It is widely used in the connection of steel bar bending machine parts, such as the connection of couplings, gears, flywheels, sprockets and shafts, and the connection of bearing seats and copper sleeves. When the two steel bar bending machine parts connected to each other are matched, the assembly fit when the actual size of the contained part (shaft) is greater than the actual size of the contained part (hole) is called an interference fit, commonly known as "large shaft hole small".
In order to ensure the normal operation of the components of the steel bar bending machine after assembly, the following two basic requirements must be met:
(1) After assembly, the minimum actual surplus can ensure the correct position between the two steel bar bending machine parts, that is, it can be used in operation.
(2) After assembly, the maximum actual surplus guarantees that the parts of the steel bar bending machine will not be damaged, or even swells and can be assembled.
Features and assembly methods The advantage of interference fit is that it can withstand large torques and dynamic loads, and it is also suitable for alternating loads and impact loads. The shape and structure are simple, neutral and centering.
The disadvantage of the interference fit is that the assembly requirements of the steel bending hoop machine parts are relatively strict and the disassembly is relatively difficult; the machining accuracy of its two mating surfaces is required to be high.
Due to the different operating conditions and structural performance of the steel bar bending machine parts on site, different assembly methods are required. The main assembly methods are manual operation assembly, mechanical pressing assembly, temperature difference method (hot or cold assembly) assembly and composite method assembly. The application scope and application equipment characteristics of these assembly methods are compared.
Objective working conditions to be considered Objective working conditions refer to the actual interference and preparations to be checked before assembly.
(1) The actual interference is different from the measured interference when measuring the fit size. Before assembly, there is a certain amount of roughness on the surface of the bar bending machine parts, and the roughness will change after assembly, so the actual interference is often smaller than the measured interference. Therefore, in order to ensure a reasonable fit, the mating surfaces of important steel bar bending machine parts need to be polished, so that the amount of interference does not change much.
The smaller the diameter of the parts of the matching steel bar bending machine and the rougher the processing, the worse the tightness of the interference fit connection. In order to avoid too large or too small interference, it is advisable to adopt the grouping and matching method according to the size of the parts of the steel bar bending machine. For the parts of the steel bending hoop that bear a large axial force or torque, the interference fit generally cannot guarantee the reliability of the fit. For stability and safety, it is advisable to use additional fastening devices, such as additional flat key connections, additional stop screws, etc.
(2) Preparations to be checked before assembly.
1) The actual shape, size and tolerance of the containing and contained parts.
2) Taper, length and lead angle of the guide part.
3) The main role of temporary lifting rings during welding operations is to serve the assembly operations on the job site: one is to assume the lifting function, and the other is to serve as a handrail during assembly operations, that is, the assembly personnel apply some tools (such as crowbars) , Clamp) and temporary
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