Suitable for both office and home. To decide whether such a device is needed, you must first understand what this type of device is. "Laser" means that this type of printer prints with a laser, and it also works with dry ink.

The article will talk in more detail about how these devices are arranged, how they work, as well as their main advantages and main disadvantages. All this will help you make the right decision.

Internal arrangement and mechanics

The photoelectric part of xerography is the basis of how the device works. What that laser printer prints on the same principle. Devices are also arranged identically. Unless there are more cartridges in color devices. The table below shows the main components of the laser device, as well as their components.

How it works - 8 steps:

1. The heating part melts the toner;
2. The melted clumps of powder stick to the paper;
3. The scraper removes the remaining toner from the drum;
4. The drum is electrostatically treated and charged (positive or negative);
5. With the help of mirrors, an image appears on the surface of the drum;
6. The drum moves along the magnetic shaft, and the toner puts a picture on it;
7. The drum transfers the image to the paper by rolling over it;
8. rolled through the oven, whereby the image is fixed.

Toner

Toner is a consumable. This is a dry powder (can be black or colored), which is the ink for laser printers. As already described above, it works like this: with the help of static, it (powder) is transferred to a charged photoconductor, due to which an image appears. It is subsequently transferred to paper.

Each manufacturer produces an original . Only with a proprietary dye, the company can guarantee the stable operation of the device. Such qualities as magnetism and dispersion are individual for dyes. Devices are made with the expectation of using a specific toner. Filling the cartridge with an alternative powder of dubious quality, the user risks disrupting the device's performance. If the required toner is not available, you can choose a compatible version with identical properties.

Attention! Attempting to use incompatible products may result in serious equipment malfunctions. You may also void your warranty.

You should be aware that toner can be harmful to health while it is in powder form. It must not be allowed to enter the respiratory tract.

When refilling or removing excess substance, it is extremely important to observe the following precautions:

• use latex gloves;
• wear a respirator or medical mask on your face;
• work with the substance only in a well-ventilated area;
• We recommend using a special vacuum cleaner to remove excess toner.

Even better - do not refill the cartridge yourself, but entrust this business to the pros. By contacting a service center, you can not worry that the toner will damage the printer or harm your health.

Laser printers have become indispensable attributes of office equipment. Such popularity is explained by the high speed and low cost of printing. To understand how this technique works, you should know the device and principle of operation of a laser printer. In fact, all the magic of the device is explained by simple design solutions.

Back in 1938, Chester Carlson patented a technology that transferred an image to paper using dry ink. The main engine of work was static electricity. Electrographic method(and it was he) became widespread in 1949, when the Xerox Corporation took it as the basis for the operation of its very first device. However, it took another decade of work to achieve logical perfection and complete automation of the process - only after that did the first Xerox appear, which became the prototype of modern laser printing devices.

First Xerox 9700 Laser Printer

The very first laser printer appeared only in 1977 (it was the Xerox 9700 model). Then printing was done at a speed of 120 pages per minute. This device was used exclusively in institutions and enterprises. But already in 1982, the first Canon desktop unit was released. Since that time, numerous brands have been involved in the development, which to this day offer more and more new options for desktop laser printing assistants. Each person who decides to use such a technique will be interested to learn more about the internal structure and principle of operation of such a unit.

What's inside

Despite the large assortment, the laser printer device of all models is similar. The work is based on photoelectric part of xerography, and the device itself is divided into the following blocks and nodes:

• laser scanning unit;
• a node that transfers the image;
• node for fixing the image.

The first block is presented lens and mirror system. It is here that a semiconductor type laser with a focusable lens is located. Next are mirrors and groups that can rotate, thereby forming an image. We pass to the node responsible for transferring the image: it contains the toner cartridge and roller carrying charge. Already in the cartridge alone, there are three main image-forming elements: a photo cylinder, a pre-charge roller and a magnetic roller (working in conjunction with the drum of the device). And here the possibility of a photocylinder to change its conductivity under the action of light that has fallen on it acquires great relevance. When the photo cylinder is charged, it retains it for a long time, but when illuminated, its resistance decreases, which leads to the fact that the charge begins to drain from its surface. This gives us the impression we need.

In general, there are two ways to create a picture.

Getting into the unit, immediately before the future contact with the photocylinder, the paper itself receives the corresponding charge. The transfer roller helps her with this. After the transfer, the static charge disappears with the help of a special neutralizer - this is how the paper ceases to be attracted to the photo cylinder.

How is the image captured? This is due to those additives that are in the toner. They have a specific melting point. Such a "stove" presses the molten toner powder into the paper, after which it quickly hardens and becomes durable.

Images printed on paper by a laser printer have excellent resistance to numerous external influences.

How the cartridge works

The defining link in the operation of a laser printer is the cartridge. It is a small hopper with two compartments - for working toner and for waste material. There is also a light-sensitive drum (photocylinder) and mechanical gears for turning it.

The toner itself is a fine-dispenser powder, which consists of polymer balls - they are covered with a special layer of magnetic material. If we are talking about color toner, then it also contains dyes.

It is important to know that each manufacturer produces its own original toner - all of them have their own magneticness, dispersion and other properties.

That is why in no case should you refill cartridges with random toners - this can adversely affect its performance.

The process of making an impression

The appearance of an image or text on paper will consist of the following successive stages:

• drum charge;
• exposure;
• developing;
• transfer;
• fastening.

How does photocharge work? It is formed on the photodrum (where, as is already clear, the future image itself is born). To begin with, there is a supply of charge, which can be both negative and positive. This happens in one of the following ways.

1. used coronator, that is, a tungsten filament coated with carbon, gold and platinum inclusions. When a high voltage comes into play, a discharge is carried between this thread by the frame, which, accordingly, will create an electric field that transfers a charge to the photoconductor.
2. However, the use of filament led to problems with soiling and degradation of printed material over time. Works much better charge roller with similar features. He himself looks like a metal shaft, which is covered with conductive rubber or foam rubber. There is contact with the photocylinder - at this moment the roller transfers the charge. The voltage here is much lower, but the parts wear out much faster.

This is the work of illumination, as a result of which part of the photo cylinder becomes conductive and passes the charge through the metal base in the drum. And the exposed area becomes uncharged (or acquires a weak charge). At this stage, a still invisible image is formed.

Technically it works like this.

1. The laser beam falls on the surface of the mirror and is reflected onto the lens, which distributes it to the desired location on the drum.
2. So the system of lenses and mirrors forms a line along the photocylinder - the laser turns on and off, the charge either remains intact or is removed.
3. Line ended? The drum unit will rotate and the exposure will continue again.

development

In this process, it is important cartridge magnetic shaft, similar to a tube made of metal, inside of which there is a magnetic core. Part of the surface of the shaft is placed in the refill toner hopper. The magnet attracts the powder to the shaft, and it is carried out.

It is important to regulate the uniformity of the distribution of the powder layer - for this there is a special dosing blade. It passes only a thin layer of toner, throwing the rest back. If the blade is not installed correctly, black streaks may appear on the paper.

After that, the toner moves to the area between the magnetic roller and the photocylinder - here it will be attracted to the exposed areas, and repelled from the charged ones. So the image becomes more visible.

Transfer

In order for the image to appear already on paper, it comes into play transfer roller, in the metal core of which a positive charge is attracted - it is transferred to paper thanks to a special rubberized coating.

So, the particles break away from the drum and begin to move onto the page. But they are kept here so far only because of static stress. Figuratively speaking, the toner is simply poured where it is needed.

Dust and paper lint can get in with the toner, but they can be removed viper(with a special plate) and sent straight to the waste compartment on the hopper. After a full circle of the drum, the process is repeated.

To do this, the property of the toner to melt at high temperatures is used. Structurally, this is assisted by the following two shafts:

• at the top there is a heating element;
• at the bottom, melted toner is pressed into the paper.

Sometimes such a "stove" is thermal film- a special flexible and heat-resistant material with a heating component and a pressure roller. Its heating is controlled by a sensor. Just at the moment of passage between the film and the pressure part, the paper heats up to 200 degrees, which allows it to easily absorb the liquid toner.

Further cooling occurs naturally - laser printers usually do not require the installation of an additional cooling system. However, a special cleaner passes here again - usually its role is played by felt shaft.

Felt is usually impregnated with a special compound, which helps to lubricate the coating. Therefore, another name for such a shaft is oil.

How color laser printing works

But what about color printing? The laser device uses four of these basic colors - black, magenta, yellow and cyan. The principle of printing is the same as in the black and white case, however, the printer will first split the image into monochrome for each color. The successive transfer of each color by each cartridge begins, and as a result of the overlay, the desired result is obtained.

There are such technologies of color laser printing:

• multipass;
• single pass.

At multi-pass option an intermediate carrier comes into play - this is a shaft or tape that carries the toner. It works like this: 1 color is superimposed in 1 revolution, then another cartridge is fed to the right place, and the second one is placed on top of the first picture. Four passes are enough to form a complete picture - it will go to paper. But the device itself will work 4 times slower than its black and white counterpart.

How the printer works single pass technology? In this case, all four separately printing mechanisms have a common control - they are lined up in one line, each has its own laser unit with a portable roller. So the paper goes along the drum, sequentially collecting all four images of the cartridges. Only after this passage does the sheet go into the oven, where the picture is fixed.

The merits of laser printers have made them a favorite for document work, both in the office and at home. And information about the internal component of their work will help any user to notice shortcomings in time and contact the service department for technical support for the operation of the device.

Today I want to talk about device and principle of operation of a laser printer. Everyone is familiar with this device, but few people know about the principle of its operation and the causes of its malfunctions. In this article I will try to clearly talk about the principle of operation of "laser printers", and in subsequent articles about malfunctions of laser printers, about the reason for their appearance, and about how to eliminate them.

Laser printer device

At the heart of any modern laser printer is a photoelectricprinciple xerography. Based on this method, all laser printers structurally consist of three main parts (assemblies):

- Laser sanitizing unit.

- Image transfer unit.

- Node for fixing the image.

The image transfer unit usually refers to the laser printer cartridge and charge transfer roller (Transferroller) in the printer itself. We will talk about the device of the “laser” cartridge later in more detail, and in this article we will consider only the principle of operation. It should also be noted that instead of laser scanning in some printers (mainly from OKІ» ) LED scanning is applied. It performs the functionseHowever, only the role of the laser is performed by LEDs.

For example, consider laser printer HP LaserJet 1200 (Fig. 1.). The model is quite successful and well-proven for its long service life, convenience and reliability.

We print on any material (mainly paper), and the paper feed unit is responsible for sending it to the “mouth” of the printer. As a rule, it is divided into two types that are structurally different from each other. Lower Tray Feeder, is called - Tray 1, and feeding mechanism from the top(bypass) - Tray 2. Despite the structural differences in their composition, they have (see Fig. 3):

- Pickup Roller- needed to pull paper into the printer,

- Block brake pad and separator needed to separate and pick up only one sheet of paper.

Directly involved in the formation of the image printer cartridge(Fig. 4) and laser scanning unit.

The cartridge for laser printers consists of three main elements (see Fig. 4):

Photocylinder,

precharge shaft,

magnetic shaft.

photo cylinder

photo cylinder(ORS- organicphotoconductivedrum), or also photoconductor, is an aluminum shaft coated with a thin layer of photosensitive material, which is additionally covered with a protective layer. Previously, photocylinders were made on the basis of selenium, so they were also called selenium shafts, are now made from photosensitive organic compounds, but their old name is still widely used.

Main property photocylinder– change the conductivity under the influence of light. What does it mean? If the photocylinder is given some kind of charge, then it will remain charged for quite a long time, however, if its surface is illuminated, then in places of illumination the conductivity of the photocoating increases sharply (resistance decreases), the charge "flows" from the surface of the photocylinder through the conductive inner layer in this place a neutrally charged region will appear.

Rice. 2 HP 1200 Laser Printer with cover removed.

The numbers indicate: 1 - Cartridge; 2 - Image transfer unit; 3 - Node for fixing the image (stove).

Rice. 3 Paper feed unitTray 2 , rear view s.

1 - Paper pickup roller; 2 - Braking pad (blue stripe) with a separator (not visible in the photo); 3 - Charge transfer roller (transferroller), transmitting paper static charge.

Rice. 4 Disassembled laser printer cartridge.

1- Photocylinder; 2- Precharge shaft; 3- Magnetic shaft.

Image overlay process.

Photo cylinder with pre-charge shaft (PCR) receives an initial charge (positive or negative). The amount of charge itself is determined by the print settings of the printer. After the photocylinder is charged, the laser beam passes over the surface of the rotating photocylinder, and the places where the photocylinder is illuminated become neutrally charged. These neutral areas correspond to the desired image.

The laser scanning unit consists of:

semiconductor laser with focusing lens,
- Rotating mirror on the motor,
- Forming lens groups,
- Mirrors.

Rice. 5 Laser scanning unit with cover removed.

1,2 - Semiconductor laser with focusing lens; 3- rotating mirror; 4- Forming lens group; 5- Mirror.

The drum has direct contact magnetic shaft m (Magneticroller), which supplies toner from the cartridge hopper to the photo cylinder.

The magnetic shaft is a hollow cylinder with a conductive coating, inside which a permanent magnet rod is inserted. The toner located in the hopper in the hopper is attracted to the magnetic shaft under the influence of the magnetic field of the core and an additionally applied charge, the value of which is also determined by the print settings of the printer. This determines the density of future printing. From the magnetic shaft, under the action of electrostatics, the toner is transferred to the image formed by the laser on the surface of the photocylinder, since it has an initial charge, it is attracted to the neutral regions of the photocylinder and repelled from equally charged ones. This is the image we need.

There are two main mechanisms for creating an image. Most printers (HP,Canon, Xerox) a toner with a positive charge is used, remaining only on the neutral surfaces of the photocylinder, that is, the laser illuminates only those areas where the image should be. The photo cylinder in this case is negatively charged. The second mechanism (used in printersEpson, Kyocera, Brother) is to use a negatively charged tuner, and the laser discharges areas of the photocylinder that should not have toner. The photo cylinder initially receives a positive charge and the negatively charged toner is attracted to the positively charged areas of the photo cylinder. Thus, in the first case, a finer transfer of details is obtained, and in the second, a denser and more uniform fill. Knowing these features, you can more accurately select a printer for solving your problems (printing text or printing sketches).

Before contact with the photo cylinder, the paper also receives a static charge (positive or negative), via the charge transfer roller (Transferroller). Under the influence of this static charge, the toner transfers from the photo of the cylinder to the paper during contact. Immediately after this, the static charge remover removes this charge from the paper, which eliminates the attraction of the paper to the photo cylinder.

Toner

Now we need to say a few words about the toner. Toner is a finely dispersed powder consisting of polymer balls coated with a layer of magnetic material. The composition of the color tuner also includes dyes. Each company in its models of printers, MFPs and copiers uses original toners that differ in dispersion, a magnetnawn and physical properties. Therefore, in no case should you refill cartridges with random toners, otherwise you can ruin your printer or MFP very quickly (verified by experience).

If, after passing the paper through the laser scanning unit, remove the paper from the printer, we will see an image that has already been formed, which can be easily destroyed by touch.

Image fixation unit or "stove"

In order for an image to become durable, it must be fix. Image freeze occurs with the help of additives that are part of the toner, having a certain melting point. The third main element of the laser printer is responsible for fixing the image (Fig. 6) - image fixation unit or "stove". From a physical point of view, fixation is carried out by pressing the molten toner into the paper structure and its subsequent solidification, which gives the image durability and good resistance to external influences.

Rice. 6 Image fixation unit or stove. Top view assembled, bottom with paper separator bar removed.

1 - Thermal film; 2 - Pressure shaft; 3 - Paper separator bar.

Rice. 7 Heating element and thermal film.

Structurally, the “stove” can consist of two shafts: the upper one, inside which there is a heating element, and the lower shaft, which is necessary for pressing the molten toner into the paper. In the HP 1200 printer under consideration, the “stove” consists of thermal films(Fig. 7) - a special flexible, heat-resistant material, inside of which there is a heating element, and a lower pressure roller, which presses the paper due to the support spring. Monitors the temperature of the thermal film temperature sensor(thermistor). Passing between the thermal film and the pressure roller, the paper heats up to approximately 200 ° C at the points of contact with the thermal film.˚ . At this temperature, the toner melts and in liquid form is pressed into the texture of the paper. So that the paper does not stick to the thermal film, there are paper separators at the exit from the oven.

Here's what we've looked at - How does a printer work. This knowledge will help us in the future to find out the causes of breakdowns and eliminate them. But in no case should you climb into the printer yourself if you are not sure that you can fix it, this will only make it worse. It is better not to save money, but to entrust this matter to professionals, because buying a new printer will cost you much more.

Before answering the question of how a laser-type printer works, it should be noted that the first image obtained by C. Carlson using static electricity and dry ink dates back to 1938. But the first prototype of a modern laser device was created in the mid-50s of the last century. It should be added that the principle of operation of a laser printer is based on the process of the so-called. laser scanning. After the document is scanned, the ink is applied and transferred, as well as the finished image is fixed. A similar principle of laser printing allows you to print text and graphics on plain paper at a fairly high speed. You can learn more about how a laser printer prints below.

If we talk about what a laser printer device is, then it must be said that any model of such a device consists of a photoconductor, a laser unit, a transfer unit and a fixing unit. In addition, the cartridges, depending on the model, use a magnetic roller or a developing roller. Paper is fed to print using a special node responsible for this action.

To answer in more detail the question of how a laser-type printer works, it is also necessary to talk about the paint (toner) used in this office equipment. So, the toner is a substance consisting of very small particles of polymer coated with a dye, with the inclusion of magnetite. In addition, it includes the so-called. charge regulator. Depending on the manufacturer, all such powders differ in such indicators as density, dispersion, grain size, magnity, etc. For this reason, refilling a laser printer with any random powder paint is not worth it, because. this will degrade the print quality.

Office equipment of this type, as a monochrome printer / MFP, has found wide application for personal use, i.e. at home. Its main advantage lies in the affordable cost, which is due to the fact that such devices do not need a large amount of software resources or memory. All they need is a controller that will allow them to carry out the most basic function, which is to print all kinds of documents. In general, it can be used to print plain text or some black and white charts and diagrams where the presence of color does not play a big role. Other advantages of monochrome laser-type devices are low cost for consumables, withstanding heavy loads and the ability to print a large number of pages. But such a printer device does not allow him to print color photographs and complex diagrams. In addition, such a device does not have high print quality.

As for color laser printers, their advantages are good printing speed and the ability to print color schemes, images and photographs. But keep in mind that such a printing device is quite expensive, which, in turn, significantly narrows its availability. Its other disadvantages are low profitability due to the high cost of consumables, high power consumption and insufficiently high quality color images. Those. such a device is not suitable for printing professional photos.

But all types of laser printers, as a rule, have the same principle of operation. The differences are only in their cost and functionality and parameters, for example, such as the resolution of a laser printer. As for the printing process itself, it can be divided into five key stages, described below.

The first stage: the formation of a photodrum charge (photoshaft)

To answer the question of how a laser printer works and how it works, it should be said that one of its main devices is a print drum coated with a special semiconductor that has high photosensitivity. It is on it that at the first stage an image is formed, intended for further printing. To do this, this part is supplied with a charge with a plus or minus sign. This is done, as a rule, with the help of a coronator (coronator) or a charging shaft (charge roller). The first is a block consisting of a wire around which there is a metal frame, the second is a metal shaft covered with foam rubber or conductive rubber.

The first way to give the photoshaft a certain charge using a coronator is that under the action of voltage between the frame and the wire (tungsten filament coated with platinum / gold / carbon), a discharge is formed. After that, an electric field is formed, which, in turn, transfers a static-type charge to the photoconductor.

The use of a coronator has a number of disadvantages, which are that the accumulation of ink / dust particles on its filament or its bending can lead to a sharp decrease in print quality, an increase in the electric type field in a certain place, and even damage to the surface of the photoconductor.

As for the second method, the charge roller in contact with the drum supplies its surface, which is highly photosensitivity, with a certain charge. At the same time, the voltage on the roller is an order of magnitude lower, which, in turn, solves the problem with the appearance of ozone. But in order to carry out the transfer of charge, contact is necessary. Consequently, the printer parts in this case wear out faster.

Stage two: exposure

The purpose of this stage is to form an invisible image from dots on the surface of a photodrum with increased photosensitivity, and without the use of a static charge. To do this, a thin laser beam shines on a four- or hexagonal mirror, after which it is reflected and hits the so-called. spreading lens. He sends it to a specific place on the surface of the drum. Next, a system consisting of several lenses and mirrors moves the laser beam along the photo shaft, resulting in the formation of a line. Because printing is carried out using dots, the laser is constantly turned on and off. The charge is also removed in a pointwise manner. After the line comes to an end, the photo roller starts to turn by means of a stepping motor and the exposure procedure continues.

Third stage: development

Another shaft in the laser printer cartridge is a metal tube, inside of which there is a magnetic core. A magnet inside the compartment attracts toner to the surface of the shaft and, rotating, takes it out. A special dosing blade allows you to adjust the thickness of the dye layer and thus prevent its uniform distribution.

After that, the ink gets between the photoconductor and the magnetic roller. In areas that have been exposed, the toner begins to be attracted to the surface of the phototube, and in charged areas it is repelled. The ink remaining on the magnetic roller usually travels further and passes through the hopper again. As for the toner that has moved to the surface of the drum, it makes the image on it visible, after which it follows on, i.e. to paper.

Fourth stage: transfer

A sheet of paper that was fed into the device passes under the photo roller. In this case, under the paper is the so-called. an image transfer roller that helps to bring the toner present on the surface of the drum onto the surface of the paper. A charge with a plus sign is applied to the core of the roller, made of metal, which is transferred to the paper through the rubber coating. The microscopic particles of toner transferred to the surface of the sheet adhere to it solely due to static attraction. All powder particles, paper fluff and dust remaining on the photoconductor are sent using a squeegee or wiper to a hopper specially designed for waste. As soon as the photoconductor completes the entire cycle, the charge roller / corotron again contributes to the restoration of charge on its surface and the whole work is repeated again.

Fifth stage: fixing

The toner used in laser printers must have the ability to melt at high temperatures. Only due to this property can it finally be fixed on the surface of the paper.

To do this, the sheet is pulled between two shafts, one of which presses it, and the other warms it up. Thanks to this, microscopic particles of the coloring matter are, as it were, fused into the structure of the page. After leaving the oven, the powder solidifies quickly enough, as a result of which the printed picture or text becomes quite stable.

It should also be added that the top roller, which heats up a sheet of paper, is in the form of a thermal film or a Teflon roller. In this case, the second option is considered more durable and reliable. However, it is expensive and is used most often in devices that must withstand heavy loads. The first option is less reliable, and is usually used for printers designed for small offices and home use.

Most modern printers are divided into laser and inkjet printers. Moreover, thanks to progress, the latter are gradually leaving the market of "household office equipment", remaining specialized. In offices, homes, and even some print centers, laser printers are the most common.

In domestic use, the main difference between inkjet printers and laser printers lies primarily in the high cost-effectiveness of the latter. The consumption of ink is practically minimal - one cartridge is enough for several thousand sheets with a sufficiently high density of ink. In addition, laser printers work very quickly and do not require special service maintenance.

Contrary to popular belief, laser printers do not "burn" characters into paper. A special toner is used to apply the image. It is he who sticks to the paper sheet, leaving symbols or pictures. By the way, because of this feature of the technology, color laser printers are practically never found, unlike monochrome (black and white).

The main functional units of a laser printer

The design of any laser printer, regardless of the specific model, manufacturer and capabilities, includes several main functional units:

• drum. It is on it that the toner is applied by means of electrostatic attraction and repulsion according to Coulomb's law;
• squeegee. It is designed to clean the drum of toner residue before applying a new one;
• coronator. This device is designed to electrostatically charge the drum;
• laser and mirror system. Being a source of coherent electromagnetic radiation, it discharges the drum pointwise;
• magnetic shaft. Toner is fixed on it for subsequent transfer to the surface of the drum;
• stove. It is designed to bake the toner left on the paper. Therefore, the sheets that come out of the laser printer have a fairly high temperature;
• control model (controller)- a microprocessor system that controls all this equipment.

Both color and monochrome laser printers are based on these functional units. Only the system and possibilities change. For example, color laser printers have four drums - for each of the fundamental colors (red, yellow, blue and black) - and a so-called transfer belt, which is designed to transfer the image formed by the corresponding toners to paper.

The principle of operation of a laser printer

The principle of operation of a laser printer in an abbreviated description is quite simple. The complete differs from one model to another, however, some fundamental elements are present in each case:

1. The drum is being cleaned. The doctor blade removes toner adhering to its surface, but not used in the previous printing cycle;
2. The coronator charges the surface of the drum. Either positive ions appear on it, or the number of negative electrons increases. This is intended to give rise to Coulomb forces.
3. A laser controlled by a rotating mirror partially discharges the surface of the drum. The toner itself is negatively or positively charged. Therefore, it repels from the charged areas of the drum area and is attracted to the discharged ones. Again, this is due to the action of Coulomb forces.
4. Toner powder is transferred from the surface of the magnetic roller to the drum.
5. From the surface of the drum, the toner adhered to it is transferred to the paper sheet.
6. The paper is sent to the “oven”, which most often consists of a heating element in the form of a halogen lamp and a pressure roller. The toner is fixed by melting under the action of high temperature and due to pressure from the shaft fixed on the spring.

If 4 separate drums and the same number of magnetic rollers are installed in color laser printers, however, the toner is not applied directly to the paper itself, but to the transfer ribbon. All four shades are first applied to it. The transfer ribbon is then rolled across the paper, and the multi-colored image is placed on the sheet. The toner is then baked and fixed.

Fundamental non-technological differences between laser and inkjet printers

Laser printers have been more popular than inkjet printers lately. If we abstract from technological differences, then they have the following advantages:

• economy. A laser printer cartridge lasts for several thousand sheets of high coverage paper.
• refueling option. Laser printer cartridges can be refilled with toner as needed without the risk of compromising their functionality. You can even carry out this operation on your own, but you should be careful, because the coloring pigment is negatively or positively charged and quickly sticks to skin, clothes and other surfaces under the influence of Coulomb forces. Inkjet printer cartridges in most cases cannot be refilled, as this leads to a violation of their tightness. For some models of this type of equipment, continuous ink supply systems can be used, but this is considered an unauthorized modification and will void the warranty agreement.
• high speed. Most laser printers can print up to 10 text pages per minute. Some work even faster.
• no need for weekly printing. The toner used in laser printers does not dry out or stick together. Therefore, periodically "chasing the print" to prevent head clogging is not necessary. Actually, there is no head in laser printers.
• print durability. Images and text on paper obtained using such office equipment do not fade or disappear over time under the influence of high humidity.
• high image resolution. Color laser printers provide print resolutions up to 9600 x 1200 dpi.

However, they also have some drawbacks compared to inkjet printers:

• high cost. On average, a laser printer in a complete set "from the factory" - that is, with incomplete cartridges - costs several times more than a similar inkjet. For monochrome, this is a 2-3-fold increase in price, for color - 10-fold and higher.
• high cost of cartridges and toner. Consumables for laser printers cost 2-3 times more than for inkjet printers. However, it is worth considering that their usage limit is also 2-3 times higher.
• bulkiness. Laser printers are usually several times larger than inkjet printers. This is also due to the complexity of the design. As a result, they require a separate place for installation.
• the need to warm up before work and the risk of overheating after prolonged typing. Despite the fact that the design of the “stove” includes a special thermoelement that does not allow the temperature to reach a critical level, in some cases it may fail or work inadequately. After that, the device overheats with the risk of system problems.
• little environmental friendliness. During operation, such devices release into the air some harmful compounds, dust, and also emit infrared and ultraviolet radiation.
• high resource intensity. Due to the presence of "gluttonous" in relation to the current elements, laser printers consume more electricity. Moreover, peak power can be so high that such office equipment will not work from household or office UPSs.
• the impossibility of stable repetition of full-color images due to the uncontrolled action of electromagnetic fields.

Thus, laser printers have both advantages and disadvantages compared to inkjet printers. However, in some use cases, they prove to be significantly more optimal or useful than their counterparts.