Sheetfoil Gravure

As a list of concave operators, in the daily production process, naturally encountered a lot of "strange" situation, here with a factory in Beijing Chen Henry monochrome off gravure machine, summed up one or two.

Fault one: printing red text, the first few shifts are all normal, and suddenly there are knife lines in the middle. Suddenly, after sharpening the knife, it will be printed again soon, and the knife line will appear in the same place.

Cause: Usually the knife line is caused by foreign matter inclusion between the doctor blade and the plate cylinder that damages the blade. So we filtered the ink, cleaned and ground the scraper. However, after the printing, the situation did not turn for the better. Often, only one order was printed and the knife edge was again gapped. Considering that the red ink particles are relatively coarse, it is easy to injure the blades. We have replaced the scraper with a smaller hardness, and at the same time, reduced the pressure of the scraper. After the reprint, the situation has improved, but the knife line will soon appear again. At this time, we noticed that the cutting line appeared in the same position each time, so the shutdown was carefully checked. When the roller was moved to the position where the teeth were to be opened, it was found that one tooth was loose and tilted slightly, and there was no obvious abnormality when the machine was operated by air pressure. Once the pressure printing was completed, the tilted teeth would continuously hit the plate. The non-graphical part of the mouthpiece causes the surface of the plate to be damaged and not smooth. The plate cylinder rotating at a high speed then damages the squeegee, so the cutting line occurs frequently at this location.

Solution: After finding out the reasons, we will adjust the flattening and fixing of the tilted tooth piece and smooth the damage of the plate with gold cabinet sandpaper. After boot printing, the fault disappeared and everything was normal.

Fault 2: When the shutdown time is long after each exchange class or other reasons, after the system is turned on again, the gauge distance on the part of the body is irregularly run up and down, and after running for a period of time, it returns to normal.

Cause: We have inspected the main drive of the machine and there is no looseness. After checking and inspecting the feeder part, the transfer time between the paper suction nozzle, the paper feeding nozzle, and the paper transfer roller is also within the normal range, and the gas path is also smooth. Considering that the machine runs normally after printing for a period of time, it can be ruled out that it is the error of the exchange time and the transfer position of each part. It should be the running rule that the paper does not go well from the process of flying to the front gauge. So stop for a period of time and then run the machine at a low speed, open the air pump and pay attention to the situation of paper feeding, and find that there is a short pause phenomenon on the paper feeding panel before the paper on which it rests reaches the front gauge. The above hair rollers and brush adjustments have no problem. It is concluded that the bearing of the connecting line belt is aging and the rotation is not working. After a long period of shutdown, the paper feeding time is unstable, and when the paper reaches the front gauge, the time is fast and slow. After running for a while, the bearing became hot, the paper feeding gradually became stable, and the printing was normal. Please come to the mechanic and replace the bearing. The fault disappears.

Failure three: printing full version of glossy oil on the ground, there is a similar imprinting pressure generated by the lack of printing is not achieved, while accompanied by the gauge from top to bottom instability, after a good version of the boot version of the running version of the phenomenon appears.

Causes: We first calibrated the plate according to the conventional solution, and stuck the sealing tape at the position where there was no imprint on the glazing blanket to increase the printing pressure. After printing, it was found that the phenomenon of inaccurate printing was transferred to other parts. In order to eliminate the possibility that the coating may be caused by the excessive dusting of the previous offset printing process, we used a rag to wipe the powder and then reprint it on the machine. The effect was still poor. At this time, the printing plate needs to be corrected again. The captain, unable to stop the ink fountain for inspection after being stopped, found that the deputy installed the fixed plate cylinder and the plate hoop in the opposite direction when loading, resulting in the plate hoop not being able to effectively lock the plate and the plate shaft. After the plate was mounted on the machine, it swayed, causing unstable pressure and uneven distance.

The solution: unload the plate, change the direction of the plate, so that one side of the plane is inward and locked. After reloading, the pressure and overprinting will return to normal and the trouble will be eliminated.

Fault 4: In a normal printing process, a piece of paper is not well sandwiched between the plate and the impression cylinder, causing the machine to stop printing. After the waste paper was removed, printing was resumed. It was soon discovered that the ink in the printing ink tank overflowed excessively for no reason.

Cause of failure: Stop the ink pump when it is turned off. After lowering the ink tank, it was found that the waste paper was not cleaned. There was a small piece of paper that had got into the ink tank and blocked the ink outlet, resulting in poor ink circulation and ink. The resulting downtime cleaning work delayed a long production time.

After summing up, a similar situation will appear again. Before the machine is turned on, it should be checked whether the ink is smooth or not. This can effectively prevent such errors from happening again.

In addition to the above-mentioned failures, pay more attention to some details in the usual print production process. It will also avoid the unexpected troubles of many jobs. For example: Feida, paper feeding panel, some components and screws on the impression roller's row should always check for looseness, otherwise an expensive printing plate is likely to be scrapped due to a missing screw. In addition, use different water-based inks or solvent-based inks, do not leave as much solvent as possible in the ink fountain. Otherwise, water-based oil wells mixed with solvents or solvent-based inks mixed with water, printed products will be difficult to see.

There is no end to India, and senior masters may encounter new problems. Based on the combination of theory and continuous accumulation and summarization of experience through actual combat, after a certain period of time, it will surely become a precious intangible asset of the company or yourself.

Author / Wu Qiang

Reprinted from: Printing Technology