J2108 waterway common faults and maintenance
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In the use of offset presses, the adjustment and use of the water roller and its associated mechanisms is very important to the printing process. Below we will take the waterway of J2108 offset printing machine as an example to introduce some common faults and maintenance of the popular waterway system in domestic offset printing machine.
Easy to produce problems and precautions
1. When replacing the new water roller, the old version can be used to correct the water roller pressure, and the ink should be washed first with gasoline to avoid contaminating the water roller. If a new printing plate is used, or if the water roller pressure is not accurate during the printing process, when correction is required, the printing plate is firstly dispensed, and the fan is to be flattened to protect the printing plate. Then select the blank part at both ends of the printing plate, or measure it with a steel piece in the blank part of the trailing tip, and the number of insertions is as small as possible to prevent the plate from being scratched and inked, and the area to be inserted into the test is used. Clean the stock solution and gum arabic to maintain its hydrophilic properties.
2. The total thickness of the pad of the printing plate should conform to the standard, so as to avoid the contact pressure between the water roller and the printing plate when the printing plate is exchanged. If it is necessary to change the thickness of the plate liner, it is expected that the pressure between them may change and be corrected.
3. When adjusting and installing the water roller, pay attention to protect the water roller and the printing plate from being neat, and at the same time, do not pinch the water roller with your fingers to prevent contamination of the water roller cloth cover.
4. Before installing the water roller, the new water roller velvet cloth or the new water roller velvet sleeve should be wetted with water or dampening solution in advance, and the fluff should be smashed to prevent the fluff from falling on the printing plate and the ink roller during the printing process. On, affecting product quality. At the same time, in the mastery of pressure, the generally wet water roller is slightly smaller than the unwetted water roller.
5. When adjusting the contact pressure of the water roller to the water roller, be sure to pay attention to the symmetry of the eccentric bearing direction, that is, the adjustment of the eccentricity of the two ends should be in the same direction, otherwise it will lead to the water and the plate cylinder and the water roller. Not parallel, the fleece sleeve on the water roller is easily pushed into a spiral shape by the axial force, and the water delivery cannot be uniform. If the eccentric direction of the two sides of the water roller is asymmetrical, it will also cause the pressure of the water roller, and the two ends are light and heavy in the middle. Therefore, when testing the water roller pressure, several places can be measured, both ends are measured, and the middle is measured to prevent The water roller is uneven or the eccentric direction is inconsistent.
6. The feng shui roll neck or bearing has been seriously worn, or the water roller of the ball bearing is used. If the bearing is damaged, the new bearing should be repaired or replaced in time to avoid the pressure being inaccurate.
7. The water roller does not allow obvious axial movement, otherwise the layout may be damaged.
8. Mastering the contact pressure between the water rollers
(1) The pressure of the two water rollers and the printing plate is to be lighter and the lower one is heavier.
(2) The pressure of the two water rollers and the water roller is also lighter, and the lower one is heavier.
(3) The pressure of the water roller and the printing plate should be slightly heavier than the pressure of the water roller.
(4) The pressure of the water transfer roller and the water-repellent roller is equivalent to or slightly smaller than the pressure of the water roller and the water-repellent roller.
First, Failure caused by improper contact pressure of the water roller
1. The contact pressure between the water roller and the printing plate is too heavy, which will cause excessive rubbing on the printing plate surface, causing the graphic part of the layout to be quickly worn out, and the sand hole is smoothed, resulting in a “flower plate” image, due to pressure Large, it will also cause the water roller to jump when it touches the printing plate, so that the jumping part is easy to get dirty, and the falling part will cause "white bar" in the graphic part (especially the flat wire).
2. If the contact pressure between the water roller and the printing plate is too light, the plate will not be supplied with sufficient water supply, the imprint will be rough, expanded, or even dirty, and the water supply to the plate will be caused by the unevenness of the water roller. Not uniform.
3, the contact pressure between the water roller and the water roller is too heavy, the water will be squeezed at a certain point of the water roller, resulting in poor water supply, affecting the normal water transfer of the two water rollers, especially on the water The contact pressure of the water roller is too heavy, which not only causes the water to be poor, but also loses the effect of the water roller, which makes the printing plate hang dirty.
4. The contact pressure between the water roller and the water roller is too light. Due to poor contact, the water roller lacks a normal source of water, so the water supply cannot be properly applied to the printing plate, causing the printing plate to be dirty: at the same time, the water roller lacks water film. The protection is quickly stained by the ink, and the effect of the water supply is lost. The ink that has been applied is promoted to cause the water-repellent roller and the water-jet roller to be contaminated by the ink, thereby affecting the water supply performance of the water roller.
Second, uneven water delivery
There are many reasons for the uneven water delivery. In addition to the above-mentioned improper adjustment of the water roller pressure, there are the following common reasons:
1. The diameter of the roll core of the water roll is not equal or the water roll is not round;
2. When sewing the water roller, the ends are tight, the middle is loose, or the ends are loose, and the middle is tight;
3. The water roll is unevenly rolled or rolled low during use;
4. The surface of the water roller is covered with ink layer, which has poor water absorption;
5, water roller velvet long-term use, the fluff is honed and polished;
6. The surface of the water bucket roller and the water roller have too much ink;
(1) The speed of the plate cylinder and the water roller are not equal;
(2) The water roller or the water transfer roller is too dirty;
(3) The surface of the water bucket is too smooth to form ink;
(4) The downtime is longer, and the water roller and the water roller are in the case of water loss or dryness, and the oil mist in the workshop environment forms a thin oil film on the roller;
(5) There is no proper amount of hydrophilic glue in the plate solution;
(6) Others.
Correct it for different reasons, and remove the dirt on the roller before printing.
Third, light ink bar (white bar)
Ink bars, also known as strips, bars, bars, etc., refer to dark or light streaks formed on the printed text. As shown in Figure 1. Light-colored marks, called light ink bars (also known as white bars, white bars), are characterized by light ink on the streaks and small dots. Dark streaks, called dark black bars (also known as black bars, black bars), are characterized by thick ink on the streaks and enlarged dots. In printing, the main reasons for the light ink roller caused by the water delivery device are:
1. The contact pressure of the water roller with the layout is too large, characterized by streaks, generally at the mouth of the mouth.
2. The wear of the machine on both sides of the water roller is severely pulsating when it is in the water. It is characterized by streaks in the full version or in a certain area.
3.the water roller rotating gear wears severely, which is characterized by streaks in the full version or a certain area.
4. The swinging time of the water stick is improperly adjusted. The characteristic is that the streaks are generated when the water stick is placed to the water stick, and the contact part of the water stick and the printing plate is placed.
Fourth, the layout is dirty
The reason:
1. The acidity of the fountain solution is too strong or too weak;
2. The water supply adjustment is too small;
3. The content of the glue in the dampening solution is insufficient;
4, the pressure of the water stick is not properly adjusted.
Five, flower version
As shown in Figure 2, the main reasons are:
1. The dampening solution is too acidic;
2, the layout moisture is too large;
3. The pressure between the water roller and the printing plate is too heavy.
Six, paste version
As shown in Figure 2, the main reason is basically the same as the dirty of the layout.
In the printing process, regardless of the cause of the dirty surface, it usually appears first in the mouth of the printing plate. The main reasons are as follows:
1. Due to the improper pressure of the water stick, the ink roller and the blanket cylinder, the mouth of the mouth is the first to contact the water roller, the ink roller and the rubber roller with a certain pressure, so the friction part of the mouth is the largest. Especially when the machine is in disrepair for a long time, when the water, the ink roller support member and the roller bushing are seriously worn, the pressure adjustment is light and the contact is poor; the weight is caused to jump, and the sand of the plate mouth portion is easily worn. There is uneven water.
Treatment method: When adjusting the water and the pressure of the ink roller against the printing plate, do not be too heavy, so that it can smoothly contact the printing plate; when the roller bushing and the water and ink roller supporting parts are worn and have large changes, Timely inlays are used for repairs, and in severe cases, parts need to be replaced to reduce mechanical wear on the plates. Attention should be paid to the maintenance of these components and take precautionary measures.
2. rubber drum mouth mat into a hard mouth: in the printing version of the heart, the paper side of the blank product is small, the operator in order to print the size of the foot, generally according to the pressure of the rubber roller mouth edge pad 1~2 Layered liner paper to increase the pressure of the mouth part and print the mouth. However, due to the excessive pressure of the plate mouth, the sand of the plate mouth is prematurely worn, resulting in poor water absorption and viscous.
Treatment method: The size of the white edge of the mouth is 10 mm according to the standard. However, in the case of products with special needs such as a large version of the heart, measures should be taken from the following aspects: 1 less 叼, 2 borrowing rollers, 3 pad rubber 叼. You can't solve the problem from the rubber squeegee alone, and you can't make it hard. The plate thickness should be pre-measured when replacing the plate, and the pad thickness error must not exceed 0.05 mm.
3. the plate part of the mouth is not flat: the plate mouth left the last roller edge print or padding, there are folds and other phenomena will also cause water, ink roller beat, the mouth is dirty.
Treatment method: When the plate is found to be uneven, if there is a mark on the last roller, it can be flattened with a wooden hoe; if the padding is folded, it should be replaced in time, and pay attention to clean and flat. It was found that the part of the plate was shiny due to friction, and when it was dirty, it could be cleaned with medicinal water and then wiped again. At this time, a new hydrophilic layer was created at the mouth of the plate. Dirty also has a certain effect.
In the printing process, in addition to the dirty part of the plate, the two sides of the plate are also easy to get dirty. The main reasons are as follows:
(1) The water roller rubber core is thin at both ends, or the flannel wrapped on the water roller is thinned at both ends. When the glue stick is flattened on a lathe, because it is an elastic body, the two ends are stressed, the middle is vibrated and the force is small, and most of the two sides have different intermediate thicknesses. When the water roller sleeve is sewn, the size is shortened, and the remaining amount of the water is not enough. The two ends of the water roller are thinned and thinned, which easily causes the two sides to get dirty.
(2) Both ends of the water roller stain the ink to reduce the water transfer performance. The amount of water used in the layout is determined by the size and number of layout images. Since the printing plates are blank on both sides and the water consumption is small, the operator often reduces the amount of water locally at both ends of the water fountain roller. If the water volume is reduced too much, the water supply will be insufficient to make the water transfer roller, the water transfer roller and the water roller dip. Stained ink, reducing water transfer performance, causing dirt on both sides of the plate.
Treatment method: The two sides of the printing plate are often blank areas, that is, the water should be strictly controlled, and the water roller should be prevented from hanging on both ends due to excessive drying, and should be removed in time after discovery.
(3) The lateral size of the plate pad is too small. In order to prevent the water on both sides of the plate pad, the lateral direction of the pad is generally smaller than the plate size. However, if the size is too small, the contact between the two sides of the plate and the water stick will be bad and dirty.
Treatment: When cutting the pad, the lateral size is controlled within 10 mm of the plate. To prevent damage to the paper by water, apply a small amount of oil to both sides of the paper to extend its life.