6.3 Maintenance of paper path
The role of the paper path is to accurately, stably and continuously transfer the paper from the paper feeding part to the paper receiving part. Therefore, the performance of the paper path directly affects the accuracy of paper transport. There are many factors that affect the accuracy of paper transport. The following detailed analysis of these factors is based on the transmission chain diagram of the paper path.
The paper drive chain diagram is as follows:
Paper feeder-Feida-Paper tongue-Paper pick-up roller and pressure roller-Double sheet controller-Paper feed belt, paperboard and paper pressure roller-Paper pressure frame-Front and side regulations ) -Swinger-Front transfer roller â… -Impression roller â… -Back transfer roller â… -Double-diameter transfer roller-Front transfer roller â…¡-Impression roller â…¡-Paper delivery roller-Paper stopper-Anti-smudge device- Powder spraying device-braking roller-fan-opening plate-front paper aligning mechanism and side paper aligning mechanism-receiving table.
1. Paper feeder
The paper feed table is one of the important factors to keep the surface of the paper stack flat. Considering from the ideal state, no padding should be inserted in the middle of the paper stack on the paper feeding table, and its surface should be in a horizontal state, which requires the paper feeding table to be absolutely horizontal. But in fact, due to the uneven distribution of air in the middle of the paper, plus the uneven thickness of the paper itself, the unevenness of the ink layer on the surface of the printed product during flip printing or register printing, etc., the final surface of the paper stack is uneven (even The paper table is absolutely horizontal). However, you should not pay attention to the level of the paper feeding table, because the level of the paper feeding table is the benchmark of the level of the paper surface. The paper feeding table is not level, and the level of the paper is unstable (the paper stack easily slides in a certain direction). Therefore, the paper feeding table should be in the ideal level as much as possible.
The lifting of the paper feeding table is realized by the motor driving the chain. Due to frequent relative movement between the chain and the sprocket, wear will occur over time. Therefore, it should be lubricated regularly. But because the chain is exposed, dust and paper dust can easily fall on it. If you add oil to the chain. Oil, dust, and paper powder can easily mix together to form oil sludge, which accelerates the chain wear, so the chain should be scrubbed frequently. If no oil is added, the chain will rust for a long time, and noise will be generated during movement.
The load-bearing capacity of the paper table is designed according to the maximum stack. Of course, it will have a certain safety factor, but it cannot be used to put everything up. If you place something too heavy on it, the chain will be stretched, and it will not cooperate with the sprocket properly, resulting in unstable lifting. The stack of paper on the paper feeding table should not be too high, so that the paper feeding can be raised to the position of the lower limit switch. Nothing (such as stools, chairs, etc.) should be placed under the paper feeder, otherwise the paper feeder will be jacked up, causing the paper feeder to tilt, which may also cause other accidents. In addition, if you continue to connect the lower button of the paper table, there will be hard interference between the chain and the sprocket and the motor. As a result, some of these components are damaged. In addition, it should be noted that when pulling paper or pushing paper with a technical paper cart, do not let the stack of paper collide with the support of the paper feeding table, otherwise the support will be bent, and the support will be broken in severe cases, and it should not be careless.
2. Feida
The quality of Feida's work directly affects the accuracy of paper delivery. The movements of Feida components (separation nozzle, presser foot, paper transfer nozzle, etc.) are all determined by design, but due to long-term operation, it will cause a certain degree of wear, but the amount of wear is very small because of its Relatively moving contact surfaces are made of wear-resistant materials. In addition, even if some errors are caused by wear, this error can be compensated by the adjustment of other mechanisms, so the accuracy requirements of Feida's paper delivery are not very strict. The relative motion mechanism of Feida is covered with a cover to prevent dust and other impurities from entering the relative motion contact surface. In fact, it is difficult to completely cover it. Adding oil to these relative motion contact surfaces may form oil sludge on the surface, but accelerate wear, so these parts should be scrubbed regularly.
The feed nozzle and feed nozzle on Feida frequently move up and down, and the relative moving contact surface uses self-lubricating material. Because its position is closest to the surface of the paper and it is in a negative pressure state, debris such as paper powder can easily fall on it. If you add oil to it, it will form sludge and accelerate the wear of these parts. Once worn, it will cause leakage, which will cause insufficient suction of the nozzle. Therefore, refueling is prohibited here. Once it is found that the inhalation is insufficient, some remedial measures can be taken, and if the measures are still invalid, they need to be replaced.
Feida can adjust not only its front and rear position, but also its left and right position, but its left and right position cannot be adjusted arbitrarily. In theory, the drive shaft of the double universal joint driving Feida must be absolutely parallel. However, due to inattention during installation, the left and right positions may be inaccurate. At this time, it must be carefully checked and debugged.
3. Paper tongue
The function of the paper blocking tongue is to make the front opening of the paper flush, but due to the impact of the forward movement of the paper, the position of the individual tongues will change. When the position of the paper changes, the paper can no longer play the role of flushing, which is easy to cause the paper to arrive early. Therefore, if it is found that the position of a certain paper tongue has changed, it should be corrected in time. It should be noted that the time coordination between the paper blocking tongue and the paper suction nozzle is correct. Since the shaft of the paper stopper tongue is relatively thin, in order to improve its impact strength, a three-point support is generally adopted. But we must pay attention to the three points on a straight line, so as to ensure its smooth operation. When it swings in the paper feeding direction, it is completely driven by the spring, and the rigidity of this spring is extremely small. As long as there is a little resistance, it cannot swing back and forth.
4. Pickup roller
The role of the paper receiving roller and the paper pressing roller is to forward the paper transferred from the paper suction nozzle to the paper feeding board. The upper surface of the paper pick-up roller is rough, mainly used to increase friction, because it is used to drive the movement of the paper transport belt. At present, the paper receiving roller on the machine uses horizontal stripes to increase friction. This friction is beneficial, so it cannot be lubricated. The speed match between the pick-up roller and the transfer paper suction has been given by design, and this point should also be noted when replacing the pick-up roller. The paper pressing roller on the paper receiving roller is mainly used to increase the pressure for generating friction, but the pressure should not be too large. For older machines, you can change the left and right positions of the platen roller. The rotation of the pressure roller is driven by friction. If the rotation of the pressure roller is not flexible, it will cause the paper to slide. It should be turned by hand frequently to observe its operation. [next]
5. Paper feeding board, finger paper cloth belt and paper pressing frame
The function of the paper board, paper cloth belt and paper pressure frame is to transfer the paper flatly to the regulation part. The cardboard is made of steel plate, as long as the flatness meets the requirements. For the paperboard made of wooden board, due to its poor resistance to deformation and poor ability to adapt to the environment, it is not appropriate to put heavy things on the paperboard or place it in extreme temperature or low humidity. The thickness of the paper belt should be uniform, so that the linear speed of the surface can be made uniform. The cloth tape should not be too loose, otherwise it will slide on the cardboard; it should not be too tight, otherwise it will wear too fast. After installation, it should be able to lift up to 3cm with a hand. The function of the paper pressing frame is to make the paper surface flat against the paperboard. This frame should always be kept in a state, otherwise the paper cannot be kept flat on the cardboard, which will cause printing problems. In addition, the working status of the brushes, pressure springs and pressure wheels on the pressure plate should also be checked frequently to see if they can play their due role.
6. Front Regulation and Side-by-Side
The front and side gauges are the two key components of paper, and it must be ensured that they are always in good working order. The pre-regulation position relies on the front gauge cap, but the front gauge cap will wear out after a period of time, so it should be replaced after a long time. The flexible and accurate action of the front gauge is the guarantee of the previous position, so it is necessary to add oil or grease frequently. The side gauge pulls the paper by means of friction wheels or friction plates. The size of the paper pulling force is related to the size of the spring force. The spring will fatigue after working in Qing time, so you should check the working condition of the spring regularly. Pay attention to the out-of-roundness of the paper pulling wheel, otherwise there will be no pulling when pulling. The work of the side gauge is driven by the power of the front gauge. It is not suitable for the lateral coarse adjustment of the side gauge when the machine is running. The rules and regulations must be locked when moving to a new position, otherwise it will jump during the work, resulting in inaccurate positioning. The surface of the rule should be kept clean, otherwise it will affect the regular position accuracy, and the surface of the rule board is not allowed to place heavy objects, otherwise it will cause deformation. As a result, the surface of the paper is uneven and wrinkled during printing. Once the deformation is found, it should be corrected in time.
7. Pass the paper tooth
Handing paper teeth plays an important role in the paper path. The quality of its work directly affects the accuracy of paper transfer. First of all, its tooth pads should be hand-held, which is the first condition to ensure that the paper is forwarded smoothly. Due to impact and other reasons, the dental pad will wear or collapse. This requires operators to check their working conditions frequently. Secondly, the bite force should be uniform, otherwise, some of the dental pads will be stressed and some will be small. The force-bearing tooth pads are prone to collapse. From the perspective of paper transfer, the bite force can be forwarded as long as it can hold the paper forward. Under this premise, the smaller the bite force, the better. The bite force is small, and the impact of opening and closing teeth is also small, which is conducive to the smooth transfer of paper. This is extremely important to ensure the quality of the print. Due to the extremely short time for paper picking and paper delivery, it requires flexible and stable movements, so the grease inside the dental shaft should be replaced regularly. In addition, the lubrication of the working circuit driving the paper transfer must also be guaranteed. Attention should be paid to the working status of the opening ball, which must be flexible. If it does not turn, it may cause the tooth-opening cam or tooth-opening bearing to wear out. The main reason for the wear of the open ball is the accumulation of impurities such as paper powder in the bearing. The open tooth swing rod and the paper delivery shaft are connected with pins. If the pins are misaligned, the accuracy of paper transfer is destroyed. From this point of view, the impact force is also required to be as small as possible.
8. Front transfer roller
The difference between the front paper transfer roller and the paper transfer tooth is that the handover process is performed completely in a relatively static state. The requirements for the row of teeth and openings are the same as above.
9. Impression cylinder
The impression cylinder is one of the most important parts in the paper path. During the printing process, the paper cannot slide in its row of teeth, which requires that its bite force must be so large that the paper cannot slide. Another factor that prevents paper from sliding is the friction coefficient of the dental pad. The larger the friction coefficient, the less likely the paper will slide. Increasing the friction coefficient is much more beneficial than increasing the pressure of the dental disc, because it does not increase the impact force of the open and close teeth. Therefore, if it is found that the friction surface of the dental pad is damaged, it should be repaired in time, and the pressure of the dental slices should not be increased blindly. The requirements for opening uranium and opening balls of the impression cylinder are the same as above, except that the requirements are stricter, because its stress is much larger than the above. The rear transfer cylinder participates in the printing in the second half of the process, so its requirements should be the same as the impression cylinder. The difference between the rear transfer roller and the impression cylinder is that the surface should be equipped with a dirt-preventing device. After the anti-scratch device is used for a period of time, its surface area ink increases, but it will bring a gift of dirt. Therefore, if stains are found, the ink on the anti-scratch cloth should be cleaned in time. If it still does not work, it needs to be replaced.
10. Borrow roller
The letter roller only acts as an intermediate paper transfer. The key to its requirements is the symmetry of its two rows of teeth. If the two sets of teeth are not symmetrical, the paper conveyance is unstable, one is fast and the other is slow. During the maintenance, the symmetry must be carefully checked. Another thing to note is its balance, because this roller is large, it needs more careful to do dynamic and static balance. The balance accuracy should be carefully checked during the overhaul. During the inspection, remove the gears on the two sides of the roller, and push the roller to rotate with your hand or other tools. If it can stop at any position, the accuracy of its static balance meets the requirements. Since the speed of the printing press is relatively low, the dynamic balance test is generally not performed.
11. Front transfer roller â…¡
The maintenance of the front transfer cylinder II and impression cylinder II is the same as the previous group.
12. Take-up roller
The role of the take-up cylinder is to transfer the printed sheets from the impression cylinder to the take-up chain. The similarity between the take-up roller and the rear transfer roller is that the surface is equipped with anti-dirt devices. Another thing that is the same is that both cylinders may participate in the printing process. The difference between them is that one bites the paper by their own teeth and the other bites the paper by the chain row. If the transfer time is inconsistent, the printed matter may be torn or cannot be removed. Therefore, during inspection, the consistency of the bite should be carefully checked. You can use a ruler to measure the size of the bite one by one with the ruler. If they are inconsistent, you should adjust it in time. Due to the impact of opening and closing teeth, the chain row of tooth pads is likely to cause position changes. Therefore, you should also check whether they are in the same position during maintenance. If they are inconsistent, they should be reset. The lubricating environment of the chain is relatively bad, but it is not lubricating and it can't work, so the chain should be scrubbed regularly to prevent the oil from drying on it and aggravating the chain wear. The degree of tightness of the chain should also be checked regularly. Too loose can easily cause instability in taking paper, and too tight can easily cause rapid wear of the chain. Generally, it is better to raise it by 4-5cm by hand.
13. Equalizer
The paper leveler is used to flatten the printed sheets. The leveling process is realized by the principle of negative pressure, which requires the heating holes to be unobstructed, and in addition, it should be regularly checked and cleaned. However, it is best not to use a paper holder when turning over the printing, because it may cause the printed product that is in contact with the flat paper holder to be dirty.
14. Anti-scratch device
Anti-smudge device is to prevent the printed products from colliding with other parts in the paper collection part. It uses the principle of air cushion, but it can also be used for anti-road victory with cloth tape. When using air cushions to prevent smudging, pay attention: the air cushion must be formed under the printed sheet, and it must be large enough. Anti-scratching devices look simple, but do n’t be careless. If the use is not good, the printed product may fall short. The powder spraying device is mainly used to prevent the printing sheet from sticking to dirt. The basic requirement of the powder spraying device is that the powder spraying is uniform, which requires the powder path to be smooth. The first is that the hole in the powder nozzle should be unblocked, if not, it can be penetrated with a thin wire. The second is the smooth air path. If the air volume is insufficient, the spraying speed will not increase. Air blockage is often related to wet powder, so it is best to use dry powder. Before leaving work every day, find a way to remove the remaining powder in the powder road. When using powder, you should also pay attention to whether there are large particles in the middle. Such particles may also cause blockage of the powder path. If there are large particles, try to crush them before putting them in. The powder nozzle of the powder spraying device should face the surface of the paper, so as to play the role of powder most effectively, otherwise the particles may be blown all around, which will cause chain wear and affect the health of the operator. The area of ​​powder spraying is relative to the effective printing area on the paper. The size of the powder spraying area can be adjusted. The horizontal size can be controlled by closing the powder nozzle, and the vertical size can be controlled by adjusting the position of the powder spray cam. The size of the powder spraying amount is limited to the minimum anti-coupling. If it is too large, it is not good for drying, and it is not good for the subsequent printing; the size is large, and the place with large ink volume is easy to stick.
15. Brake roller
The brake roller is used to reduce the speed of the sheet. It absorbs the air under the printing sheet to form a negative pressure, increasing the resistance of the printing sheet in the forward direction, so as to achieve the purpose of deceleration. Therefore, the suction circuit of the brake roller must be smooth, and if it is not smooth, it must be repaired in time. However, in reverse printing, it is better not to use a brake roller, and other deceleration mechanisms can be used to achieve deceleration. Because the use of brake rollers may cause rubbing on the back. The brake rollers of some printing machines now also have a blower function, that is to say, the suction function is used for single-sided printing, and the blower function is used for double-sided printing.
16. Fan
The fan is used to pressurize and slow down the printed sheets. The greater the wind force of the fan, the greater the possibility of causing the cast to spread around. From this point of view, the smaller the fan speed, the better. When the fourth printing is active, the fans on both sides can be dispensed with, but it is harmful and unfavorable (it causes difficulties for the suction of the brake roller).
17. Open tooth plate
The opening plate is used to control the key row to release the printed sheet sooner or later. Although the open tooth plate frequently rubs against the open tooth bearing of the suction paper key row, it does not need to be lubricated with oil, because once worn, it can still be compensated by changing the position of the open tooth plate. In addition, if lubricated with oil, it will accelerate the wear of the open tooth plate due to the formation of oil sludge.
18. Alignment mechanism
The front paper aligning mechanism and the side paper aligning mechanism are used for aligning printed sheets, which is convenient for stacking and subsequent operations of printed sheets. Be flexible in their actions, so they should be lubricated frequently.
19. Paper receiving table
Refer to the paper feeder for the maintenance of the paper feeder. However, compared with the paper feeding table, its stability during operation is poor. Because of its increased inertia, some brakes are used on some printing machines to reduce inertia. The inertia decreases when the paper feed table rises, so the work is stable.
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