Exclusion of difficult problems in offset printing (5)

After this analysis, the machine factor and the paper factor were negated, and the problem that had just arisen was focused on, prompting people to think of the possibility that the backside imprinter would stick to the impression cylinder. Because the back of the printed two-color prints, often due to imprinting has not dried out and gradually accumulate in the surface of the impression cylinder, this ink deposits are both irregular and thicker, equal to gradually increase the rubber roller and irregularly The pressure between the impression cylinders causes the paper to be pressed on the rugged surface, thus causing a bow fault. After seeing the impression cylinder, it is indeed the accumulation of ink. When cleaning and then printing this failure is gone, before and after spent more than 10 minutes.
Of course, some of the faults are more complex, and the analysis method alone cannot solve the problem. It is necessary to use the detection method and the test method.
Second, the detection method The so-called detection method is the use of a magnifying glass, micrometer card, iron dial indicator, isoparameter, vibration oscilloscope, and other tools and measuring instruments, to observe the fault, the inspection and measurement of the parts To find out the cause of the malfunction. Often use the detection method to find failures such as bars, ghosts, and voids.
The time required for the detection method to resolve the fault is much longer than the analysis method. Generally, before the detection method is adopted, the analysis method is firstly used for analysis, and then the necessary detection is focused on one or two points to find the cause of the fault.
For example, the dots on the printed matter produce false defects. For the entire picture, the transmission side is empty and the control side is completely solid. Similar problems like this, how to solve?
After analysis, we can know that there are two main reasons for this type of failure: the first may be ink failure, and the layout graphic is not full of ink: the second may be a pressure failure, and the pressure regulator of a roller is self-propelled. The pressure disappeared.
The factors of ink failure include: the end of the layout is too watery; the pressure of one end of the ink roller is light on the plate; the pressure between one end of the ink roller and the ink roller is too small; the surface of the ink roller is aged, cracked, etc.
The factors of pressure failure include: the pressure between the plate cylinder and the blanket cylinder disappears; the pressure between the blanket cylinder and the impression cylinder disappears.
The detection method should be carried out easily afterwards, because the layout is too watery. When the machine is running, it can be seen in the light. First, eliminate this factor. Then check the pressure between the ink roller and the layout roller and the ink roller. Meet the requirements of consistent pressure at both ends. If the surface of the ink roller is aged and cracked, replace with a new one. The ink roller part is normal, the fault is still not resolved, and then the pressure between the rollers is checked. The electric fuse (20 fuse) and the micrometric card can be used to test the roll gap without removing the printing plate and blanket. When the clearance between the rollers exceeds the value specified in the instruction manual, the pressure regulator is adjusted so that the gap between the two ends of the roller bearing meets the requirements in the manual, and the fault can be eliminated.
Third, the test method Test method is commonly referred to as "try it." Some inexperienced new workers and those who do not have comprehensive analytical skills often use this method. The test method takes a long time, it is easy to take a detour, and it brings some loss to the production. However, once successful, operators not only accumulated experience, but also improved the technology.
The test method is generally more effective for the use of new papers, inks, plates, and the like. But sometimes the common failures that occur in the printing process are caused by the lack of experience of new workers, and it is also regarded as a new problem to be tested. This often complicates simple problems and wastes many man-hours.
For example: The overprint is not accurate when one end is not in place, and it is not allowed to be about 2mm. The reason for this failure is that the paper is skewed and the end of the paper is not in place, or the hard paper with 80g/m2 or more is ejected from the front gauge. . Some operators have to correct the rules, teeth pressure, and the handover relationship. They have spent a lot of time, and people have been very tired. The result has still not been ruled out. Therefore, after the failure in the printing process is advocated, the reason for the failure is sought through consultation. New workers must especially discuss with higher-tech middle-aged and older workers in order to troubleshoot the problem faster and improve product quality. He also learned the techniques of troubleshooting and improved the operation level.
In short, for the failures encountered in offset printing production, it is advisable to use analytical and test methods to find out the cause of the failure. When a complex fault is encountered, comprehensive analysis and inspection methods must be used to eliminate all kinds of faults quickly and well, so as to improve product quality and increase effective working hours. (To be continued)