https://www.putianvibrator.com/product/ac-standard-vibration-motor/
An AC vibration motor intentionally produces centrifugal force through eccentric weights, so balance is a fundamental part of its design. The position and configuration of these components influence the vibration generated by the motor.

During production, manufacturers need to maintain control over shaft assembly, rotor balance, eccentric components, and related tolerances. This is not simply a final inspection issue. The manufacturing process itself needs to be organized so that the finished motor follows the intended mechanical characteristics.