A case of troubleshooting ghost prints

Newly purchased a PZ-41020B four-color offset printing press. After the machine is in place, ghosting occurs during the trial printing stage. After repeated debugging, it has been difficult to effectively solve.

Symptoms: After analyzing the printed matter, it was found that the phenomenon of ghosting mainly manifests itself in black characters, and is intermittent. Sometimes the local text is slightly more, but it is less obvious; sometimes the entire layout is, and it is obvious and irregular.

Troubleshooting: There are no problems with checking the paper and the liner. The cutting and installation of the blanket is also standardized. Therefore, the factory technicians speculate that the spring may be fatigued and the elasticity of the spring may be reduced, resulting in inconsistent movement during the opening process. Remove all the garter springs on the drum and replace them with imported springs with excellent performance. The result is that the fault still exists. Then all the unit shields were all opened, and they were checked one by one according to the printing sequence of K→C→M→Y. As a result, it was found that the embossing sleeves of the embossing cylinders of the K-color group had slight loosening and the gap was increased. After the assembly is positioned, the fault is eliminated.

Failure Analysis: The machine's assembly accuracy is not enough, it will produce jitter during the operation, resulting in the K-color group rubber roller on the black ink before and after the blot is inconsistent, resulting in ghosting failure.

Source: (Shandong Linyi Daily Newspaper Printing Company Wang Fei)