Sheetfed gravure
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Some of the faults and problems that occurred during the production process of sheet-fed gravure printing were almost the same as the gravure printing of the web, which was caused by some knife lines and inaccurate overprinting. However, the reasons for its formation and the solutions are not the same.
As an operator of a list of concave machines, in the daily production process, naturally encountered a lot of "weird" situation, here combined with a Beijing-based Henry monochrome monochrome gravure printing machine, summed up one or two.
Fault 1: Printing red text, the first few shifts are all normal, and the knife line is suddenly generated in the middle. After the knife is ground, the screen is opened again in the same place.
Cause: Usually, the cut line is caused by the foreign matter caught between the scraper and the plate cylinder. So we filter the ink, clean and grind the scraper. However, the situation did not improve after the printing, often only a lot of printing, the blade will once again gap. Considering that the red ink particles are thick and easy to damage the blade, we replaced the blade with a smaller hardness and reduced the pressure of the blade. The situation improved after the printing was reopened, but the knife line appeared again soon. At this time we noticed that The knife lines appear in the same position each time, so the machine is carefully checked. When the drum is moved to the position where the tooth is about to open, it is found that one of the teeth has been loosened and slightly lifted. There is no obvious abnormality when the machine is running under air pressure. Once the pressure is printed, the raised teeth will continuously hit the plate. The non-graphic part of the cornice causes damage to the surface of the plate and is not smooth. The plate cylinder that rotates at a high speed in turn damages the blade, so the rule line frequently appears in this part.
Solution: After finding out the cause, we adjusted the raised teeth to a flat and fixed position, and polished the damage of the layout with gold cabinet sandpaper. Start printing, the fault disappears, everything is normal.
Fault 2: Each time the exchange shift or other reasons have a long downtime, after the power is turned on again, the gauge of the abutment part is irregularly up and down, and after a period of operation, it returns to normal.
Cause: We checked the main drive part of the machine and there was no looseness. After checking and checking the Feida part, the transfer time between the paper separation nozzle, the paper feed nozzle and the paper feed roller is also within the normal range, and the gas path is also very smooth. Considering that the printing is normal after the machine has been running for a period of time, it can be ruled out that the exchange time and the handover position of each part are wrong. It should be the running rule that the paper does not go well during the process of flying to the front gauge. Then, after stopping for a period of time, the machine was operated at a low speed, the air pump was turned on, and the paper was observed. It was found that there was a short pause on the paper feeding panel before the paper reached the front gauge. The above brush and brush adjustments are no problem. It is concluded that the bearing of the connecting belt belt is aging, the rotation is not working, and the paper feeding time is unstable after a long shutdown, and the paper is fast and slow when it reaches the front gauge. After running for a period of time, the bearing becomes hot, the paper is gradually stabilized, and the printing is normal. Please come to the mechanic, replace the bearing, and the fault disappears.
Fault 3: Printing the whole version of the varnish, there is a similar print pressure is not produced by the imprint does not achieve the image, accompanied by the instability of the gauge up and down, the set version of the boot after a period of time after the run version phenomenon.
Cause: We first register the plate according to the conventional solution, and paste the sealing tape at the position where there is no imprint on the glazing blanket to increase the printing pressure. After printing, it was found that the phenomenon of false printing was transferred to other parts. In order to eliminate the glazing caused by the excessive dusting of the printing process in the previous printing process, we used a rag to wipe the powder and then reprint it on the machine. The effect is still not good. At this time, the plate needs to be corrected again. After the captain stopped the machine, he lowered the ink bucket and checked it. He found that the assistant had reversed the direction of the plate cylinder of the fixed plate cylinder and the plate when loading the plate, so that the collar could not effectively lock the plate and the plate. After the plate is mounted on the machine, it shakes, resulting in unstable pressure and uneven distance.
Solution: Unload the plate and change the orientation of the plate so that the side of the plane is inward and locked. After reinstallation, the pressure and overprinting are back to normal and troubleshooting.
Fault 4: During a normal printing process, a piece of paper is not caught between the printing plate and the impression cylinder, causing the machine to stop printing. After the waste paper was removed, the printing was continued, and it was soon found that the ink in the ink tank of the printing plate overflowed without any reason.
The cause of the malfunction: Shut down the ink pump, and after dropping the ink tank, it was found that the waste paper was not cleaned up, and a small piece of paper was drilled into the ink tank, blocking the ink outlet, causing poor ink circulation and overflowing ink. The resulting downtime cleaning work delayed long production times.
After summing up, there will be similar situations in the future. Before starting the machine, you should check whether the ink is smooth or not, so you can effectively avoid such errors.
In addition to the above various faults, pay more attention to some details in the usual printing production process. It will also avoid many unexpected troubles. For example: Feida, paper feeding panel, some parts and screws on the embossing cylinder row should be checked for looseness, otherwise an expensive printing plate may be scrapped due to a falling screw. In addition, use different aqueous inks or solvent-based inks, and do not leave too much solvent in the ink fountain when replacing. Otherwise, the water-based oil well city is mixed with solvent or solvent-based ink mixed with water, and the printed product will be difficult to see.
The printing world is endless, and senior masters may also encounter new problems. On the basis of combining the theory, we will continue to accumulate and sum up experience through actual combat. After a certain period of time, we will become a valuable intangible wealth of the enterprise or yourself.