I have more than one printing machines, one of which is a four-color printing press Heidelberg CX102 which the differential function arranged, the purpose of eliminating skin ink generated during printing. The principle of the differential is to make the rotation speed of the plate cylinder and the plate water roller unsynchronized, and the former old printing machine is the surface contact and the rotation speed of the plate cylinder and the plate water roller. After using the new equipment, once the ink is applied during the printing process, the differential is opened and the ink is removed by the differential of the water roller.
Our company will regularly carry out the maintenance of the printing machine. After cleaning the Heidelberg CX102 four-color printing machine, it will encounter such a fault when printing the four-color big flat net job: when the job is printed to 13,000 impressions, the workpiece distance A horizontal "bar" appeared in the mouth 15 cm. After the troubleshooting and analysis of the fault, we found that it was caused by the differential.
In this paper, the author summarizes the troubleshooting process and the thinking about the differential generation for peer reference.
Troubleshooting
First of all, we suspect that when the press was maintained, the re-installed rollers did not adjust the pressure, causing the "bar" to appear. Therefore, we checked the 1 to 4 sets of the ink roller, including the pressure of the transfer roller and all the rollers in the waterway, but the pressure was normal, and no abnormalities or improper adjustments were found.
Then, we scrubbed the blanket and re-printed the paper. The “bar†still existed, and there was no slight reduction. We decided to reduce the amount of water and try again, but the fault still did not disappear.
Once again, we suspect that it is because of the long lunch time, the equipment is shut down for a long time, causing the printing plate to hang from the mouth 15 cm away from the mouth, but after cleaning the plate with the cleaning paste, the fault is still not eliminated.
Finally, the class teacher asked the machine to troubleshoot the steps, decided to make up two versions of the test print, because the big flat net is a light-colored flat net, the naked eye does not seem to see the print plate has a version, but based on the previous troubleshooting steps See, the suspected point of improper adjustment of the roller pressure of the equipment has been ruled out, so the patch is feasible. Because the big flat net is blue-green, so the two versions with more outlets are pre-printed. After the patch is loaded on the machine, the paper is printed again. It is found that the “bar†has almost disappeared, only a little bit. We immediately felt the "bar" caused by the plate version, so we filled the other two plates and the "bar" disappeared completely.
Although the fault has been solved, we still have doubts. According to the usual printing durability of the CTP version, it is possible to print more than 50,000 impressions, but now only 13,000 impressions are printed, and the paper is used. Or is it the usual coated paper, why is there such a small amount of printing on the plate? After careful analysis, we agree that it is caused by the differential use of the Heidelberg CX102 four-color printing press.
Advantages and disadvantages of difference
The differential of the Heidelberg CX102 four-color press has the following advantages and disadvantages.
Advantage
(1) Improve printing efficiency
When there is ink, there is no need to stop the machine. Generally, the differential can be eliminated, and the pressure difference of the layout is used to "scrape" the ink, which improves the printing efficiency by 2 times and improves the printing quality. Because in general, when high-precision work pieces are frequently shut down to process the ink, the color will appear to be different when the machine is frequently turned off, especially the darker parts will be more obvious, which will affect the overall color of the work. consistency.
(2) Water saving
Differential will reduce water consumption. When we visited a printing house, we found a situation where managers often check the captain's water usage and hope that the machine can save water as much as possible. As a result, the captain will often be differential, because after the differential is turned on, the pressure between the plate cylinder and the plate water roller will be significantly greater, so that the water consumption will be relatively small.
2. Faults
(1) Shorten the life of the water roller
Generally, the price of the original imported water roller is more than 10,000 yuan. Frequent use of the differential will cause the plate water roller to wear seriously, which will shorten the service life of the plate water roller by one time. This is because the differential itself is to remove the ink by friction between the plate water roller and the plates of different speeds through different speeds of the gears. For a long time, the friction will definitely cause the surface of the plate water roller to be damaged more quickly.
(2) The plate wears faster
Frequent opening differentials can cause plates to wear faster. Under normal circumstances, short-run jobs of less than 10,000 impressions are not obvious, but when encountering large-volume jobs, the patch is more frequent, as the fault we encountered above.
Responses
By analyzing the advantages and disadvantages of the difference, our company's technical staff met to discuss and decided to minimize the use of differentials, specifically from the following aspects.
Under normal circumstances, it is forbidden for the machine personnel to use the differential, and take measures as far as possible to avoid the generation of ink. In the cutting process, the sharpness of the cutting knife is controlled to avoid the edge of the cut paper. Before going to the machine, wipe the paper around with a damp cloth and wipe the cut paper powder so that the ink will be rarely produced during printing, so there is no need to open the difference. During the printing process, the ink is stirred agitated to reduce the drying of the ink surface. In special cases, additives are added to the ink to improve the fluidity of the ink and reduce the generation of ink.
If these measures are taken to eliminate the occurrence of ink smear, and the paper does have hair loss and powder loss, consider the differential, but turn it off immediately after use, and do not use it for a long time.
In short, the differential design has its own characteristics. When using 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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