printing equipment4

2022-03-05 21:14
5

③ Disassembly and assembly of printing machinery

Mechanical repairmen have to face the problems of disassembly and assembly when repairing the printing machinery, especially the assembly, which will directly affect the mechanical performance. The low assembly quality will cause serious wear and tear of the machinery.

a) Mechanical disassembly

Because there are many types of printing machinery and different shapes of parts, it is difficult to describe them one by one. General disassembly principles are introduced here.

First of all, before disassembly, you must understand the structure, function and principle of the machine, and consult relevant technical data and instructions first. From the actual situation, determine the parts to be disassembled. The parts that can not be disassembled should not be disassembled as far as possible, but the parts that cannot be disassembled must undergo overall inspection to ensure the quality.

Secondly, in the process of disassembly, the external accessories and oil pipes shall be disassembled from the outside to the inside, and then the disassembly shall be carried out in the order of assembly first and then parts. For the matching position of more important parts, marks and numbers shall be made during disassembly, and disorderly stacking shall be avoided. It is also important to use tools reasonably during disassembly. The tools must adapt to the disassembled parts. For example, a suitable wrench shall be selected for the removal of threaded connectors, and special tools shall be used for the removal of static mating parts. It is not allowed to hammer, pry, etc.

In addition, conditions shall be created for assembly during disassembly. For non interchangeable parts, they shall also be marked or placed in pairs during disassembly, so as to reset during assembly, which can ensure assembly accuracy and reduce unnecessary wear.

b) Mechanical assembly

The fitting accuracy and dimensional accuracy must be ensured during assembly. In order to ensure the fitting accuracy, the selection method, repair method and adjustment method can be adopted during assembly. Dimensional accuracy mainly refers to the error degree of the assembly size of each part in the assembly, that is, in the assembly, pay attention to eliminate the cumulative error and avoid the adverse impact on the machine due to the increase of the cumulative error.

The seal in assembly is also very important. In the printing press, the seal is mainly used for air pump, gearbox and other parts. When the seal fails, air leakage and oil leakage will occur. Therefore, the sealing materials selected in the repair shall be appropriate, the assembly shall be reasonable, and the liquid sealant shall be selected for static sealing. According to the different nature of use, dry adhesion type, dry peelable type, non dry adhesive type and semi dry viscoelastic type shall be adopted respectively.

The preparation work before assembly must not be ignored. Its contents include inspection before assembly, cleaning during assembly and assembly of components. Finally, the test run after assembly has two functions: one is to check the quality of assembly; The second is to adjust the machinery.

c) Cleaning of mechanical parts

The cleaning of mechanical parts is an indispensable link in machine repair. The cleaning content is mainly oil and rust removal.

There are three methods of degreasing and cleaning: alkali solution degreasing, organic solvent degreasing and metal cleaning. The alkali solution mentioned here is mainly the alkali solution added with emulsifier, which has a good effect on cleaning mineral oil. The so-called organic solvent generally refers to gasoline and kerosene, which can dissolve all kinds of grease without damaging parts. In addition to gasoline and kerosene, alcohol, acetone, ether and other organic solvents can be selected for small parts and bonding parts with high precision. Metal cleaning agent is a new type of synthetic detergent, which has a strong decontamination ability due to its wetting, penetration, emulsification, dispersion and other functions due to the reduction of interfacial tension by base surfactant. The use of this cleaning agent is non-toxic, non-corrosive, non combustion, non explosion, pollution-free, has certain anti rust ability, low cost, and has been widely used.

Derusting and cleaning methods mainly include mechanical method and chemical method. Mechanical derusting is generally carried out with steel wire brush, scraper, abrasive cloth, etc. sometimes it can also be carried out with electric grinding wheel and steel wire wheel. Mechanical derusting is easy to leave scratches on the working surface, which is only suitable for the surface derusting of unimportant parts. Chemical derusting generally uses hydrochloric acid, sulfuric acid and phosphoric acid to remove alkaline metal oxides. The method is simple and the derusting effect is good. When using this method to remove rust, we should master the concentration ratio of solvent.


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