1. Double and multiple faults
For the currently widely used pneumatic continuous overlapping paper feeding, when two or more sheets of faults occur, the work hours may be lost or the blankets may be damaged, or the machine parts may be damaged, causing the roller to jump. . The causes and solutions are as follows:
1. Improper adjustment of the separation head
â‘ The suction volume of the paper suction nozzle is too large, adjust the air volume adjustment knob or the adjustment valve on the air pump to reduce the suction volume; you can also replace the small suction nozzle rubber ring. The position of the separation nozzle is too low. Raise the position of the nozzle.
â‘¡The blow volume of the loose paper blowing nozzle is too large. Adjust the air volume adjustment knob or the adjustment valve on the air pump to reduce the blow volume, so that it can blow up 5-10 sheets of paper. The position of the loose paper blow nozzle is too low. Raise the position of the loose paper blow nozzle.
â‘¢ The air blowing amount of the pressure paper blowing nozzle is too small, increase the air blowing amount. The amount of paper pressed by the paper pressing nozzle is too small, increase the paper pressing amount.
â‘£The inhalation amount of the paper feeding nozzle is too large, reduce the inhalation amount or replace the small nozzle rubber ring.
⑤ The position of the paper blocking brush is too high to play the role of blocking the paper, and lower its position. Insufficient position of the paper blocking brush into the paper stack, increasing the amount of penetration.
2. Causes of paper
â‘ The paper has static electricity, which makes it difficult to feed the paper. The solutions include installing a static eliminator, increasing the indoor humidity, or using antistatic agents.
A. Install a static eliminator. There are several types of static eliminators used in printing machines, such as inductive static eliminators, high-frequency high-voltage static eliminators, power frequency high-voltage static eliminators, etc., which should be placed near the drum during installation.
B. Increase indoor humidity. The generation of static electricity is related to the relative humidity of the operating environment. Generally, when the relative humidity of the workshop is lower than 40%, static problems are easy to occur. Therefore, when printing, sprinkle some water around the paper stack and the machine, or use an air humidifier to adjust and improve the printing workshop Relative humidity to avoid the generation of static electricity (generally the humidity should be maintained at 55% -65% at 20 ° C).
C. Humidify the paper. When the moisture content of the paper is low, the paper is easily charged with static electricity. When the paper has serious static electricity, it is necessary to hang the paper or put the paper in a relatively humid environment for a period of time, but pay attention to prevent the occurrence of ruffles on the paper.
â‘¡ The ink on the paper is not dry, and the upper and lower papers stick together. After the ink is dry, print on the machine.
â‘¢If the paper is not loaded, reload the paper. The paper cutting error is too large, re-cut the paper.
Second, empty sheet failure
When a blank sheet failure occurs, if the machine fails to detect it, the ink that should be transferred to the paper is transferred to the impression cylinder, which will cause the next dozen sheets of paper to have marks on the back, resulting in waste. The causes of vacancy are:
â‘ The suction volume of the paper-separating nozzle is too small, increase the suction volume or replace the large rubber band. In addition, the air path may be blocked, and the air path may be repaired. The position of the separation nozzle is too high to hold the paper, and lower the separation nozzle. The paper separation nozzle is not parallel to the surface of the paper stack, adjust the angle of the nozzle or use a wooden wedge to pick up the paper stack.
â‘¡The amount of air blowing from the loose paper blower is too small, increase the amount of air blowing. The position of the loose paper blowing nozzle is too high or too low, adjust the position of the loose paper blowing nozzle.
â‘¢The paper pressure brush or paper pressure piece extends into the paper stack too much, adjust it to a proper position.
â‘£ Too much paper is pressed by the paper pressing nozzle to reduce the paper pressing amount.
Third, crooked failure
Skewed sheet means that the paper is skewed, and the skewed paper will cause the rules to fail to position the paper normally and stop the machine, wasting man-hours. When the paper is skewed, we can observe the jagged shape between the edges of the running paper from the paperboard. The causes of crookedness are:
â‘ The inhalation amount on the left and right of the paper separation nozzle is inconsistent, which is generally caused by the blockage of the air path, and the air path can be cleaned. The left and right heights of the paper separation nozzle are different, adjust its position. The size of the rubber ring on the left and right sides of the paper suction nozzle is different, and use the same size rubber ring. The up and down movement of the paper separation nozzle is not flexible, remove it for maintenance.
â‘¡The position of the left and right pressure brushes is not consistent, adjust it to a consistent position.
â‘¢ The height position of the left and right loose paper blow nozzles is inconsistent, adjust it to the consistent position.
â‘£The movement of the paper-handling nozzle is not flexible, remove it for maintenance.
⑤ The paper blocking tongue is not on the same plane or the working time is wrong, adjust the paper blocking tongue or the paper blocking cam.
â‘¥The time of pressing the paper by the two oscillating pressure rollers is inconsistent. Adjust the control cam to make the time of pressing the paper consistent.
⑦The tension of the conveying belt is different, adjust the tensioning wheel to make the tension of the conveying belt consistent.
⑧The paper feeder itself is skewed, adjust the position of the paper feeder.
⑨Paper skew caused by improper placement of the pressure roller or inflexible rotation, adjust to a suitable position, and regularly add a small amount of lubricating oil.
4. Unstable paper feeding
Unstable paper feeding means that the paper feeding speed is uneven, and it is fast and slow. When the paper feed is fast, the paper will enter the front apron, the paper feed will be slow, and the paper will not be in place. In both cases, overprinting will be inaccurate and the product will be scrapped. For this reason, the paper feed speed must be adjusted faster and slower for a while, making it difficult to understand. Many machines have not been solved for a long time because of this problem, which affects the quality and reduces the output. The causes and solutions are as follows:
â‘ After the paper feed nozzle feeds the paper in place, there is still suction, which causes the paper that has entered the paper feed shaft to be blocked due to the backward pulling force of the nozzle, resulting in a pause. Because the paper is overlapped, it will affect the previous sheets of paper at the same time and slow down the speed. When the machine is shut down halfway, if the air pump is turned off first and then the paper is stopped, the last few sheets of paper on the paper path will be slightly faster due to the influence of the suction of the nozzle, which will cause unstable paper feeding. There are two solutions:
A. Adjust the front and back movement cams of the paper feed nozzle, so that during manual inspection, the paper should be placed when the paper feed distance of the nozzle is about 10mm to the limit position, and no suction will occur.
B. Block the air groove of the suction piston. For example, "Beiren" SZ201 paper feeder adopts the method of clogging the air slot, and the effect is better. The method is as follows: remove the piston and fill the tail of the air groove with a copper block for 3 ~ 5mm. The copper block should be welded firmly to prevent accidents caused by falling off.
â‘¡The paper feeding is unstable due to the belt.
A. The belt is too loose, tighten the belt, and the tension of each belt should be as consistent as possible.
B. The belt tensioner runs poorly, clean it with kerosene and add lubricating oil.
C. The paper conveying board produces resistance to the wire belt, and removes the dirt on the steel leather pad holder of the paper belt on the paper conveying board to eliminate the resistance.
D. Use double-layer cable tape to avoid jitter caused by uneven thickness of the cable tape.
â‘¢ The diameter of the paper feed roller jumps (not round) and replace with a new paper feed roller.
â‘£ The gap between the running parts of the paper conveying parts is too large. Check the parts and make necessary repairs or replacements.
⑤ Excessive accumulation of paper wool and oil dirt on the clutch will cause inflexible clutch action. If the clutch is not reached at the position where the clutch is hung, the clutch will be fed quickly and slowly. Cleaning the clutch can solve the problem.
â‘¥The bearing inside the passive roller of the paper conveying belt is damaged, and it does not rotate when it appears, which is also the cause of unstable paper conveying. During the inspection, you can lift the cardboard, loosen the belt, and turn the belt by hand to find the problem. The problem can be solved by replacing the bearing.
Fifth, the paper arrives early or late
When the paper does not reach the front position when the side gauge begins to locate, the pre-specified line is called late arrival of the paper, and the early arrival of the paper refers to the improper coordination of the paper feeding time of the paper machine and the falling time of the pre-regulation, so that the paper arrives ahead of the pre-defined time The pre-specified bit line. Regardless of whether the paper arrives early or late, it will make the rules unable to achieve the normal positioning of the paper, resulting in inaccurate overprinting. The causes and solutions are as follows:
â‘ The paper feeding time of the paper feeder does not match the falling time of the previous rule properly. The correct matching time should be when the current gauge falls to the positioning position, the bite edge of the paper is 5 to 8mm away from the previous prescribed bit line. For the J4105 machine with chain drive, you can first loosen the three fastening screws on the sprocket, then turn the paper feed handwheel to adjust the paper to the appropriate position, and then tighten the three screws; Heidelberg Speed-Master The series can also adjust the mating time by changing the gear meshing relationship in the transmission box of the paper machine.
â‘¡The height of the paper stack is lower than the allowable height of the front paper block, and the paper being sent out is blocked, causing the paper to arrive late. The height of the paper stack should not be lower than the axis of the swing axis of the front paper block. Generally, the height of the paper stack should be lower than the top of the front paper block by 5-10 ?. In this case, the feeder can be properly raised; if the paper stack is too high, even higher than the top of the front paper block, causing the paper to arrive early. At this time, you can reduce the height of the feeder or insert a wedge to reduce the height of the paper stack. The adjustment requirements are the same as described above.
â‘¢The falling time of the oscillating platen roller is late or the wear is serious. The swinging pinch roller should be used to send out the paper at the paper feeding nozzle. When the suction is about to stop and the suction has not stopped, it just falls and presses the paper. The pressure can be felt when the machine stops. It should be replaced in time when the wear is severe.
â‘£Feeder's paper feeding time is too late (relative to the swinging platen). Under the premise that the swing time of the squeeze platen wheel is correct, adjust the transmission time of Feida according to its hem time (Beiren's PZ4880-01 and Heidelberg Speed-Master both have a relative position adjustable in Feida's transmission box Sprocket.
⑤ The tension of the belt is small, or the pressure of the paper feed roller is too light, which causes the paper to arrive late. Otherwise, the paper will arrive early. The solution is to tighten the belt to a proper level or adjust the pressure of the paper feed roller properly.
In the offset printing process, there are many factors that affect paper feeding. If the paper feeding fault is found during the operation, it can be eliminated according to the above method to ensure the smooth production.
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