Modern printers are mostly divided into laser and inkjet based on their operating technology. Moreover, thanks to progress, the latter are gradually leaving the “household office equipment” market, remaining specialized. In offices, homes, and even some printing centers, laser printers are most often found.

In household use, the main difference between inkjet printers and laser printers is primarily the high efficiency of the latter. Ink consumption is almost minimal - one cartridge is enough for several thousand sheets with a fairly high ink density. In addition, laser printers operate very quickly and do not require special 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 paper sheet, leaving symbols or pictures. By the way, because of this feature of the technology, color laser printers are practically not found, unlike monochrome (black and white).

Main functional components of a laser printer

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

• drum. It is on this that the toner is applied through electrostatic attraction and repulsion according to Coulomb's law;
• squeegee. It is designed to clean the drum of any remaining toner 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. The toner is fixed on it for subsequent transfer to the surface of the drum;
• stove. It is designed to bake the toner remaining on the paper. Therefore, the sheets coming 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 capabilities 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 ribbon, which is designed to transfer the image formed by the corresponding toners to the paper.

Operating principle of a laser printer

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

1. The drum is being cleaned. The squeegee blade removes toner from its surface that has adhered but was not used in the previous printing cycle;
2. The corona device charges the surface of the drum. Either positive ions appear on it, or the number of negative electrons increases. This is intended to generate Coulomb forces.
3. Laser controlled rotating mirror, partially discharges the surface of the drum. The toner itself is negatively or positively charged. Therefore, it is repelled 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. The 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 influence of high temperature and due to pressure from the shaft mounted on a spring.

If color laser printers have 4 separate drums and the same number magnetic shafts, however, the toner is not applied directly to the paper itself, but to the transfer belt. All four shades are first applied to it. The transfer tape is then rolled over the paper and the multi-colored image ends up on the sheet. The toner is then baked and cured.

Fundamental non-technological differences between laser and inkjet printers

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

• efficiency. A laser printer cartridge can handle several thousand sheets of high-coverage paper.
• possibility of refueling. Laser printer cartridges can be refilled with toner as needed without the risk of affecting their functionality. Conduct this operation You can even do it yourself, but you should be careful, since the coloring pigment is negatively or positively charged and, under the influence of Coulomb forces, quickly sticks to skin, clothing and other surfaces. In most cases, inkjet printer cartridges cannot be refilled, as this leads to a violation of their seal. Some models of this type of equipment can use continuous ink systems, but this is considered an unauthorized modification and will void the warranty agreement.
• high speed. Most laser printer models are capable of printing up to 10 pages of text per minute. Some work even faster.
• no need for weekly printing. The toner used in laser printers does not dry out or clump. Therefore, there is no need to periodically “run the print” to prevent the head from clogging. Actually, there is no head in laser printers.
• durability of prints. Images and text on paper obtained using such office equipment do not fade or disappear over time under the influence of high air humidity.
• high image resolution. Color laser printers provide printing resolutions of up to 9600 X 1200 dpi.

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

• high cost. Average laser printer Completed “from the factory” - that is, with incomplete cartridges - it 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 they 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 installation space.
• the need to warm up before work and the risk of overheating after prolonged printing. 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 this, the device overheats with the risk of system problems.
• low environmental friendliness. When operating, such devices emit some harmful compounds, dust, and also emit infrared and ultraviolet radiation into the air.
• high resource intensity. Due to the presence of current-hungry elements, laser printers consume more electricity. Moreover, the peak power can be so high that such office equipment will not work on household or office UPSs.
• 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 analogues.

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

Laser printer device

The operation of any modern laser printer is based on photoelectricprinciple xerography. Based on this method, all laser printers are structurally composed of three main parts (assemblies):

- Laser sanitation unit.

- Image transfer unit.

- Image fixing unit.

The image transfer unit usually means a laser printer cartridge and a charge transfer roller (Transferroller) in the printer itself. We will talk about the structure of the laser cartridge in more detail later, but in this article we will consider only the operating principle. It should also be noted that instead of laser scanning in some printers (mainly OKІ» ) LED scanning is used. It performs the functionseHowever, only the role of a laser is performed by LEDs.

For example, consider laser printer HP LaserJet 1200 (Fig. 1). The model is quite successful and has proven itself with a long service life, convenience and reliability.

We print on some material (mostly 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. Bottom Tray Feed Mechanism, is called - Tray 1, and feed mechanism from the top(bypass) - Tray 2. Despite the design differences in their composition, they have (see Fig. 3):

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

- Brake pad and separator block required to separate and pick up only one sheet of paper.

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

A laser printer cartridge consists of three main elements (see Fig. 4):

Photocylinder,

Precharge shaft,

Magnetic shaft.

Photocylinder

Photocylinder(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 based on selenium, which is why they were also called selenium shafts, they are now made from photosensitive organic compounds, but their old name is still widely used.

Main property photocylinder– change conductivity under the influence of light. What does it mean? If a photocylinder is given any charge, it will remain charged for quite some time. for a long time, however, if its surface is illuminated, then in the illuminated areas the conductivity of the photo coating increases sharply (resistance decreases), the charge “flows” from the surface of the photocylinder through the conductive inner layer and a neutrally charged area appears in this place.

Rice. 2 HP 1200 laser printer with cover removed.

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

Rice. 3 Paper feed unitTray 2 , view from the back s.

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

Rice. 4 Laser printer cartridge in disassembled condition.

1- Photocylinder; 2- Pre-charge shaft; 3- Magnetic shaft.

Image overlay process.

Photocylinder using a pre-charge shaft (PCR) receives an initial charge (positive or negative). The amount of charge itself is determined by the printer's print settings. After the photocylinder is charged, the laser beam passes over the surface of the rotating photocylinder, and the illuminated areas of the photocylinder 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,
- Groups of forming lenses,
- Mirrors.

Rice. 5 Laser scanning unit with cover removed.

1,2 - Semiconductor laser with focusing lens; 3- Rotating mirror; 4- Group of forming lenses; 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 supplied charge, the value of which is also determined by the printer’s printing settings. This determines the density of future printing. From the magnetic shaft, under the influence 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 areas of the photocylinder and repelled from equally charged ones. This is the image we need.

It is worth noting here 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 photo cylinder, that is, the laser illuminates only those areas where the image should be. In this case, the photo cylinder is charged negatively. The second mechanism (used in printersEpson, Kyocera, Brother) is the use of a negatively charged tuner, and the laser discharges areas of the photo cylinder where there should be no toner. The photocylinder initially receives 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 rendering of details is obtained, and in the second, a more dense and uniform filling. Knowing these features, you can more accurately choose a printer to solve your problems (printing text or printing sketches).

Before contacting the photocylinder, the paper also receives a static charge (positive or negative) using the charge transfer roller (Transferroller). This static charge causes the toner to transfer from the photo cylinder to the paper during contact. Immediately after this, the static charge neutralizer 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 toner. Toner is a finely dispersed powder consisting of polymer balls coated with a layer of magnetic material. The color tuner also contains dyes. Each company in its models of printers, MFPs and copiers uses original toners that differ in dispersion, magnetnspine and physical properties. Therefore, under no circumstances should you refill cartridges with random toners, otherwise you can very quickly ruin your printer or MFP (tested by experience).

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

Image fixation unit or “stove”

In order for the image to become durable it needs fix. Freezing the image occurs with the help of additives included in the toner that have 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 molten toner into the paper structure and then solidifying it, which gives the image durability and good resistance to external influences.

Rice. 6 Image fixation unit or stove. At the top is the assembled view, at the bottom with the paper separator strip 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 of which there is a heating element, and the lower shaft, which is necessary for pressing the melted toner into the paper. In the HP 1200 printer in question, 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, at the points of contact with the thermal film, the paper heats up to approximately 200° C˚ . At this temperature, the toner melts and is pressed into liquid form into the texture of the paper. To prevent the paper from sticking to the thermal film, there are paper separators at the oven exit.

This is what we actually 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 get into the printer yourself if you are not sure that you can fix it, this will only make it worse. It’s better not to save money, but to entrust this matter to professionals, because buying a new printer will cost you much more.

It's hard to imagine modern life without a printer. At schools they print out scripts, at the university - essays, at work - contracts, and even at home we sometimes urgently need to transfer this or that information to paper. There are several types of printers, they are classified by type of printing, by format, by size and even by the type of printed materials. Let's look at the printing principle of an inkjet and laser printer.

How does an inkjet printer work?

We will try to briefly highlight the printing principle of an inkjet printer. Its print quality is slightly worse than laser. However, their cost is significantly lower than laser ones. The inkjet printer is ideal for use at home. It is easy to operate and easy to maintain. The printing principles of inkjet and laser printers are noticeably different. This is manifested in both ink supply technology and equipment design. So let's first talk about how it prints jet printer.

Its operating principle is as follows: an image is formed in a special matrix, and then this matrix prints the image on the canvas using liquid dyes. Another type of inkjet printer is equipped with cartridges that are installed in a special unit. In this case, with the help of the print head, ink is supplied to the print matrix, and it transfers the image to paper.

Methods for storing ink and applying it to paper

There are three ways to apply ink to canvas:

Piezoelectric method;
. gas bubble method;
. drop-on-demand method.

The first method, when printing, leaves an ink dot on the canvas due to the piezoelectric element. With its help, the tube compresses and unclenches, preventing excess ink from getting onto the paper.

Gas bubbles, also known as injection bubbles, leave an imprint on the canvas due to high temperatures. Each nozzle of the printing matrix is ​​equipped with which heats up in a fraction of a second. The resulting gas bubbles are pushed through the nozzle and transferred to the consumable.

The drop-on-demand method also uses gas bubbles during operation. But this is a more optimized technology that significantly increases the speed and quality of modern printing.

An inkjet printer stores ink in two ways. There is a separate removable reservoir from which ink is supplied to the print head. The second method for storing ink uses a special cartridge, which is also located in the print head. To replace the cartridge, you must also replace the head itself.

Let's talk about inkjet printers

Inkjet printers have gained particular popularity due to their ability. When printing, an image is formed by superimposing basic tones of different saturations on top of each other. The set of primary colors is abbreviated CMYK. These include: yellow, magenta, cyan and black.

Initially, a three-color set was offered, which included all of the above tones, except for the black tint. But when layering yellow, cyan and magenta at 100% saturation, it was not possible to achieve black. The result was brown or gray. Therefore, it was decided to add black ink.

Features of an inkjet printer

The main indicators of high-quality printer operation include noise, print speed, print quality and durability.

Printer performance properties:

• The printing principle is inkjet. The ink is fed through special nozzles and printed on the canvas. Unlike needle printers, where applying ink is a shock-mechanical process, inkjet printers operate very quietly. You can’t hear how the printer prints, you can only hear the noise of the motor that moves the print heads. does not exceed 40 dB.
• The printing speed of an inkjet printer is much higher than that of a pin printer. The print quality also depends on this indicator. Printer printing principle: the higher the speed, the worse the print. If you choose a high-quality print, the process slows down and the ink is applied more thoroughly. The average of such a printer is approximately 3-5 pages per minute. More modern models have increased this figure to 9 pages per minute. Color printing takes a little longer.
• Font is one of the main advantages of an inkjet printer. The quality of font display can only be compared with a laser printer. You can improve print quality by using good paper. It should have quickly absorbing properties. Nice image obtained on paper with a density of 60-135 g/m². Copier paper with a density of 80 g/m² also performed well. To quickly dry the ink, use the paper heating function. Despite the fact that the printing principles of inkjet and laser printers are completely different, high-quality equipment allows you to achieve a similar effect.
• Paper. Unfortunately, the inkjet printer is not suitable for printing on roll media. And to get multiple copies you will have to use multiple printing.

Disadvantages of Inkjet Printing

As it turned out above, inkjet printers print with liquid dyes using a matrix. The image is formed from dots. The most expensive part in a printer is the print head; some companies have built the print head of the printer into the cartridge to reduce the overall dimensions of the device. The printing principles of inkjet and laser printers are significantly different from each other.

The disadvantages of this printer include:

• Low printing speed.
• If the printer has not been used for a long time, the ink may dry out.
• Consumables have high cost and low resource.

Benefits of Inkjet Printer Printing

• Attractive price, ideal price-performance ratio.
• The printer has very modest dimensions, which allows it to be placed in a small office without causing inconvenience to the user.
• The cartridges are easy to refill yourself, just buy the ink and read the instructions.
• Connectivity For large print volumes, this will significantly reduce costs.
• High quality photo printing.
• Wide selection of print media.

A little about the laser printer

A laser printer is a type of equipment designed to print text or images onto paper. The history of the creation of this type of equipment is quite unusual. And it has a marketing approach, unlike the inkjet printer, which was created using hundreds of scientific concepts.

It was only in 1969 that Xerox began to develop the printing principle of a laser printer. Scientific work was carried out for several years; many methods were used to improve the existing apparatus. In 1978, the world's first copier appeared that used a laser beam to create a print. The printer turned out to be huge in size, and the price did not allow anyone to purchase this unit. After some time, Canon became interested in the development, and in 1979 the first desktop laser printer was released. Afterwards, many companies began optimizing copiers and releasing new models, but the printing principle of a laser printer has not changed.

How does a laser printer print?

Prints obtained in this way have high performance characteristics. They are not afraid of moisture, they are not afraid of abrasion and fading. Images obtained in this way are very high quality and durable.

The printing principle of a laser printer in brief:

• A laser printer applies an image to a canvas in several stages. The toner (special powder) melts under the influence of temperature and sticks to the paper.
• A squeegee (special scraper) removes unused toner from the drum into the waste storage tank.
• The caronator polarizes the surface of the drum and, through electrostatic forces, assigns a positive or negative charge to it.
• The image is formed on the surface of the drum using a rotating mirror, which directs it to the desired location.
• The drum moves along the surface of the magnetic shaft. There is toner on the shaft, which sticks to those parts of the drum where there is no charge.
• The drum then rolls over the paper, leaving toner on the canvas.
• At the final stage, the paper with toner sprayed on it is rolled through an oven, where the substance melts under the influence of high temperatures and reliably adheres to the paper.

The printing principle of a laser printer has much in common with the technology used in copiers.

Color laser printers and their main differences

The printing process on a color printer differs from black and white in the presence of several shades, which, when mixed in a certain proportion, can recreate all the colors known to us. Color laser printers use four separate compartments for each ink color. This is their main difference.

Printing on a color printer consists of the following stages: image analysis, its raster image, arrangement of colors and their corresponding toners. Then a charge distribution is formed. Afterwards the procedure is the same as for black and white printing. The ink sheet passes through an oven where the toners are melted and firmly bonded to the paper.

Their advantage is that the printing principle of a laser printer makes it possible to achieve very thin beams that discharge the desired areas. As a result, we get a very high-quality high-resolution image.

Advantages of modern laser printers

The advantages of laser printer printing include:

• High printing speed.
• Durability, clarity and durability of prints (they are not afraid of a humid microclimate).
• High image resolution.
• Low cost of printing.

Disadvantages of laser printer printing

The main disadvantages of laser printers:

• During equipment operation, ozone is released. This means you need to work with it in a well-ventilated area.
• High power consumption.
• Bulky.
• High cost of equipment

Based on all the pros and cons, we can conclude that inkjet printers are perfect for home use. They have an affordable price and small dimensions, which is important for many users.

A laser printer is suitable for offices and other institutions where there are a lot of black and white printouts and speed of document processing is important.

The history of laser printers began in 1938 with the development of dry ink printing technology. Chester Carlson, working on the invention of a new way to transfer images to paper, used static electricity. The method was called electrography and was first used by the Xerox corporation, which released the Model A copier in 1949. However, for this mechanism to work, certain operations had to be performed manually. Ten years later, the fully automatic Xerox 914 was created, which is considered the prototype of modern laser printers.

The idea of ​​"drawing" what would later be printed directly onto the copy drum with a laser beam came from Gary Starkweather. Since 1969, the company has been developing and in 1977 released a serial laser Xerox printer 9700, which printed at 120 pages per minute.

The device was very large, expensive, and intended exclusively for enterprises and institutions. And the first desktop printer was developed by Canon in 1982, a year later - new model LBP-CX. HP, as a result of cooperation with Canon, began production of the Laser Jet series in 1984 and immediately took a leading position in the market of laser printers for home use.

Currently, monochrome and color printing devices are produced by many corporations. Each of them uses its own technologies, which may differ significantly, but general principle The operation of a laser printer is typical for all devices, and the printing process can be divided into five main stages.

The print drum (Optical Photoconductor, OPC) is a metal cylinder coated with a photosensitive semiconductor on which an image is formed for subsequent printing. Initially, the OPC is supplied with a charge (positive or negative). This can be done in one of two ways using:

• corotron (Corona Wire), or coronator;
• charge roller (Primary Charge Roller, PCR), or charging shaft.

A corotron is a block of wire and a metal frame around it.

Corona wire is a tungsten filament coated with carbon, gold or platinum. Under the influence of high voltage, a discharge occurs between the wire and the frame, a luminous ionized area (corona), an electric field is created that transfers a static charge to the photodrum.

Usually a mechanism is built into the unit that cleans the wire, since its contamination greatly impairs the print quality. Using a corotron has certain disadvantages: scratches, accumulation of dust, toner particles on the filament or its bending can lead to an increase in the electric field in this place, a sharp decrease in the quality of printouts, and possibly damage to the surface of the drum.

In the second option, a flexible film made of special heat-resistant plastic wraps the supporting structure with a heating element inside. The technology is considered less reliable and is used in printers for small businesses and home use, where heavy equipment loads are not expected. To prevent the sheet from sticking to the stove and twisting it around the shaft, a strip with paper separators is provided.

Color print

Four primary colors are used to form a color image:

• black,
• yellow,
• purple,
• blue.

Printing is carried out on the same principle as black and white, but first the printer splits the image that needs to be obtained into monochrome images for each color. During operation, color cartridges transfer their designs onto paper, and their superimposition on each other gives the final result. There are two color printing technologies.

Multipass

This method uses an intermediate carrier - a roller or toner transfer ribbon. In one revolution, one of the colors is applied to the tape, then another cartridge is fed to the desired location and the second is superimposed on top of the first image. In four passes, a complete image is formed on the intermediate medium and transferred to paper. The printing speed of color images in printers using this technology is four times slower than monochrome.

Single pass

The printer includes a complex of four separate printing mechanisms under general management. The color and black cartridges are lined up, each with a separate laser unit and transfer roller, and the paper runs under the drums, sequentially collecting all four monochrome images. Only after this does the sheet go into the oven, where the toner is fixed on the paper.

Have fun typing.

Includes seven sequential operations to create given image on a piece of paper. This is a very interesting and technological process that can be divided into two main stages: applying the image and fixing it. The first stage is associated with the operation of the cartridge, the second takes place in the fusing unit (oven). As a result, in a matter of seconds we get the image we are interested in on a white sheet of paper.

So, what happens in such a short period of time in the printer? Let's figure this out.

Charge

Let us remember that toner is a finely dispersed substance (5-30 microns), and its particles very easily accept any electrical charge.

In the cartridge, the charge roller ensures uniform transfer of negative charge to the photodrum. This happens when the charge roller is pressed against the photodrum, and rotating in one direction (while uniformly imparting a negative static charge to the photodrum), causes it to rotate in the other.

Thus, the surface of the photodrum has a negative charge evenly distributed over the area.

Exhibition

In the next process, the future image is exposed on a photodrum.

This happens thanks to a laser. When a laser beam hits the surface of the photodrum, it removes the negative charge in this place (the point becomes neutrally charged). Thus, the laser beam forms the future image according to the specified coordinates in the program. Exclusively in those places where it is necessary.

This way we get the exposed part of the image in the form of negatively charged dots on the surface of the photodrum.

Development

Next, toner is applied to the exposed image on the surface of the photodrum in an even thin layer using a developing roller. The toner particles take on a negative charge and form a future image on the surface of the drum.

Transfer

The next step is to transfer the negatively charged toner image from the drum to a blank sheet of paper.

This occurs when the transfer roller comes into contact with a sheet of paper (the sheet passes between the transfer roller and the image drum). The transfer roller has a high positive potential, causing all the negatively charged toner particles (in the form of an image formed) to be transferred to the sheet of paper.

Consolidation

The next step in laser printing is to fix an image from a toner onto a sheet of paper in a fusing unit (in the oven).

At its core, this is the process of “baking” onto paper. A sheet of toner, passing between a thermal roller and a pressure roller, is subjected to thermo-baric (temperature and pressure) treatment, as a result of which the toner is fixed on the sheet and becomes resistant to external influences. mechanical stress.

In our picture you see a thermal shaft and a pressure roller. Thermal roll is used in a number of laser printing devices. A halogen lamp is used inside the thermal shaft, which provides heating (heating element).

There are other models of laser printing devices, where thermal film is used instead of a thermal roller (as a heating element). The difference between them is that the halogen heater takes longer to operate. It is worth noting the fact that devices with thermal film are very susceptible to mechanical influences from foreign objects (paper clips, staples from a stapler) on a sheet of paper. This is fraught with failure of the thermal film itself. She is very sensitive to damage.

Cleaning

Since during this whole process a small amount of toner remains on the surface of the photodrum, a squeegee (cleaning blade) is installed in the cartridge to clean residual microparticles of toner from the photodrum shaft.

As it rotates, the shaft is cleaned. The residual powder ends up in the waste toner bin.

Removing charge

During the last stage, the photodrum shaft comes into contact with the charge roller. This leads to the fact that the “map” of negative charge is again aligned on the surface of the drum (up to this point, both negatively charged places and neutrally charged ones remained on the surface - they were the projection of the image).

Thus, the charge roller again imparts a uniformly distributed negative potential to the surface of the photodrum.

This ends the cycle of printing one sheet.

Conclusion

Thus, laser printing technology includes seven successive stages of transferring and fixing an image onto paper. On modern devices This process of printing one image on A4 paper takes just a few seconds.

When worn out internal parts, such as the photodrum, charge roller or magnetic shaft, are replaced. These components are located inside the cartridge, and you can see them in the picture above. Due to wear of these elements, print quality deteriorates significantly.

A little about the history of laser printing

And finally, a little about the development of laser printing technology. Surprisingly, laser printing technology appeared earlier, for example, the same matrix printing technology. Chester Carlson invented a printing method called electrography in 1938. It was used in photocopiers of that time (60-70s of the last century).

The very development and creation of the first laser printer was directed by Gary Starkweather. He was an employee of Xerox. His idea was to use copier technology to create a printer.

First appeared in 1971 first laser printer Xerox company. It was called the Xerox 9700 Electronic Printing System. Serial production was launched later - in 1977.