The fuser unit is a very important component of laser printers. The fuser unit, which is essentially two heated rollers, uses pressure and heat to fuse the toner powder onto the paper.
Depending on your printer model, the fuser unit may be sold separately or it may be included in the printer's maintenance kit.
How Does A Fuser Work?
At the end of the laser printing process, the paper gets passed through the fuser after the loose toner powder is placed on the paper via static electricity. The fuser melts the toner particles, binding them to the page. The speed at which the paper passes through the fuser is what keeps the paper itself from burning. If the speed were slower, the paper would combust and burn. There is also a thermostat built into the fuser that makes sure heat from the fuser never exceeds a certain temperature.
During the fuser melting process, the paper gets pulled through two rollers which make up the fuser assembly. The top roller holds the heat that melts and permanently presses the toner particles into the paper. The bottom roller is sometimes also heated such as in the case of duplex (double-sided) printing.
When Do I Replace The Fuser?
Fuser units eventually need to be replaced after frequent use. Most laser printers will inform you when the fuser unit needs to replaced. An easy way to identify when a fuser unit needs to be replaced is when there is smudging or smearing on your printout. Smudging and smearing occurs because the fuser will not heat the toner particles enough to fully melt them onto the page.
One of the differentiating factors for laser printers vs. inkjet printers is the laser printer's use of a fuser, which when functioning correctly, assures that there is no smudging or smearing on your printout.