Introduction to stepper motors
What is a stepper motor?
A stepper motor is a type of DC motor designed to move in discrete steps, allowing precise control of angular position without the need for feedback systems in many cases. Unlike traditional brushed DC motors that rotate continuously, stepper motors divide a full rotation into a number of equal steps, enabling accurate open-loop positioning.
How do stepper motors work?
Stepper motors operate by energizing coils in a specific sequence, causing the rotor to move incrementally. Each pulse sent to the motor corresponds to a step, and by counting these pulses, the motor’s position can be controlled precisely. This makes stepper motors ideal for applications requiring repeatability and accuracy without complex feedback mechanisms.
White paper: Select your optimal motor technology for your application
In this white paper, we will look at the various advantages and disadvantages of different motor technologies.
The most well-known and the most obvious ones are the power requirements and the available voltage, i.e. will a standard power supply network with 400 VAC or 230 VAC or batteries be used.
However, by examining an application in more detail, it quickly becomes apparent that there are other parameters too. These include the torque required, how precisely the motion needs to be controlled, or if the motor is simply used to drive something.
Other questions that may be asked are: what is the inertia of the load, so that the motion can be controlled?
Read all about this in our white paper.
Advantages and limitations of stepper motors
Advantages
- High holding torque: Once positioned, stepper motors hold their position firmly without the need for continuous power increase.
- Open-Loop control: Many stepper motor systems operate without encoders or feedback devices, simplifying design and reducing cost.
- Safety: Stepper motors typically operate at extra low voltages (under 72V DC), making them safer for many industrial and hobbyist applications.
- Cost-effective: Compared to servo motors, stepper motors offer a budget-friendly solution for many positioning tasks.
- Good repeatability: They provide consistent step angles, ensuring reliable repeatability in applications like 3D printing and CNC machining.
- Stepper motor (open loop)
Typical applications of stepper motors
Stepper motors are widely used in applications where precise, repeatable positioning is required but the complexity and cost of closed-loop servo systems are not justified. Common uses include:
- 3D printers: For accurate layer-by-layer printing.
- Robotics: Simple robotic arms and pick-and-place machines.
- Vehicle interiors: Electric windows, ventilation systems, and seat adjustments.
- Printers and scanners: Precise paper feed and print head positioning.
- Hobbyist projects: DIY robotics and automation.
Limitations
- Speed limitations: Stepper motors generally have lower maximum speeds compared to brushless DC or servo motors.
- Torque drop at high speed: Torque tends to decrease as speed increases, limiting their use in high-speed applications.
- Open-loop risks: Without feedback, stepper motors can lose steps under heavy load or sudden changes, leading to positioning errors.
New developments in stepper motor technology
Closed-loop stepper motors and full servo stepper systems
New generations of stepper motors combine the simplicity of stepper motors with the performance of servo systems. Key features include:
- Single cable technology: Power and encoder signals combined in one cable, simplifying installation.
- Rotatable plug with encoder options: Single-turn or multi-turn encoders enable closed-loop control, allowing the motor to remember its position after power cycles without rehoming.
- IP65 rating: Suitable for harsh industrial environments.
- Holding brake option: For secure positioning when powered off.
- Vector control and field weakening: Advanced control techniques typically used in servo motors are applied to stepper motors, improving speed and torque performance.
- Integrated safety functions: Features like safe torque off and safe stop are built into the drive, enhancing machine safety.
This new class of stepper motors offers servo-like performance at a fraction of the cost, making them ideal for applications where traditional servo motors might be overkill.
Selecting the optimal motor for your application
Main factors
- Application type: Is it a simple driving application (e.g., conveyor) or a controlled motion task (e.g., pick-and-place)?
- Power and torque requirements: How much force and speed are needed?
- Precision and repeatability: What level of positioning accuracy is required?
- Environmental constraints: Space, cooling, and voltage availability.
- Total cost of ownership: Including maintenance, software, and expertise.
- Control complexity: What level of control system sophistication is feasible?
Stepper motor selection considerations
For applications requiring precise positioning with moderate speed and torque, stepper motors are often the most cost-effective choice. They excel in:
- Low to medium payloads.
- Applications with frequent start-stop cycles.
- Environments where safety and simplicity are priorities.
However, if your application demands high speed, dynamic response, or very high torque, brushless DC or synchronous servo motors might be more appropriate.
Tools to simplify motor selection
Accurate motor selection requires detailed application data and simulation. Advanced sizing tools like Festo’s Electric Motion Sizing Tool help by:
- Inputting parameters (payload, speed, acceleration, forces)
- Simulating motion profiles step-by-step
- Evaluating many motor and drive combinations
- Providing torque-speed curves, power consumption, thermal load reports
- Generating bills of materials and integration guides
These tools reduce design time, technical risks, and total cost of ownership.
Energy efficiency and environmental impact
Stepper motors, especially when combined with modern control techniques like vector control and field weakening, can be highly energy efficient. Tools are also available to estimate energy consumption and carbon footprint, helping companies make environmentally responsible choices.
Summary: Why choose a stepper motor?
Stepper motors continue to be a versatile, dependable, and economical choice for many motion control applications. Their ability to deliver precise positioning without the need for complex feedback systems makes them especially well-suited for:
- Small to medium payload applications
- Systems requiring strong holding torque
- Environments where safety and simplicity are priorities
- Projects with budget constraints that still demand accuracy
With ongoing innovations such as closed-loop stepper motors and integrated drive solutions, stepper technology is evolving to meet more demanding industrial requirements—offering servo-like performance with reduced complexity and cost.
For engineers and designers, utilizing advanced sizing tools and consulting with experts can help ensure the selection of the most suitable motor solution—whether that be a stepper motor, brushless DC motor, or servo motor—tailored to your unique application needs.