Maintenance rubber roller has a coup
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As one of the important parts of the offset printing machine, the rubber roller has a close relationship with the quality of the printing product. Therefore, how to use and maintain the rubber roller scientifically and correctly is very important. Take a 4-color offset press as an example: the whole set of ink rollers of the four color groups of the machine is worth about 50,000 yuan. If carefully protected and scientifically adjusted, the average service life can reach 2 years; if used improperly, the average use Life expectancy will be shortened to 1 year or half a year. Therefore, strengthening employees' sense of responsibility and improving their operational skills are of great significance in ensuring product quality, reducing maintenance costs, improving economic efficiency, and promoting enterprise development.
1. Analysis of the causes of abnormal damage of rubber roller
According to the author's many years of practical experience, the reasons for the abnormal damage of the rubber roller are generally the following.
(1) When installing and disassembling, it is not handled with care and the roller or rubber surface is damaged.
(2) The rubber roller shaft head and the bearing are not tightly coupled or the bearing performance is not good, so that the rubber roller is subjected to friction, extrusion, etc., and it is easy to accelerate the cracking and aging of the rubber roller.
(3) Too much accumulation of ink, ink residue and other impurities on the rubber roller accelerates the friction and aging between the rubber rollers, making the surface of the rubber roller full of numbness, and it is impossible to accurately transfer water and transfer ink.
(4) improper selection of cleaning agent for rubber roller, such as gasoline, reducing agent, strong acid, strong alkali, etc., will cause cracking and slag on the surface of rubber roller rubber.
(5) The pressure between the rubber rollers is too large, so that the rubber roller is deformed by extrusion, the rubber heat expands, and the rubber core is directly unshelled, which causes the rubber roller to be scrapped.
(6) The high temperature of the workshop causes the rubber roller to dissipate heat in time during the operation, and the rubber cohesion temperature is continuously increased to accelerate the aging of the rubber.
(7) The ink is dried too fast and the emulsification is serious, and it will accumulate at both ends of the rubber roller, thereby increasing the pressure between the rubber rollers in the disguised phase and accelerating the wear and tear.
(8) The ink release button at both ends of the ink fountain is closed, causing no ink replenishment at both ends of the rubber roller, so that the rubber roller is often in a dry friction state and damaged.
(9) In a multi-color printing machine, since the number of colors of a certain printing product is small, the rubber rollers of other color groups are idling for a long time, so that they are in a dry friction state and are damaged.
(10) The printing plate is not tight or the clamping clip is not tight, so that the printing plate tip is often broken. When the rubber roller is pressed against the plate cylinder, the rubber surface of the rubber roller will be scratched, causing the rubber roller to be scrapped.
(11) The rubber roller is improperly stored, for example, it is not stored in the dark, and the rubber roller is crushed and scratched by sharp objects.
There are many reasons for the abnormal damage of the rubber roller, but if you analyze it carefully and find out the root cause of the problem, you can avoid the damage of the rubber roller.
2. The correct use of rubber roller
1. Correctly install the rubber roller bearing
First of all, the rubber roller should be cleaned on both sides, and then the bearings with specifications and models that meet the design requirements of the machine should be selected, and a layer of lubricating oil should be evenly applied on each mating surface, and the bearing should be evenly applied with a special sleeve for mounting the bearing. Make it fit in place. Do not apply force directly to the bearing surface to avoid damage to the bearing.
2. Specification to adjust the pressure between the ink rollers
During the printing process, the water roller and the ink roller must continuously and evenly supply the printing plate with an appropriate amount of water and ink, so as to obtain a print with consistent ink color. Therefore, between the rubber roller and the rubber roller, between the rubber roller and the printing plate, the proper pressure must be maintained to achieve good ink transmission. In order to ensure the pressure between the water roller and the ink roller, the method of measuring the width of the ink bar must be adopted, mainly including the following points.
(1) Evenly add an appropriate amount of yellow ink on a clean rubber roller, and then run the machine to evenly distribute the ink on the surface of the ink roller.
(2) Jog the printing press and check the width of the pressing bar. It is worth noting that before the width of the pressing bar is viewed, the printing machine should be allowed to stand still for about 20 seconds, and then the printing machine can be clicked to obtain a clear pressing bar again.
(3) The pressure between the plate roller and the fountain roller should be preferentially adjusted, and then the contact pressure between the plate roller and the printing plate should be adjusted, and then the pressure between the other ink rollers should be adjusted separately.
(4) Referring to the printing machine operation instructions, the pressure bar width between the ink rollers is generally 4 mm. However, for an ink roller having a small diameter and a good elasticity, the pressure bar width is preferably 3 mm; conversely, the pressure bar width is preferably 5 mm.
(5) The width of the pressure bar between the water rollers should be 5 to 6 mm. The pressure of the water roller on the metering roller should generally be such that the water film at both ends of the water roller has no obvious water droplets.
(6) When all the water roller and ink roller pressure are adjusted, it is necessary to fix each adjusting screw in time to avoid all the running positions after the printing machine rotates.
3. Correctly disassemble the rubber roller
Each time the rubber roller is disassembled, the adjustment screws should be loosened twice between the employees. When reinstalling the rubber roller, only 2 turns in the opposite direction can be used. Even if there is an error, it can be done quickly. At the same time, it is necessary to check the quality of each bearing. If it feels that it is shaking or blocking, it must be replaced immediately.
3. The correct maintenance method of the rubber roller
1. Ensure the lubrication of each bushing and shaft seat
In actual work, the water roller seat and the ink roller seat are often severely worn, and the roller will be crushed after the bearing is broken, which will cause greater loss. Therefore, before all the rubber rollers are installed, the bearings, bushings, shaft seats, brackets, etc. on both sides of the rubber roller should be smeared with lubricating oil to minimize the friction of the ink roller due to the back and forth movement of the ink roller. Its friction against the bearing housing.
2. Maintenance of various color roller of printing machine
The rubber roller of any printing machine will gradually become smaller after 2 to 3 months of use, thus affecting the accurate transmission of water and ink. At this time, the rubber rollers of each color of the printing press should be sequentially maintained, and the pressure between the rubber rollers should be re-adjusted.
3. Cleaning of the rubber roller
The rubber roller should have good ink absorption and ink transmission, and the surface of the high-quality rubber roller is fine and smooth. However, since the rubber roller has to be in contact with water, ink, paper, etc. for a long time, it is inevitable that residues will accumulate on the rubber roller. Although the rubber roller is cleaned every time, some residues cannot be completely washed away. Over time, a smooth crystal layer resembling calcium is formed, which is firmly attached to the surface of the rubber roller and blocks it. The pores make it lose its elasticity and become harder, which seriously affects the ink transfer and water transfer performance, and thus cannot stably control the ink color of the print.
At present, although many companies have developed dampening solutions to prevent the calcification of rubber rollers, and the effect is good, but the price is more expensive, it can not be widely used. In order to solve this problem, printing companies should often use special lifting paste and starting water to clean the rubber roller, but this method is time consuming, laborious, and invisibly increases the production cost. Therefore, the author believes that a better method is to wash the rubber roller with a small amount of citric acid water after each wash, to make some calcium impurities on the surface chemical reaction, and then clean.
Some people think that it is a waste of time to use and maintain the rubber roller so carefully. I don’t know the ancients’ belief that “the sharpening of the knife does not miss the woodwork” and the “cooking can make perfect”. As long as the standardization operation is maintained for a long time, the technical skills can be continuously improved. For the sake of simplicity, the man-hours consumed thereby are greatly reduced, and the rubber roller is more fully utilized.