however, and that’s what makes the toner stick to the drum.
At this point, the image exists on the drum, complete with toner. If you could look inside the printer as it operates (you can’t, by the way, because of the safety features in place) and stop the drum from rotating for a moment, you could see the page on the drum, just as it is to be printed.
As the paper feeds into the printer, the transfer corona applies a +600v (positive) charge to the paper. When the paper passes by the drum, the -100v charged toner on the drum jumps off onto the positively charged paper. Then, the paper runs past a static charge eliminator, which is a row of teeth with a negative charge that reduces the paper’s highly positive charge.
The image is now on the paper, but it’s not secure there; it’s just loose toner held in place by gravity and a weak electrostatic charge. For permanent application, it must be fused. Fusing is basically melting the toner’s plastic particles so they stick, or fuse, to the fibers in the paper.
The fuser roller is a nonstick cylinder with a high-powered lamp inside it that heats the paper to around 330 to 355 degrees Fahrenheit. As the paper passes by it, the toner melts. A fabric or felt-cleaning pad, in constant contact with the fuser roller, helps keep it clean. With many laser printers, you change the cleaning pad whenever you change the toner cartridge.
If you have ever been warned not to use inkjet-type transparencies in a laser printer, the fuser is the reason. Any material that melts at less than 350 degrees is going to melt inside a laser printer, resulting in a huge mess and the need to replace the fuser roller assembly. Cha-Ching!
The final part of the fusing assembly is the pressure roller. It’s a rubber roller that presses against the fuser roller; the paper feeds between it and the fuser roller on its way through the printer. The fuser roller can leave an indent on the softer pressure roller because of the heat it produces, so the printer’s internal software will rotate the assembly periodically to keep this from happening.
Neat huh? Another tip – When creating letter head, envelopes or other collateral you are going to print on … make sure it’s done right. We might melt your heart, but your laser printers wont melt our letterhead 🙂