Common faults related to paper feeding
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In printing, many problems often occur due to improper adjustment of the machine, handling of raw materials, and inadequate use. The occurrence of a fault phenomenon is sometimes caused by many different reasons; for the same reason, sometimes it causes different faults. Therefore, this creates the complexity of the failure. To solve the problem well, you must find out the source of the failure. In order to correctly find or estimate the root cause of the failure, the operator must not only have certain work experience, but also have certain theoretical knowledge and combine theory with specific practice, so that the problem can be quickly and correctly has been solved.
Any failure, if the source is not clear, make no purpose adjustments and corrections, not only will the real failure not be solved, but the other will cause other normal parts to malfunction, which makes the problem more complicated. Therefore, we should pay special attention to this when correcting the fault, and strive to avoid such bad work habits.
There are many printing failures caused by paper feeding. In order to make the operator easy to analyze, judge and troubleshoot, and skillfully master the paper feeding operation skills, the common common faults are introduced as follows:
One, two or more sheets
1. The suction of the separation nozzle is too large, and the following sheets of paper are simultaneously sucked up. This type of failure is caused by the following conditions:
(I) the inspiratory volume adjustment is too large;
(2) The rubber band is too large;
(3) The separation nozzle is too close to the paper surface;
(4) The paper is too thin.
Solution: 1 reduce the air volume; 2 replace the small rubber band, or cut the rubber band small, the rubber ring on the paper nozzle can be removed when the paper is thin; 3 adjust the length of the paper foot to increase the paper pile And the distance between the paper separation nozzle, or adjust the eccentricity above the separation nozzle rod to increase the distance from the paper stack surface; 4 press the paper stopper brush down.
2. The paper separation nozzle is too close to the paper edge, even beyond the paper edge, or the paper is not stacked properly, and the paper cutting size is inconsistent, which causes multiple sheets of paper to be sucked up by the paper separation nozzle at the same time.
Solution: The former increases the distance between the separation nozzle and the paper edge by adjusting the front and rear position of the separator, and the latter should re-stack. For paper that is not cut properly, try to make the trailing edge neat when stacking; if the difference in size is large and affect the positioning accuracy, replace the paper or separate the different sizes of paper separately.
3. The height of the paper stack exceeds the allowable height of the paper block. The height of the paper stack should be less than about 5 mm of the paper block. Due to improper upsetting of the paper or improper adjustment of the stack height, the stack height of the stack exceeds the allowable range, and two or more sheets of paper are brought into the paper table.
Solution: 1 When the paper is upturned, it can be reversed; 2Because the double stack generated by the paper stack is too high, the dragging side can be inserted into the wooden wedge for control. J2203, J2108 and other offset presses can also be used to reduce the height of the separator.
4. The paper tip is tilted upwards. When the airflow blown by the loose paper nozzle touches the paper edge, there is an arc on the edge of the paper that is curled up. The airflow meets the arc and is divided into two parts, and a part of the airflow lifts the paper, and another Some of the airflow turned down and the paper could not be separated, making the paper stop brush useless. At the same time, the edge of the paper is generally elastic. When the paper is pressed, the paper is shrunk. When it is lifted, it is lifted up, causing double sheets, multiple sheets, and even paper sheets to be fed into the paper. station.
Solution: 1 Remove the paper and perform reverse knocking; 2 Adjust the bottom angle of the separation nozzle so that it is parallel to the paper stack.
5. Pressing the paper foot or the paper stopper brush into the paper is too small. The paper presser presses too little paper, and the stack automatically rises and is unstable, so that it can't hold down the paper below; the paper stop brush is too high or too little into the paper edge, and loses the effect of wrapping and brushing the paper below.
Solution: If the separation nozzle is on the edge of the paper, move the paper separator as a whole forward; if the edge of the separation nozzle is about 5 mm from the edge of the paper, adjust the paper foot or paper stopper to Standard working position (described above).
6. The paper is not loose and the paper is stuck.
(1) White paper cutting incision adhesion.
(2) When printing semi-finished products, the upper color is the full version of the solid or multi-color overlap. Due to the excessive thickness of the ink layer, the paper will stick up and down; water stains and inks are also likely to cause upper and lower adhesion.
Solution: 1 Before the printing, that is, when loading paper, it should be slightly opened, smashed, loosened, and smashed. 2 The semi-finished product adheres due to the excessive thickness of the ink layer, and a small stack and a small stack are loosened when loading the paper. 3 Because the number of semi-finished products is small, the first color ink does not dry out and the adhesion of the next color printing occurs. When the paper is picked up, it is repeated several times to make enough air enter the paper to promote the oxidative drying of the ink. The pile of paper on the machine should be piled up a little to avoid the adhesion of the paper below due to heavy pressure.
7. When the paper is electrostatically charged, when the surfaces of the two objects rub against each other, the electrons on the surface of one object will be transferred to the surface of the other object. When the two objects in contact are separated, since many electrons cannot return to the atom in which they were originally located, this creates an inequality in charge. Paper is an insulator and has poor electrical conductivity, especially in dry air, making it difficult to replenish lost electrons. Static electricity is generated when the charge is stabilized in the formed region. Paper with static electricity can hold another piece of paper or other objects in contact with it, causing paper feeding difficulties during printing, causing problems such as skew, double sheets, multiple sheets, and misfeeds. When the static electricity is large, it may even stagnate on the surface of the paper feeding table, making the production impossible.
Solution The workshop with constant temperature and humidity control should appropriately increase the relative humidity between the workshop and the air-paper to keep the paper with a certain water content.
In the workshop without constant temperature and humidity, you can sprinkle some water on the floor of the workshop. This kind of treatment method has a certain effect on reducing the static electricity of the paper, but improper handling will cause the relative humidity of the workshop to be too high, causing the paper to expand and contract, resulting in defects such as wrinkles and overprinting, so it should be used with caution.
Second, empty paper
1. The distance between the paper stack and the paper separation nozzle is too large. The distance between the bottom surface and the paper stack surface at the lowest position of the paper suction nozzle is about 6-8 mm for thin paper and 2 to 3 mm for thick paper. When the distance between the separation nozzle and the paper stack is too large, if the vacuum of the air pump is insufficient, it is easy to generate an empty sheet.
Solution: 1 shorten the length of the platen foot bar, so that the distance between the paper separation nozzle and the paper stack surface is reduced; 2 adjust the eccentricity above the paper separation nozzle rod to reduce the height of the paper separation nozzle.
2. The paper tip is curled downwards. Because the paper tip is curled downward, the airflow blown by the loose paper mouthpiece is not easy to enter the paper gap and cannot be separated. At the same time, when the paper is sucked down by the paper suction nozzle, the paper surface is rolled down, which is easy to cause the nozzle to leak, and the paper cannot be sucked up.
Solution: 1 Adjust the adjusting screw on the separation cylinder to change the angle of the bottom surface of the separation nozzle so that it is parallel with the paper surface; 2 Move the paper down and knock the paper on the front side.
3. The distance between the paper nozzle and the paper stack is too large.
Solution: Adjust the height of the paper feed nozzle. When the paper nozzle is at the lowest position, the distance between the bottom surface and the paper stack surface: SZ201 type paper feeding device is about 1.5mm; SZ206 type paper feeding device is about 5mm. The height of the paper feed nozzle can be adjusted individually or as a whole. (as mentioned above)
4. The paper stopper brush is too low or protrudes into the paper pile too much. The application of the paper stopper brush should be closely matched with the loose paper mouthpiece. When the air volume of the loose paper mouthpiece is normal, it can blow the paper edge and the height is about 5mm, which is also the distance that the paper stopper brush should leave the paper pile. . When the paper suction nozzle is used to suck the paper, it just touches the paper surface that is blown up, or 1 to 2 mm above the paper surface. The paper stopper brush is pressed too low, so that the paper can not be blown, which increases the distance from the paper separation nozzle to the paper surface, resulting in an empty sheet; sometimes the paper stopper brush protrudes too much, although the paper separation nozzle can The paper is sucked but it is also bounced off by the brush, causing an empty sheet.
Solution: If the paper stopper brush is moderately elastic, adjust its height and the distance to the stack to the above data.
5. Most of the airway blockage is blocked by the airway. The blockage comes from paper wool and dust, and is mostly blocked in the section of the suction nozzle pipe and the control piston. Because the piston has oil stains, the paper wool and dust are stuck by the oil stain when they are sucked into the place, and the more accumulated, the more the suction air path is blocked, resulting in insufficient suction and emptying.
Solution: Regularly clean the gas path and control the piston. The machine that prints rough paper should be cleaned once a week.
6, insufficient suction. Due to the accumulation of ink on the nozzle and rubber band or the rubber band wear and tear, air leakage during the paper suction causes insufficient suction and can cause empty sheets. The transfer nozzle is especially serious.
Solution: Strengthen the inspection and do the cleaning work, especially if the previous ink color is on the ground, especially the color should be noticed.
Third, the paper skew
1. Paper skew caused by the paper separator:
(1) The suction of the two separation nozzles or the two transfer nozzles is different, especially the working positions of the two transfer nozzles are inconsistent;
(2) The working positions of the paper jams on both sides are inconsistent;
(3) The paper is not loose and partially adhered;
(4) The paper is electrostatically charged;
(5) The working positions of the two loose paper blowing nozzles are inconsistent;
(6) A nozzle is clogged, leaking, etc.
For the solution, please refer to the above solution for double and empty faults.
2. The pressure of the paper take-up roller is inconsistent or the time of pressing is different, or the roller is not flexible.
Solution: 1 adjust the pressure of two paper rollers and the pressing time, as described above; 2 scrub the roller with kerosene to make it flexible.
3. The elastic band is inconsistent. The belt is tight and the thickness is not uniform, the tensioning wheel is tight, and the running speed of the belt is inconsistent, causing the paper to be skewed.
Solution: 1 The thickness of the four belts on the paperboard should be uniform and adjusted to the same degree of tightness; if the 2 tensioning wheels do not rotate, they can be scrubbed with kerosene and then lubricated with oil.
4. The weight of the paper roller on the belt is inconsistent. If the position of the pressure roller is not accurate or the rotation is not working, the paper will be inconsistent.
Solution: 1 Keep the platen on the belt running freely, often wipe the paper, dust and other dirt on the cardboard. 2 The position of the platen roller should be symmetrical on both sides, light and heavy.
5, the paperboard is broken on the paper, the paper safety bar and the marble ball frame fall. Generally, the paperboard of the printing machine is covered with paper strips to prevent the paper corners from colliding with the seams at the front and rear ends of the paperboard. When the leading edge of the paper touches the broken portion of the paper, it will cause the paper to be skewed. The paper safety bar and the ball rack fall also cause this kind of malfunction.
Solution: 1 Always check or replace the paper strip on the paper feeding table; 2 Eliminate the falling phenomenon of the paper feeding safety bar and the marble ball holder.
6. The separation nozzle of the separation nozzle is worn. Separating the paper by the separation nozzle is accomplished by moving the separation nozzle in the rail up and down, plus the air volume. In order to ensure a smooth separation of the paper, the separation nozzle lever must be moved under the control of the track. Therefore, if used for too long, the track will produce different degrees of wear. Long-term non-cleaning and no lubrication are the main reasons for the track wear. When worn, it causes the nozzle rod to move along the track, causing sloshing, causing the separated paper to be skewed.
Solution: 1 Usually, the nozzle rod and the track should be regularly lubricated and lubricated, and preventive measures should be taken; 2 pairs of rails that have been seriously worn should be in time to be set back to the original state.
7. The positioning of the transfer nozzle cam is not allowed. The movement of the paper feed nozzles of the low speed machine and the J2201 two-color machine currently used are controlled by two cams. If the two cams do not move inconsistently, the twisting phenomenon of the transfer nozzle may occur, causing the paper to be skewed.
Solution: When the paper feed nozzle is returned to the position and at the lowest point, the fixing screws can be loosened to adjust the two cams.
8. The paper suction nozzle is too low. The paper pick-up nozzle is adjusted too low or naturally loose and displaced; sometimes the unevenness of the printed paper is uneven on both sides or parts, and the ink piles on the semi-finished products are piled up, etc., and the pile is high and low, in the upper part of the stack, the previous one The tip of the sheet of paper will be pressed by the paper pick-up nozzle that has fallen, which will cause resistance to the forward paper feed, and the paper feed will be slow and skewed.
Solution: 1 The uneven paper pile can be leveled by wooden wedge or with a paper tape; the paper-pressing rod of the 2-point paper nozzle should not be adjusted too low (adjust the position as described above) to avoid falling. Squeeze the pile of paper.
Fourth, overprinting is not allowed
In the process of paper feeding, except for the skew of the paper, the overprinting of the printed matter may be inaccurate. The following various reasons may also cause the overprinting to be inaccurate:
1. The paper feeding device feeds paper too fast or too diffuse, but it does not match the front gauge, causing the paper to “go over the head” or “undertake”.
Solution: Adjust the speed of the paper feeding device, the operation method is as described above.
2. The pressure of the paper feed roller is too light, causing the paper to “go out”.
Solution: Adjust the pressure of the roller to make it light and heavy, even and appropriate.
3. The paper feeding belt is too loose to produce sliding, or the belt tensioning wheel and the fixed pulley are short of oil and the rotation is not flexible, causing “under walking”.
Solution: 1 tighten the belt; 2 remove the tensioning pulley and the fixed pulley, and refuel to make it fully lubricated.
4. The position of the platen roller on the paper feeding table is incorrect. The pressure is too light or too heavy, causing “under walking” or “over the head”.
Solution: 1Put the position of the platen roller to make it connect with each other accurately; 2 tighten or loosen the compression spring to increase (or decrease) the pressure.
5.the paper is too thin, too soft, the paper edge stress is insufficient, the paper edge curls, causing the paper to "go over the head" or "pull over the head."
Solution: Twist the edge of the paper and the specified position on the side to enhance the paper edge stress.
6. The distance between the paper and the side gauge is too far or too close, which may cause “under pulling” or “pull over”.
Solution: Keep the paper feed distance 5-8mm.
Fifth, The prints caused by the pickup roller and the brush wheel are dirty.
The main color is not dried yet, and the latter color is printed. The smear caused by the pickup roller is easy to find because it has both the front and the back; the smear caused by the brush wheel is on the back, so it is not easy to be found. Modern high-speed offset presses are stacked paper feeds, when the paper is delivered. When the gums hold the paper, the paper advances nearly twice as fast as it does on the paper table. High-speed friction between the two sheets of paper, under the pressure of the brush wheel, the back side of the paper has a greater friction, so that the ink on the lower sheet of paper hits the back of the sheet.
Solution: When the pickup roller is dirty, move the paper feed roller to the blank space on both sides. In addition, it is necessary to strengthen the back inspection, and at the same time, the brush wheel can be lighter. If it is a double-sided print, it is necessary to increase the amount of dry oil to ensure that the blot is dry and prevent smudging.
Sixth, the paper is not flat
Paper unevenness means that the paper being conveyed is not flat. In normal printing, paper feeding and overprinting are often affected by uneven paper. The causes and solutions for the unevenness of paper feeding are as follows:
I. The water content of the paper is not uniform. When this phenomenon occurs, it will cause the paper to curl, tight edges and other deformations, which will cause paper unevenness and affect overprinting.
Solution: The paper is conditioned before printing to match the temperature and humidity of the printing shop, and it can also reduce the sensitivity of the paper to moisture. In addition, it is necessary to strictly control the moisture in the printing.
2. The local ink layer is too thick.
Solution: When feeding paper, you can use paper plate and paper plate to gently press the paper. In addition, do not increase the amount of ink in the printing. For the ink with a large amount of ink, the final printing should be arranged.
3. Unevenness when printing thin paper or three-open paper. When printing thin paper or three-open paper of 60g/m2 or less, since the paper thin or the three-open paper is a narrow strip, the paper feeding is not well controlled, and paper feeding is likely to occur.
Solution: 1 When printing the above paper, first control the air volume, loosening the mouthpiece to blow 5-8 sheets of paper on the surface of the paper stack; 2 can be adjusted by adjusting the angle of the platen on the paper frame, ie The front end platen has a larger angle and is in the outer "eight" shape. When the middle raised paper is conveyed forward, the convex hull is gradually arranged to be flattened by the axial force generated by the outer "eight" shaped platen. . Practice has proved that using this method to solve the unevenness of printing paper or three-open paper has a certain effect.
Seventh, paper wrinkle arch (also known as "bow wrinkle", "folding", etc.)
1. The paper foot is too big. Since the paper blowing foot is too large, the paper is bulged in the middle, and if the bulging phenomenon cannot be eliminated during the paper feeding process, the paper wrinkles are caused. Especially for thinner papers, the bulging phenomenon is more difficult to eliminate.
Solution:
1 reduce the amount of air blown by the presser foot;
2 When printing thinner paper, the suction force of the suction nozzle should be appropriately reduced and the pressure of each platen roller, ball and brush on the paper feeding table should be reduced;
3 Adjust the position of the paper feed bar and the front platen appropriately.
2. The paper ball, platen roller or brush wheel is not in the wrong position or the pressure is too heavy.
Solution :
1 Adjust the position of the paper ball and the wheel.
2 Adjust the pressure of each platen and wheel.
3 Appropriately lift the platen roller when printing thin paper.