What are the design parameters of a motor shaft?
Author:
Release Time:
2025-08-19
Motor The shaft is a cylindrical component that extends from the motor and its housing. It serves as the primary support and connector for the armature portion of the motor, and also functions as the output component for the power generated by the motor. The motor shaft is used to provide the motor’s speed and torque, making it one of the indispensable and critical components of the motor.
An improperly designed motor shaft may have an insufficient shaft radius, and stress concentrations caused by changes in the installation position could lead to catastrophic failure after a very short service life. Therefore, the shaft must meet certain technical requirements.
Strength and stiffness
When a motor is running, the types of mechanical forces and torques acting on the shaft vary depending on the motor’s model and the characteristics of its transmission mechanism. The primary forces include: the gravitational force of the rotor assembly itself, the unidirectional magnetic attraction caused by rotor eccentricity, the centrifugal force due to unbalanced weights, and the load torque applied to the shaft at its extended end by the driving mechanism. Therefore, the motor shaft must first possess sufficient strength to ensure that it does not undergo residual deformation or damage during operation and machining. At the same time, the shaft must have adequate rigidity so that its deflection remains within acceptable limits under operating conditions. Additionally, the shaft’s critical rotational speed should be carefully considered; there must be a sufficient margin between the shaft’s operating speed and its critical speed to prevent resonance. This is particularly important for motors operating at high speeds, where it may be necessary to perform a critical-speed analysis when required.
Surface roughness
Surface roughness is a crucial parameter for controlling surface quality. In the case of sliding bearings, excessively high surface roughness can directly disrupt the oil film on the contact surfaces, thereby increasing bearing wear. However, excessively low surface roughness can lead to molecular-level friction between the shaft and the bearing, which is equally detrimental.
Straightness (T.I.R.)
If the straightness of the entire shaft does not meet the requirements, it will cause imbalance in the shaft core section, leading to motor vibration. In the bearing section, this imbalance will result in an inclined contact surface between the shaft and the bearing, producing substandard motors with low speed and high current. In the shaft extension section, it will cause vibrations and noise in the connecting components. In short, the straightness of the shaft is a necessary condition for the normal operation of the motor; in special environments, the shaft material must also possess a certain degree of corrosion resistance.
During the manufacturing process of a shaft, it is essential to ensure that its straightness meets specific requirements. These requirements stem from two main aspects: first, the precision requirements of the driven components in the application; and second, the requirements for the motor’s own normal operation. The precision requirements for the driven components are determined by the user based on the accuracy of the application’s components, while the requirements for the motor’s own normal operation are derived from a comprehensive consideration of factors such as the clearance between the motor shaft and bearings, the motor’s vibration levels, its noise characteristics, and its performance specifications. 。
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