Analysis of "Failed Print" in Printing Process

Elongation or shortening of imprinting is common in the printing process. Such failures are mostly related to paper, printing pressure, lining properties and materials, tooth decay and other factors. The author encountered a special case.

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, tooth decay, and lining, all found no problems. The stencils were reprinted, tested after being installed, and the failure was still there. Therefore, it was suspected that the machine had encountered more serious problems. The author carefully listened to the situation introduced by the workshop's relevant operators and carefully examined the printed sheets. It was found that both the axial and radial directions of the imprinted sheets were significantly shortened, and the other three-color overprints were very accurate. After a simple inspection of the machine, basically no problems were found. According to the situation of the printed sheet and the machine, it is not certain that it is the failure of the machine, it may be caused by other reasons, so to avoid unnecessary troubles, we do not blindly adjust the machine. When working with related operators in the printing and printing shop to study the specific operating details, the author believes that there are no problems with the operating procedures and processes of the operators and the film is completely accurate.

So where exactly is the problem? The original printing plate was originally dried a week ago and has not been used because of production scheduling. 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 at all. However, just a week ago, when it was rainy and cloudy, the air was very damp for a few days, so it was possible that the original film was stretched due to moisture, resulting in the imprinting of four plates. Afterwards, the weather improved, and the temperature and humidity control measures of the printing workshop were not very effective. When the sunburned version was used, the film was shortened due to dry weather shrinkage. In order to confirm this judgment, we compared the scratched plate with the newly printed plate and the film and found that the scratched plate was actually longer than the film and the newly printed plate. Then all the black, magenta, and yellow plates on the machine were removed and compared with the printed sheets. The results confirmed the author's judgment. After trial printing after reprint, troubleshooting.