The purpose of disassembly is to facilitate maintenance. As the structure of mechanical equipment has its own characteristics, there are differences in the weight, structure, precision and other aspects of parts. If the parts are disassembled improperly, they will be damaged, causing unnecessary waste, or even unable to repair. In order to ensure the quality of maintenance, it is necessary to plan carefully before disassembly, estimate the possible problems, and disassemble step by step.
01 The structure and working principle must be made clear before disassembly
There are many kinds of mechanical equipment with different structures. The structural characteristics, working principle, performance and assembly relationship of the disassembled parts should be made clear, so as to have a clear idea, and the careless and blind disassembly is not allowed. For the unclear structure, it is necessary to refer to the relevant drawings and materials to make clear the assembly relationship and matching nature, especially the fastener position and exit direction.
Otherwise, it is necessary to analyze and judge while trying to dismantle, and sometimes it is necessary to design appropriate dismantling fixtures and tools.
02 Make preparations before disassembly
Preparation work includes: selection and cleaning of disassembly site; power off, wiping and oil discharging before disassembly; protection of electrical, easily oxidized and rusty parts, etc.
03 It should not be disassembled as far as practical needs are concerned
In order to reduce the disassembly workload and avoid damaging the matching property, the parts that can still ensure the service performance may not be disassembled, but necessary tests or diagnosis shall be carried out to ensure that there are no hidden defects. If you are not sure how the internal technical status is, you must check it before disassembly to ensure the maintenance quality.
04 Use correct disassembly method to ensure personal and mechanical equipment safety
Generally, the disassembly sequence is opposite to the assembly sequence. Firstly, the external accessories are disassembled, then the whole machine is disassembled into parts, and finally all the parts are disassembled and put together according to the parts. According to the connection form and size of parts, appropriate disassembly tools and equipment are selected. It is necessary to pay attention to the protection of the non detachable connection or the assembly parts with reduced precision after disassembly.
05 For shaft hole assembly, the principle of the same force used for disassembly and assembly shall be adhered to
When disassembling the assembly parts of the shaft hole, it is usually necessary to insist on how much force to assemble and how much force to disassemble. In case of any abnormality, find out the cause to prevent the parts from being damaged, roughened or even damaged during disassembly.
06 Disassembly should create conditions for assembly
If the technical data are not complete, it is necessary to record the disassembly process, so as to reassemble according to the principle of “disassembly before assembly”. When disassembling precise or complex components, assembly sketch shall be drawn or marks shall be made during disassembly to avoid wrong assembly.
After the parts are disassembled, they should be cleaned thoroughly, oiled to prevent rust, protect the processing surface and avoid loss and damage. Slender parts should be suspended to prevent bending deformation. Store precision parts separately to avoid damage. Pay attention to prevent the loss of small parts. The parts that cannot be exchanged shall be stored or marked in groups.
07 Basic technical requirements for disassembly
(1) Before disassembly, the structure of equipment and its components must be clearly understood, so that they can be assembled after disassembly and repair;
(2) Generally, disassembly should be carried out in the reverse order of assembly;
(3) During disassembly, the direction, thickness end and size of the parts must be clearly identified;
(4) The removed parts must be placed orderly and regularly to avoid disorder and accumulation;
(5) The removed parts should be connected together as much as possible according to the original structure (such as screw, nut, washer, pin, etc.). If necessary, some parts need to be marked on the table (with steel seal letters), so as not to affect their original matching properties due to assembly errors;
(6) Parts that may not be disassembled or may reduce the quality of connection after disassembly, such as seals, rivets, etc., shall not be disassembled as far as possible; when some equipment or parts are marked not to be disassembled, it shall be strictly prohibited to disassemble;
(7) For slender parts, hang the cube after removal to avoid deformation;
(8) For the matching parts, when one of them must be removed, the parts with higher value and more difficult to manufacture should be preserved Blow off method Use the impact energy produced by hammers or other heavy objects when striking or striking the parts to remove the parts.
(1) Advantages: simple tools, easy operation, no need for special tools and equipment.
(2) Disadvantages: if the method is not right, the parts are easy to be damaged or damaged.
(3) Application: it has a wide range of applications, and almost all parts can be disassembled by knocking.
(4) Note:
1) According to the size and weight of the disassembled parts and the firmness of the combination, choose a hammer with appropriate size and pay attention to the strength;
2) Protective measures should be taken for the knocked down parts, such as copper rod, bakelite rod, wood hammer striking wood plate, etc. to protect the axle sleeve, sleeve striking wheel rim, etc;
3) The purpose of the test is to investigate the bonding strength of the parts and explore the direction of the parts. If you hear a solid sound, stop knocking immediately and check to see if it is caused by the opposite direction or the missing fastener. If the parts are seriously corroded, some kerosene can be added for lubrication;
4) Pay attention to safety.
Drawing method
The drawing method shall be used for the parts with high precision, which are not allowed to be knocked or can not be disassembled by the stripping method. It is disassembled by special puller.
(1) Advantages: the disassembled parts are not impacted, the disassembly is safe, and the parts are not easy to be damaged
(2) Disadvantages: special puller needs to be made.
(3) Application: it is suitable for parts with high precision and without knocking.
(4) Note: in the process of pulling and unloading, most of them are shafts and sleeves
1) Carefully check whether the positioning fasteners on the shaft and sleeve are completely disassembled;
2) Find out the removal direction of the shaft. Generally, it is always the big end of the shaft, the empty big end and the impassable end of the spline shaft.
3) Prevent the burr and dirt from falling into the fitting hole and blocking the parts.
4) The sleeve that does not need to be replaced should not be disassembled, which can avoid the deformation of the disassembled parts. The replaced sleeve cannot be punched at will, because the surface of the matching hole will be damaged after the end is roughened.
Top pressure method
Use screw C-type chuck, mechanical press, hydraulic press or Jack and other tools and equipment for disassembly. It is suitable for interference fit parts with simple shape. In machine repair disassembly, many parts can not be disassembled on the press, the application is relatively less.
Temperature difference method
This method can be used when the disassembly size is large, the fit interference is large, or it can not be disassembled by means of knocking and jacking, or to make the fit parts with large interference and high precision easy to disassemble. For example, when disassembling the bearing and shaft, it is often necessary to heat the inner ring of the bearing with hot oil. Before heating, isolate the shaft close to the bearing with asbestos to prevent the shaft from thermal expansion. Hook the inner ring with the claw of the puller to apply a certain tension to the bearing, and then quickly pour the heated hot oil of about 100 ° C on the bearing ring. After the inner ring of the bearing is heated and expanded, the bearing can be pulled out with a puller.
Law of sabotage
If it is necessary to dismantle the fixed connecting parts such as welding and riveting, or the shaft and sleeve bite each other, or the auxiliary parts are damaged in order to save the main parts, the destructive disassembly can be carried out by turning, sawing, chiseling, drilling, cutting and other methods.