Across all manner of automation, robotics, and precision engineering projects, stepper motors play an imperative role. They are typically used to power applications that require precise and controlled movement and positioning, ranging from 3D printers and CNC machines to laser cutters, engraving machines, and computer peripherals.
By converting electrical pulses into precise movements, stepper motors allow for exceptional control without the need for feedback sensors.
Why Is Choosing the Most Suitable Stepper Motor So Important?
If you are to achieve success with your precision motion control project, you can’t depend on using just “any” stepper motor.
Selecting the right stepper motor will greatly help ensure your application runs smoothly, reliably, and efficiently. The stepper motor you use will need to meet the project’s requirements in terms of speed, accuracy, power, and physical constraints, such as size and mounting.
If, on the other hand, the stepper motor that you select isn’t a good match for your application’s requirements, performance issues such as missed steps, inadequate torque, and excessive wear are much likelier to occur.
It is therefore of huge importance to understand the key specifications of your application, so that you can match them to the best available stepper motor option.
5 Factors to Consider When Deciding on A Stepper Motor
To choose the stepper motor that best suits your intended task, you will need to first define your system’s essential requirements.
This will entail giving careful thought to factors such as:
- Torque
This is arguably the most critical element to think about when narrowing down the possibilities for a stepper motor. You will need enough torque to move your load and to overcome friction and inertia.
As part of this, it will be necessary to consider both the holding torque and the dynamic torque.
The former is the maximum rotational force that a stepper motor can exert when it is stationary to hold a load in place. Dynamic torque, meanwhile, is the rotational force a stepper motor can produce while it is moving; this will always be less than the holding torque.
- Step Angle/Resolution
This determines the number of steps a full rotation takes. For example, a common 1.8-degree motor has 200 steps per revolution.
A smaller angle translates to higher resolution and smoother movement. However, it does potentially lower torque.
- Speed
Stepper motors excel at low to medium speeds, of up to 1,000 revolutions per minute (RPM). However, their torque drops significantly as speed increases, due to inductance.
If, then, your application is a high-speed one, you will need your chosen stepper motor to have a lower inductance and a higher current rating. This will allow for current to build up rapidly in the coils before the next step pulse is applied, thereby maintaining sufficient torque.
- Inertia Matching
The inertia of the stepper motor’s rotor should ideally be close to that of the load. Making the right choice here will help ensure optimal performance and efficiency, with the motor able to properly control the load during acceleration and deceleration.
A significant inertia mismatch, on the other hand, could lead to the motor stalling, vibrating, or losing steps.
- Physical Size (NEMA Frame Size)
The National Electrical Manufacturers Association (NEMA) standard defines common mounting sizes, such as NEMA 17 or NEMA 23. You will need whatever stepper motor you choose to physically fit your assembly.
A Well-Chosen Digital Tool Can Help You Select the Right Stepper Motor
It can be a complex task to manually calculate the necessary torque, speed, and inertia, as you seek to determine the stepper motor that best suits your project.
Plus, dealing with all those physics principles and formulas with a “pen and paper” approach can be time-consuming and leave a high risk of human error creeping in.
Fortunately, it is a relatively quick and easy task to calculate requirements with the stepper motor performance calculator on the website of the electrical component supplier, RS.
Of course, various similar calculators can be found elsewhere online.
Whatever specific digital tool you do choose, they tend to operate on a broadly similar basis: you input such parameters as current, inductance, voltage, and steps per revolution, before reviewing the outputs the calculator produces. The latter tend to include maximum speed, minimum time per step, and maximum power.
Conclusion: Step Into Precision
By methodically assessing such aspects as torque, speed, and step angle in light of your project’s demands, you can help ensure you make the right choice of stepper motor.
That, in turn, will put you in a strong position to build a high-performing and reliable system that lives up to your expectations.
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