Comment fonctionnent les imprimantes laser

How laser printers work

THE laser printers are the most common and affordable printers; they can handle large volume printing and are cheaper on printing cost. Compared with inkjet printer, the disadvantage of laser color printers is that they are more expensive than inkjet color printers, and due to the structure of laser color printer, it is larger and heavier.

About laser printer

The history of printing begins as early as 350BCE, and since the first printing of wood in China around 200CE, our printing technology has developed many advanced methods. The printing industry is important because it helps us share knowledge and communicate.

In the modern world, we have developed new methods of printing, through many types of printers. They have their own advantages and disadvantages, and understanding the function of a printer can help you better choose the one that suits your needs and find a solution when it comes to a faulty print.

The laser printer is based on the principle of electrophotography, which is the use of electrostatic force to pick up the toner powder and deposit it precisely on the paper.
The main component of a laser printer is the drum, a photoreceptor. It is made from a metal cylinder and coated with a photoconductive material that can be charged by an electric field then parts of the surface and is discharged by a laser beam.
The image will be created on the drum surface by a loading and unloading process.

The laser printer requires 5 steps to complete a print cycle

1. Drum Charging – The drum surface is charged by the corona wire or primary charge roller with a negative electrostatic charge.
2. Exposure to light – In this step, the laser beam with a digital signal comes into contact with the surface of the drum. The exposed area becomes conductive and discharges the surface of the drum (with positive electrostatics). A latent electrical image is created on the drum surface.
3. Development – ​​It converts the latent electrical image into a visible toner image, the toner powder charged with negative electrostatics and brought close to the drum surface. The positive charge surface will attract the negative toner powder to the surface. The visible toner image is created on the drum.
4. Image Transfer – The drum rotates and contacts the positively charged paper.

The printer cartridge is a consumable for a laser printer, different printer manufacturers have their own designs for the printer cartridges for the particular print engine. The largest and most popular printer manufacturers are Hewlett-Packard (HP), Canon, Brother and Lexmark. They have different designs on printer cartridges, which can be separated into several parts, the major part is drum cartridge and toner cartridge.

laser printer brand

HP and Canon share the same print cartridge design, which includes all major parts of the electrophotography process, they make the drum and toner in the same cartridge. It is more user-friendly and customers only need to replace 1 supply of consumables, but it will be more expensive for this design. As HP and Canon share print cartridge design, some compatible cartridges for HP and Canon are universal for each other. Canon 128 is universal with CE278A.

laser printers

Brother designed a different structure on their printer cartridge, they separated the drum and toner into 2 different cartridges. The advantage of this design is that the price of the cartridge becomes cheaper, but customers need to have basic knowledge to understand the difference between a drum and a toner cartridge.

Lexmark designed their printer cartridge for larger printing, separating the printer cartridge into different parts, all the main parts are separate. Most customers need to replace the toner cartridge, it becomes a toner powder container only.

About toner

Toner is a dry pigmented powder with a size of 8-12 micrometers. Normally, color laser printer needs four colors: Black, Cyan, Magenta and Yellow. The common and main ingredients of a toner are polymer (70-90%), pigments eg carbon black (3-10%), wax (5-15%), silica (5%) and dioxide (1%). Different toner formulas should match the printer specifications, e.g. charging voltage, fuse temperature and toner color.

When you have the basic knowledge to know how a laser printer works, you can easily identify the laser printer problem and find the solution. The most common printing problem from a laser printer is faded print, ghosting on print, vertical or horizontal line on print, full page black or white.

For example, when you get faded print, the first reaction will probably be to assume that the toner levels are low. Actually, the faded print can be caused by the wrong setting of the printer, especially when you use the compatible toner instead of an original toner. Most compatible toners have been designed as a universal for all laser printers , print density may need to adjust when using compatible toner. Ghosting in printed matter is very often likely when the cartridge in which the drum and toner are separated. When the drum reaches its useful life cycle, it may not discharge properly and cause ghosting.