Offset Overprint Accuracy Related Questions (19-22)

19. What's wrong with paper unilateral overprint?

The paper feed is skewed: the feeding belt and the paper feed roller are poorly adjusted, which often causes the paper feed to skew; the speed of paper arrival is different. This situation may cause irreversible overprint on the unilateral side, resulting in this situation. Paper feeders have problems at the same time that they should be checked and resolved one by one. Sometimes the two lines on both sides are of different lengths. Although the forces are the same after being tightened, the speed of the two lines is different. It also causes the side to be slow and slow.

Faults at the same time as the rules component: The front regulation paper tongue is low and the paper enters the front gauge. Some operators will increase the pressure of the flat brush, press the ball on the edge of the paper, causing the paper to appear not to go through the position but also to walk through; the swinging bite force is insufficient, the paper pulls Out; Sideways lift too slowly, pull the paper out of the swinging teeth, it is easy to handle as if it is not in place.

20. What is the problem with the bilateral symmetry of the paper?

The roller bearing on the swinging hand is seriously worn: the roller swinging on the hand, it has a large amount of movement, heavier and irregular force, not only the surface is easy to wear, the bearing ball of the inner circle is also easy to wear, resulting in bilateral symmetrical walking Did not do well.

The wear of the transverse pin on the swinging hand is severe: the transverse pin shaft is more likely to cause a biased wear in the reciprocating motion, resulting in a backward phenomenon when the swinging pinch teeth are fed, thus causing the malfunction that the bilateral symmetrically fails to reach the position.

Swing cam feed position is not accurate: If it is the original cam is mainly caused by the cam wear, and sometimes put on their own processing of the new cam, because the processing does not meet the original design requirements, resulting in overprinting is not allowed.

twenty one. What is going on with bilateral symmetry?

There are three common causes for bilateral symmetry.

The swinging spring is too loose: the swinging spring is forcing the child to keep close to the cam. When the spring is too loose or the metal fatigue loses enough tension, it is possible to lose control and make the roller The large cam shakes off during a period of time, which easily leads to a bilaterally symmetrical failure.

The front gauge is lifted prematurely: the front guard picks up the time, the low speed machine should be at the same time as the dump bucket just left the striker; the high speed machine should swing the grippers to open and close the tooth roller just after leaving the cam, because the feed is overlapped If the front gauge is lifted too early, the paper has not been controlled by the bite of the paper teeth, and the following sheet of paper continues to advance. Under the effect of friction, the upper sheet of paper is subjected to a large forward momentum. Easy to walk through the fault.

Swing cam feed position wear: Swing cam feed position, due to the greater force, easy to wear. When the front half of the paper feeding lobe produces a bumpy and bumpy shape, the swinging bite teeth will generate a slight amount of jitter when the paper is handed to the indentation roller, resulting in symmetrical symmetry. When the paper feed lobe is worn badly, it can be removed and leveled with a knife or sand.

twenty two. What's wrong with overprinting bilaterally?

(1) The two preceding rules are not on a straight line, and the width of the paper is not the same. This is caused by poor operation. The front rule controls the bite rate of the bite. Both sides are best to maintain a distance of 5mm, when installing the printing plate, take the pull plate method to achieve the size of the graphic and positioning specifications, this is the correct method of operation. If you make mistakes, you will not go to pull the plate and move the front gauge, resulting in a wide disparity in the amplitude of the two front gauges, causing irregular printing.

Because the width of the two front gauge papers is very different, the paper edge is not a line but a point shape when it touches the front gauge, so that the paper's impact is concentrated on two points. At these two points, the paper can not withstand the forward momentum and curl. Due to the difference in the thickness of the paper, the frontal impact force is very large and small, resulting in inconsistent forward momentum of the two points of the former regulation, thus resulting in inaccurate overprint.

(2) The embossing cylinder bites the paper shaft or the sleeve wear: the embossing cylinder bites the paper shaft, the swinging bite shaft or the sleeve wears, so that the bite teeth are in an unstable state in the process of biting paper, thus Irregular overprinting is not allowed. This kind of fault 6f's speed machine is relatively easy to produce, because the impact force of the low-speed machine dump bucket is large, and the rotation speed of the paper-gripping shaft is also large. The high-speed machine swings the indirect delivery paper, and the width of the bite is small, so the bite shaft and its sleeve are not easy to wear. But pay attention to oil eye blockage and prevent oil cuts.

(3) Imprinting roller bite paper spring brace spring break: The brace spring of low speed machine sucking paper shaft requires good toughness, but it is easy to break due to problems such as steel quality and quenching. The bungee is strung on the ripped iron and will not fall even if it is broken. It is not easy to be noticed. It will only be discovered when the overprinting situation becomes more and more serious, but it has caused a lot of waste products, and sometimes the brace spring is used for a long time. Gradually lose support. It will also result in overprinting.

(4) The front end of the low-speed paper feeding iron is too far away from the front gauge: the front end of the low-speed paper conveying iron plate sags to the gap between the front gauges, resulting in a large amount of sag due to paper thickness or machine vibration. There are small moments when the current regulations are lifted, and the paper is stretched freely by its own elasticity, resulting in inaccurate overprinting of the day.

(5) Swing biting teeth have a short rest time: The swinging bite teeth of the high speed machine should be in a static state when biting paper to ensure the accuracy of the paper bite. The rest time is controlled by the adjusting screw on the mountain.

When the pendent teeth are in contact with the mountain, the rollers on the holding hands should be on the smallest face of the cam. According to the factory standard, the clearance is o. 03 a. 05 mm. If less than o. There is no gap at 03mm, indicating that the delivery time is too short or there is no rest time at all, so that it is in an unstable state and it is very easy to cause faults that are not allowed to register on both sides.

(6) The distance between the swinging bite teeth and the biting paper tooth of the impression cylinder is too short: the high speed machine swings the flag of the paper catcher to touch the cam during this time. It is very short, when the embossing roller bite the paper bite, it is 0°, and when the swinging pinch teeth open, it is 359°, and only rotates by 1°. According to the calculation, it is about 2.62 mm. For such a short distance, the transfer is completed at high speed and it is very short. Of course, the handover time can be extended appropriately, but the premise is not to tear the paper. If the handover distance is smaller, it may happen that the swinging gripper teeth have begun to release, and the impression cylinder bites the paper teeth. The phenomenon of biting paper has not yet begun, and sometimes slow transfer is still good, but due to vibration and other factors during high-speed operation, the transfer is not good, resulting in overprinting is not allowed.

(7) Indentation roller teeth and open-close teeth roller wear roller bearing wear, high-speed machine's embossing roller bite paper teeth open and close roller bearings, with two types of 201 bearings connected in series Two bearings are respectively in contact with two overlapping cams to control opening and closing time. Because the periphery of the open and close tooth roller bearing is directly in contact with the cam, in actual use, existing homes with bearing damage and chipping continue to occur, resulting in inaccurate overprinting. In addition, the open and close teeth of the swinging gripper have similar wear.

(8) Loosening and breaking of pins on swing penknife and embossing cylinder bite paper shaft pendulum: High-speed machine's swing bite shaft and impression roller's bite shaft end is equipped with about three inches long open pendulum Rods, pendulums, and shafts are fastened with pins. The force applied by these pins is relatively large, and therefore they are more prone to loosening or breakage: overprinting is not allowed.

(9) Faults in the "flip bucket" and the striker of the low speed machine: The faults in the low speed machine's tipping bucket and the striker's latch have a great relationship with the overprinting accuracy, and many failures are encountered in this respect. For example: The dump pin breaks and should be replaced with a new one. Roll over the sides of the roller and add a washer to the inner shaft end, but do not overtighten it. The positions of the tipping bucket and the knocking moon are not correct: the fixed wall panel is controlled to move or replace the new lang: just, the problem of inaccurate position of the dump lever and the control lever may occur, resulting in inaccurate shaking of the paper bite when biting paper, if it is new The tipping bucket that was replaced means that there is a problem with the accuracy of the tipping process and should be replaced with another one. If the small wall plate moves, the position of the small wall plate should be corrected, and the inner and outer walls should be flush when correcting. When the contact point between the dump bucket and the control latch wears into a groove, replace the new tipping bucket or use a foreign man's trowel to flatten the slot; add a correspondingly thicker striker. The striker is worn out or knocked out to replace the new one. The striker is hit by a bend and it should be replaced with a new one.

(10) Paper teeth touch against the mountain: Before correcting the nip force of the paper by the embossing cylinder, a paper length or thickness gauge with a thickness of 0.3 mm should be inserted on the backing beforehand. When the teeth are leveled and the pressure is evenly adjusted, remove the papers from the padding on the back of the place. When the backing and backing screws should not touch, this is one of the conditions to ensure the correct bite of paper bite. But sometimes due to tooth pad wear, inappropriate correction of biting teeth, turning and other factors when repairing the machine, causing the backing of the backing with the mountain screws, affecting bite paper bite force, resulting in overprinting is not allowed.

(11) bite paper teeth bite force is too light: cause bite paper teeth bite force is too light or a few bite paper teeth teeth for many reasons. A, bungee spring, tensile spring broken or metal fatigue (all too light); B, the pad is low (all or most of the light); C, bite paper fastening screws loose (some are too light); D , Back screw against the mountain (all too light); x, rigid occlusal smooth (mostly too light); F, bite paper bad correction (individual or mostly too light).

Due to the above reasons, biting paper teeth work abnormally, resulting in inaccurate overprinting. If it is a two-color machine, it will even make one or two colors overprint impossible.

When correcting the bite force of bite teeth, the pad thickness should be o. A 3 mm paper strip is then corrected from the middle, which is the principle of correcting the teething. Further to both sides, the latter pressure should definitely not exceed the previous one. When individual corrections are made, it is also necessary to first check whether the gaps in the mountains meet the above criteria. Fang meets, and then corrects from the middle to the sides. If there is an individual bite in the bite of the paper teeth, it should be loosened.