What are the design principles of stepper motor?

1.Basic introduction of stepper motor

A stepper motor (also called a step motor) is a type of brushless DC electric motor that converts electrical pulse signals into precise, incremental rotational motion. Unlike conventional motors that rotate continuously when powered, a stepper motor moves in fixed, discrete angular steps—each electrical pulse drives the motor shaft to rotate by a specific angle (called the step angle, typically 1.8° for most hybrid stepper motors, meaning 200 steps per full 360° rotation).

2.Working steps of stepper motor

1.Pulse Reception: A controller (like a PLC or Arduino) sends an electrical pulse to a stepper driver.

2.Phase Energization: The driver interprets the pulse and sends current through specific electromagnetic coils (phases) in the stator.

3.Magnetic Alignment: Energizing these coils creates a magnetic field. The rotor (an internal magnet or iron core) aligns itself with this field by snapping to the nearest stator pole.

4.Sequential Switching: The driver then turns off the first phase and energizes the next adjacent phase. The rotor rotates to align with this new magnetic field, completing one "step".

5.Direction Control: The direction (clockwise or counter-clockwise) is determined by the specific order in which the phases are energized.         

3.Structure advantages of stepper motor

1.Brushless Structure for High Reliability & Long Lifespan:No brush wear or carbon dust accumulation, eliminating common failure points in brushed motors. This drastically reduces maintenance needs and extends service life (often >10,000 hours of continuous operation).

2.Open-Loop Positioning Capability (No Encoder Required):Each electrical pulse corresponds to a fixed mechanical step angle, so position can be calculated by counting pulses—no need for complex feedback loops.Simplifies system design, reduces component costs, and minimizes wiring complexity.

3.High Holding Torque at Zero Speed:Maintains position stability without continuous power adjustments.Eliminates the need for mechanical brakes in many applications , reducing system weight and cost.Holding torque is available immediately upon power-up, with no "settling time" for position locking.

4.Modular & Compact Design for Easy Integration:Compact footprint and high torque-to-volume ratio, making them suitable for space-constrained applications .Standardized mounting interfaces ensure compatibility with a wide range of gearboxes, lead screws, and coupling components.Easy to customize without major design modifications.

5.Low Sensitivity to Load Variations (Within Rated Torque):Position accuracy is not affected by small load fluctuations (e.g., minor changes in workpiece weight in a pick-and-place robot).Predictable performance across a wide range of speeds (from standstill to rated speed) without torque degradation.

6.Low Cost & Simple Drive Circuitry:Lower upfront cost compared to servo motors of similar torque ratings.Driven by basic stepper drivers (e.g., TB6600, TMC2209) that convert digital pulses to motor motion—no need for expensive servo drives with complex control algorithms.Compatible with common controllers (Arduino, PLC, CNC controllers) without specialized programming.

4.Design principles of stepper motor

1.Maximize magnetic flux utilization: The stator and rotor tooth profiles (e.g., trapezoidal, involute teeth) are designed to ensure that the magnetic flux generated by the stator windings fully couples with the rotor. This is achieved by minimizing air gap (typically 0.05–0.2 mm) between stator and rotor, which improves magnetic field intensity and torque density.

2.Balance inductance and resistance: Low inductance windings are suitable for high-speed applications (faster current rise/fall in windings reduces phase switching delay); high inductance windings are better for low-speed, high-torque scenarios. Winding wire gauge and number of turns are calculated based on the target voltage, current, and torque requirements.

3.Shaft design requirements: The output shaft is made of high-strength steel (e.g., 45# steel) and quenched to HRC 40–50 to improve wear resistance. Radial runout of the shaft is controlled to ≤ 0.02 mm to avoid vibration caused by misalignment with the load.

4.Structural rigidity design: The motor housing is made of die-cast aluminum (good thermal conductivity) or steel (high rigidity for large frame motors). The housing structure is optimized to withstand vibration and shock (meet 10g vibration and 50g shock resistance requirements for industrial applications).

5.Protection rating matching: For indoor, clean environments (e.g., 3D printers, office equipment), IP20 protection (preventing solid particles > 12 mm) is sufficient. For harsh environments (dust, humidity, oil mist), adopt IP54 or higher protection—sealed bearings, rubber gaskets, and waterproof winding insulation are used to prevent foreign matter and moisture from entering the motor interior.

6.Open-Loop/Closed-Loop Adaptation Principle:For open-loop applications, optimize holding torque and pull-out torque to meet load requirements without step loss. For closed-loop applications, reserve mounting positions for encoders on the motor rear end cover to facilitate the integration of position feedback components.

7.Microstepping compatibility: The stator winding design must match the driver’s sine/cosine current output to ensure smooth microstepping motion. High-precision applications require the motor to support up to 128× microstepping without obvious torque ripple.