Trouble-shooting analysis to eliminate the shortening of printing in the printing process

The phenomenon of lengthening or shortening of prints is very common in the printing process. Most of these failures are related to factors such as paper, printing pressure, the nature and material of the liner, and teeth.

Fault phenomenon

The operation of a four-color offset printing machine has been good, but when switching printing operations, the set of printing plates that were just installed showed a marked shortening of the second-color printing plate (cyan version).

Failure analysis and elimination

After repeatedly checking the pressure, gripping teeth, and lining, no problems were found, and the blue plate was reprinted and printed after installation, and the failure remained. The operator carefully checked the printed sheet and found that the axial and radial directions of the green print were significantly shortened, while the other three-color overprints were very accurate. Do a simple check on the machine, basically no problem. According to the situation of the printed sheet and the machine, it is not certain that it is a malfunction of the machine, and the machine cannot be adjusted blindly. After studying with the relevant operators in the printing and printing workshops, it is believed that there are no problems with the operation procedures and processes, and the film is completely accurate.

So what's the problem? It turns out that this set of printing plates was produced a week ago and has not been used. The plate-printing staff found that the green plate could not be used due to scratches, so he made another photo. In the work, I often encounter the damage of the printing plate and make up the sun. There was no problem. However, it was a rainy day a week ago, and the air was very humid for a few days, so the original film was stretched due to moisture, which caused the printing of the four plates to elongate. After that, the weather improved, and the temperature and humidity control measures in the printing workshop were not good enough. When the green printing was supplemented, the green printing was shortened due to the dry and shrinking weather. In order to confirm this judgment, I found the scratched printing plate and the newly dried printing plate to compare with the film, and found that the scratched printing plate was longer than the film and the newly dried printing plate, and then The black, magenta, and yellow printing plates on the machine were all removed and compared with the printed sheets to confirm the judgment. After reprinting and trial printing, the fault is eliminated.

Fault revelation

First, film also has properties similar to that of paper that tends to stretch after being damp.

Second, if there is a failure in the printing process, the cause must be carefully analyzed to distinguish whether it is a machine failure or a process and operation failure.

Thirdly, the operator should study hard, accumulate more, and have a wealth of professional knowledge in order to eliminate the fault, especially when dealing with such seemingly complex but simple faults.

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