(5) Vibration and impact of the drive system load. The structure of the sheet-fed offset press is complex, and there are quite a lot of impact and vibration parts. For example, the clutch of the drum, the roll gap into the roll, various types of reciprocating paper-feeding mechanisms and cam-driven mechanisms, and paper-handling mechanisms for opening and closing the paper, The ink roller is oscillating and the water transfer roller is oscillating.
Due to the vibration and impact of these mechanisms, the uniform rolling between the drums will be destroyed, resulting in instantaneous speed changes and relative slip between the drums to form a bar. Especially when the main motor belt is loosened, these shocks and vibrations worsen the operation of the offset press. There are defects in design and manufacturing, and there are also factors that regulate improper use.
(6) Excessive wear of transmission components. Various types of parts of the transmission system such as transmission belt wear and slip, wear and deformation of various key links, wear and slip of couplings, wear of cams, gears, and bearing parts. Excessive wear of these parts affects offset press to varying degrees. The balance of operation and the possibility and severity of the emergence of bars.
3. Design issues The appearance of the offset press depends not only on the structure of the core part of the drum and its bearings, but also on whether the print cylinder rests on the pillow, but also on the structure and rigidity of the machine wall plate, frame, and chassis, as well as the water supply, There are many factors such as the structure and reliability of the inking components. This article only briefly describes the defects of the occipital and the underlying infusion system.
(1) Pillow and No Pillow There are two kinds of printing methods for sheet-fed offset presses: one is the printing method of contact with the drum shoulders, namely the printing method of the pillow.
The use of an offset press that does not contact the shoulder iron may cause vibration of the drum during high speed operation due to the impact of the idler and reciprocating motion of the drum and the presence of the intermittent motion mechanism, the bearing clearance of the drum, and the backlash of the gear. Easy to produce bars. For offset presses with pillows, the shoulder iron diameter is equal to the pitch circle of the gears. The roller gears are always in precise meshing operation. The center distance of each printing roller is fixed, the tooth gap is not enlarged, and the drum shoulders are iron. The contact pressure is greater than the printing pressure of the drum, so during the operation of the drum, the impact of bearing clearance, work surface and neutral shift will not affect the printing quality.
The vibrations caused by the rollers are eliminated, especially in the case of bearing and roller gear wear. Therefore, it can be said that the offset printing machine can effectively prevent the emergence of the lever and ensure the quality of printed products.
(2) The defects of the lower ink system, two-color satellite-type five-roller arrangement, and BB-type four-roller arrangement, offset presses, and the structure of the upper ink system and the lower ink system are different.
The first color ink roller is directly above the plate cylinder, while the second color four ink rollers, two directly below the plate cylinder, the other two in the lower position of the plate cylinder. The ink roller of the first color group, the second color group and the pressure of the printing plate surface are obtained by the pressure of the two compression springs, and the compression springs used in the two color groups are the same.
Due to the influence of the gravity of the ink roller, the pressure of the two color groups on the layout pressure varies greatly when the compression spring pressure is the same. Therefore, if the second color group is debugged using the same tuning method as the first color group, it is very easy to cause malfunctions, and there are network dots, ink film unevenness and white bars. Therefore, the pressure adjustment of the second color group should be larger than that of the first group, or the pressure spring can be replaced with a spring with a larger elastic force.
In addition, the entire structure of the second color group of the J2205 offset press is not a single unit with the main roller unit, and it is a removable type. Therefore, the vibration of the second color group is large, and it is easy to cause the appearance of a lever. (Finish)
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