How to Reduce Motor Vibration from the Manufacturing Stage

How to Reduce Electric Motor Vibration During Manufacturing

Motor vibration can result from a variety of causes, including rotor imbalance, improper component fit, electromagnetic forces, and incorrect installation. Addressing these factors early—especially during manufacturing—is essential for ensuring performance and reliability.

Rotor imbalance, in particular, is strongly related to rotor speed and mass. For low-speed, multi-pole motors, many manufacturers may skip dynamic balancing to save time and cost. However, this decision must be weighed against the specific motor type, usage conditions, and required precision.

To minimize inherent rotor imbalance, manufacturers should focus on controlling face and radial runout of key components such as the rotor core, end rings, and cooling fans. Casting defects on aluminum rotors and imbalances in balance columns should be corrected. In some cases, even non-mating surfaces require precise machining.

Dynamic balancing is critical for high-speed motors, and the balancing equipment must match the motor’s rated speed. For rotors with a length-to-diameter ratio over 1/6, dynamic balancing is highly recommended. For flatter rotors (ratio under 1/3), static balancing may be sufficient. If fans cannot be balanced together with the rotor, they must be statically balanced on their own.

For general-purpose motors, the permissible unit imbalance $e$ should comply with standard guidelines, while motors for precision applications require stricter control. The residual imbalance G can be calculated by the formula:

Fan rotors with higher diameters and speeds require even tighter balance tolerances. Suitable dynamic and static balancing machines should be selected accordingly. A half-key should be placed in the keyway during balancing, and any added weights must be firmly secured and rechecked.

For motors using ball bearings on both ends, adding a wave spring or preload device at the shaft end can reduce axial vibration and noise by minimizing axial play.

Improving motor vibration characteristics also requires:

• Enhancing rotor dynamic balance precision

• Aligning stator and rotor core ends accurately

• Minimizing mechanical and electromagnetic axial forces

• Ensuring high machining accuracy for air gap and bearing fit

• Strengthening the rigidity of the housing and end covers

• Using high-precision, stable bearings

• Ensuring symmetrical component layout

• Machining non-functional surfaces of cast or welded parts

• Baking wound rotors vertically to ensure uniform resin curing

By optimizing these practices, manufacturers can effectively reduce vibration at its source—creating more reliable and longer-lasting motors.