Generation and elimination of harmful vibration of

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Production and elimination of harmful vibration of printing press

printing press belongs to mechanical equipment with complex mechanism, which is composed of multiple components, and the motion conditions of each component are different, including uniform motion, variable speed motion, linear motion, curve motion, etc. Since all components are not absolute rigid bodies, mechanical deformation will occur when subjected to fixed external forces; When subjected to alternating force, it will also produce vibration, which will make the actual motion law of the component deviate from the theoretical motion law, especially on the high-speed printing press. Sometimes, we will use the vibration of components to achieve the intended purpose, and some adverse vibration will become an important factor affecting the quality of prints. Therefore, we will comprehensively analyze the causes of harmful vibration and how to reasonably avoid it from three aspects: the design, manufacture and operation of the printing press

I. design of printing machine

for the circular sheet fed offset press, the imprint cylinder, rubber cylinder and plate cylinder in the printing parts directly affect the quality of the printed matter, so the design of these parts is very important. Because there are gaps in each drum, in the normal printing process, when the gaps meet or separate, the pressure between the drums will change repeatedly and instantaneously, and the impact will cause the drum vibration; In addition, each drum itself is an asymmetric structure, which will inevitably lead to the imbalance of the drum during rotation, and the resulting internal stress changes will cause the drum to produce axial deformation and vibration. Therefore, when designing the drum, we should try our best to avoid drum imbalance, optimize the drum structure and avoid the resulting vibration. At present, offset printing machines basically adopt the form of sequential clutch pressure, which is also to avoid greater vibration of the machine caused by simultaneous clutch pressure. In addition, the reasonable arrangement of the three rollers plays a decisive role in eliminating vibration

in addition, as a complex mechanical system, the interaction and interaction of the connecting links between the components of the printing press are also worth considering. The vibration generated between components can make this self-healing system very promising in solving the risk of long-term use of materials, prolonging the service life of materials and improving the reliability. It is transmitted through the connection links between components. For example, the power of the offset press is transmitted from the motor to the imprint cylinder, and then from the imprint cylinder to other components. In turn, the vibration of other components can also be transmitted to the imprint cylinder, thus affecting the imprint process, Lead to quality defects of prints. For another example, when the paper feeding tooth adopts the swing structure, the speed is prone to sudden change. Therefore, in the design, it is necessary to make the driving cam surface of the paper feeding tooth as smooth as possible. It is best to adopt the rotary paper feeding tooth structure and use the synthesis of motion to accurately complete the action requirements. In the structural design of rotary paper delivery teeth, a large number of silicon hydroxyl groups on the surface of attapulgite should also have poor compatibility with non-polar polymers, and try to adopt symmetrical design, which can greatly eliminate the interaction of connection links. Under the condition of meeting the motion requirements, flexible connection, such as chain connection or belt connection, can also be used to eliminate the mutual influence of vibration; It can also be driven directly and cut off the connection. Each moving component is driven by its own motor. For example, many rotary press and commercial rotary offset press have adopted shaftless transmission technology

in addition, when designing the printing press, we also need to analyze whether the vibration of each mechanism is random vibration or periodic vibration. If it is periodic vibration, we generally need to further calculate the vibration frequency of the mechanism, and determine the impact of the mechanism on the print quality according to this data

II. Printing machine manufacturing

no matter how well a printing machine is designed, its design will be meaningless if the manufacturing level cannot meet the requirements. Because manufacturing is the realization of design scheme and the key link that affects the quality of printing. When processing and manufacturing various components of the printing machine, especially those with high design tolerance requirements, the vibration of the processing machine and the workpiece itself should be avoided as far as possible, and the vibration should be avoided as far as possible to transmit the processing error to the processed workpiece, thus affecting the accuracy and performance of the workpiece. Especially in the processing of the drum, due to the asymmetry of the drum structure and the strictness of the processing tolerance requirements, the processing mode of low speed, low cutting amount and low feed rate should be adopted during the processing, and the strength and hardness of the drum should be improved through the heat treatment process. When machining the mating surface, try to eliminate unnecessary clearance to meet the technical requirements of the design

III. printing machine operation

6 types of materials among the top 7 consumables of SMIC international are purchased domestically; Nanshan Group aluminum alloy thick plate has passed the certification of Boeing and signed the supply contract; The volume and weight of the MW rare earth permanent magnet electromechanical machine of CSIC are reduced by 50% and 40% respectively compared with the traditional electromechanical machine; The localization rate of key equipment and materials for the world's first high temperature gas cooled reactor nuclear power plant with the characteristics of the fourth generation nuclear power has exceeded 85%; Liquid metal is preliminarily used in 3D printing, flexible intelligent machines, vascular robots and other fields. Improper operation of the printing machine will also produce vibration. In addition to strictly abiding by the operating procedures, operators should also fully consider the impact of machine vibration on the quality of prints based on experience. For example, the pressure between the ink roller and the ink roller, the ink roller and the plate cylinder, the roller and the cylinder, the water roller and the water roller, and the water roller and the plate cylinder should be properly adjusted. 5. The commissioning pressure of hydraulic universal material testing machine is too small, and the pressure between inking, water and rollers cannot meet the requirements; If the pressure is too high, it is easy to produce instant impact vibration between the ink roller and the drum, resulting in inaccurate overprint

in addition, there are many mechanical factors that affect the quality of prints, such as the firmness and levelness of the foundation during the installation and commissioning of the machine; The level of machine installation, the uniformity of force on each support foot, etc

at present, because people have higher and higher requirements for the quality of printed matter, and at the same time, in order to create higher benefits in a short time, printing enterprises also constantly improve the speed requirements of printing machines. At high speed, the impact of vibration on the stability of machines will become more apparent. Therefore, we should fully analyze the factors causing vibration and make adjustments in order to eliminate harmful vibration

School of printing and packaging engineering, Xi'an University of technology, Wang Fang, Zhang Haiyan

source: printing technology - equipment and special printing

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