In this article we are going to talk about stepper motor actuators including what they are, how they work and how they can benefit your product design. When selecting a linear actuator, you'll find that there are many options available and it can be a challenge to understand the advantages and drawbacks of each. Keep reading to learn more about stepper motor actuators, and when you should consider implementing them into your product design over a DC actuator.
What is a Stepper Motor Actuator?
Simply put, stepper motor actuators are actuators that are capable of high precision because the motor travels in discrete steps, rather than simply on or off. We released our first line of stepper actuators, the S20 series, in 2022. Since then, we have produced a second line of stepper motor actuators, the P8-ST series. Stepper actuators have several advantages over DC actuators including:
- Longevity. All things being equal, a stepper motor actuator will outlast a DC motor actuator. This is because stepper motors do not rely on brushes as DC motors do. Brushes are a wear item, and degrade over time.
- Precision. Stepper motors are capable of much higher precision than DC motors. This results in an actuator that can be more closely tuned to your exact requirements.
- Efficiency. Stepper motor actuators are more efficient by design and will consume less electricity over time. This will reduce your costs over the lifespan of the actuator.
Of course there are counterpoints to the above benefits. Every technology has drawbacks and stepper actuators are no exception. The primary drawbacks to stepper actuators are price and complexity. They are more expensive to purchase than DC actuators, and also require a stepper motor driver to operate increasing both the price and complexity of implementation.
How is a Stepper Actuator Motor Driven?
Stepper motor actuators are more complicated than standard DC actuators and require a stepper controller to drive the motor. The driver switches current through the motor's coils in sequence rotates the motor in discrete steps rather than continuous spin. This is why a stepper can not run off a simple voltage source the way a DC actuator can.
Why Use a Stepper Motor Actuator?
Generally, they are used in applications that require high precision. Precision here is the step size, the smallest linear distance the actuator can move in a single command. The S20 is direct drive and the step size is 0.01mm. The P8-ST line uses a gearbox with several gearing options; it is capable of roughly 0.006mm per step on a 49:1 gear ratio, or 0.0018mm at 165:1. A higher ratio shrinks the step size and adds holding force, but the actuator moves slower. A lower ratio moves faster but can not hold or push as much. If you require very precise movement and are willing to trade off some force or speed to get it, a stepper motor actuator may be the best choice for your application.
Improving Precision with Microstepping
The gear ratio is not the only way to change the step size. Actuonix stepper drivers also support microstepping, which splits each full step into smaller electrical increments by adjusting the current ratio between the two motor coils. Microstepping breaks each full step into smaller partial moves, so the motor glides instead of jumping from point to point.
We recommend microstepping when you want quieter, smoother operation, usually at lower speeds where you are not relying on full steps extra holding force.
How Does a Stepper Actuator Motor Hold Position?
A stepper actuator holds its position even with the power off, as long as the load remains under its backdrive force rating. On the S20, that rating is 40 N with the power off, rising to 60 N once power is back on. The P8-ST holds 9 N to 25 N with the power off, depending on gear ratio, and over 30 N to over 100 N once powered.
Actuonix Stepper Motors
Most stepper actuators in the market are high-cost, high-volume products built for large OEMs and out of reach for smaller product developers. Hence, we designed the S20 and P8-ST stepper lines to close this gap. The same precision, at a size and price accessible to individual builders and small teams. The S20 is based on our popular L12 actuator, with the DC motor and gearbox swapped for a NEMA 8 stepper. The P8-ST is the latest, ground-up design, smaller than our PQ12, and is our most compact actuator to date.
Frequently Asked Questions
Why does a stepper actuator sometimes miss steps under load?
It happens when the applied load gets too close to the actuator's maximum rated force. We recommend staying within 50% to 75% of that maximum, with the driver's step frequency ramped up gradually at higher speeds.
What driver does a stepper actuator need?
Actuonix steppers pair with standard 4-wire drivers such as the Tic T825, which supports USB, TTL serial, I²C, analog voltage, quadrature encoder, and RC inputs.
What operating temperature range can a stepper actuator handle?
The S20 and P8-ST are both rated for -10°C to +40°C. Running the actuator outside this range can affect its performance and shorten its lifespan.
Choose Actuonix Stepper Actuators
We take pride in the development of high-quality products that are cost-effective. We test every single actuator we sell before it leaves our facility and that helps us keep our quality and customer satisfaction high. If it doesn't meet our standards for quality, we don't ship it. It's that simple.
Our sales staff are available five days per week to assist you with your questions and help you find the right actuator for your next product or project.
