Stepper motors typically produce more noticeable noise at low speeds. This is primarily due to their operating principle. A stepper motor operates by dividing a full 360-degree rotation into hundreds of discrete steps (for example, a motor with a 1.8° step angle requires 200 steps per revolution). This type of motion is inherently discontinuous, and noise is mainly generated for the following two reasons:
The "stepping" nature of stepper motors: With each step, the driver sends current pulses to the motor's coils, causing the rotor to "jump" from one position to the next. This motion is inherently discrete, involving rapid acceleration and deceleration at each step. At low speeds, the time interval between steps is longer, allowing you to clearly hear the "clicking" or vibrating sound produced by each individual step. As these discrete step sounds accumulate, they form a noticeable low-frequency noise. At higher speeds, the stepping frequency increases to a point where individual step sounds merge into a continuous higher-pitched tone, which is perceived as less intrusive.
Resonance phenomenon: Stepper motors and the mechanical systems they drive have a natural resonant frequency (typically occurring at speeds in the range of tens to hundreds of RPM). When the motor operates near this resonant speed, even minor vibrations can be significantly amplified, leading to substantial noise and vibration. In severe cases, this can even cause the motor to lose steps. This is one of the primary sources of low-speed noise issues.
In summary, the noise produced by stepper motors at low speeds is an inherent characteristic. It is not a malfunction but rather a natural consequence of the motor's operating principle and control method.