1.Basic introduction of linear stepper motor
A geared stepper motor is a combination of a stepper motor and a gearbox, which allows it to reduce speed while increasing torque. This makes it ideal for applications requiring high precision, high torque at low speeds, and fine positioning, such as robotics, CNC machinery, and 3D printers. Each pulse sent to the motor results in a precise, incremental step of rotation, making them very accurate and controllable.
2.Working principle of geared stepper motor
1.Electrical pulses: A stepper motor driver sends a sequence of electrical pulses to the motor’s coils (stator).
2.Rotor movement: Each pulse energizes a specific set of coils, creating a magnetic field that pulls the rotor into a new position, moving it by a fixed “step angle” (e.g., (1.8^{\circ })).
3.Precise control: The speed and angle of the motor are precisely controlled by the frequency and number of pulses sent by the controller.
4.Gearbox reduction: The motor’s output shaft is connected to a gearbox, which contains a series of gears.
5.Torque increase and speed decrease: The gearbox uses a specific gear ratio to reduce the speed of rotation while significantly increasing the torque at the output shaft.
6.Final output: The gearbox’s output shaft provides a motion that is slower, more powerful, and smoother for the connected load, such as a robotic arm or conveyor belt.
3.Using advantages of geared stepper motor
1.Significantly Higher Torque Output:The gearbox multiplies the torque generated by the motor according to its gear ratio (N:1). For instance, a 50:1 gear ratio can boost the motor’s effective output torque by nearly 50 times (factoring in gear efficiency).This allows a relatively small motor to drive larger loads or overcome higher friction without requiring a larger, more expensive standard stepper motor.
2.Enhanced Resolution and Positioning Accuracy:A stepper motor has a fixed step angle (e.g., 1.8°). With a gearbox ratio of N:1, the output shaft’s effective step angle is reduced to 1/N of the original. For example, a 1.8° stepper motor with a 50:1 gearbox achieves a minimum step angle of 1.8°/50=0.036°, enabling ultra-fine motion control.The smaller effective step angle, combined with micro-stepping techniques, results in much smoother operation with less vibration at extremely low speeds.
3.Optimized Inertia Matching and Increased Rigidity:Inertia Ratio Reduction: Load inertia significantly impacts motor performance. When transmitted through the gearbox, the load inertia is reduced at the square of the gear ratio when reflected to the motor shaft. The mechanical rigidity provided by the gearbox makes the system less sensitive to variations in frictional load. It maintains stable positioning accuracy even in vertical drives or under changing friction conditions.
4.Resonance Avoidance and Smooth Operation: A Geared Stepper Motor operates the motor itself at a higher speed, while the output shaft runs slowly due to the gear reduction. This allows the motor body to bypass its inherent resonance frequency zone, resulting in smoother and quieter operation at the output.
5.Compactness and Cost-Effectiveness:The gearbox is usually integrated directly onto the motor’s rear, forming a compact unit. This saves installation space and simplifies mechanical design compared to using a separate high-torque motor or external gear reducer.
4.Selection requirments of geared stepper motor
1.Torque: Calculate the necessary holding and running torque, ensuring the final selection has a sufficient torque margin (at least 50%) to account for friction, wear, and resonance. High-torque applications are needed for heavy loads, while high-speed applications have lower torque requirements.
2.Speed: Determine the maximum speed and acceleration needed. This is critical for selecting a motor that can meet the dynamic demands without losing steps.
3.Accuracy and Positioning: Consider the required degree of accuracy, especially for applications like 3D printers or CNC machines, which may need high stop accuracy or closed-loop control.
4.Load Inertia: The motor’s torque-to-inertia ratio is important. A motor with a high ratio can accelerate and decelerate quickly. A larger load inertia will require a motor with a lower speed and higher torque.
5.Environmental Factors: Evaluate the operating environment for conditions such as temperature, humidity, and vibration, and select a motor with appropriate durability and special designs if necessary.
6.Torque and speed relationship: Remember that a motor’s output torque is inversely proportional to its speed. For high speed, choose a motor with low inductance; for low speed and high torque, choose a motor with high inductance and resistance.
7.Gearbox selection: Choose a gearbox that provides the correct gear ratio to achieve the required output speed and torque after the reduction.
8.Mounting and shaft: Ensure the physical dimensions of the motor and gearbox are compatible for mounting and that the motor shaft can properly connect to the gearbox.
9.Motor and drive compatibility: Ensure the motor is compatible with the chosen motor driver, considering voltage, current, and control method.
10.Control Method: Choose a suitable control method based on your application’s requirements, such as open-loop vs. closed-loop.
11.Safety and quality: Always add a safety factor for torque and consider a motor from a reputable manufacturer with a good reputation for quality and reliability.