Specifications

Figure 3 A laser printer’s print engine largely revolves around a photoreceptor drum that receives the doc-
ument image from the laser and applies it to the page as it slowly rotates.
Toner Fusing
After the toner is transferred from the photoreceptor drum to the page, the page continues its journey
through the printer by passing over yet another corotron, called the detrac corotron. This corotron
essentially cancels the charge that was originally applied by the transfer corotron just before the appli-
cation of the toner. This is necessary because an electrostatically charged piece of paper tends to stick
to anything it contacts, such as the printer’s paper handling rollers or other pieces of paper.
At this point in the printing process, you have a sheet of paper with toner sitting on it in the pattern
of the printed page. The toner is still in its powdered form, and because the page is no longer stati-
cally charged, nothing is holding it in place except gravity. A slight breeze or tremor can ruin the
image at this point. To permanently fuse the toner to the page, it passes through a pair of rollers
heated to 400° Fahrenheit or more (see Figure 4). This heat causes the plastic toner particles to melt
and adhere to the fibers of the paper. At this point, the printing process is complete, and the page
exits the printer. It is the nature of the toner and the fusing process that causes the characters of a
laser-printed document to have a raised feel and appearance to them that is very attractive, whereas
an inked page feels perfectly flat.
Laser Scanning Unit
Laser
beam
Toner
hopper
Toner
Photoreceptor
Developer
roller
Paper
Detrac
corotron
Transfer
corotron
Fuser
Discharge
lamp
Charge corotron