Analysis and elimination of common faults of the h

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Analysis and elimination of common faults of web offset press

common faults of web offset press can be divided into three categories: paper loading part fault, printing part fault and folding part fault. To eliminate the fault, you must carefully read the random instructions and mechanical schematic diagram, master the printing performance and mechanical performance of the machine, and fully understand the structure and purpose of each part of the machine. Only by doing this can you have a correct analysis of the fault, and then make the correct troubleshooting measures

I. common faults and troubleshooting of the paper loading part

the paper loading part is the whole process of ensuring a stable and uniform paper supply to the printing part. Common faults are: paper tape folding, paper tape tight edge. The above faults are mainly caused by the quality problems of the paper drum. However, in order to save raw materials, the faults can be eliminated by adjusting the paper guide roller and magnetic particle braking. If the effect is not obvious, the direction of paper roll movement can also be changed to eliminate such faults. When the paper is rolled tightly, the paper tape is easy to break, which affects the normal paper supply. If this kind of phenomenon is found, you can wet the tight side with a water brush, and the fault is eliminated

II. Common faults and troubleshooting of printing unit

printing unit is the main part of offset rotary machine. Whether the printing unit operates normally directly affects the key part of product quality. Common faults of printing unit can be divided into three categories: faults of water supply part; Ink supply failure; The imprinting part is faulty

1. Analysis and troubleshooting of common faults in water supply

water supply devices can be divided into indirect water supply and direct water supply. Indirect water supply is to atomize the water through the brush to achieve the purpose of water supply. Direct water supply refers to the transfer of water through the mutual contact of water rollers to achieve the purpose of water supply. No matter which way of water supply is adopted, the purpose is to fully wet the printing plate and maintain the balance of water and ink

(1) analysis and troubleshooting of common faults of indirect water supply

composition of indirect water supply part: the indirect water supply part is composed of bucket roll, brush roll, cross water roll and plate water roll

the common faults of indirect water supply are: the water supply is too large or too small, and the water supply at one end of the printing plate is too large or too small, that is, the water supply at both ends of the printing plate is inconsistent. The above problems directly affect the normal operation of the machine. The specific manifestations of various faults are: the amount of water is too large to make the ink lose luster, gray light, and the ink is not full. In serious cases, ink emulsification will occur. If the water volume is too small, the printing plate will not be fully wetted, resulting in deformation and ambiguity of graphics and texts. The specific elimination method can be adjusted according to the structure of the water supply mechanism and the functions of various components. In the water supply part, the brush roll and the cross water roll are fixed and cannot be adjusted, while the bucket roll and the plate water roll are adjustable. The depth of the bucket roll in the water tank is large, the water supply volume is large, the depth is small, and the water supply volume is small. The depth of the bucket roll in the water tank is controlled by the adjustable eccentric at both ends of the bucket roll. According to this feature, the water supply volume of the printing plate can be adjusted appropriately. The gap between the water roller and the water roller is adjusted by the water roller. The gap between the two should not be too large or too small. Too large and too small parts cannot be fully transferred. Too small parts of the water will be squeezed out, and the purpose of travel introduction and transfer of the full-automatic tensile testing machine cannot be achieved. The gap between the water roller and the water roller is consistent and balanced. It can be adjusted with 15 wire steel sheet

(2) common fault analysis and troubleshooting of direct water supply mechanism

the direct water supply mechanism is composed of bucket roll, water transfer roll, water string roll, and water roll of sizing plate under its base by adjusting or increasing or decreasing

the common faults are basically the same as those of the indirect water supply mechanism. The troubleshooting method is to adjust the pressure between the water transfer roll and the bucket roll and the water string roll. The pressure at both ends of the water roll must be adjusted to the balance position. This kind of water supply mechanism generally uses the water roll. It should wash the water tank frequently, change the water roll frequently, and check the pressure between the water rolls frequently, because the pressure between the water rolls changes with the water after the new water roll is used for a period of time, The water volume will change. If you master these points, the faults of the water supply part will be eliminated

2. Common troubleshooting of the ink supply part

the ink supply mechanism is composed of an ink bucket roller, an ink transfer roller, an ink string roller, and a plate relying ink roller

the faults are: insufficient ink supply, excessive ink supply, unstable ink supply, etc. according to the analysis, the above faults are caused by the pressure between the ink rollers does not meet the requirements. Troubleshooting: the pressure between ink rollers can be adjusted with 15 wire steel sheets, which requires pressure balance. Due to the large temperature difference between winter and summer, the pressure can be appropriately increased in winter and reduced in summer

3. Troubleshooting of the embossing part

the embossing part is the core part of the printing unit, and it is also the most accurate part of design and manufacturing. Generally, it is not possible to use a frame level to level and adjust the pressure and other mechanical parts in the two directions perpendicular to each other on the outer ring of the working cylinder. The faults include weak ink color, unclear dots, lack of wool, broken channels, and insufficient ink transfer, which are all caused by the loss of elasticity of the rubber or the small size of the shirt. As long as the rubber is replaced or the thickness of the shirt is appropriately increased, it can be eliminated

III. folding unit fault analysis and troubleshooting

folding unit is a whole with close cooperation and interdependence among various components. The normal operation of the whole machine will be affected if a component fails. To troubleshoot, we must understand the performance, motion law and role of each component. Observe and analyze the faults carefully, and then decide what method to take to eliminate them. Remember not to eliminate the faults that occur due to inaccurate analysis and inadequate observation. Some faults appear to be the problems of the next process, but in fact are the problems of the previous process. If you cannot observe and analyze them, it is difficult to eliminate the faults. For example:

the faults caused by improper adjustment of the machine parts are caused by unclear performance, motion law and structure of the machine parts. Generally, the faults are that the folding does not meet the quality requirements, the paper tape is damaged, the movement time of the steel needle changes, the folding knife and the clamping plate do not cooperate well, the time change of the 16K folding knife, etc. these faults are caused by not understanding the motion law of the machine parts. The main troubleshooting method is to change the movement time, which is generally controlled by eccentricity. These faults can be eliminated by changing the eccentric high point

failure caused by wear of parts: the failure caused by wear of parts is due to insufficient oil filling for high-speed moving parts and insufficient lubrication of parts, which accelerates wear of parts and shortens service life. The parts were not replaced in time due to normal wear and tear

faults caused by parts damage

parts damage is generally caused by the service life of the parts has reached the end of the year, or by improper operation due to high selling price. There is an abnormal sound when the machine is moving, the machine cannot work normally, the parts do not work, etc. the troubleshooting of parts damage is mainly to replace or repair the parts, and the faults of the parts can be eliminated

source: Western printing

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