Details easy to be neglected in the maintenance of

2022-08-01
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There are many reasons for the failure of the offset press, such as mechanical structure, operation error, mechanical wear, untimely lubrication and so on. After a mechanical accident, the repaired machine often breaks down again during normal printing due to negligence in some details, resulting in unnecessary economic losses. The following two failures are frequently encountered when I use the pressure source (i.e. pressure test pump) to provide the total pressure of the main pressure system according to the experimental conditions when I repair the machine, but they are easy to be ignored. They are summarized as follows for peer reference

1. Failure caused by wear of the direct pin on the main shaft of the paper transfer mechanism

the paper transfer part of domestic offset press mostly adopts the back and forth up swing paper transfer mechanism. In order to avoid the paper feeding tooth row colliding with the embossing cylinder body when the paper feeding is completed and returned, the machine is equipped with a paper feeding eccentric sleeve mechanism. The mechanism has a lock nut at the outer end of the operating surface, which is used to adjust the axial clearance of the paper transfer mechanism. There is a washer in front of the nut and a 3mm washer on the washer × 4mm notch. This gap is the same as that embedded at the adjusting thread on the paper delivery shaft of the operating surface φ The 3mm straight pin is used to ensure that the nut can only swing back and forth with the paper delivery shaft when locked, and cannot make circular motion with the eccentric sleeve. Otherwise, the nut becomes tighter and tighter, locking the paper delivery eccentric sleeve. When the paper delivery shaft is placed to the upper limit, the force of the large tension spring cannot reset the paper delivery mechanism, and the large tension spring will be stretched and deformed. At this time, if the vehicle is not stopped in time, it will cause a major mechanical accident. On the main shaft φ If the 3mm straight pin is worn out after years of use, it will lose its limiting effect. It is not easy to attract the operator's attention here, and it is easy to cause multiple machine accidents. Almost all the increment comes from the battery

2 Failure caused by inattention to bearing replacement and assembly details

the second color group of domestic two-color offset press is mostly equipped with a plate printing mechanism, which provides convenience for operators to find one or two color overprint rules. However, some operators often do not operate according to the requirements of the machine operation manual in order to save time, and excessively print the plate, resulting in damage to the internal two thrust bearings. If the assembly position of the two loose rings and the two tight rings is neglected when replacing the bearing, the plate printing mechanism will not be able to lock the plate cylinder during the printing process, resulting in inaccurate overprint of printing products. The correct installation method is that the two tightening rings (inner diameter surface is the processing surface) are installed opposite to the outside (by the relative moving surface), and the two loose rings (inner diameter surface is the rough surface) are installed adjacent to the inside (by the relative stationary surface). It should be noted that the circumferential pulling plate should be operated when the machine is running

if the pendulum does not turn clockwise

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