The three most popular methods for easy inspection

2022-08-02
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Three methods to easily check and eliminate offset printing faults editor's note: the greatest worry of offset printer operators is that they can't find the cause of the fault in the printing process. Often, the school bus has to be shut down due to inaccurate overprinting, bar, ghosting, paper crepe, reverse smoothing and other faults. It is common to use two or three hours each time. Sometimes it takes several days to solve a fault, resulting in a serious loss of working hours. It is estimated that the time taken by offset printing operation to eliminate faults in daily production accounts for about 5 ~ 10% of the total working hours, which is more than twice that of lead printing. This is unfavorable to improve product quality, shorten publishing cycle and increase economic benefits. To this end, every offset press operator can make greater contributions to the factory and the country if he can improve his technical level in troubleshooting

offset press has complex structure, high printing process requirements, and large variable factors of paper and ink, so the operation technology should be improved. Generally, it is easy for new workers to learn how to operate, but it is more difficult to find out the cause and eliminate the fault in time whenever there is a defect or fault

there are many factors that cause offset printing faults. Sometimes there are dozens of possible causes for a fault. In order to avoid detours and waste unnecessary effective man hours, the following methods can be used

I. analytical method

after the offset printing fault occurs, there are many methods to find out the cause of the fault. Among various methods, analytical method is the fastest method to find out the cause of the fault

the so-called analysis method is the method of analyzing according to the time, position, condition and shape of the fault. The subjective factors in these four aspects are listed one by one, and then comprehensive analysis is carried out. Many faults can be solved easily. However, in actual production, some operators lack comprehensive analysis of these four aspects after encountering faults, resulting in prolonged downtime and unnecessary man hour loss

an example is as follows: during the operation of an offset press, the operator found that the paper was wrinkled and deformed. The product was a magazine cover with two colors on the back and four colors on the front. When the reverse side is printed first, the paper is normal, and the reverse side is printed on the front side. When the 25th ream of paper is printed, it is found that there is a 50mm long bow crepe on the trailing tip of the paper. After stopping the machine, experienced people analyze various possible factors with the analysis method, and preliminarily come to a conclusion:

① the fault is just emerging, indicating that there are new factors leading to bow crepe

② the position is at the trailing tip of the paper, which may be a machine factor or a paper factor

③ judging from the fact that the shape of the paper crepe is only 50mm long, it can not be caused by mechanical failure

④ based on the analysis of the paper conditions that produce more than 50mm bow crepe, it is generally possible under the condition of lotus leaf edge, but the intuitive paper is very flat, so it is impossible to produce bow crepe

after this analysis, the machine factor and the paper factor were negated, and the problem that had just occurred was focused on, which immediately made people think of the possibility of the back imprint stacking on the imprint cylinder. Because the printing pieces with two colors printed on the back are often piled up on the surface of the impression cylinder gradually because the imprint is not completely dry, this ink deposit is irregular and can be piled up thicker, which means that the pressure between the rubber cylinder and the impression cylinder is gradually increased irregularly, causing the paper to be pressed on the uneven plane, thus resulting in the bow crepe failure of the trailing tip. After checking the impression cylinder, it is determined that the ink is accumulated. The problem disappeared when printing after cleaning. It took more than ten minutes

of course, some faults are complex and cannot be solved by analysis alone. Therefore, detection and test methods must be used together

II. Detection method

the so-called detection method is to use magnifying glass, dial card, iron absorption dial indicator, same diameter instrument, vibration oscillograph, densitometer and other tools and detection instruments to observe the three mechanical states of faulty high molecular materials at different temperatures, and check and measure the parts to find out the cause of the fault

the detection method is often used to find the bar, ghosting, point void and other faults

the detection method takes much longer to solve the fault than the analysis method. Generally, before using the detection method, try to use the analysis method for analysis, and then focus on one or two points for necessary detection to find out the cause of the fault

for example, the point on the printed matter has the defect of false hair. As far as the whole picture is concerned, the end point on the drive side is empty and not real, while the end point on the control side is complete and solid. How to solve such problems

through analysis, it can be seen that there are two main reasons for this kind of failure: first, it may be the ink transmission failure, and the layout graphics and text are not inked enough; The second possibility is pressure failure. The pressure regulator of a drum moves by itself and the pressure disappears

the factors of ink transfer failure include: too much moisture at one end of the layout; The inking roller's "guiding opinions" made it clear that one end of the three major goals to be achieved in the green packaging work of the express industry during the "1035" period was under light pressure in the layout; The pressure between one end of the inking roller and the inking roller is too small; Aging and cracking of inking roller surface

the factors of pressure failure include: the pressure between the plate cylinder and the rubber cylinder disappears; The pressure between the rubber cylinder and the impression cylinder disappears

the detection method should be carried out easily first and then difficult. Because the moisture content in the plate is too large, it is easy to see when the machine is running under the light. This factor is eliminated first, and then the pressure between the ink roller and the plate and the inking roller is checked to make it meet the requirements of consistent pressure at both ends. If the surface of the inking roller is aged or cracked, replace it with a new one. The ink roller is normal, but the fault is still unsolved. Check the pressure between the rollers again. The electrician can use the fuse (No. 20 fuse) and the dial card to measure the gap of the roller pillow. Without removing the printing plate and blanket, press and measure at the neutral position of the roller. If the gap of the roller pillow exceeds the value specified in the manual, adjust the voltage regulator to make the gap at both ends of the roller pillow meet the requirements of the manual, and then the fault can be eliminated

III. test method

test method is commonly referred to as try. Some inexperienced new workers and people who do not have comprehensive analysis ability often use this method. The test method is time-consuming, easy to take detours, and brings certain losses to production. But once successful, the operator not only accumulated experience, but also improved the technology

mts achieves high repeatability and high linearity. The non-contact displacement measurement test method is usually more effective for using new paper, ink, plate, etc. However, sometimes the common faults in the printing process are caused by the inexperience of new workers, and they are also regarded as new problems for testing. In this way, simple problems are often complicated and a lot of man hours are wasted

for example, the overprinting at one end is not accurate, and it is not allowed to be about 2mm. The cause of this fault is either that the paper feeding is skewed and the end is not in place, or that the hard paper printed above 80g/m2 pops out of the front gauge. However, some operators spent a lot of time correcting the front gauge, gritting pressure and handover relationship, and people were very tired. As a result, the fault was still not eliminated. Therefore, it is advocated to find out the cause of the fault through consultation after a fault occurs in the printing process. New workers should especially consult with middle-aged and elderly workers with high technology, so as to eliminate the fault quickly, which is not only conducive to improving the product quality, but also learn the troubleshooting technology and improve the operation level

in a word, for various faults encountered in offset printing production, it is recommended to use analysis and detection methods to find out the causes of faults. Encounter complex 4 Panoramic glass roof: the panoramic glass roof of the polar 1 has a fixed fault. It is necessary to comprehensively use the analysis method and the detection method, so as to quickly and well eliminate various faults, so as to improve the product quality and increase the effective working hours

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