10.A - Maintaining laser printers Flashcards
The speed of the printer is described in terms of?
Pages Per Minute (PPM)
Image quality is measured in?
Dots Per Inch (DPI)
Image quality can range from?
600dpi to 1200dpi
The cost of a printer over its life time is called?
Total Cost of Ownership (TCO)
What are some options a printer may have?
Additional memory, duplex (double-sided) printing, large format(A3 and greater)
A Multi Function Device is described as?
Is a piece of office equipment that performs the functions of a number of other specialized devices. MFDs typically include the functions of a printer, scanner, fax machine, and copier.
Describe how a laser printer works.
Type of printer that uses a laser beam to project an image onto an electrically charged drum; toner adheres to the drum and is transferred onto the paper as the paper moves through the mechanism at the same speed the drum rotates. The toner is fixed using high heat and pressure, creating a durable print out that does not smear or fade.
Why are laser printers popular?
They are cheap (both to buy and to run), quiet, and fast, and they produce high quality output.
Describe the processing stage of a laser printer.
Laser printers produce their printed output in a series of dots. The computer encodes the page in a printer language and sends it to the printer. The printer’s formatter board processes the data to create a bitmap (or raster) of the page and stores it in the printer’s RAM.
Describe the charging stage of a laser printer.
The electrostatic photographic (EP) drum, or imaging drum is conditioned by a corona wire powered by a high voltage power supply assembly. The corona wire applies a uniform -600 V electrical charge across the drum’s surface.
Describe the exposing stage of a laser printer.
The surface coating of the photosensitive drum loses its charge when exposed to light. A laser neutralizes the charge that was applied by the corona wire selectively, dot-by-dot and line-by-line, as the drum rotates. The pulsing light beam is reflected by a rotating polygonal mirror through a system of lenses onto the photosensitive drum. The drum ends up with a whole series of raster lines with charge/no-charge areas that represent an electrostatic latent image of the image to be printed.
Describe the developing stage of a laser printer.
The toner is fed evenly onto a magnetized roller (the developer roller) from a hopper. The toner carries the same negative charge polarity as the drum, once areas of charge have been selectively removed from the photosensitive drum by the laser, the toner is attracted to them and sticks to those parts of its surface. The drum, now coated with toner in the image of the document, rotates until it reaches the paper.
Describe the transferring stage of a laser printer.
The paper transport mechanism includes components such as gears, pads, and rollers that move the paper through the printer. The printer detects the paper type. A single sheet of paper is lifted from the selected input tray and feed it into the printer. To do this, a pickup roller turns once against the paper stack, pushing the paper into a feed and separation roller assembly (the manual feed tray uses a separation pad rather than rollers). This assembly is designed to allow only one sheet to pass through.
When the paper reaches the registration roller, a signal tells the printer to start the image development process. When the drum is ready, the paper is fed between the photosensitive drum and the high voltage transfer roller (or secondary corona). The transfer roller applies a positive charge to the underside of the paper. This causes the toner on the drum to be attracted to the paper. As the paper leaves the transfer assembly, a static eliminator strip (or detac corona) removes any remaining charge from the paper, which might otherwise cause it to stick to the drum or curl as it enters the fuser unit.
Describe the fusing stage of a laser printer.
After the toner is placed on the paper, it passes into the fuser assembly. The fuser unit squeezes the paper between a hot roller and a pressure roller so that the toner is fused, or melted, onto the surface of the paper.
The hot roller is a metal tube containing a heat lamp; the pressure roller is typically silicon rubber. The heat roller has a Teflon coating to prevent toner from sticking to it.
Describe the cleaning stage of a laser printer.
The photosensitive drum is cleaned to remove any remaining toner particles using a cleaning blade, roller, or brush resting on the surface of the drum. Any residual electrical charge is removed using either a discharge(or erase lamp) or the primary charge roller.
