Electromechanical linear actuators provide precise linear motion by transforming rotary motion from an electric motor into linear motion. These actuators are used in many applications, such as biomedical devices, aerospace systems, automotive manufacturing, industrial robotics and computer disk drives. There are many different variations of electromechanical linear actuation systems, with the most popular ones incorporating either a DC servomotor or a stepper motor. These devices have certain advantages and disadvantages depending on the applications in which they are used. The primary factors in choosing between the two usually involve performance, price and ease of implementation.

Servomotors consist of a rotor with permanent magnets and a stationary stator with windings. Electrical current in the stator windings creates a magnetic field that develops torque and rotation of the rotor. Servomotors have a limited number of poles (usually between four and 12), and must run closed-loop, where an encoder or resolver provides positional feedback. The main advantages of servomotors are that they can operate at high speeds (greater than 2,000 RPM) and can maintain high torque at these high speeds. The major drawback of servomotors is that they are complex and expensive, since they often require additional hardware, such as an encoder, gearbox and controller.

Stepper motors are essentially plug-and-play devices that are easy to setup and use, with a significantly lower overall cost than servomotors with greater availability. They have a high pole count, usually between 50 and 100, where one rotation of the motor requires many more current exchanges through the windings than a servomotor. This gives linear stepper actuators high positional accuracy while operating in open loop, eliminating the cost and complexity of an encoder or resolver. Stepper motors can also generate high torque at zero speed and are generally more compact and economical than servomotors. Furthermore, stepper motors do not have contact brushes in the motor that may wear out, making them more reliable and giving them a significantly longer lifespan than servomotors. The primary disadvantage of stepper motors is that they cannot generate high velocities and acceleration, and as velocity increases, their torque is reduced. Stepper motor linear actuators are therefore ideal for low-cost applications that require a compact size and do not require high torque at high speeds.

A new breed of linear stepper actuators

Not all stepper motors are created equal. Numerous factors contribute to their overall size and cost, such as the design approach, component manufacturing, assembly and testing processes. For applications that require miniature linear actuators, OEMs have traditionally had few choices. They could select from a limited field of oversized actuators, resulting in high complexity that affected other machine features, such as size, power consumption, weight and cost. Alternately, they could create their own actuator from scratch, requiring a significant investment in time and other resources.

In response to this market need, Actuonix Motion Devices has developed a new line of miniaturized linear stepper actuators optimized for use in different industries that require high precision with reduced cost. These actuators are available in a standard rod-style stepper actuator as well as a stepper track actuator.

Figure 1. Actuonix S20 linear stepper actuators. Source: ActuonixFigure 1. Actuonix S20 linear stepper actuators. Source: ActuonixThe Actuonix S20 rod-style actuator (Figure 1) provides high-precision positioning in a compact configuration. Its miniature size is possible due to a NEMA 8 motor mounted directly to the actuator shaft, making it ideal for mounting in tight spaces. The S20 is available in five different stroke lengths from 15 mm to 100 mm.

The Actuonix T20 track-style stepper actuator is a completely new design that also uses a NEMA 8 motor, which is mounted to a custom slide rail and block assembly. It provides a compact profile that offers incredibly precise movement along its stroke. The T20 is available in two different stroke lengths: 60 mm and 120 mm.

The Actuonix line of linear stepper actuators pushes the boundaries of miniaturization and maintains tight tolerances, but still relies on standard manufacturing processes, such as extrusion and injection molding. Because of their compact sizes and different stroke lengths, the S20 and T20 linear stepper actuators ensure that the optimum-sized actuator is suitable for many OEM designs.

Actuonix in action

The Actuonix in-house, dedicated technical staff designs and develops the linear stepper motor actuators and performs final assembly and testing. A reliable, overseas supply chain with expertise in miniaturized manufacturing provides high-quality, low-cost components and parts. Together, this partnership enables the company to produce highly innovative, cost-effective linear stepper actuator solutions at a fraction of the cost of similarly performing competitive products. For example, all of the linear stepper actuator models cost under $100, including the steppers and mounting hardware, which are shipped fully integrated and ready for assembly into OEM devices. Similar competitive products would cost upwards of $600.

Actuonix Motion Devices is a leading manufacturer and innovator of low-cost, high-quality micro linear actuators and linear servos. Based in Victoria, Canada, Actuonix developed its first affordable micro linear actuator in 2004. They are the only manufacturer of inexpensive, high-quality micro linear servos and actuators with a wide breadth of product selection, connectivity and control options, and the ability to customize to client needs. The company now offers a wide range of products including 164 different types of micro linear actuators, linear servos and track actuators, and new models are continuously under development and added to their lineup.

More information about Actuonix products and capabilities can be found on their website.