Analysis and elimination of common faults in web offset presses
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Common defects in web offset presses can be divided into three categories: partial paper failure, partial printing failure, and partial folding. To troubleshoot, you must carefully read the random instructions and mechanical schematics, master the printing performance and mechanical properties of the machine, fully understand the structure and use of the various components of the machine, only to achieve these points can have a correct fault After the analysis, make the correct exclusions.
First, the common faults and exclusion of the paper
The upper paper part is the whole process of ensuring smooth and uniform feeding of the printing part. Common faults are: the paper tape folds and the paper tape is tight. Analysis of the above faults is mainly due to the quality problems of the paper tube, but in order to save raw materials, the paper can be adjusted by adjusting the paper guide roller and the magnetic powder brake. If the effect is not obvious, the direction of the paper roll can be changed to eliminate such faults. . When the paper roll is tight, the paper tape is easy to break, which affects the normal paper feeding. It is found that such a phenomenon can be wetted on the wet side of the water brush, and the fault is eliminated.
Second, the printing unit common faults and elimination
The printing unit is the main part of the offset printing machine. The normal operation of the printing unit directly affects the key parts of the product quality. Common faults in the printing unit can be divided into three categories: failure of the water supply part; failure of the ink supply part; failure of the embossed part.
1. Analysis and elimination of common faults in water supply
Water supply devices can be divided into two types: indirect water supply and direct water supply. Indirect water supply is the purpose of water supply by atomizing the water through the brush. Direct water supply means that the water is transferred to each other through the water roller to achieve the purpose of water supply. No matter which way is used for water supply, the purpose is to fully apply the printing plate. Wet to maintain ink balance.
(1) Analysis and elimination of common faults in indirect water supply
The composition of the indirect water supply part: the indirect water supply part is composed of a water bucket roller, a brush roller, a water roller, and a plate water roller.
Common faults of indirect water supply include: the water supply is too large or too small, and the water supply to the printing plate is large or 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 manifestation of various faults is: the partial deviation of the water makes the ink color tarnish, the gray color is dull, the ink color is not full, and the ink emulsification occurs in severe cases. When the water volume is too small, the printing plate can not be fully wetted, resulting in deformation of the graphic and the ambiguity. The specific elimination method can be adjusted according to the structure of the water supply mechanism and the function of each component. In the water supply part, the brush roller and the water roller are fixed and are not adjustable, and the water roller and the water roller are adjustable. The depth of the water roller in the water tank is large, the water supply is large, and the depth is small. The water supply is also small, and the depth of the water bucket roller in the water tank is controlled by the adjustable eccentricity at both ends of the water fountain roller. According to this feature, the water supply amount of the printing plate can be appropriately adjusted. The gap between the plate water roller and the water roller is adjusted by the plate water roller. The gap between the two rollers should not be too large or too small. The oversize and the size cannot be fully transferred. If it is too small, a part of the water will be squeezed out. Can not achieve the purpose of transfer. The gap between the plate water roller and the water roller is uniform and balanced. It can be adjusted with 15 wire steel sheets.
(2) Analysis and elimination of common faults in direct water supply organizations
The direct water supply mechanism is composed of a water bucket roller, a water transfer roller, a water roller, and a plate water roller.
The common faults and the indirect water supply mechanism are basically the same. The elimination method is to adjust the pressure between the water transfer roller and the water roller and the water roller to eliminate the pressure at both ends of the water roller. The water supply must be adjusted to the equilibrium position. The mechanism generally uses water rollers. The water tank should be cleaned frequently. The water roller should be changed frequently to check the pressure between the water rollers. Because the pressure between the water rollers changes with the water after the new water roller is used for a period of time, the water volume is changed. There will be changes, and when these points are mastered, the failure of the water supply will be ruled out.
2, the common troubleshooting of the ink supply part
The ink supply mechanism is composed of an ink fountain roller, an ink transfer roller, a tandem roller, and an offset ink roller.
The faults are: insufficient ink supply, large ink supply, unstable ink supply, etc. Analysis of the above faults is caused by the pressure between the ink rollers not meeting the requirements. Remedy: 15 wire steel can be used to adjust the pressure between the ink rollers. Pressure balance is required. Due to the large temperature difference between winter and summer, the pressure can be appropriately increased in winter when adjusting, and the pressure can be appropriately reduced in summer.
3, embossed part troubleshooting
The embossed part is the core part of the printing unit, and it is also the most accurate part of the design and manufacture. Generally, the pressure and other parts cannot be adjusted. The fault is faint in ink color, unclear dot, and insufficient ink transfer in the absence of hair. It is caused by the loss of elasticity of the rubber or the too small size of the garment. As long as the new rubber is replaced or the thickness of the garment is appropriately increased, the thickness can be excluded.
Third, folding unit failure analysis and elimination
The folding unit is a unit that is closely matched and interdependent. The problem of one part will affect the normal operation of the whole machine. To eliminate the fault, it is necessary to understand the performance of each part, the law of motion and its role. It is necessary to carefully observe and analyze the faults that have occurred, and then decide what method to take to eliminate them. Remember not to analyze the faults that occur, and to eliminate them. If some faults are on the surface, they are the problems in the next process. In fact, they are the problems of the previous process. If they are not observed or analyzed, the faults It is difficult to rule out. such as:
The fault caused by improper adjustment of the machine is due to the performance of the machine, the law of motion, and the structure is unclear. Generally, the folding does not meet the quality requirements, the paper tape is damaged, the movement time of the steel needle changes, and the folding knife and the clamping plate cannot Very good cooperation, 16K folding knife time changes, etc., these faults are caused by the understanding of the movement law of the machine. The main elimination method is to change the exercise time. The exercise time is generally controlled by eccentricity, and the eccentricity can be changed to eliminate these faults.
Faults in the wear of the machine parts: The failure of the machine parts is caused by insufficient oiling of the high-speed moving parts, the parts cannot be fully lubricated, the wear of the parts is accelerated, and the service life is shortened. The parts are not worn out in time due to normal wear and tear.
Failure caused by damage to the machine
The damage of the machine is generally due to the service life of the machine has been reached, or the operation is improper, the machine has abnormal sound during the movement, the machine can not work normally, the machine does not work, etc. The damage of the machine is mainly replaced or repaired. Machine failures can be eliminated.