Printer structure, principles, and common faults

Printer structure and principle

A printer is a complex and sophisticated mechanical and electronic device. Regardless of the type of printer, its structure can basically be divided into two parts: mechanical device and control circuit. These two parts are closely related. The mechanical devices include the printing head, the word car mechanism, the paper walking mechanism, the belt transmission mechanism, the ink (toner) supply mechanism, and the toner cartridge transmission mechanism. They are all the implementing mechanisms of the printer system, the control circuit is uniformly coordinated and controlled, while the control circuit of the printer includes the CPU control circuit, driving circuit, input and output interface circuit and detection circuit.

Although the printer's appearance is ever-changing, the printed images and colors are also different, the principle of which, we can divide commonly used printers into three types: matrix printer, inkjet printer and laser printer.

The structure and working principle of the three printers are briefly introduced.
The working principle of the dot matrix printer is as follows: the code sent by the host is processed by the printer input interface circuit and sent to the printer's main control circuit. under the control of the control program, generate character or graphics encoding, drive the print head to print a column of dot matrix graphics, and horizontal movement of the word car, generate column spacing or word spacing, then print the next column, print one column; after one line is printed, start the paper going into the paper to generate line spacing, and press enter to print the next line. The above process is repeated until the printing is complete.

The key to getting the dot matrix printer name is its print head structure. The structure of the print head is relatively complex. Generally speaking, it can be divided into the print needle, drive coil, positioner, and incentive disk. Simply put, the operating process of the print head is like this: when the print head gets a current pulse from the drive circuit, the drive coil of the electromagnet will generate a magnetic field to attract the print pin, which will drive the print pin to hit the ribbon, print a dot on the print paper. This type of printer is called a Needle printer because it directly performs the print function.

The working principle of the inkjet printer is basically the same as that of the dot matrix printer. The essential difference between the two lies in the structure of the print head. The Print Head of an inkjet printer is composed of thousands of ink channels with extremely small diameter (about several microns). The number of these channels is the number of jet holes of an inkjet printer, it directly determines the printing accuracy of the inkjet printer. Each channel is attached to an execution unit that can generate vibration or heat. When the control circuit of the print head receives the driving signal, these execution units are driven to produce vibration, and the ink in the channel is squeezed out; or the high temperature is generated. The ink in the heating Channel produces bubbles, jet the ink into the jet hole. The jet Ink arrives at the print paper to generate a picture! This is the basic principle of piezoelectric and bubble Inkjet Print headers. The control principle of the inkjet printer is basically the same as that of the dot matrix printer. I will not go into details here!
The structure and working principle of the laser printer.

When a Computer Host sends data to a printer, the printer first saves the received data in the cache. After receiving a complete piece of data, the printer sends the received data to the printer's processor, the processor organizes the data into a signal stream that can drive the printing engine action. For a laser printer, this signal stream is a set of pulse signals that drive the laser head to work.

The core technology of laser printers is the so-called electronic imaging technology, which combines imaging and electronics principles and technology to generate images. The core component is a photosensitive toner cartridge. The laser emitted by the laser transmitter shines on a prism-shaped mirror. As the mirror rotates, the light passes through from one end of the toner cartridge to the other end in turn (various focus lenses exist in the middle, make the points scanned to the surface of the toner cartridges very small), the toner cartridges rotate in 1/300 inch or 1/600 inch steps, and the scan is performed in the next line. The toner cartridge is a cylindrical surface coated with organic materials, with a charge in advance. When there is light irradiation, the affected part will change the resistance. The data signals sent by the computer control the laser emission, and the light scanning on the surface of the toner cartridge is constantly changing. Some places are under illumination, the resistance decreases, the charge disappears, and some places are not directed by light, there is still a charge, and the surface of the toner cartridge forms a shadow composed of a charge.

Toner is a fine plastic particle with a charge. Its charge is opposite to the polarity of the charge on the surface of the toner cartridge. When the surface of the toner cartridge with a charge passes through the display roll, the charged parts absorb the toner particles, and the shadow becomes a real image. When the toner cartridge rotates, another group of transmission systems sends the printed paper in. After a group of electrodes, the printed paper carries the same polarity but much stronger charge as the surface of the toner cartridge, after the paper passes through the toner cartridge, the toner on the surface of the toner cartridge is attracted to the printing paper, and the image is formed on the paper surface. At this time, the toner and printer are only combined by the gravity of the charge. Before the printing paper is sent out of the printer, the plastic Toner is melted after high temperature heating, it is fixed on the paper surface during cooling.

After the toner is transmitted to the printing paper, the toner cartridge Surface continues to rotate. After a cleaner, remove the remaining toner to enter the next print cycle.

From the above principle, we can see that the essential difference between the laser printer and dot matrix and ink jet printer is that the laser printer prints a whole page of imaging at a time, which is printed page by page; the dot matrix and inkjet printer print a row back and forth at the first time, which is printed row by row. Therefore, the printing speed of the laser printer is faster than that of the Needle printer and the ink jet printer under the same printing requirements, which is also an advantage of the laser printer.
Three printer features and application scope

Dot Matrix printer uses a mechanical hitting print head, so it has a strong penetration ability, can print multi-layer copy paper, with the copy function, in addition to printing unlimited length of continuous paper. The consumables used are ribbons, which are the cheapest among the three printers. Its disadvantage is that it is large in size and weight, with high printing noise, low accuracy, and slow speed. Generally, it has no color image printing function. Suitable for professional applications with special requirements, such as finance, taxation, and financial institutions. Common models include Epson's SCSI series, such as LQ-680K; star AR, Cr series, such as AR-6400 etc.

Inkjet printer printing accuracy is high, usually can print color images, and the size and weight can be very small,
Even printing can be carried with you, and the printing noise is very small. The ink, the material used, is the most expensive among the three printers! Moreover, if you want to print beautiful images, you must use the same expensive dedicated printing paper for good printing effect. Therefore, the cost of using the inkjet printer is very high! At the same time, it does not have the copy and continuous paper function. Suitable for scenarios with high printing quality requirements but small numbers, such as families and small offices. Common models include Epson stylus photo series, such as stylus photo 900 and Canon I series, such as i6500 and i355.
The printing accuracy of the laser printer is also very high, basically no big difference with the inkjet printer. It uses the consumables-toner cartridges at a cost between A Needle printer and an inkjet printer. Color images can also be printed, and the requirements for print media are not as high as those for inkjet printers. The printing speed is the fastest among the three printers, and the noise is also small. However, the volume and weight are larger than those of the inkjet printer. You can only print pages one by one without copying or printing the continuous paper. Suitable for scenarios with large numbers of printing and heavy tasks, such as large business organizations, design and printing fields. Common models include HP's LaserJet series, such as laserjet1010 and Color LaserJet 8550.
Common printer faults and Solutions

A printer is a mechanical and electrical integrated precision equipment with a complex structure. Compared with other computer external equipment, the printer has a high failure rate, but is usually easier to handle, the following describes common faults and solutions for each of the three types of machines.

Common Problems of dot matrix printer

Compared with the other two types of printers, dot matrix printers have the largest proportion of their mechanical components in the machine. Therefore, there are many mechanical problems, especially in the main operations, such as print headers, word car agencies, paper organizations, and so on.

The print work of the dot matrix printer is ultimately completed by the print head, the print head is the most heavy part of its workload, so it is also the most prone to problems. Common problems with the print header include broken needles, printing blur, and so on.

The print head is broken by one or more lines of the printed text, or a horizontal stroke is missing. To determine whether the needle is broken, you need to remove the back cover of the print head and press down the armature of each needle to see if there is a needle sticking out at the front of the print head. If not, you can think that the needle has been broken, generally, you can change the new needle. Of course, each needle may also be normal, but there are similar broken needle performance problems, this is generally caused by the print head of the needle drive coil open circuit or short circuit or needle drive circuit failure, if you need to check the above Circuit section, we will not detail it here.

The Print Head of the dot matrix printer is heavy, so after a period of time, the print head may be blocked by dirt, resulting in printing fuzzy; and the print needle may also become short due to mechanical wear, as a result, the intensity of hitting is reduced, and the print is also unclear. In the case of congestion, You can soak the print head in anhydrous alcohol and clean it with an ultrasonic cleaning machine. In the case of needle wear, you can properly adjust the distance between the print head and the paper, if the fault is not significantly improved, the print head can only be replaced. Of course, the tape is used with no ink, or the printing head and paper distance is too far, may also lead to printing blurred, but this is not a problem of the print head itself, you only need to replace the new ribbon or adjust the spacing.

The dot matrix printer is printed row by row, and each printed row of text will be moved back and forth once. Therefore, the word car mechanism is also the location with high fault. Common Faults include misplacement of printed text, the text car hits the wall, and the text car moves abnormally.

The offset of the printed text is not fixed because the starting position of the printed text is not fixed. The starting position is shifted to the left or right after one or more lines of text are printed. The offset distance is not fixed, the text is out of stock and cannot be read. An exception occurs when a text car moves around, which indicates that the text car cannot run or the running speed is uneven. After power-on, the text car cannot return to the initial position. During the printing process, the print head does not press ENTER or the carriage return is abnormal. The most basic and direct cause of the above problems is the heavy load on the motor of the car. This is generally because the word car rail is too dirty or rusty, so that the drag of the car to move back and forth is too large or the resistance is uneven, resulting in the above problem. To solve the above problems, we usually need to clean up the slide rails and add high-quality lubricants. If the situation is serious, we need to separate the slide bearing parts from the slide rails, to ensure that the word car runs freely. After such processing, the dislocation and abnormal movement can be basically solved.

When a car hits a wall, the printer continues to move forward after returning to the left boundary during the printing process. When the printer hits the left boundary, the motor of the car generates an abnormal sound. This is usually because the sensor at the initial position of the printer does not detect the car. Generally, you only need to adjust the sensor to the right. In a few cases, check the detection circuit. Of course, the drag on the slide rails is too high, which can also lead to wall failure.
In addition, the motor damage or drive circuit damage may cause the above fault. In this case, you need to check the above circuit.

Compared with the print head and the word car, the paper walking mechanism has a low load and a low failure rate. Common examples include non-paper or uneven paper walking and paper shortage.

The reason for non-paper or non-paper uniformity is usually that the paper motor or drive circuit is damaged, the transmission machinery is faulty, and the driving software does not match. Generally, the paper-driven motor is damaged in many cases. It is usually because the user turns the paper handle by hand or forces the paper to be torn when printing normally, as a result, the load of the paper motor is too heavy and burned out. In this case, when the power is down, you can manually turn the paper feed handle to experience a slight vibration, which is quite different from the smooth rotation of the motor when the motor is normal. Generally, changing the paper motor can solve the problem. Most of the mechanical faults are caused by the incloseness of the drive gears or the slipping of the gears. At this time, you need to carefully observe the transmission mechanism, and then re-locate the misplaced or detached gear or replace the worn gear. Most of the situations where the printer has no rules to go through the paper are due to the mismatch of the driver software. As long as you perform a printer self-check test and direct text printing under the DOS, if the paper can be normally taken, you can determine that the printer has no hardware faults, the problem is that the driver software.

Paper shortage occurs when the printer is powered on and the printed paper is installed, and the Panel still shows the paper shortage status, so it cannot be printed online. In this case, the paper Sensor and Its circuit should be checked. Paper sensors are generally mechanically switched and photocoupled. After the mechanical switch type is used for a long time, it is easy to have poor contact with the contact, resulting in the failure to detect the paper. In this case, you need to clean or replace the sensor. For the photoelectric coupling type, pay attention to whether there is dust to block the sensor slot, usually clean up to solve the problem.

Inkjet Printer Common Faults

Similar to the dot matrix printer, the printer head is also the most difficult part of its work, so there are also the most problems, common printing handwriting blurred, print broken, and so on.

Most of the reasons for the above problems are due to long-term unused printers or the addition of non-original ink, which leads to obstacles to the ink delivery system or the blockage of the nozzle (that is, the print head. The troubleshooting method is generally to execute the cleaning operation. If the congestion is serious, you also need to remove the nozzle, soak in the purified water of about 50-60 ℃, and clean it with an ultrasonic cleaning machine, after cleaning, you must dry it before using it. If no obvious effect is found after multiple cleaning operations, it indicates that the nozzle has been blocked and the nozzle can only be replaced. Another case is that the life of the nozzle has reached, and the precision of the nozzle has been greatly reduced, leading to printing fuzzy. In general, for Epson inkjet printers, the life of the nozzle is about 20-30 ink cartridges; for Canon, the life of the use of 10 ink cartridges is about to come.

The cleaning pump nozzle of the inkjet printer has many faults and is also one of the main factors that cause the blockage. The printer cleaning pump nozzle plays a decisive role in the protection of the printer nozzle. After the return of the nozzle car, it is necessary to clean the pump nozzle for weak pumping treatment, the nozzle for sealing protection. When a new ink cartridge or nozzle is disconnected from the printer, the suction pump at the lower end of the machine needs to pump the nozzle. The higher the accuracy of the nozzle, the better. However, in actual use, its performance and air tightness will decrease due to prolonged time, dust and residual solidification of ink in this mouth. If the user does not perform regular inspection or cleaning on the printer, it will cause the printer's nozzle to continuously encounter a fault similar to the blockage. Therefore, we need to maintain this part frequently. The specific method is: remove the upper cover of the printer to remove the car, use the Needle Tube inhalation of purified water to rinse it, especially to fully clean the micropores embedded in the mouth. We would like to remind users that they should never use ethanol or methanol to clean this part, which will cause dissolution and deformation of the micropore gasket embedded in this component, do not touch the lubricating oil to the pump nozzle, grease will make the pump nozzle parts of the rubber seal ring deformation and cannot seal to protect the nozzle.

For Epson inkjet printers, there are also common failures of the printer's "ink-driven" light on the Panel after the new ink cartridges are changed. Under normal circumstances, when the ink has been used up, the "ink full" light will be on. After the new ink cartridge is changed, the "ink" light on the printer panel is still on. In this case, The first reason is that the ink cartridge is not properly installed or there is a problem with the ink cartridge itself and the detection circuit, another possibility is to take the old ink cartridge and replace the new one when it is shut down. After the ink cartridge is changed, the printer will fill the ink delivery system with ink, and this process will not be able to be performed when it is shut down, making it impossible for the printer to detect the re-installed ink cartridge. In addition, some printers use an electronic counter inside the printer to measure the ink capacity (especially in the statistics on the usage of color ink). When the counter reaches a certain value, the printer determines that the ink is used up. During the process of changing the ink cartridge, the printer will reset its internal electronic counter to confirm that the new ink cartridge is installed. If you change the new ink cartridge when you shut down, the counter in the printer fails to be reset, so the "ink-free" is still reported ". The solution is to re-install the ink cartridge at startup. However, if the fault persists, you must try to use a normal cartridge to verify whether it is a cartridge problem or a detection circuit problem.

Like Epson printers, Canon and HP Inkjet Printers cannot detect ink cartridge faults, but these two brands of Inkjet Printers have different sprinklers than Epson, which can be detached and replaceable independently, and the general nozzle and ink box are integrated form. Therefore, most of the problems that cannot be detected are caused by the contamination or corrosion of the electrical contacts on the cartridge rack where the cartridge is installed, resulting in poor contact with the cartridge, so the cartridge is not detected. The solution is to clean the contacts with alcohol or replace the cartridge holder.

Because inkjet printer and dot matrix printer are printed row by row, their word car mechanism and paper walking mechanism are similar, and the problem is similar. I will not go into details here.

Common Faults of laser printers

Compared with the other two types of printers, the mechanism of the laser printer is complicated, and the fault is also complicated. The following describes the most common faults.

Laser printer paper jam

The most common fault for laser printers is Paper jams. When such a fault occurs, the indicator on the Operation Panel will flash and send an alarm signal to the host. The troubleshooting method is very simple. You only need to open the host cover and remove the paper to be stuck. However, you must take the paper in the direction of the paper and never turn any knob in the opposite direction. If the paper is often congested, check the paper feed channel. Paper wheel is the most vulnerable part of laser printing. When the paper in the paper tray is normal, but the paper cannot be taken, it is often the paper wheel wear or the paper spring is relaxed, the pressure is not enough, the paper cannot be sent to the machine. At this time, you generally need to replace the paper wheel. In addition, the installation of paper disks is not correct, and the quality of the paper is poor (thin, thick, damp), may also cause paper jam or failure to take paper.

Blank laser printer output

The cause of this failure may be that the display roller did not suck toner (the DC bias of the display roller was not added), or the toner cartridge was not grounded, and the negative charge could not be leaked to the ground, A laser beam cannot work on a drum, so it cannot be printed on paper. The photosensitive drum is not rotated, and no images are generated and uploaded to the paper. Therefore, you must determine whether the photosensitive drum can be rotated normally. Disconnect the printer power supply, remove the toner cartridge, open the socket on the lid, mark the non-photosensitive parts of the photosensitive drum, and then re-load it into the machine. Start the system for a while and check whether the mark is moved. Then, you can determine whether the drum is working properly.

If the toner is not supplied normally or the laser beam is blocked, it will also cause white paper. Therefore, check whether the toner is used up, whether the ink cartridges are correctly loaded into the machine, whether the sealing tape has been removed, or whether there is a shelter on the laser irradiation channel. Note that the power supply must be shut down during the check, because the laser beam is harmful to the eyes.

Print paper output black

The failure of the primary corona discharge or the failure of the control circuit causes the laser to emit continuously, resulting in a black print of the output content. At this time, you should check whether the corona discharge wire is disconnected, whether the high voltage of the corona exists, and whether the beam detector in the laser beam path works normally, because these aspects are directly related to the output effect. This problem is complicated to solve. It is generally not recommended for beginners to repair themselves.

Weak output handwriting

The ink in the toner cartridge is relatively small, the developing voltage of the display roller is low, or the toner is not polarized and cannot be transferred to the photosensitive drum. Take out the toner cartridge and shake it gently. If the printing effect is not improved, replace the toner cartridge or ask professional maintenance personnel to handle it. In addition, there is a switch under the toner cartridges of some printers to adjust the intensity of the laser, so that it matches the sensitivity of the toner. If this switch is not set correctly, the printing handwriting will also fade.

White strip at Output

If there is dirt on the mirror installed on the top of the photosensitive drum, the laser is absorbed when it encounters dirt on the mirror, and cannot reach the photosensitive drum, thus forming a narrow white stripe on the printing paper. Observe the Laser Transmission Channel carefully and clean the channel to solve the problem.
The transfer roller is placed below the print channel, which will also attract dust and paper chips. Some parts will become dirty or contaminated, so as to prevent the toner from being transferred from the toner cartridge to the printing paper, it also forms a narrow white stripe on the print paper. The ink cartridge is invalid, which usually causes the handwriting to fade in a large area. Remove the toner box and shake it gently to make the toner in the box evenly distributed. If the improvement is not great, replace the toner box.

Black on one side of the print paper

When the laser beam is scanned outside the normal range, the position of the mirror on the top of the photosensitive drum changes, the toner cartridge becomes invalid, and the toner is concentrated on one side of the box. All of these may cause a single side of the printer to become black. Check the position of the laser Channel and its mirror, correct the deviation or remove the toner cartridge and shake it gently to make the toner in the cartridge evenly distributed. If the toner cartridge still cannot be improved, replace the toner cartridge. They are all ways to solve the problem of unilateral blackening.

Duplicate dirty marks on printed paper

When a piece of paper passes through the printer, there are about 12 kinds of rolls in the machine turning more than one circle. The largest toner cartridge drum turns 2 to 3 circles, and the paper delivery roller may turn more than 10 circles. When dirty traces with equal intervals appear on the paper, they may be caused by dirty or damaged roll. Assume that a roll is stained with dirt. If the dirty trace is close to each other, it may be formed by a small roll. When the dirty trace is close to each other, check the larger roll. Measure the distance between dirty traces, and use the following formula to calculate the roll diameter that causes dirty traces: Roll Diameter = dirty trace distance/π; in this way, you can determine the problem caused by the roll and clear or replace it to solve the problem.

In addition to the specific faults of the above three printers, they also have some common faults, such as online printing or printing garbled characters, and startup failure (that is, no power supply.

Generally, there are several reasons why the printer cannot print or print garbled characters online: the printer is not connected to the computer, and the computer and printer need to be turned off at this time, reconnect the cable firmly. If the printed cable is defective, the cable can be tested on a normal machine to check whether any fault exists. If the cable is verified to be defective, replace the new cable; if an incorrect printer is selected in the software, check the printer selection menu of the software to see if the correct printer is selected. If the correct printer port is not configured, check the configuration menu of the software, ensure proper access to the printer port. If the computer used is not a parallel port, ensure that the printer cable is connected to the correct port. The most serious problem is that there is a problem with the electrical circuit of the printer interface, which is usually caused by the insertion and removal of the printing cable when the printer is powered on, in rare cases, it may also be caused by lightning strikes or electric ground wires. The failure of the interface circuit is usually serious and requires mainboard-level maintenance. We will not detail it here.

The problem of no power supply is usually caused by unstable power supply voltage, or continuous operation for a long time. Poor ventilation leads to overheating and damage of power supply. Generally, plate-level maintenance is also required. It should be noted that many printers, especially inkjet and small laser printers, do not have a hard power to open the key, as long as the power line is connected, the power supply is always working, therefore, when the voltage is high at night, the power supply is easily burned out. Therefore, we recommend that you do not use the printer for a long time, it is best to disconnect its power, so as to avoid a long time fault.

A printer is a high-precision device. It should be used as far as possible to stay away from the working environment of high temperature and dust, and always perform maintenance as far as possible, such as cleaning guide rails and fuel lubrication, only a good working environment and careful maintenance can ensure the long-term normal use of the machine.

 

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1. Do not replace your (not damaged) accessories.
2. Replace accessories unrelated to the fault.
3. If warranty is expired, pay attention to the maintenance cost. For example, if the print head is changed, the price is close to the purchase of a new machine.
4. If it is clear (prompting that the hardware has expired, contact the maintenance personnel...), do not repair it. At this time, you will be tapped into a large amount of money. You can solve the problem with your next software.
5. Pay attention to the expansion of the fault (because he can say that your machine has a fault before repair ...).
6. Pay attention to the guaranteed service life after repair (same fault.
........
Technical attention is also very simple.
Make sure that the fault range and size are clearly indicated during the delivery and repair process.
If there is no word or the handwriting is unclear, the fault should be roughly determined whether the nozzle is blocked or damaged. The maintenance price difference between the two kinds of faults is great.
If the fault is caused by a paper mechanism, pay attention to the misplacement or wear of components.
......
Print and observe the test page and Test Pattern in person after repair.

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I. How to replace the ink cartridges in the printer
First shut down the printer power, put down the front of the paper frame, and then turn on the top of the machine cover; then turn on the printer power, press the printer clean Jian 35 seconds, the printer nozzle will be removed from the left to the cartridge replacement position (note that the print nozzle will automatically return to the original position after 30 seconds); remove the yellow seal from the prepared new cartridge, remove the ink cartridge lid from the nozzle, remove the ink cartridge from the machine, replace it with a new ink cartridge, close the ink cartridge cover completely, and then press the paper feed/paper return key, the printer will start to execute the new ink filling program. After a few minutes, it will be okay when the ink filling program is completed!

Different cartridge replacement methods are different!

Ii. Why is the printing effect poor?
The printing effect is poor. In addition to the reason for ink, it also includes the following factors:
Print settings: resolution/printing speed/drawing software/Computer Color configuration/different computer and printer Color Performance principle/the same ink cartridge, printer model is different, the print effect is also different.
Print Head condition: Print Head aging/print head inkjet volume unstable/print head circuit board burned out or short circuit, etc.
Paper type: the quality of the paper is different, which may lead to blurred colors, ink diffusion, and other phenomena.

Iii. Common Faults
Troubleshooting method new cartridge installation, display the ink cartridge installation is not in place, you need to re-install the Printing Head of the metal film aging or loose caused by poor contact, it is recommended to send repair site printing appear horizontal lines, white lines or light color, the mark and label are not removed according to the instructions when the image is blurred or cannot be printed. As a result, the air hole is still closed, when the air cannot enter the cartridge label, the ink pipe can be completely torn off to enter the air # d8d8d8 or there are sundries in the print head to start the printer Automatic Cleaning program one to several times (note that the nozzle inspection diagram must be printed after each cleaning, to observe the cleaning effect) or shut down the printer for several hours to see if it has been improved, or load the cleaning ink cartridge for cleaning. If the problem persists, it is recommended that you send the print head to the repair site to block the print head and not return to the protective cover, so that the cartridge should be replaced as soon as possible, you can start the cleaning program or load the cleaning ink cartridge for cleaning. After printing, make sure that the print header is back to the protective cover, so that the ink cartridge should be replaced as soon as possible. You can start the cleaning program or load the cleaning program.

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