Common faults and maintenance of J2108 waterway
(This article is an original article from Bisheng. It is forbidden to reprint, and reprinting must be corrected)
We all know that in the use of offset presses, the adjustment and use of the water roller and its related mechanisms are very important to the printing process. Below we will take the waterway of the J2108 offset press as an example to introduce some common faults and maintenance of the popular waterway system in domestic offset presses.
Problems and precautions
1. When replacing the new water roller, the old version can generally be used to correct the pressure of the water roller, and the ink should be washed with gasoline first to avoid contaminating the water roller. If a new printing plate is used, or if the pressure of the water roller is found to be inaccurate during the printing process, correction is required. First, the printing plate should be wiped with glue and wiped with a flat fan to protect the printing plate. Then choose the blank part at both ends of the printing plate, or use a steel sheet to measure the blank part of the trailing edge, and the number of interpolation tests is as small as possible to prevent the printing plate from being scratched and stained with ink. The original solution and gum arabic solution are cleaned to maintain its hydrophilic properties.
2. The total thickness of the pads of the printing plate should meet the standard, so as not to affect the contact pressure between the water roller and the printing plate when changing the printing plate. If it is necessary to change the thickness of the plate liner, it should be expected to change the pressure between them, and give corrections.
3. When adjusting and installing the water roller, pay attention to protect the cleanliness of the water roller and the printing plate, and do not pinch the water roller with your fingers to prevent contamination of the water roller fleece cover.
4. Before installing the water roller, the new water roller velvet cloth or new water roller velvet cover should be wetted with water or fountain solution in advance, and the fluff should be wiped off to prevent the fluff from falling on the printing plate and the ink roller during the printing process. On, affect product quality. At the same time in terms of pressure control, generally wet water rollers are slightly smaller than unwet water rollers.
5. When adjusting the contact pressure of the water roller to the water channeling roller, we must pay attention to the symmetry of the direction of the eccentric bearing, that is, the adjustment of the eccentricity at both ends must be in the same direction, otherwise it will cause water and the plate cylinder, water channeling roller. Not parallel, the flannel cover on the water roller is easily pushed by the axial force into a spiral shape, and the water delivery cannot be even. If the eccentric direction of the three blades on both sides of the water roller is asymmetric, it will also cause the pressure of the water roller, the two ends are light and the middle is heavy. Therefore, when testing the pressure of the water roller, you can measure a few more places, measuring both ends and the middle to prevent Disadvantages such as uneven water roller or inconsistent eccentric direction.
6. If the neck or bearing of the Feng Shui roller has been severely worn, or the water roller with ball bearings is damaged, the bearing should be repaired or replaced in time to avoid inaccurate pressure control.
7. The water roller is not allowed to have obvious axial movement, otherwise the layout may be damaged.
8. Master the contact pressure between the water rollers
(1) The pressure of the two water rollers and the printing plate should be lighter on the top and heavier on the bottom.
(2) The pressure of the two water rollers and the water channeling roller should be lighter on the top and heavier on the bottom.
(3) The pressure of the water roller and the printing plate is slightly heavier than the pressure of the water channeling roller.
(4) The pressure of the water transfer roller and the water channeling roller is equal to or slightly lower than the pressure of the water roller and the water channeling roller.
1. 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 friction on the printing plate surface, causing the graphic parts of the printing plate to be worn out quickly, and the sand holes are smoothed, resulting in the appearance of "flower plate" due to excessive pressure. If it is large, it will cause the water roller to jump when it touches the printing plate, making the jumped part easy to get dirty, and the falling part will cause "white bars" in the graphic part (especially the flat screen cable).
2. The contact pressure between the water roller and the printing plate is too light, so that the plate surface cannot be supplied with sufficient water, and the print will be coarse, swollen, or even dirty. At the same time, due to the unevenness of the water roller velvet cover, the water supply to the plate surface is caused. Uneven.
3. The contact pressure between the water roller and the water channeling roller is too heavy, which will cause the water to be squeezed on a certain point of the water channeling roller, resulting in poor water supply, affecting the normal water transfer of the two water rollers, especially the upper water roller The contact pressure of the water roller is too heavy, which not only causes the water to be unsmooth, but also the water roller will lose its effectiveness, and it is easy to make the printing plate hang dirty.
4. The contact pressure between the water roller and the water channeling roller is too light. Due to the poor contact, the water roller lacks the normal water source, so it can not supply water to the printing plate normally, causing the printing plate surface to be dirty: At the same time, the water roller lacks a water film Protected, and quickly contaminated by ink, and lose the role of water supply, the stained ink spreads again and causes the water channeling roller and the bucket roller to be contaminated by ink, which affects the water supply performance of the water roller.
2. Uneven water delivery
There are many reasons for uneven water delivery. In addition to the improper adjustment of the water roller pressure mentioned above, there are also the following common causes:
1. The diameter of the roller core of the water roller is not equal or the water roller is not round;
2. When sewing the water roller, both ends are tight and the middle is loose, or both ends are loose and the middle is tight;
3. The thickness of the water roller is uneven or it is rolled down in use;
4. The ink layer is formed on the surface of the water roller, and the water absorption is poor;
5. Long-term use of water roller velvet, its fluff is polished and polished;
6. Too much ink on the surface area of ​​the water bucket roller and the water channeling roller;
(1) The linear speed of the printing plate cylinder and water channeling roller are different;
(2) The ink on the water roller or water roller is too dirty;
(3) The surface of the water bucket is too smooth, and it is not easy to form ink;
(4) The shutdown time is long, when the water channeling roller and the water bucket roller are lost or dried, 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 according to different reasons, and remove the ink on the roller before reprinting.
3. Light ink bar (white bar)
Ink bars, also known as heads, bars, bars, etc., refer to dark or light streaks formed on the printed text. As shown in Figure 1. Light color marks, called light ink bars (also known as white bars, white stripe heads), are characterized by light color of the graphic ink on the mark marks and small dots. Dark streaks, called deep black bars (also known as black bars and black bars), are characterized by thick graphics and ink on the streaks and enlarged dots. In printing, the causes of the light ink roller caused by the water delivery device are mainly:
1. The contact pressure between the water roller and the plate is too large, and it is characterized by streaks, usually at the mouth.
2. The mechanical parts on both sides of the water roller are seriously worn, and will jump when water is hit. It is characterized by a full version or a streak in a certain area.
3. The rotating gear of the water channeling rod wears seriously, which is characterized by streaks in the full version or a certain area.
4. Improper adjustment of the swinging time of the water channeling stick. The characteristic is that the streak is produced when the water stick is swung to the water channeling stick, and the contact part between the water stick and the printing plate is produced.
4. 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. Insufficient glue content in fountain solution;
4. Improper adjustment of water stick pressure.
Five, flower version
As shown in Figure 2, the main reasons are:
1. The fountain solution is too acidic;
2. The layout is too watery;
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 layout dirty.
In the printing process, no matter what causes the plate to become dirty, it usually always appears first at the mouth of the plate. The main reasons are as follows:
1. The gripper is dirty due to improper pressure of the water stick, ink roller and rubber cylinder: the gripper of the printing plate first contacts the water roller, ink roller and rubber cylinder with a certain pressure, so the gripper part bears the most friction. Especially when the machine is in disrepair and the water, ink roller support parts and roller sleeve are seriously worn, the pressure adjustment is light, and the contact is bad; if it is heavy, it will cause a jump, which is easy to wear the sand of the printing plate mouth. , There is uneven water.
Treatment method: When adjusting the pressure of the water and the ink roller on the printing plate, do not be too heavy, so that it can contact the printing plate smoothly; when the roller bushing and the water and ink roller support parts are worn and have large changes, it is necessary to The sleeve is repaired in time, and the parts need to be replaced in case of seriousness to reduce the abrasion of the printing plate by mechanical force. Usually pay attention to oiling and maintenance of these parts and take preventive measures.
2. The rubber roller gripping pad becomes a hard mouth: when the product has a large printing plate center and a small margin on the paper, the operator generally adds 1 ~ 2 to the rubber roller gripping edge according to the pressure in order to print the size. Layered liner paper to increase the pressure of the gripper part, so that the gripper seal is printed solidly. However, due to the excessive pressure on the gripper of the printing plate, the sand at the gripper of the printing plate will wear prematurely, which will result in poor water absorption and dirtying.
Processing method: The size of the white edge of the mouth is 10 mm according to the standard. But when there are products with special needs such as large version of the heart, you should take measures from several aspects: â‘ less gripping, â‘¡ borrowing rollers, â‘¢ cushioning rubber gripper. You can't solve the problem from the rubber gripper alone, let alone make a hard mouth. When changing the printing plate, the thickness of the printing plate should be measured in advance, and the thickness error of the pad should not exceed 0.05 mm.
3. The part of the printing plate gripper is not flat: the printing plate gripper has the last mark or liner on the edge of the cylinder, and the phenomenon of folding will also cause the water and ink roller to jump and the gripper will be dirty.
Treatment method: when it is found that the printing plate is not flat and there are marks on the last roller, it can be knocked flat with a wooden hammer; the lining should be replaced in time, and pay attention to clean and flat. It is found that the gripping part of the printing plate is shiny due to friction, and it has poor water absorption. When it is getting dirty, you can first wipe the dirty dirt with a potion, and then wipe the glue again. Dirty also has a certain effect.
In the printing process, in addition to the dirt on the gripper of the printing plate, the two sides of the printing plate are also easy to get dirty. The main reasons are as follows:
(1) Both ends of the water roller rubber core are thin, or the flannel covering the water roller is thinned at both ends. When the rubber stick is processed and smoothed on the lathe, because it is an elastic body, the two ends have a large force, and there is tremor in the middle and the force is small. Most of them have different thicknesses of the middle of the two ends. The size of the water roller sleeve is shortened, and there is no sufficient closing margin. The water roller is thinned and thinned at both ends, which is easy to cause dirt on both sides.
(2) The ink is contaminated at both ends of the water roller, which reduces the water transfer performance. The size of the water consumption of the layout is determined by the size and amount of the graphics on the layout. Because the two sides of the printing plate are blank and the water consumption is small, the operator often reduces the water volume at both ends of the water bucket roller. If the water volume is reduced too much, it will cause insufficient water supply and make the water transfer roller, water transfer roller, and water roller stained. Stained ink reduces the water transfer performance and causes the printing plate to become dirty on both sides.
Treatment method: Both sides of the printing plate are often blank areas, that is, to strictly control the moisture, and to prevent the ink from hanging on both sides of the water roller due to excessive drying, and should be removed in time after discovery.
(3) The horizontal size of the printing plate pad paper is too small. In order to prevent water on both sides of the printing plate pad paper, the horizontal direction of the general pad paper is smaller than the printing plate size. However, if the size is too small, it will cause poor contact with the water stick on both sides of the printing plate and become dirty.
Treatment method: When cutting the printing plate pad paper, the horizontal size should be controlled within 10 mm smaller than the printing plate. In order to prevent damage to the pad paper due to water, a small amount of engine oil can be applied to both sides of the pad paper to extend its service life.
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