Many machines depend on actuators to function. In particular, these devices foster operation by converting energy into different forms. The result of this conversion is motion. As a result, they help with movement-related tasks such as lifting, pushing, and turning.
An actuator can work manually, electrically, or by fluids such as hydraulics. And that’s one way to classify them. But, the most common way of categorising these devices is the direction of the motion they create. Two main categories exist: linear and rotary.
In this post, our interest is in linear actuators. We’ll cover the different types, how they work, the pros and cons, and how to install them.
What Are Linear Actuators?
Linear actuators create motion in a straight line, which is where they get the name “linear.” They notably differ from rotary actuators that move in a circular path. Rotary actuators are more prevalent among machines. As a result, most linear actuators work by converting circular motion into a straight one rather than creating from scratch.
Since they move in an unswerving pattern, linear actuators feature a simple design. The design consists of fewer moving parts than rotary alternatives. With this, they quickly reach high speed. You’ll find linear actuators in applications in various industries. These include automotive, marine, aerospace, material handling, and factory automation.
Types of Linear Actuators
Linear actuators vary depending on their power source. The most common types you’ll come across include:
Hydraulic Linear Actuators
Most hydraulic actuators are linear rather than rotary. These devices rely on hydraulic fluids and oils to create motion and have been used for years. Hydraulic linear actuators are common in industries like engineering and marine. They’re helpful where heavy-duty machine tools are prevalent.
The above is thanks to their ability to handle high force, power, and dynamic operations. But there are downsides to using this actuator type. Some include leakage problems, high heat, and noise. Also, you may need extra equipment for them to work efficiently.
Pneumatic Linear Actuators
Pneumatic linear actuators get power from pressurized gas. For that sole reason, they are suitable for high-speed applications. However, this type is less dependable for situations requiring high force and pressure. Typically, pneumatic linear actuators are limited to 100 PSI applications or less. They’re common in pumps, door closers, switches, and air compressors, to name a few.
Electromechanical Linear Actuators
Electromechanical linear actuators are most times confused with mechanical actuators. However, the difference is that they feature an electric motor rather than a knob or handle. The majority of them work by converting motion from rotary to linear.
While reliable, electromechanical linear actuators are usually limited in a direction. It’s either the device can pull or push. For pull, examples include belt and chain drives. For push, cam actuators are perfect options.
Piezoelectric Linear Actuators
Piezoelectric linear actuators also utilize electric motors, similar to the electromechanical type. They’re unique, nevertheless, as they employ voltage to expand materials. You’ll find this linear actuator type in scientific and industrial applications, and they’re relatively durable.
Notably, Piezoelectric devices are less likely to suffer wear and tear and consume less power. A few other types of linear actuators exist, depending on the application. You can find out more here.
Linear Actuator Working Principle
Simply put, linear actuators create straight motion or make a rotary one move in a linear direction. The different parts that make this happen include:
- Front attachment
- Push or push tube (inner tube)
- Screw and nut
- Rear attachment
- Protection tube (outer tube)
- Sealing system
Note that the primary actuator is the push/pull tube.
Other critical parts for the device to work depend on the type. For example, an electromechanical linear actuator will also need a motor, cable, and gearbox. Accordingly, the working principle will also differ.
Considering electromechanical linear actuators, here’s how they work:
- First, power gets to the electric motor, and it starts rotating.
- The rotation kicks the gearbox into motion, sending the torque to the screw.
- Then, the screw drives the push/pull tube, converting the rotary motion into a linear one.
Advantages and Drawbacks of Linear Actuators
The main advantage of linear actuators is their fast operation. As mentioned earlier, they can easily reach high speeds since they move in a straight direction. A piezoelectric actuator, for instance, can attain an acceleration of over 10,000 Gs.
Another notable advantage is their affordability. This is particularly true for electromechanical and piezoelectric actuators. Both consume low power. Furthermore, linear actuators make operating heavy-duty machines more manageable, especially the hydraulic types.
However, all types of linear actuators have their disadvantages. Earlier, we touched on the downsides of hydraulic-operated ones, including high heat, noise, and leakage problems. With piezoelectric actuators, the disadvantage is that they’re relatively expensive. Also, they’re fragile and can only handle short travel.
Electromechanical actuators feature somewhat complex designs since they come with more moving parts. Consequently, this increases the chances of wear and tear.
How to Install a Linear Actuator
Installing a linear actuator is a relatively technical process. Nevertheless, you can walk around it with the right guide and instructions. The below will help:
- Start by connecting the mountain brackets to your application. The brackets will typically feature a pin you can screw.
- Next, carefully connect the wiring. Notably, this will differ for different actuator types. To get it right, follow the wiring diagram in the product packaging.
- Turn on your application to confirm that the actuators are moving.
That’s essentially all it takes to install a linear actuator. The bulk of the work is during the wiring. If you can’t handle the task yourself, it’s OK to call an expert.
In summary, linear actuators are critical for many systems to operate optimally. They are present in simple applications like door closers and complex ones like lifts. While they have many advantages, they also have downsides, depending on the type.
Ultimately, for the best performance, you should use the correct application. For instance, a hydraulic or electromechanical one can work if it’s a high-force situation. But your target should be a pneumatic actuator if you need high speed.