Various faults will be encountered in the printing production process. Some of the faults have the same phenomenon, but the reasons are different, "like and not like", so the methods for solving the problems are also different. This requires careful analysis, finding the right reason, and solving the problem in a targeted manner. The author uses two specific failure cases to explain the importance of appropriate medicine.
Case
Rolling film debonding caused by equipment failure
I have encountered such failures in the production process. When printing a seven-color product, the gravure printing machine occasionally showed a slight anti-sticking phenomenon in the roll film after printing. This product is a regular product of the factory, and no such phenomenon has occurred before. When the technician arrived at the site, the ink, materials, and production process were repeatedly compared and tested accordingly, but the printed product had no problems, and the problems occurred again when the batch was produced. Therefore, the technician thinks that the drying system of the printing machine has failed, and this problem is thrown into the hands of the equipment maintenance personnel. When maintenance personnel arrive at the site, inspect and test the oven of the printing press and its guide sticks, heat exchanger and steam trap, heating control system and instrument and electric valve, supply and exhaust fan and air volume, etc. The parameter is within the normal range. The entire system sees no problems, but anti-sticking still occurs.
Finally, a careful analysis of the rewinding situation of the roll film on the rewinding machine found that about 500 meters of the printed matter about 6000 meters had reverse adhesion, and from the slight reverse adhesion that was not easy to find to the visible reverse adhesion, The gradual disappearance is a process of gradual development and disappearance. The biggest possibility of this situation is the accidental failure of the temperature control system. The thermocouple and the electric valve control device have a higher probability of problems. Therefore, the thermocouple was replaced, but this phenomenon still happened occasionally, and the electric valve was replaced After the controller, after a period of observation, the problem of anti-sticking no longer occurred, and the problem was solved.
Case
White spots caused by solvent evaporation
The second failure case is that when I used a special gravure printing machine for thermal transfer film production, I found irregular white spots on the coating layer, which is a problem that often occurs when producing such varieties. The operator adjusted the humidity of the plate roller and dry hot air according to the general processing method, but the white spot phenomenon could not be solved. When the technician arrived at the site, he thought that the problem might be the coating amount and the moisture content of the hot air drying. The coating amount was adjusted by replacing the plate roller, and the moisture content of the hot air was changed. The test was repeated dozens of times The situation has improved, but the problem cannot be solved fundamentally.
Under such circumstances, the technician judges that there is a problem with the drying system of the equipment and requests the equipment department to solve it. After the equipment maintenance personnel arrived at the scene, they conducted a careful and detailed inspection of the equipment's oven, heat exchanger, steam valve, temperature control system instruments and electric valves, humidifier, fan and air volume according to the usual method. Normal, the air volume, humidity and temperature are within the range of control requirements, which can basically eliminate the problem of the equipment.
Finally, through the analysis of the samples, it was found that these white spots occurred in all parts of the product, and the problem was universal, so the problem of materials and coating liquid should be considered. After replacing materials from different manufacturers, the problem remains. Therefore, the coating liquid supplier was asked to test it, and it was found that the solvent volatilization rate of the batch of coating liquid was significantly higher than the original coating liquid. After the coating liquid was replaced in time for production, no white spots occurred again.
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