In modern industrial production, as the power core, the stability of the motor shaft is crucial. Once the shaft deforms or breaks, it not only causes equipment shutdown, but may also lead to serious production accidents and economic losses. Thoroughly exploring the causes of such problems with the shaft is of great significance for preventing malfunctions and ensuring the safe operation of equipment.

1、Material factors

① Defects in the material itself

The shaft is usually made of high-quality steel, such as 45 steel, alloy steel, etc. But if there are problems such as high impurity content, segregation, and porosity during the steel smelting process, it will significantly reduce the strength and toughness of the material. For example, excessive impurities such as sulfur and phosphorus in steel can cause the material to become brittle. When subjected to external forces, cracks are more likely to occur and propagate, ultimately leading to fracture.

② Improper material selection

Different working environments and load conditions have varying requirements for the performance of shaft materials. In high-temperature environments, if a shaft made of ordinary carbon steel is used, the mechanical properties of the steel will decrease with increasing temperature, resulting in insufficient strength and easy deformation. In high-speed and high torque working conditions, if materials with inadequate strength and toughness are selected, the shaft will also be difficult to withstand the load, increasing the risk of deformation and fracture.

2、Design factors

① Unreasonable structural design

The structural shape and size of the shaft directly affect its force distribution and load-bearing capacity. If the diameter of the shaft is designed too small to meet the actual load requirements, deformation or even fracture may occur due to stress concentration. In addition, unreasonable design of transition parts such as rounded corners and steps on the shaft can also cause stress concentration. For example, if the fillet radius is too small, the stress in this area will be much higher than in other parts when subjected to alternating loads, becoming the starting point for crack initiation.

② Calculation errors in strength and stiffness

In the design phase, it is necessary to perform strength and stiffness calculations on the shaft to ensure its stable operation during operation. If there are errors in estimating parameters such as load size and direction during the calculation process, or if the selected calculation formula and safety factor are inappropriate, it will result in insufficient actual bearing capacity of the designed shaft. For example, when calculating the torque acting on the motor shaft, the impact load during the starting and braking processes was not taken into account, resulting in deformation of the shaft due to overload during actual operation.

3、Manufacturing and processing factors

① Processing accuracy does not meet the standard

The machining accuracy of the shaft has a significant impact on its performance. If the coaxiality error of the shaft is too large, an unbalanced force will be generated during the rotation process, leading to intensified shaft vibration and deformation after long-term operation. The surface roughness of the shaft neck does not meet the requirements, which will increase the friction between the bearing and accelerate wear, thereby affecting the stability of the shaft. In addition, dimensional errors and positional deviations in keyway machining can also damage the structural strength of the shaft and reduce its load-bearing capacity.

② Improper heat treatment process

Heat treatment is an important process for improving the performance of shaft materials. Excessive quenching temperature or holding time can cause coarse grains in steel and reduce its toughness; If the quenching cooling speed is too fast, it is easy to produce quenching cracks. Insufficient tempering results in ineffective elimination of residual stresses within the material. In subsequent use, these residual stresses may overlap with working stresses, leading to deformation or cracking of the shaft.

4、Installation and maintenance factors

① Improper installation

During the installation of the motor, if the coaxiality between the shaft and other components (such as couplings, pulleys, etc.) is not calibrated, it will cause additional bending stress on the shaft during operation, resulting in deformation. Meanwhile, assembling the coupling too tightly or too loosely can also cause problems. Being too tight can cause additional stress on the shaft, while being too loose can easily lead to loose connections, causing vibration and accelerating damage to the shaft.

② Lack of maintenance and upkeep

Long term operation of motor shafts requires regular lubrication, inspection, and maintenance. If the lubrication is insufficient, the friction between the shaft and the bearing increases, generating a large amount of heat, resulting in a decrease in material properties, and also exacerbating wear, deteriorating the operating condition of the shaft. In addition, if the dynamic balance detection and correction of the shaft are not carried out in a timely manner, the amount of imbalance will accumulate with the increase of running time, causing the shaft vibration to intensify, ultimately leading to deformation or fracture.

5、Operating condition factors

① Overload operation

In actual operation of the motor, if the load exceeds the rated value, the torque and bending moment borne by the shaft will also increase accordingly. Long term overload operation can cause fatigue of the shaft material, resulting in micro cracks inside, which gradually propagate and ultimately lead to fracture. For example, in lifting equipment, if an overloaded heavy object is lifted, the motor shaft will bear excessive torque, increasing the risk of damage.

② Frequent start stop and impact loads

Frequent starting and stopping of the motor can cause significant impact torque on the shaft, which is much higher than the load during normal operation. In addition, during the work process, if the equipment suddenly gets stuck or materials become blocked, it will also generate instantaneous impact loads. Repeated impact can cause fatigue cracks on the surface or inside of the shaft, accelerating the damage of the shaft.

③ Vibration and Resonance

During the operation of the motor, if there are problems such as unstable foundation, uneven installation, and rotor imbalance, it can cause shaft vibration. When the vibration frequency is close to the natural frequency of the shaft, resonance occurs. The huge amplitude and stress generated by resonance can cause the shaft to rapidly deform or even break. For example, during the operation of a fan motor, if the uneven accumulation of dust on the impeller leads to rotor imbalance, it may cause resonance and damage the shaft.

The deformation or fracture of the motor shaft is the result of multiple factors working together. From material selection, design and manufacturing, to installation, maintenance, and operating conditions, every step needs to be strictly controlled. By deeply understanding these reasons and taking targeted preventive measures, the probability of shaft failure can be effectively reduced, ensuring the stable and safe operation of the motor and the entire equipment system.

Hengda Electric has always been dedicated to the research and development, production, and service of various types of motors. With advanced technology and equipment, lean manufacturing processes, reliable product quality, and satisfactory after-sales service, the company provides customers with the most suitable motor professional solutions and creates greater social value.