What Linear Actuators Are
Linear actuators often act as servomechanisms, like linear servo motors. In this application, they can either provide and transmit a precise amount of energy to work another mechanism or equipment part, or they may do the actual work themselves.
Nearly all factory automation processes use linear actuators to push, lift, rotate, or transport products or equipment during various manufacturing processes. Operators can even use them to move solar panels. Some linear actuators and units operate in vacuum, radiation, cryogenic, corrosive, and underwater environments.
They are found frequently in devices such as reed switches, electric motors, stepper motors, linear motors, pneumatic cylinders, and more.
Linear actuators assist in robotic processes in a wide range of industries, including automotive, biotechnology, pharmaceuticals, food, packaging, and electronics.
Electric and Pneumatic Actuators are devices that convert energy to motion. They can also be used to apply force. An actuator is responsible for moving and controlling a mechanism or system, for example, by opening a valve. An actuator requires a control signal and a source of energy. The control signal is relatively low energy and may be electric voltage or current, pneumatic or hydraulic fluid pressure, or even human power. Its main energy sources are the high energy versions of those mentioned above, excluding human power.
An actuator responds by converting the source’s energy into mechanical motion when it receives a control signal. In the electric, hydraulic, and pneumatic sense, it is a form of automation or automatic control.
Pneumatic actuators are devices that convert energy typically in the form of compressed air into mechanical motion. Thus, it enables considerable forces to be produced from relatively small pressure changes. A pneumatic actuator mainly consists of a piston or a diaphragm that develops the motive power. It keeps the air in the upper portion of the cylinder, allowing air pressure to force the diaphragm or piston to move the valve stem or rotate the valve control element.
History of Linear Actuators
We do not know for sure when humans made the first linear actuator. However, we can say that during the early Industrial Revolution, manufacturers began using tools that worked similarly to modern linear actuators. By the beginning of the 19th century, they were using tools that worked with the help of linear actuators.
In 1979, Bent Johnson invented the electric linear actuator. While his goal was simply to make better a friend’s wheelchair, his invention quickly became popular. Just a few years after he invented it, Johnson’s electric linear actuator was popular in a wide range of industries, particularly agriculture, where it allowed users to automate processes.
In the 21st century, we have been able to diversify the applications of linear actuators through advances like the creation of the micro actuator. Modern linear actuators, depending on their design, are more intuitive, powerful, and efficient than the linear actuators that came before them.
Linear Actuator Design
When designing a custom linear actuator, manufacturers must consider design elements including materials (always a strong material like stainless steel or anodized extruded aluminum), size, load capacity (measured in lbs.), actuator power source, level of automation, load speed, input voltage, and IP rate. Note: In general, the higher an actuator is IP rated, the more protection it offers.
Manufacturers base their design choices on application specifications like the environment in which the actuator will be used (including its accessibility), the weight of the loads the actuator will move, how far the actuator must move the load, how fast the actuator must move the load, how frequently the actuator must move the load, and any industry standards.
To picture the layout and connections of the linear actuator they will construct, manufacturers often start by drawing or computer generating a wiring diagram. Generally, manufacturers offer both standard series actuator models and custom actuator models. To learn more about your options, get in touch with your potential suppliers.
Features of Linear Actuators
Linear actuators may work using a wide range of energy forms. The various forms of energy that power linear actuators include are hydraulic, pneumatic, mechanical, electromechanical, and piezoelectric power.
Actuators are not only powered by a variety of mechanical, electrical, pneumatic, and hydraulic designs, but they also create motion based on several different principles. Many linear actuators, for example, use a ball screw design consisting of a screw rod which rotates in and out of a housing, providing linear motion.
Types of Linear Actuators
Different types of processes use various actuator designs, including ball screw actuators, rotary actuators, miniature linear actuators, telescopic actuators, electric linear actuator, electro-mechanical actuators, fluid power linear actuators, pneumatic actuators, piezoelectric actuators, linear motors, linear chain actuators, and valve actuators.
Ball screw actuators, also called drive screws, are highly accurate and rigid actuators. They convert rotary motion into mechanical energy using a combination of ball nuts and ball screw drives. Their screw components rotate using either a synchronous timing belt drive, a worm gear drive, or a direct drive. This pushes the drive nut along the screw, which in turn pushes the rod out. Rotating the screw in the opposite direction retracts the rod. A cover tube protects the screw nut from environmental elements and contamination. Radial thrust bearings permit the screw to rotate freely under loaded conditions.
Rotary actuators are not linear at all, although, like rotary tables, they serve purposes similar to those of linear actuators in assembly automation applications by providing radial motion.
Rodless actuators are actuators that carry loads to their destination, rather than push or pull them with a rod. Manufacturers can design rodless actuators to function as pneumatic actuators, hydraulic actuators, or electric actuators, depending on application requirements.
Stepper motor linear actuators are actuators that work using a DC stepper motor. DC stepper motors are electric and brushless and make full rotation easier. Assuming the motor component aligns with the application’s required speed and torque, stepper motor linear actuators do not require a position sensor. Most often, customers purchase these actuators for laser and optics positioning applications.
Miniature linear actuators are simply linear actuators built on a much smaller scale than regular linear actuators. They are called mini linear actuators and micro linear actuators. While they are generally electric, linear actuators may use pneumatic power, hydraulic power, or piezoelectric power. The latter-most provides highly precise, short movements.
Telescopic actuators utilize a fairly new “spindle” technology to provide linear motion; because they are telescopic, the length of the actuator can fit inside a fairly small housing, making telescopic actuators highly space-efficient. Telescopic, or spindle actuators provide vertical mechanical motion.
Electric linear actuators, also known as electric cylinders, work using a drive mechanism that converts electrical energy into linear displacement. They feature electric motors, a limit switch (to limit motion), and an output shaft. Customers most often purchase them for use in automotive systems, where they need automatically opened and closed dampers, automatic braking, or automatic locking doors.
Electrohyrdaulic linear actuators are used to control fluid flow through a valve, a brake is typically installed above the motor to prevent the fluid pressure from forcing the valve open. If no brake is installed, the actuator is activated to reclose the valve, which is slowly forced open again. Unfortunately, this cycle repeats, and the motor and actuator will eventually be damaged.
Electromechanical linear actuators are electric linear actuators driven by mechanical transmission. The most common type of electromechanical actuator is the 12-volt linear actuator.
Fluid power linear actuators are linear actuators that produce linear displacement using a piston and cylinder. The motion of these components may be powered by differential air pressure, gas, or hydraulic fluid. Fluid power linear actuators are useful in applications such as welding, damper door opening and closing, and clamping.
Pneumatic actuators exclusively use gas to move pistons. Pneumatic actuators are easy to use and inexpensive, but they are loud, clunky, and inconvenient.
Piezoelectric actuators are employed for the specialty applications of supplying extremely small, precision movement, and manipulating fluid films. They use the electric charge that builds in some materials (e.g. some ceramics, crystals) to expand and thereby create motion.
Linear chain actuators help users pull or push a load in a straight line. They are made up of lengths of chain, sprockets, and driving gears.
Linear motors are motors that work without a lead screw to convert power. These motors use actuators that feature magnetic field structures covering their length. Linear motors are durable, long-lasting, and versatile. However, they do have a relatively low load capacity.
Valve actuators are a type of electric actuator that works exclusively with valves.
Linear Actuator Advantages
Depending on their design, linear actuators offer users a wide range of advantages. First, all linear actuator types are powerful. Second, some, like linear motors, work with high repeatability. Also, they are all versatile and fairly inexpensive. They are applicable in areas where the conditions involve extreme temperatures; a typical temperature range is -40 to 250 degrees Fahrenheit. They avoid the use of hazardous materials and protect from an explosion. Some offer extremely high efficiency. To learn more, talk to your supplier.
Linear Actuator Disadvantages
They are sensitive to sudden extreme changes in temperature as well as vibration. Also, compressed air is more expensive than electricity. It is essential to ensure there are no leaks in a pneumatic system because compressed air escaping leads to energy loss.
Linear Actuator Accessories
There are many accessories you can purchase along with your linear actuator in order to make it work better or help you control it better. Examples of such accessories include digital timers, monitoring tools, speed controllers, and fuses. To find out if any particular accessories are right for your application, talk to your supplier.
Linear Actuator Proper Care
The components of linear actuator proper care include those related to storage, maintenance, and lubrication.
First, to keep debris and dust from building up on and in your linear actuator, keep it in its factory packaging until it is time to use it.
Second, create an inspection schedule. During these inspections, check the actuator for issues like misalignment and improper oil distribution. Promptly fix any problems you find, even the smallest. This way, no issue will get out of hand.
Third and finally, keep your linear actuator properly lubricated. Proper lubrication ensures that your actuator does not give in to corrosion, wear, or abrasion. For the best advice on how often you should lubricate your linear actuator and what type of lubrication you should use, talk to your supplier.
Linear Actuator Standards
Linear actuator standards differ by location, industry, and application. In the United States, you can turn to the guidelines offered by organizations like ANSI and ASME. If you are working at an international company, you may want to check out ISO (International Standards Organization) standards. Many industries adapt the guidelines offered by organizations like these as their own. Either way, you need to check with your industry leaders to make sure you know what certifications to ask about before purchasing an actuator.
Also, regardless of your application, we recommend you familiarize yourself with IP (Ingress Protection/International Protection) ratings, so that you know which one you want your actuator to have. If you want your actuator to work well and last a long time, you need to make sure that it is rated for the environment your application will present.
Things to Consider About Linear Actuators
Before you purchase a linear actuator, you need to make sure that it matches your application in the following ways: speed capabilities (speed of actuator extension and retraction), load rating (the maximum weight the actuator can move), stroke length (how far the actuator can reach or extend), power to weight ratio (how much power the actuator has compared to how heavy/large it is), device life, and power source and programmability (simple inputs vs. complex programming).
For the best results, we recommend you write all of this down, along with details including your budget, your deadline, your delivery preferences, and your post-delivery preferences.
After you have written all of this down, check out the many high quality linear actuator manufacturers we have listed on this page. All of those we have listed are top-rated, reliable, and experienced. You will find their various profiles in the middle of this page. As you look them over, compare their services and product offerings to your specifications list. Based on your requirements, pick out three or four linear actuator manufacturers you believe have the most potential to serve you well. Then, reach out to each of them to discuss your application. After you have spoken to each of them at length, compare and contrast what they have to offer, and choose the right company for you. Good luck!
Linear Actuator Informational Video