In the domestic printing industry, during the printing process of the offset press, parts or things often fall into the machine cylinder, crushing the cylinder body. The rubber cylinder and the impression cylinder of the cylinder body are crushed. Moreover, it is a small range of roller body crushing or depression. The common method is for a repairman to mix agricultural machinery glue with fine iron powder and apply it to the roller depression of the depression. The arc surface is flattened and repaired.
Recently, the largest book printing company in Guangxi-Guangxi Minority Printing Factory introduced the CD102V Heidelberg German four-color offset printing machine four plate cylinders and the imported American Harris eight-color offset printing press eight plate cylinders, a large area of ​​production Rust corrosion, the surface of the drum body is severely rusted and corroded from the bite to the trailing end, both sides of the body and outward. After removing the rust powder, the drum body is measured by the caliper and plug gauge. The depression has reached 0.35mm, and the deep depression has reached 0.65mm. The two imported multi-color offset presses have only been printed for six or seven years. The rust and corrosion of the printing cylinder made the CD102V four-color folio offset press in Heidelberg, Germany, unable to produce. The US Harris eight-color offset printing press also seriously affects the quality of product printing. After the accident, the factory attached great importance to it and asked relevant experts at home and abroad, as well as experts in Hong Kong to maintain offset presses. They agreed that this large area of ​​corrosion and such a deep depression made it impossible to repair. The factory did not have the ability and technology to repair the roller, and in the absence of any other methods, determined to take a great risk and invited the engineering and technical personnel of Beijing Heidelberg Xiang Printing Machinery Maintenance Service Center to repair these two offset printings Machine's twelve plate cylinders. Without agreements, funds and unit guarantees, these two machines worth tens of millions of yuan were boldly handed over to the center for repair. The factory leaders had great trust in the center and the center used high-tech new technologies To apply the new technology used in the military production of the army general to the repair of civilian printing machinery, and at the same time make their own testing instruments and repair tools, after more than a month of hard work day and night, all twelve plate cylinders were coated with electrolytic brushes The manual method uses the principle of electrolytic reduction of metal copper, chromium and nickel to paint the entire plate cylinder uniformly over and over again. Moreover, the surface brushing is quite flat, and the test error is less than 0.04mm. Using manual electrostatic brushing within such a small error range, this can be said to have created a miracle in the domestic printing industry. After the start-up printing and acceptance, the printed samples of the full version and the flat screen are almost the same as those of the new machine. After testing the technical parameters and errors, they are also within the technical parameters. The quality of the printed products also meets the quality requirements. The repair cost only cost more than 50,000 yuan. The two imported machines were put into the production of printed textbooks again, and the quality was quite good. If the mechanical spraying of the cylinder is used or the new plate cylinder is replaced, so that the cylinder is installed back to its original position, the accuracy of the original machine will definitely not be achieved, and the repair cost will be at least several hundred thousand yuan, or even millions. The reasons for this accident and the corresponding countermeasures in offset printing technology and management in the future are analyzed for reference only by colleagues in the printing industry.
1. The surface of the printing plate cylinder should be coated with chromium and nickel
For four-color Heidelberg offset presses and eight-color offset wheels, if the surface of the plate cylinder is coated with zinc or iron, the metal zinc or iron will chemically react with the acid in the bucket solution (rust, oxidation), and the cylinder body cannot be tight. Pasting pads and printing plates, such as the cylinder surface soaked in acid for a long time, will definitely cause corrosion and rust. If the plate cylinder body is changed to chrome or nickel coating, the above accidents will definitely not occur.
2. The water bucket solution should not penetrate the surface of the plate cylinder
If the operating staff on the machine does not follow the technical requirements of the plate mounting process, the plate liner (0.3 mm thick polyester tablet, commonly known as gun bottom glue) is not lined up or damaged and is not replaced in time. , Causing the printing plate to be uneven on the plate cylinder, not to be obedient, especially the damaged liner does not coincide with the upper plate and the two ends of the lower plate cylinder body, and the acidic water bucket solution penetrates the surface of the plate cylinder body . The contact of the acidic water bucket solution with the surface of the plate cylinder will inevitably cause corrosion and rust on the surface of the plate cylinder. The plate must be close to the liner, and the liner should be close to the surface of the cylinder body. There can be no gap between them, so that the acidic water bucket solution can completely prevent the surface of the plate cylinder from infiltrating. Will corrode and rust.
3. The pH value of the water bucket solution is not well controlled, and the acidity is too strong
In the offset printing process, the machine personnel should strictly control the concentration of the water bucket solution. During the operation process, the pH value should be controlled at 5 to 6 on the premise that the pattern is clear, the layout is blank and not greasy, and the layout is not dirty or slurred. .5 is better. Printing in strong acid will also result in low printing durability and high emulsification value of the printing plate. The printed ink is not easy to dry and causes the back to be dirty, the color of the ink is dull, not bright and not bright.
Fourth, the layout is too moisture
During the offset printing process, the machine operator failed to strictly control the moisture on the surface of the printing plate, because the moisture control is slightly larger, the printing plate is not easy to be dirty, and the moisture control is less. Once the climate or external environment affects, the printing plate is easy to hang dirty , The product will be scrapped. Therefore, we should overcome the idea of ​​controlling the water content of the page instead of "big rather than small".
It is very important for the operators of offset printing machines to master the balance of water and ink. To measure the level of an offset printing technician, it depends on whether the work of Sanping (roller leveling, water roller leveling, and ink roller leveling) is done well, and whether the water and ink balance is well controlled. .
V. Strengthen process technology management
The modern enterprise system requires enterprise leaders to pay attention to the technical training of employees, include this work in the annual plan, train employees in technical theories in phases and batches, and use strict, technical, and standardized methods to strictly manage process technology. The main reason is that the process water management and the pH concentration of the water bucket solution are not well controlled in the process management. The management is not in place. The offset press staff does what they want, which is the cause of human accidents. Strengthening the internal process technology management of the enterprise, improving the technical quality of employees, and paying attention to the quality of work can ensure product quality. Through the occurrence of this machine accident, we have to draw lessons from it, and we will never have the above similar accidents in the future.
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