The purpose of disassembly is to facilitate inspection and repair. Since the structure of mechanical equipment has its own characteristics, the parts vary in weight, structure, accuracy and other aspects. If they are disassembled improperly, the parts will be damaged, resulting in unnecessary waste and even irreparability. In order to ensure the quality of repairs, careful planning must be made before disassembly, estimates of possible problems may be encountered, and disassembly must be carried out step by step.
1. Before disassembly, you must first understand the structure and working principle.
There are many types of machinery and equipment with different structures. The structural characteristics, working principles, performance, and assembly relationships of the parts to be dismantled should be clarified, so that they are well aware of it, and they cannot be dismantled carelessly or blindly. For unclear structures, relevant drawings and information should be consulted to clarify the assembly relationship and matching properties, especially the position and exit direction of the fasteners. Otherwise, it is necessary to analyze and judge while trying to dismantle, and sometimes it is necessary to design appropriate disassembly fixtures and tools.
2. Make preparations before disassembly
Preparation work includes: selection and cleaning of the disassembly site; cutting off power, wiping, and draining oil before disassembly; protecting electrical, easily oxidized, and easily corroded parts, etc.
3. Based on reality, try not to dismantle things that can’t be dismantled, and be sure to dismantle things that need to be dismantled.
In order to reduce the workload of disassembly and avoid damaging the matching properties, parts that can still ensure performance may not be disassembled, but necessary tests or diagnosis must be carried out to ensure that there are no hidden defects. If you are not sure about the internal technical status, you must disassemble and inspect it to ensure the quality of repairs.
4. Use correct disassembly methods to ensure the safety of people and mechanical equipment
The disassembly sequence is generally the opposite of the assembly sequence. First remove the external accessories, then disassemble the complete machine into components, and finally disassemble all parts into parts and place them together according to the components. Select appropriate disassembly tools and equipment according to the connection form and specifications of the components. For non-detachable connections or joints that reduce accuracy after disassembly, care must be taken to protect them during disassembly.
5. For shaft hole assemblies, the principle of using the same force for disassembly and assembly should be adhered to.
When disassembling the shaft hole assembly, you should generally insist on how much force you use to assemble and how much force you use to disassemble. If an abnormality occurs, find the cause to prevent the parts from being bruised, roughened, or even damaged during disassembly.
6. Disassembly should create conditions for assembly
If the technical information is incomplete, necessary records must be kept of the disassembly process so that reassembly can be carried out according to the principle of “disassemble first and then assemble” during installation. When disassembling precision or complex components, an assembly sketch should be drawn or marked during disassembly to avoid misassembly. After disassembling the parts, clean them thoroughly and apply oil to prevent rust to protect the processing surface to avoid loss and damage. Slender parts must be hung, and care must be taken to prevent bending and deformation. Precision parts should be stored separately to avoid damage. Be careful not to lose small parts. Parts that are not interchangeable must be stored in groups or marked.
7. Basic technical requirements for disassembly
(1) Before disassembly, the structure of the equipment and its components must be understood clearly so that it can be disassembled and repaired before assembly;
(2) Generally, disassembly should be carried out in the reverse order of assembly;
(3) When disassembling, the loosening direction, thickness end, and large and small ends of the parts must be clearly identified;
(4) The disassembled parts must be placed in an orderly and regular manner to avoid clutter and accumulation;
(5) The disassembled parts should be connected together as much as possible according to the original structure (such as screws, nuts, washers, pins, etc.). When necessary, some parts need to be marked (with steel stamped letters) on the table to avoid errors during assembly and affect their original matching properties;
(6) Parts that do not need to be disassembled or that may reduce the quality of the connection after disassembly should not be disassembled as much as possible, such as seals, riveting, etc.; when some equipment or parts are marked as not allowed to be disassembled, disassembly should be strictly prohibited;
(7) Slender parts should be hung in cubes after removal to avoid deformation;
(8) For matching parts, if one of them must be dismantled, the parts with higher value and difficulty in manufacturing should be preserved.
1. Disassembly method
Use the impact energy generated when a hammer or other heavy object hits or hits the part to remove the part.
(1) Advantages: The tool is simple, easy to operate, and does not require special tools and equipment.
(2) Disadvantages: If the disassembly method is incorrect, the parts may be easily damaged or destroyed.
(3) Application: It has a wide range of applications, and almost all general parts can be disassembled by knocking.
(4) Things to note:
1) According to the size, weight and firmness of the disassembly parts, choose a hammer of appropriate size and pay attention to the intensity of force;
2) Protective measures should be taken to remove the dismounted parts. Usually, copper rods, bakelite rods, wooden hammers and wooden boards are used to protect the removed shaft sleeves, sleeve rims, etc.;
3) Test the disassembled parts to check the firmness of the parts and test the direction of the parts. If you hear a solid sound, stop disassembly immediately and check to see if it is caused by the opposite direction or missing fasteners. When parts are found to be severely corroded, add some kerosene for lubrication;
4) Pay attention to safety.
2. Pulling method
Use precisionThe drawing method should be used for parts that are too high to be struck or cannot be disassembled by disassembly. It is disassembled using a special puller.
(1) Advantages: disassembly parts are not affected by impact, disassembly is relatively safe, and parts are not easily damaged.
(2) Disadvantages: Special pullers need to be made.
(3) Application occasions: Suitable for parts with high precision that are not allowed to be struck and parts that cannot be struck.
(4) Precautions: During the pulling and unloading, most of the shafts and sleeves are used.
1) Carefully check whether the positioning fasteners on the shaft and sleeve are completely disassembled;
2) Check the removal direction of the shaft. Generally, it is always the big end of the shaft, the empty big end and the blocked end of the spline shaft.
3) Prevent parts burrs and dirt from falling into the mating holes and blocking the parts.
4) Sleeves that do not need to be replaced should generally not be disassembled to avoid deformation of the disassembled parts. Replacement sleeves cannot be punched at will, because roughening the ends will damage the surface of the mating hole.
3. Top pressure method
Use tools and equipment such as screw C-type chucks, mechanical presses, hydraulic presses or jacks for disassembly. Suitable for interference fitting parts with simple shapes. In machine repair and disassembly, many parts cannot be disassembled on the press and have relatively few applications.
4. Temperature difference method
This method can be used when the disassembly size is large, the fitting interference is large, or it cannot be disassembled by knocking off, pressing, etc., or to make fitting parts with large interference and high precision easy to disassemble. For example, when disassembling bearings and shafts, it is often necessary to heat the inner ring of the bearing with hot oil before disassembly. Before heating, use asbestos to isolate the part of the shaft close to the bearing to prevent the shaft from expanding due to heat. Use the claws of the puller to hook the inner ring, apply a certain tension to the bearing, and then quickly remove the heated 100°C bearing. Hot oil is poured on the bearing ring. After the inner ring of the bearing is heated and expands, the bearing can be pulled out with a tensioner.
5. Destruction method
If it is necessary to dismantle fixed joints such as welding and riveting, or if the shaft and sleeve bite each other, or if the secondary parts are destroyed to save the main parts, destructive disassembly can be carried out by turning, sawing, chiseling, drilling, cutting and other methods.
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