Newspaper printing equipment - maintenance (two)
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2 mechanical parts maintenance knowledge
Mechanical faults can be generally classified into accidental faults and natural faults. Accidental faults are mostly caused by improper maintenance or adjustment, violation of operating procedures, etc., and should be avoided as much as possible. Natural failures, although difficult to avoid, can increase the effective working time of the machine by increasing the level of use and maintenance.
There are three main failure modes of mechanical parts: fracture, deformation and surface failure. The following describes the wear, deformation, cleaning method and disassembly assembly of printing machinery parts.
a) Wear of printed mechanical parts
In the course of working, if the surface of the relatively moving part has a size, shape and surface quality change, it is called wear.
The main causes of part wear are friction and molecular attraction. Wear can be divided into abrasive wear, mechanical friction wear and adhesive wear. The reasons that affect the wear of mechanical parts are: speed, pressure, lubrication, temperature, materials, processing and coordination.
b) deformation of printing machinery parts
In the maintenance process, wear is one of the main factors of mechanical damage, but the micro-deformation of the parts is easily neglected. After assembling the repaired wear parts, the technical performance of the machine is not up to standard. This is related to metal deformation. In actual production, the deformation of the basic parts is particularly important, because if the basic parts are deformed, it will affect the interrelationship of all the parts assembled on the basic parts and the mechanical properties of the mechanism. Therefore, in the repair process of parts, it is necessary to check the wear of the mating surface, and also check the mutual positional accuracy of the parts (especially the basic parts). For the mechanical overhaul of the first overhaul, be sure to pay attention to the internal stress. Is there any deformation after 12 to 20 months? For hot-worked parts, there should be appropriate measures to remove internal stresses.
3 Printing machinery disassembly and assembly
Mechanical repair personnel must face disassembly and assembly problems when repairing printing machinery, especially assembly, which will directly affect the mechanical properties, and the assembly quality is not high, which will cause serious mechanical wear.
a) Mechanical disassembly
Since there are many types of printing machines and the shapes of the parts are different, it is difficult to describe them one by one. Here are the general disassembly principles.
First of all, you must understand the structure, function and principle of the machine before disassembly, first consult the relevant technical information and instructions. From the actual situation, determine the disassembly part, the part that can be removed should not be dismantled as much as possible, but for the part that is not disassembled, it must be checked overall to ensure the quality.
Secondly, in the disassembly process, it should be disassembled from the table and the inside, first remove the external accessories, oil pipes, etc., and then disassemble according to the order of the parts after the first assembly. For the more important parts, the marking should be marked when disassembling. List the numbers and avoid stacking them in a mess. It is also important to use the tool properly during disassembly, and the tool must be compatible with the part being disassembled. If the threaded connecting piece is removed, the appropriate wrench should be used. Special tools should be used to disassemble the static fittings, and the hammers and chaos should not be used.
In addition, the disassembly should create conditions for assembly. For non-interchangeable parts, they should also be marked or placed in pairs for disassembly in order to ensure assembly accuracy and reduce unnecessary wear.
b) mechanical assembly
The assembly accuracy and dimensional accuracy must be ensured during assembly. In order to ensure the matching accuracy, the matching method, the repair method and the adjustment method can be used in the assembly. Dimensional accuracy mainly refers to the degree of error in the assembly dimensions of various parts in the assembly. That is to say, in the assembly, attention should be paid to eliminating accumulated errors and avoiding adverse effects on the machine due to the increase of cumulative error.
The seal in the assembly is also very important. In the printing machine, the seal is mainly used for the parts such as the air pump and the gear box. When the seal fails, air leakage and oil leakage may occur. Therefore, the sealing material selected in the repair should be appropriate, the assembly should be reasonable, and the liquid sealant should be used for static sealing. According to the nature of use, dry adhesion type, dry peelable type and non-dry type are used respectively. And semi-dry viscoelastic type.
Preparations prior to assembly must not be overlooked, including pre-assembly inspections, assembly cleaning, and assembly of components. Finally, the test run after assembly, its role is two, one is to check the quality of the assembly; the second is to adjust the machine.
c) Cleaning of mechanical parts
The cleaning of mechanical parts is an indispensable part of the machine repair. The cleaning content is mainly degreasing and derusting.
The methods of degreasing cleaning mainly include three methods: alkali solution degreasing method, organic solvent degreasing method and metal cleaning and degreasing method. The alkali solution mentioned here is mainly an alkali solution to which an emulsifier is added, which has a good effect for cleaning mineral oil. The so-called organic solvent generally refers to gasoline, kerosene, etc., which can dissolve various oils and fats without damaging parts. In addition to gasoline and kerosene, for small parts and bonding parts with high precision, alcohol, acetone and ether can be used respectively. And other organic solvents. Metal cleaning is a new type of synthetic detergent. It has a strong decontamination ability due to the reduction of interfacial tension caused by the surface surfactant to produce wetting, penetrating, emulsifying and dispersing. The cleaning agent is non-toxic, non-corrosive, non-flammable, non-explosive, pollution-free, has certain anti-rust ability, and has low cost, and is widely used.
The rust cleaning method mainly includes mechanical methods and chemical methods. Mechanical descaling is generally carried out with wire brushes, scrapers, abrasive cloth, etc., and sometimes with electric grinding wheels and wire wheels. Mechanical rust removal tends to leave scratches on the work surface and should only be used for surface rust removal of unimportant parts. Chemical rust removal generally uses hydrochloric acid, sulfuric acid and phosphoric acid to remove alkaline metal oxides. The method is simple and the rust removal effect is good. When using this method to remove rust, it is necessary to master the concentration ratio of the solvent.