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Printing Machine Reflections On Differential Function Of Heidelberg CX102 Printing Machine
- May 31, 2018 -

My company has several printing presses, one of which is the Heidelberg CX102 four-color printing press, which is equipped with a differential function, in order to eliminate the ink skin produced during the printing process. The principle of differential is to make the rotational speed of the plate cylinder and the plate-type water roller not synchronized, while the previous old printers are all in contact with the surface of the plate cylinder and the plate roller, and the rotation speed is synchronized. After using the new device, once the ink skin appears during the printing process and the differential is turned on, the ink skin will be eliminated by the difference of the refraction water roller.

Our company will regularly maintain the printing press. After one maintenance of the Heidelberg CX102 four-color printing press, we encountered such a failure when printing the four-color large flat web job: when the job is printed to 13,000 India, the distance from the job is A horizontal "bar" appeared at the mouth of 15 cm. After troubleshooting and analysis of the failure, we found that it was caused by a differential.

In this paper, the author summarizes the troubleshooting process and the resulting reflections on differentials for peer reference.

Troubleshooting

First of all, we suspect that the re-installed rollers did not regulate the pressure when the printer was being maintained, resulting in the appearance of “striking bars”. Therefore, we checked the 1-4 printing rollers, including the transfer roller and the pressure of all the rollers on the waterway, but the pressure was normal and there was no abnormality or improper adjustment.

Then, we scrubbed the blanket and reprinted the paper. “Belts” still existed. We did not reduce it. We decided to reduce the amount of water and try again, but the failure was still not eliminated.

Again, we suspect that it was not because of the long lunch time. The machine stopped for a long time and caused the printing plate to remain dirty at a distance of 15 cm from the mouthwash. However, after the plate was wiped with a cleaning paste, the failure was still not eliminated.

Finally, with the class teacher inquired about the steps to troubleshoot the machine and decided to make two copies of the test. Because the flat screen is a light-colored flat screen, it seems that the printed version is invisible to the naked eye, but based on the troubleshooting steps from the previous Look, it has ruled out the doubt that the device roller pressure is improperly adjusted, so it is feasible to make up the version. Because the large flat screen is a bluish-green one, it made up the two versions with more outlets to try and print first. After printing on the blank version, it reprinted the paper and found that the “spreadhead” almost disappeared, only a little. We immediately felt that it was the "spread" that was caused by the misprint of the printing plate. Therefore, we made up for the other two printing plates, and the "spread" completely disappeared.

Although this failure was solved, we still have doubts that according to the normal printing rate of the CTP version, it is generally possible to print out more than 50,000 copies, and now only 13,000 copies are printed. Or is it usual for coated paper, why would such a small amount of print appear to cause off-screen printing? After careful analysis, we agreed that it was due to the use of differential printing on the Heidelberg CX102 four-color press.

Differential advantages and disadvantages

Heidelberg CX102 four-color printing presses have the following advantages and disadvantages.

1 advantages

(1) Improve printing efficiency

When the ink stick appears, there is no need to stop the machine. Normally, the differential can be eliminated. The ink pressure is used to “scrape” the ink sheet, which increases the printing efficiency by a factor of 2, and improves the printing quality. Because under normal circumstances, high-precision work in the frequent shutdown of the ink, there will be a certain difference in the color of the frequent stop the boot, especially the darker colors will be more apparent, this will affect the overall color of the job consistency.

(2) Water saving

Differentials reduce water use. When we visited a printing factory, we discovered a situation where managers often checked the captain’s water situation and hoped that the machine could save water as much as possible. As a result, the captain will often open a differential, because after the differential is opened, the pressure between the plate cylinder and the plate roller will be significantly larger, so that the amount of water used will be relatively small.

2. The disadvantage

(1) Shorten the Life of Roll Water Roll

The price of the original imported water roller is more than 10,000 yuan. Frequent use of the differential will result in serious wear of the water roller, which in turn leads to a one-fold reduction in the service life of the water roller. This is because the differential itself is used to drive the printing roller through the different speeds of the gears and the printing plates at different speeds to generate friction to remove the ink. After a long time, the friction will certainly cause the surface of the printing roller to be damaged faster.

(2) Plate wear faster

Frequent opening differentials can cause the plates to wear faster. Under normal circumstances, short-lived jobs with less than 10,000 impressions are insignificant, but when faced with large-volume jobs, the supplemental release is more frequent, as in the above-mentioned failures.

Responses

Through the analysis of the advantages and disadvantages of differentials, our company's technical personnel met and discussed and decided to minimize the use of differentials, specific starting from the following aspects.

Under normal circumstances, it is forbidden to use differentials for machine personnel and take measures as far as possible to avoid the occurrence of ink skin. Control the sharpness of the knife in the cutting section to avoid cutting the paper with hair. Before putting on the machine, wipe the paper with a damp cloth, and wipe the cut paper powder cleanly. In this way, the ink skin will be rarely generated during printing, and no differential movement is required. During the printing process, the ink is frequently stirred to reduce the dryness of the ink surface. In special circumstances, additives are added to the ink to increase the fluidity of the ink and reduce the occurrence of ink skin.

If these measures cannot be taken to eliminate the occurrence of ink skin, and the paper really does fall hair and powder falls, consider opening differentials, but immediately switch off after use and must not be used for a long time.

In short, the differential design has its own characteristics. When we use differentials, we must combine different jobs and different quality requirements and selectively use them. How to find the best combination point is what we need to do now.


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