Compared to other components, the rotor of an electric motor has more machining processes, such as the fabrication of the rotor core, the machining of the shaft, the assembly of the rotor core and the shaft, as well as the turning of the rotor surface and the dynamic balancing of the rotor.
In all these machining processes, a reference point is involved. Generally, the center holes at both ends of the shaft are used as the machining reference for shaft turning, grinding, and rotor surface turning. This ensures the coaxiality of the rotor surface with each cylindrical surface of the shaft. The shaft keyway machining and rotor dynamic balancing processes use the bearing position as the machining reference, which ensures the consistency of the reference between the machining process and the motor assembly state.
In special circumstances, especially for large motors, due to the relatively large weight of the rotor and the influence of other factors such as equipment, the machining datum may need to be adjusted. Therefore, the control of the form and position tolerances of each component during the machining process is particularly important. The protection of the datum position and the corresponding position of the equipment that mates with the datum position during the machining process is also particularly important.
Motor Knowledge Extension 1: Selection Characteristics
● The design datum reflects the design requirements of the part and is generally used as the main datum. Important dimensions are usually marked by the design datum.
●The process datum reflects the requirements for part machining and measurement, and must be taken into account.
● When selecting dimensional references, it is best to unify the design references and the manufacturing references (references should coincide).
The selection of dimensional datum is a very important issue. The correctness of the datum directly affects the rationality of the entire part's dimensional annotation. An inappropriate dimensional datum will prevent the part's design requirements from being met and will create difficulties in machining and measurement.
● The radial dimension of the datum coincident shaft is based on the axis, and the diameter of each shaft segment is marked along the axis. Important end faces, contact surfaces (such as shaft shoulders), or important machined surfaces are used as datums in the length direction.
● For disc-type parts, the axis of the shaft hole is usually used as the radial dimension reference, and the important end face (the surface with the highest machining accuracy and the contact surface with other parts, etc.) is used as the length dimension reference.
●The main references for fork-type parts in the length, width, and height directions are generally the axis of the hole, the plane of symmetry, and the relatively large machined surface.
●The main references for the length, width, and height of box-type parts are generally the axis, the plane of symmetry, and the larger machining plane.
2. Application of benchmarks in engineering
A datum is a widely used concept in mechanical manufacturing. From marking part dimensions during design, positioning workpieces during manufacturing, measuring dimensions during verification, to determining the assembly positions of components during assembly, the concept of a datum is applied to all aspects of mechanical product manufacturing. A datum is a point, line, or surface used to determine the geometric relationships on a production object.
Datums are divided into design datums and process datums. Process datums are further divided into process datums, positioning datums, measurement datums, and assembly datums.
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