When it comes to the creation of machines that require accurate positioning – such as 3D printers, CNC (computer numerical control) routers, and robotic arms – stepper motors play a critical role.
After all, engineers, makers, and manufacturers have long appreciated stepper motors because of the remarkable precision they can provide.
However, it is also true that the market presents a broad range of stepper motor models, sizes, and specifications. So, it might be far from obvious which option would be the best fit for your project.
Getting your decision wrong could risk such consequences as inadequate torque, overheating, or the complete failure of the system. That is why, below, we have outlined the key things you will need to think about when selecting a stepper motor for your project.
A Brief Introduction to Stepper Motors
The term “stepper motor” refers to a brushless, synchronous electric motor, the operation of which converts digital pulses into mechanical shaft rotation.
These direct current (DC) motors differ from many other standard types of electric motors, in that they don’t simply rotate continuously for an arbitrary number of spins until the shutoff of the DC voltage passing to the motor.
Indeed, stepper motors divide a complete rotation into a series of precise and equal steps. As these motors make incremental steps rather than continuous ones, they operate with remarkable accuracy, without feedback systems such as encoders being needed.
What Factors Need to Be Considered for Stepper Motor Selection?
So, you have made the decision that a stepper motor would be the right fit for your project. You might have arrived at this stance on the grounds that precision and repeatability are more important for your intended application than high speed, as can indeed be the case for some robotics applications, medical devices, and CNC machines.
Whatever the exact situation, you will next need to start whittling down your options. That will mean giving careful thought to such factors as:
- The Torque Requirements
When you are looking to select the right stepper motor for your application, you will need to bear in mind its holding torque. This is defined as the maximum amount of torque a given motor can produce to hold a position when stationary.
However, the amount of torque you will require will depend on the application; in cases of larger and heavier loads, higher torque will be needed.
By seeking out a reputable stepper motor torque calculator online, you will soon be able to confidently determine how much torque you will need for your stepper motor, based on the specific application and load requirements.
- The Step Angle and Resolution
The term “step angle” refers to the angular displacement of a motor’s shaft for each step it takes. The “resolution”, meanwhile, is the number of steps a motor can take to complete a single, full revolution of its shaft.
Stepper motors with smaller step angles tend to have lower speeds, due to the need for more steps to be taken to complete a full rotation. They are associated with higher resolution, but more precise positioning.
If, then, you are on the lookout for a stepper motor that suits a high-precision task such as 3D printing, you are likely to be best-served by a motor with a smaller step angle.
- The Motor Size (Frame Size)
The frame sizes of stepper motors are frequently indicated by NEMA sizes (those letters standing for “National Electrical Manufacturers Association”, a trade association in the United States that sets standards for electrical equipment such as stepper motors).
You will need to know about the different frame sizes that exist when selecting a stepper motor, give the major impact this will have on its performance and suitability for a given application.
In summary, opting for a larger frame size for your stepper motor will mean you can probably expect impressive torque, but it will take up more space, and power consumption may be higher.
Smaller motors, meanwhile, suit compact spaces and applications requiring quick and short movements. They might not, though, have sufficient torque to handle heavier loads or extended periods of high-speed operation.
How Can You Be Sure of Choosing the Right Stepper Motor?
Ultimately, your decision-making process on a stepper motor will need to involve careful consideration of such factors as torque, speed, and resolution, in the context of the requirements of your intended application.