Photocopier (MFP)

Overview

A photocopier, today almost always a colour laser multifunction printer, reproduces documents by scanning an original to a digital image and then printing that image onto paper using electrophotography. The same engine serves as a network printer, a scanner, and a fax, so one floor-standing machine handles a whole office's document work. It works by xerography: a laser writes a charge pattern onto a photosensitive drum, toner sticks to that pattern, and heat fuses the toner permanently into the paper.

The machine is a tall stack of modules on a steel frame. The Chassis & Covers is that frame and its covers. On top, the Scanner Unit and the Auto Document Feeder capture originals. Inside, the Laser Scanner Unit writes the image onto the Imaging Unit's drum, the Fuser Unit bonds the toner, and the Paper Path moves sheets from the trays through the engine. Output is sorted by the Finisher, all coordinated by the Main Controller Board and driven from the Operation Panel.

How it works

To copy, the Auto Document Feeder feeds an original past the Scanner Unit sensor, producing a digital image. The Main Controller Board processes that image and sends it to the print engine. The Laser Scanner Unit modulates a laser across a spinning mirror to sweep lines of light onto the charged drum in the Imaging Unit, discharging the spots that should carry toner.

Toner, charged coloured powder, is attracted to that latent image on the drum, then transferred onto a sheet pulled from the Paper Path. The loose toner is still only resting on the paper until it passes through the Fuser Unit, where heat and pressure melt it into the fibres to form a permanent print. Colour pages repeat the develop-and-transfer step for cyan, magenta, yellow, and black. Finished sheets travel to the Finisher, which stacks, offsets, and staples sets, while the operator manages jobs at the Operation Panel.