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.

The principle of operation of all laser printers is quite similar to the operation of copiers. Initially, a magnetized area is created on the paper, to which the toner (printing powder) is then attracted. Then, a sheet of paper enters the so-called furnace, where the powder is melted.

The principle of operation of a laser printer

The principle of operation of all laser printers is quite similar to the operation of copiers. Initially, a magnetized area is created on the paper, to which the toner (printing powder) is then attracted. Then, a sheet of paper enters the so-called furnace, where the powder is melted. At the end of the process, the powder cools and solidifies. As a matter of fact, this is how the finished image on paper is obtained.

Despite the relatively high cost, in comparison with inkjet ones, even representatives of the entry-level price level will make it possible to receive black and white images, although they will be of obvious high quality. At the same time, the print speed is also not comparable. As for maintenance, it is quite simple and unpretentious, in particular, laser printer cartridges are refilled quickly and, most importantly, inexpensively.

The main advantages of laser printers

To date, laser printers are the most popular and sought-after office equipment, this was facilitated by a number of reasons:

1. high print quality, incomparable with inkjet counterparts;
2. reliability and long service life;
3. economy of resources:

• refilling a laser printer is several times less frequent than refilling/replacing cartridges in an inkjet printer;
• if not used for a long time, the toner for laser printers does not dry out and does not become unusable;

1. affordable pricing policy (despite the fact that laser printers are somewhat more expensive than inkjet printers, their quality of work and long service life will more than pay off all costs);
2. high speed printing;
3. relatively large print volumes;
4. resistance of printed copies to water and sunlight;
5. low noise level during operation;
6. low cost of printing (about 5 kopecks per 1 sheet);
7. environmental friendliness and safety for the environment and the human body.

Specifications or how to choose a laser printer?

When deciding to purchase a laser printer, most users often make the wrong choice due to not knowing the technical characteristics.

Due to the fact that a laser printer is able to completely form the image to be printed on the sole drum, it is extremely important to have a large amount of memory and a digital processor with a high frequency. So, for a laser printer with black and white printing, the optimal memory size can be considered 4-8 MB, and for a color one - from 32 MB. In modern printers, the amount of memory can be increased with additional modules.

As for the optimal processor frequency, it varies from 25 to 150 MHz. In turn, the allowable print resolution is from 600 to 1200 dpi.

Resources of a laser printer allow you to print about 8-12 thousand copies in one calendar month. Also, when choosing a model, you should pay attention to the resource of the cartridge, which implies the number of copies that can be printed without refueling.

Many believe that the laser printer is so named because it burns images onto paper with a laser. However, one laser is not enough to get a quality print.

The most important element of a laser printer is the photoconductor. It is a cylinder covered with a photosensitive layer. Another necessary component of toner is coloring powder. Its particles are fused into a sheet of paper, leaving the desired image on it.

The imaging drum and toner hopper are most often part of the same one-piece cartridge, which in addition has many other important parts - the charge and developer rollers, the cleaning blade and the waste toner bin.

Now let's look at how this all happens in more detail.

Printer steps

An electronic document is sent for printing. At this point, the printed circuit board processes it, and the laser sends digital pulses to the cartridge. By charging the photoconductor with negative particles, the laser transfers an image or text to it that needs to be printed.

When the laser beam hits the drum, it removes the charge and uncharged zones remain on its surface. Each toner particle is negatively charged and in contact with the drum unit, the toner adheres to uncharged fragments under the influence of static electricity. This is called image development.

A special roller with a positive charge presses a sheet of paper against the photoconductor. Because oppositely charged particles attract, the toner sticks to the paper.

Next, the paper with toner is heated to a temperature of about 200 degrees using a thermal shaft of the so-called stove. Due to this, the toner expands and the image is firmly fixed on the paper. Therefore, documents freshly printed on a laser printer are always warm.

The last step is to charge the photoconductor and clean it of any remaining toner using a cleaning blade and waste toner box.

This is how the printing process works. The laser paints the future image with charged particles. The photoconductor catches and transfers the ink powder to the paper. Toner adheres to paper due to static electricity and fuses to it.

The copier works on the same principle.

Benefits of a laser printer

It is believed that the print speed of a laser printer is higher than that of an inkjet printer. On average, this is 27-28 prints per minute. Therefore, they are used to print a large number of documents.

The device does not make much noise during operation. The print quality is very high at a low print cost, which is achieved due to the low consumption and price of the toner. The cost of most models of laser printers is also quite affordable.

For many years there has been a debate about whether a laser printer is harmful to health. The particles of toner used in laser printing are so small that they easily enter the human body, settle and accumulate in the respiratory tract. With constant contact with toner for 15-20 years, headaches, asthma and other diseases can develop.

However, printer manufacturers assure that there is no harm in daily use of the printer. Production technologies are constantly being improved, and cartridges are tested in laboratories.

Danger can arise only when you try to open and refill the cartridge yourself. Toner particles can get into the lungs and are very poorly excreted from the body, so it is better to entrust the refilling of the printer to specialists.

The speed, service life and print quality of laser printers are really on top. This device is indispensable in the work and everyday life of many users and is not as whimsical as capricious inkjet printers, who often have problems with printing when refilling.

If you still got not the most successful model of a laser printer and you did not use it much at all, then do not despair. KupimToner buys new printers from different brands, as well as accessories for them, offering a decent price.

In a printer based on laser printing technology, everything works by using static electricity. How it works? A laser beam hits the photoconductor in the cartridge and forms an image. At the next stage of image formation, the photoconductor comes into contact with the toner and at the point of contact, where the laser shone and changed the charge, the toner sticks. By the same principle, toner sticks to the paper from the photodrum, and then it is baked in the so-called “stove”. The paper comes out warm from the stove. Don't worry, it's already a little cold.

Learn more about the laser printer printing process

When the photosensitive drum rotates, a positive charge is formed on its surface, which is applied to the photo roller using a laser beam. The positive charge attracts the toner particles, which are negatively charged, and they adhere to the surface of the drum.

The sheet of paper is positively charged and passes under the rotating photo roller during the printing process. Negatively charged toner particles are transferred from the drum to the sheet of paper, thus the image is transferred to the paper. Further, the toner, which is on the paper, is fixed under the influence of heat.

Unlike printing on dot-matrix and inkjet printers, where the image is transferred to paper line by line, with laser printing, the text on an A4 sheet is formed in just 3 turns of the drum unit.

Laser printers are based on the printing system used in copiers. In copiers, a special lamp transfers the image from the copied sheet to the photosensitive surface of the drum in the form of an electrostatic charge. The photoconductor converts the optical image created by the light reflected from the copied image into its electrostatic equivalent, which attracts toner particles with the opposite charge to the surface of the drum.

However, the laser printer does not have the original image; instead, it has a matrix of 1s and 0s in its memory that transmits the image. In the case of black and white printing, 1 sends a signal to the microprocessor and a laser beam is directed to the photoconductor. When the beam touches the surface of the drum, a positive charge is formed in this place, and negatively charged toner particles will adhere to the drum in this very place. Accordingly, 0 does not transmit a signal and no charge appears on the surface of the drum, and later these areas will remain white on paper. How to get rid of white stripes when printing, read the article -

In domestic conditions, laser and inkjet printers are popular. The principle of printing such devices is fundamentally different, which cannot but affect the operational features. In some cases it is best to use laser products, while in others it is best to use inkjet products. However, to make the final choice in favor of a particular device is possible only after considering the scheme of work.

Working principle of inkjet printer

Still, at home, it is the inkjet printer that is most often used. The principle of printing it is to form an image using liquid ink. They are transferred to the media through special nozzles located on the head. The number of such holes depends on the model of the printer. Usually their number ranges from 16-64 pieces.

Since an inkjet printer prints using liquid ink, it dries on the head nozzles if it is left idle for a long time. This requires cleaning of the printing element, which involves the additional consumption of colorants.

Such devices consist of the following components:

• supporting structure;
• power supply;
• print head;
• cleaning system;
• devices for supplying media;
• control node.

A color image is obtained by superimposing three primary colors on top of each other. Black ink is often added to them, so that it is possible to use devices for the usual printing of texts and black-and-white drawings, saving on color inks.

Core Inkjet Printing Technologies

Different models may have their own advantages and disadvantages. The principle of printing representatives of inkjet printers may also differ slightly depending on the technology used. The difference lies only in the way the ink is transferred to the solid media.

1. The piezoelectric method involves the formation of ink dots on paper using special devices that are connected to the diaphragm. The electric field has a direct effect on the piezoelectric element, and it expands the tube to fill the capillary system. The main advantage lies in the flexible control of the droplet dimensions, which makes it possible to obtain high-quality images with high resolution.
2. The gas bubble method implies the presence of heating elements directly in the nozzles. Electricity is passed through them. During the heating process, gas bubbles are formed, which push the right portion of liquid ink through the holes. After the heater cools down, a fresh portion of the coloring matter enters through the nozzles. High quality is noted for detailed drawing of lines, but when printing solid areas, there may be slightly blurry places.
3. The thermal jet method, as in the previous case, involves the use of a heating element. However, a special mechanism is used with it, which allows for faster injection of colorants. As a result, device performance increases. The color palette of the resulting image differs in contrast.

The inks used may vary. Water-based ink contains a soluble dye and certain additives to adjust the viscosity. Their advantage lies in their low cost. Pigment inks are UV and moisture resistant. The print quality in this case is less dependent on the media.

Using continuous ink supply

With the principle of printing an inkjet printer, everything became clear. Special cartridges are used to store dyes. However, there is a special system that allows you to continuously supply ink in order to save money. In this case, the capsule reservoirs are installed directly on the print head.

The system is a set of containers connected by a silicone cable, through which ink is supplied from donors to the main unit. Thanks to this device, the constant presence of the original dyes in the print head is achieved. Many large format office fixtures have a built-in ink system that cannot be seen from the outside.

The principle of operation of the laser device

A completely different branch of the development of printing devices is laser technology, which can be used to achieve high-quality deposition of colorants on paper. The formation of characters and images occurs due to the beam illumination of the device elements with photosensitivity. The resulting copies with text or graphic information are resistant to fading and abrasion.

Inkjet and laser printers have completely different printing principles. Toners act as colorants, which can be transferred to a solid carrier in three ways.

1. Using a two-component development system. The dye particles needed to be transferred to a special photosensitive drum cannot be fixed on a magnetic roller without a special magnetic carrier charged by agitation.
2. With the use of one-component toner without additional impurities. Particles of matter in this case are endowed with magnetic properties. In some devices, electrostatic application can be carried out. With this option, the toner does not require magnetization.
3. Using a two-component dye, mixed at the factory.

Unlike an inkjet printer, the principle of printing a laser analog is based on building an image using the photographic method. The laser beam hits a special shaft, the surface of which is electrified due to impact ionization of the internal air.

Design of laser devices

Laser printers succeed in obtaining high-quality printing due to technological features. They include the following elements.

1. The photodrum, which is a cylinder made of aluminum. It is treated with a photosensitive material that tends to change electrical resistance in the presence of lighting.
2. The magnetic roller is used to transfer the toner from the reservoir directly to the drum or developing roller installed in some models of modern printers.
3. The doctor blade acts as a cleaning blade. With its help, excess coloring matter is removed from the screen roller. It can be made of plastic, steel or fiberglass.
4. The waste toner hopper is made in the form of a container. This compartment may be separate from the cartridge or together with it. The filling speed of such a tank depends on the quality of the toner.
5. The laser unit is designed to create an invisible image on the surface of the photoconductor by highlighting specific areas. The intensity of the beam can vary significantly.
6. The primary charge roller is made in the form of a metal rod covered with a layer of rubber. This element allows you to ensure the uniformity of the negative charge.
7. The transfer tape is necessary for applying an intermediate result from color cartridges.
8. The development unit allows you to transfer the toner directly onto the electrostatic image created on the surface of the photoconductive element.

Laser printing process

Not everyone fully understands the principle of printing laser printers from computer science courses. Inkjet devices operate according to a simplified scheme, so there are no special questions about them. How does the laser printing process work?

1. First, the photoconductive roller is charged. An electric charge is evenly distributed over its surface by rotating the roller. The rotating rod system reduces voltage and reduces the amount of ozone produced.
2. A laser scan is performed. At this moment, the charged surface of the shaft passes under the light beam. The laser hits only those places where the coloring matter will be applied in the future.
3. The toner is applied. A roller that has a negative charge transfers it to the toner. The dye from the hopper is attracted directly to the magnetic shaft, after which it comes into contact with the photoconductive element in those areas where the negative charge remains.
4. The transfer roller in contact with the solid carrier is no longer negatively charged but positively charged. Particles of the coloring matter fall on the surface of the paper due to electrostatic action.
5. The toner distributed over the carrier is fixed by heat and pressure. The thermal chamber consists of two shafts between which the paper moves. The temperature is controlled by a special sensor. The dye is melted and incorporated into the texture of the paper.

comparison table

It is suggested to look at the table to compare the properties of inkjet and laser printers, which print principle is very different.

Options	Printer type
	laser	Jet
Text printing
Obtaining color images in the form of diagrams and graphs
Printing photos
Performance
Number of pages printed after replacing ink cartridges

Having briefly considered the principle of printing an inkjet printer, one cannot fail to note the features of operation.

1. It is not recommended to use the device less than once a week to avoid ink drying out.
2. It is necessary to purchase high quality dyes, otherwise the head can quickly become clogged.
3. The correct paper should be used and should be marked as suitable for inkjet printing.
4. It is essential to keep the product clean, as dust wears out moving parts.

Features of working with laser devices

The main advantage of laser printers is the absence of the need for regular operation. It can even be used once a month. This will not affect the quality of work or wear of parts. However, you must use only original toner cartridges, otherwise there is a high risk of damage to the device. In addition, third-party supplies may simply not work.

Before purchasing a device with a lot of positive reviews, you need to find out additional information about the cost:

• Supplies;
• wear parts;
• one page printout.

Sometimes it turns out that it is easier to purchase a new device than to replace any parts.

Final part

Having briefly considered the principle of printing inkjet and laser printers, we can draw certain conclusions about the acquisition of certain devices. However, the final choice will depend on what goals are pursued during operation. For printing large volumes of text information, it is more profitable to buy laser devices. If you need to get high-quality photos, then it is better to give preference to inkjet counterparts.