Eliminates blots during the printing process to shorten the failure

The phenomenon of stretched or shortened blots is common in the printing process. Such failures are mostly related to paper, printing pressure, the nature and material of the lining, and tooth decay.

Fault phenomenon

The operation of a four-color offset printing press has been good, but when the printing job was changed, the printed version of the second color printing plate (clear printing plate) appeared to be significantly shortened.

Failure analysis and exclusion

Repeated inspections of pressure, cavities, and linings revealed no problems. The stencils were re-dried, and they were installed and tested. The failure persisted. The operator carefully examined the printed sheets and found that both the axial and radial directions of the imprinted sheets were significantly shortened, while other three-color imprints were very accurate. A simple check on the machine is basically no problem. According to the situation of the printed sheet and the machine, it is not certain that the machine is faulty and the machine cannot be adjusted blindly. After studying with the relevant operators of the printing and printing shop, it was considered that there were no problems with the operating procedures and the process, and the film was also completely accurate.

Where is the problem? The original printing plate was dried a week ago and has not been used. Before printing on the machine, it was discovered that the cyan version could not be used due to scratches, so the sunburned one. In the work, you often encounter damage to the printing plate and make up the sun. There is no problem. But one week ago, it was a rainy day and the air was very humid for a few days. Therefore, the original dried film stretched due to moisture, resulting in the imprinting of the four plates. After the weather improved, coupled with the ineffectiveness of the temperature and humidity control measures in the printing workshop, when the sun was cured, the film was shortened due to dry weather shrinkage. In order to confirm this judgment, the scratched plate and the newly printed plate were compared with the film. As a result, it was found that the scratched plate was longer than the film and the newly printed plate, and then All the black, magenta, and yellow printing plates on the machine were removed and compared with the printed sheets to confirm the judgment. After trial printing after reprint, troubleshooting.

Fault revelation

First, the film also has properties similar to the ease of elongation of the paper after it has been wetted.

Secondly, failures in the printing process must be carefully analyzed and the reasons for distinguishing between machine failures and process and operation failures cannot be blindly followed.

Third, the operators should study and accumulate at ordinary times, and they have accumulated a wealth of expertise in order to eliminate many problems, especially when dealing with such seemingly complicated but simple faults.