Case Analysis of Paper Breaking in Offset Printing Process

In the offset printing process, there are many reasons for the paper breakage failure, which is generally caused by uneven force of the tooth decay or aging of a certain tooth spring. The following two cases of paper breakage are caused by the wear of the thrust bearing of the impression cylinder. Generally, this kind of situation rarely occurs. Once it occurs, the reason for troubleshooting is also a waste of time.

Case number one

Fault performance: The paper has been smashed, and almost every one has been smashed.

Reason for troubleshooting:

1 After all the emergency stops, check all the rows of teeth and find that the paper was smashed when the fourth group of impression cylinders and the delivery tray were handed over. The author initially suspected that the problem was in the opening time, but the failure was not adjusted after the opening time. disappear.

2 When checking again, it was found that the opening pressure ball of the fourth group of impression cylinders was heated and there was wear and tear, so it was suspected that the opening of the ball caused by the opening of the ball was not allowed, resulting in the paper being smashed, but replacing the new pressure ball. The fault did not disappear.

3 The author immediately checked the force of each tooth in the tooth row to see if it was caused by uneven force, but the test results showed that the force of the tooth was normal.

4 During the inspection, the author smelled a burnt smell of oil. After inspection, it was judged to be emitted from the fourth set of protective covers. The protective cover was opened and the outside of the thrust bearing was touched by hand. The temperature was very high, and its temperature was very high. The oil flowing out around and below contains iron filings, so the problem is judged here.

Solution: Replace the 7 parts on the thrust bearing and clean the installation parts to clear the oil pipe leading to the part. It is worth noting that the order should be numbered when taking parts, which provides a reference for the subsequent installation of new parts, to avoid the installation sequence error. After loading, the printer will start printing and the fault will disappear.

Case 2

Fault performance: The first and second cavities on the paper operation side were smashed.

Reason for investigation: After investigation, it was found that the paper was smashed at the third group of impression cylinders, and it felt very difficult to get the car when there was a little resistance. At the same time, there was a "beep" sound inside the third group of protective covers. Open the protective cover and notice that the sound is emitted from the thrust bearing when you click the car. Touching the outside with your hand, the temperature is obviously high, and the temperature of the thrust bearing of other units is normal. Therefore, based on the previous experience, the problem is the same. Appears on the thrust bearing.

Solution: Same as case one.

summary

From the above two cases, we can get the following experience: in the case of the thrust bearing wear, the impression cylinder will sway back and forth in the axial direction (ie horizontal direction), even if the turbulence is small, it will make the paper At the moment of the handover of the tooth row, a beating occurs, causing a deviation in the handover time, which causes the paper to be broken. One of the causes of the wear of the thrust bearing is that the tubing that lubricates the component is not smooth, resulting in a large frictional force during operation, which accelerates the wear of the thrust bearing; the second reason is the wear of the machine and the components. Therefore, in the process of equipment maintenance and daily maintenance, we must pay attention to the inspection of the oil circuit, ensure that the oil pipe is unblocked, and replace worn parts in time to avoid affecting normal production.

　　 The above content is selected from the second issue of 2011, Printing and Printing , Packaging and Decoration, and more journal content. Please pay attention to the journal channel.