Theory-13 :- Laser Printing Process

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Laser Printing Process



There Are Following Steps for Laser Printing Process


NOTE *easy way to remember this is CLEAN CARS WILL DRIVE TO FAST

  1. Cleaning – The Photosensitive drum is cleaned before it can take on a new image
  2. Conditioning or Charging – To make the drum receptive to new images, it must be charged. The EP drum is given a negative charge by the primary corona wire around ‐600 and ‐1000 volts
  3. Writing ‐ A laser beam is use to write to the EP drum causing dots on the drum to lose some of the negative charge and become relatively positive charge
  4. Developing ‐ A toner is transferred from the toner cylinder to the EP drum by attracting the area of the drum that has a   Relative positive charge
  5. Transferring ‐ The transfer corona wire puts a highly positive charge on the paper once the paper has a positive charge the negatively charge toner particle leaps from the drum into the paper
  6. Fusing ‐ The compression roller and fusing roller press and melts the toner into the paper the fuser gets very hot Laser printers generally follow the following processes to produce a page of print:

  • Cleaning Conditioning
  • Writing
  • Developing
  • Transferring
  • Fusing

Cleaning Before a new page is printed; any remnants from the previous page are cleared away. The drum is swept free of any lingering toner with a rubber blade, and a fluorescent lamp removes any electrical charge remaining on the drum. Any toner removed in this step is not re‐used but is put into a used‐toner compartment on the cartridge.

Conditioning The entire drum is uniformly charged by the primary corona wire. This charge conditions the drum for the next step.

Writing The laser printer controller uses a laser beam and a series of mirrors to create the image of the page on the drum. The laser beam is turned on and off in accordance with the image to be created on the drum. At the spot where the laser's light contacts the photosensitive drum, the charge is reduced. After the entire image has been transferred to the drum, the controller starts the page sheet through the printer, stopping it at the registration rollers.

Developing A magnet inside the developing roller attracts the iron particles in the toner. This roller rotates near the drum and the toner is attracted to the areas of the drum that have been exposed by the laser, creating the print image on the drum.

Transferring The back of the paper sheet is given a positive charge that attracts the negatively charged toner from the drum onto the paper as it passes. After this step, the paper has the image of the page on it, but the toner, which is held only by simple magnetism, is not yet bonded to it.

Fusing The fusing rollers apply heat and pressure to the toner, which melts and presses it into the paper to create a permanent bond. The rollers are covered with Teflon and treated with a light silicon oil to keep the paper from sticking to them. Your printer will have come with a user manual that should explain the necessary cleaning and maintenance that should be undertaken. On the manufacturers' websites you will find a support section where you can download support details on their products.

Theory-12:-Laser Printer Components

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Laser Printer Components

The following are the main parts of a laser printer:  

  • Drum
  • High‐voltage power supply
  • DC power supply
  • Paper transport
  • Primary Corona
  • Transfer Corona
  • Fusing rollers
  • Controller

Drum The drum inside the toner cartridge is photosensitive, which means it reacts to light. The drum holds an electrostatic charge (except where it is exposed to light). The laser beam is reflected onto the surface of the drum to create a pattern of charged and not-so-charged spots, representing the image of the page to be printed.

High‐voltage power supply The process uses very high voltage to charge the drum and transfer and hold the toner on the paper. The high-voltage power supply converts AC current into the higher voltages used by the printer.

DC power supply Like a computer, most of the electronic components in the laser printer use direct current. For example, logic circuits use +5V DC (volts direct current), and the paper transport motors use +24V DC.

Paper transport Inside the laser printer are four types of rollers that move the paper through the printer. Each rubberized roller or set of rollers is driven by its own motor. The four roller types in the paper transport system are the feed, registration, fuser and exit roller. This is where most paper jams in a laser printer occur.

Primary Corona Also called the main corona, this device forms an electrical field that uniformly charges the photosensitive drum to +600V to reset it prior to receiving the print image and toner.

Transfer Corona This mechanism moves a page image from the drum to the paper. The transfer corona charges the paper; the charge pulls the toner from the drum onto the paper. As the paper exits the transfer corona, a static charge eliminator strip reduces the charge on the paper so that it won't stick to the drum. Not all printers use a transfer corona; some use a transfer roller instead. When working on a printer with a transfer roller, be careful not to touch the roller. The oils from your skin can spot the transfer roller and cause improperly charged paper, resulting in defects in the printed image.

Fusing Rollers The toner is melted permanently to the page by the fusing rollers that apply pressure and heat (between 165 and 180C) to it. The fuser - not the laser - makes the printed pages hot.

Controller This is the motherboard of the laser printer, and it has architecture and components like a PC motherboard. The controller communicates with the PC, houses the memory in the printer, and forms the image printed on the page. Memory expansion is possible on virtually all laser printers. Adding memory allows the printer to reproduce larger documents or graphics in higher resolutions or to support additional soft fonts.

A printer that experiences frequent memory overflow errors may require more memory or has a bad memory board. Check what was being printed when the fault occurs, as memory overflow is more likely to be the cause.