Experience exchange: analysis of common faults in web offset presses
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Fault analysis and elimination of the paper unit
There are two types of common faults in the paper unit: one is caused by unqualified raw materials, such as the paper roll is not round and deformed, mainly caused by extrusion during transportation; the tension on both sides of the paper roll is not equal, and the surface of the paper roll is uneven. Rope-like, etc., are all problems that are often encountered in the production process. As long as the qualified paper roll is replaced, the fault can be eliminated. The second type of fault is caused by improper operation, such as paper breakage, wrinkles, etc., which are caused by the operator's lack of understanding of the adaptability of the paper. This type of fault can generally be eliminated by adjusting the tension controller.
Failure analysis and elimination of printing unit
1. Common faults in the water supply section
Fault analysis: The water supply is too large, so that there is too much excess water on the printing plate, and the ink emulsification is accelerated. It is reflected in the product that the ink color is light, dull, the dots are not full, and the layout is unstable.
Remedy: First, check whether the depth of the water roller in the water tank meets the requirements. If it is too deep, the water supply will increase, and vice versa. The eccentric device at both ends of the water roller can adjust the water roller in the water tank. The position makes the water supply normal; secondly, it is checked whether the pressure between the plate water roller and the plate cylinder is within the technical requirements. The specific method is to judge the printing plate by the ink bar in the state of pressing the plate cylinder. The pressure is generally suitable for the ink bar between 4 and 7 mm, or with a 0.15 mm thick feeler gauge. The adjustment can be achieved by adjusting the force of 2 kg.
2. Common faults in the ink supply part
Fault analysis: The instability of the ink color is manifested on the printed sheet when the ink amount is large and small, extremely unstable, and difficult to control. This is because the gap between the ink rollers is too large, causing the ink layer on the surface of the ink roller to be unstable, and the amount of ink supplied changes accordingly.
Remedy: Adjust the gap between the ink rollers, measure with a 0.15mm thick feeler gauge, and adjust with a force of 2kg. It should be noted that if the pressure between the ink rollers is adjusted too much, the friction will increase, and the heat at both ends of the ink roller will easily damage the ink roller; however, if the pressure adjustment is too small, the ink supply amount will be unstable and the printing will not be normal. .
3. Common defects in the stamping part
Fault analysis: If the pressure is too small, the ink transfer is not enough, the product print is imaginary, the dot is not full, the handwriting is missing, and the picture is unclear; if the pressure is too large, the printing plate will be reduced in printing resistance, handwriting and graphic Deformation, the machine load increases.
Remedy: The method of changing the thickness of the blanket lining can be used, but in special cases, this method can not eliminate the fault or exclude it from being unsatisfactory or incomplete. At this time, it is necessary to adjust the pressure (gap) between the rollers. Note that it is necessary to refer to the random manual and the mechanical schematic, consult the accurate technical data, and adjust with special tools to make the pressure reach the technical index.
Failure analysis and elimination of folding unit
Fault analysis: the occurrence of folding is not allowed, the specification of the signature does not meet the quality requirements, the page is missing, the bad page, the paper jam and other faults. The above failures may occur if the wear of the mechanical components exceeds the technical requirements, the mechanical components are damaged, and the moving parts are not adjusted.
Remedy: First of all, carefully observe the product, because the faults generated can be expressed on the product. As long as you have an accurate understanding of the performance, function, and movement of each mechanical component, you can judge the specific location of the fault by observing the product; after determining the cause of the fault, you can check the corresponding component; by listening, touching, It seems that judgment, careful observation, and discovery of problems. When the machine is damaged, it will show that the motion sound is not stable, and the moving parts often have heat. When the moving parts are worn, the moving parts are not in motion. These problems can be eliminated by replacing the parts.
After the failure, an accurate understanding and judgment of the generated fault should be made. Because the same fault may be caused by different reasons, the troubleshooting method is different, and different faults can sometimes be eliminated by the same method. Therefore, in practical work, it must be applied flexibly.