12-Volt Linear Actuators
12-volt linear actuators convert 12 volts of direct current—or DC—electrical energy to provide linear mechanical motion. Although this linear motion is not at a very high speed, there are several benefits that 12 volt linear actuators have to offer. These advantages include a high power level, durability, and reliability.
New technological advancements have been made in designing 12-volt linear actuators. These new designs are more space-efficient and allowed for electronic hardware that is more advanced. 12 volt linear actuators are also known as micro motors, electric motors, or linear motors. The use of 12-volt linear actuators are frequent in industries such as industrial manufacturing, marine, medical, dental, military, robotics, and aerospace. Applications such as factory automation, robotic material handling, diving, movement of flight surfaces, stabilization of rotating devices, metal working, medical infusion systems, drug delivery systems, bed positioners, dental chairs, patient lifts, military aircraft, and armored ground vehicles. 12-volt linear actuators do not require a large motor and thus do not require a large amount of energy, thus making them popular among a wide range of businesses.
In the robotics industry in particular, new developments in research have been made regarding uses for 12-volt linear actuators. Scientists have been able to program robots to imitate human attributes such as legs or arms, and have even successfully created robots that are fully autonomous. New robotic machines have been developed to completely replace the functions that until recently have been performed exclusively by humans. For example, self-driving cars have been under testing and development, as well as numerous other inventions that will greatly benefit countless applications and industries.
With the continuous and rapid advancement of technology, manufacturers have become more and more dependent on robotic devices to assist in production, and especially on the abilities of linear actuators. Therefore, we must ensure that the components that are manufactured to sustain these robotic devices are just as reliable. 12-volt linear actuators allow for precise motion control for movement in a straight line.
The History of the 12-Volt Linear Actuator
Bent Jensen is credited for the invention of the 12-volt linear actuator. The Danish inventor took over his father's company in 1976. The company, which started as Christian Jensen & Sons, used to produce grinding mills, flat belt and V-belt pulleys, forges and grinding mills. When Bent took over the company, he gave himself five years to invent a new product that would propel the company further.
Bent Jensen, a mechanical engineer, came up with linear actuators three years after taking over the company. He based his model on a project he had done in college, improving a wheelchair for a fellow student. In 1986, Jensen started an electronics department, ensuring that the actuators would use control boxes from the same company. This is when the 12-volt linear actuator came to life.
The 12-volt linear found its place in a wide range of industrial applications. To this end, the company opened branches in Europe, the USA, and China. Companies manufacturing actuators took the idea and some bettered it to produce more compact and efficient 12-volt linear actuators.
Put simply, a 12-volt linear actuator rotates a lead screw. This lead screw sports a continuous helical thread, similar to threads on a bolt, machined on its circumference and running throughout the screw's length. On this lead screw is threaded a lead nut also having continuous helical threads. This nut does not rotate with the lead screw, but is instead attached to a non-rotating part of the volt linear actuator.
Therefore, the lead screw starts to rotate, the nut is driven along its threads. The direction of rotation of the nut is dependent on the direction of rotation of the lead screw. When linkages are connected to the nut, this motion is converted to useful linear displacement. Most 12-volt linear actuators are built as heavy duty, high rate of rotation or as a compromise between these two attributes.
12-volt linear actuators are built for applications that need accuracy and high movement resolution rather than those that need high force and very high rotation rate. Most linear actuators are mounted on butterfly valves or dampers. Given their design and application, those choosing 12-volt linear actuators will consider travel, rotation rate, force, durability, and accuracy.
The structure of a 12 volt linear actuator is very basic, only consisting of three main components.
- DC motor. DC motors come in two main types: brush and brushless. Brushed DC motors consist of three main parts: a commutator with mechanical brushes, a wound iron-core armature, and a permanent magnet stator. The brushes in the motor connect the power source to the motor’s rotating coil—or armature—that generates voltage from the motion resulting from a magnetic field. Alternatively, their brushless counterparts features a set of coils and a permanent magnetic rotor that can be found within the stator. The commutator in a brushless DC motor is controlled electronically, as opposed to a mechanically commutation system.
- Screw drive. Screw drives can be categorized in two ways: lead screws and ball screws. Lead screws consist of threaded rods that generate linear motion by way of rotational movement. Lead screws are also known as translation or power screws. Ball screws feature a ball that is encased within a nut. They are capable of generating the same linear motion, but the ball reduces friction.
- Set of gears. These gears are used to increase precision in motor control. Either planetary gears or worm gears are utilized. Planetary gears, or epicyclic gears, consist of a set of three gears which revolve around a central gear. Planetary gears are a vital component for applications that require complex gear ratios for the smooth transition of torque. Worm gears, also known as worm drives, consist of a gear and a screw-like threaded metal rod known as a worm. Unlike screws, which are threaded all the way down, worms are threaded only in the middle of the rod. Worm gears possess the ability to add torque to the screw’s rotation under multiple circumstances, and to transfer motion between axes. Out of these two types of gears, worm gears are used more frequently, due to their ability to provide an adequate amount of torque to the rotation of the screw.
The motor in a 12-volt linear actuator is designed as a separate cylinder attached to the sides of the actuator. This motor cylinder may be parallel or perpendicular to the actuator. In some instances, the motor is attached to one end of the actuator. A drive motor features a typical construction where a solid drive shaft is geared to the actuator's drive screw or drive nut.
However, there are also compact actuators where the actuator and the motor are housed in one structure. In this case, the motor shaft's inner diameter is made large to make the drive shaft hollow.
Compact linear actuators use specially designed motors that try to fit the motor and actuator into the smallest possible shape. The drive nut and drive screw now occupy the center of the motor. This does not require extra gearing between the drive screw and the motor. In some compact 12-volt linear actuators, the motor is made with a small outside diameter, but with extended pole faces. This gives the motor a high torque while still ensuring it fits in small diameter spaces.
Custom 12-volt Linear Actuators
When a DC linear actuator is needed for a special application, a custom design might be needed. These units are made of different materials including stainless steel, aluminum, and plastic. Customers can customize actuators based on the material they need.
Though there are actuators designed for different applications, one would need to make some changes such as:
- Attaching custom electrical connector
- Changing the length of connection wire
- Modifying the limit switch position
- Shortening the stroke length of the 12-volt linear actuator below the available products
- Adding a custom shaft end or rod end attachment fitting
- Fitting a non-stock DC gear ratio motor to alter rate of rotation/force characteristics of the actuator
- Changing the lubricants used to lower temperatures
When heavy customizations are required, most companies allow clients to give them a design to work with. Some company websites feature 2D/3D CAD Model tools, which allow clients to show a basic design of the actuator they need. Some companies also offer online prototype ordering where clients have parts delivered to them within 24 hours. This is ideal when a client needs to heavily manipulate the 12-volt linear actuator.
Types of 12-Volt Linear Actuators
Mechanical Linear Actuators
Mechanical linear actuators typically convert rotary motion into linear motion. This normally occurs through three main mechanisms:
- The manufacturer may apply a ball screw, lead screw, roller screw or screw jack. When the actuator nut is rotated, the screw shaft moves along a line.
- Wheel and axle may also be applied where chain drive, belt drive, hoist, winch, rigid chain, rack, and pinion or rigid belt are used. Here, a rotating wheel will move a belt, rack, cable or chain to produce linear motion.
- Thirdly, there are cam actuators that work similar to a wedge while providing limited travel. A cam shaped like a wheel rotates to provide thrust at the shaft base.
While some mechanical linear actuators pull, others only push. The hydraulic and pneumatic cylinders in an electric actuator can be designed to generate force in two directions. A car jack applies the principle of mechanical linear actuators.
There is another line of mechanical linear actuators based on a segmented spindle. Here, the rotation of a jack handle is mechanically converted into linear displacement of the jack head. Mechanical actuators can be seen in use in the lasers and optics industry where they manipulate the position of rotary stages, mirror mounts, linear stages and goniometers among other positioning instruments.
To enhance accuracy, there are index marks on control knobs. Even better, some 12-volt linear actuators will feature encoders and digital position readouts. Knobs used in these linear actuators are similar to those used on micrometers, only their purpose here is to position adjustment and not measurement.
Piezoelectric Linear Actuators
Typically, the piezoelectric effect is a property of selected materials to expand when a voltage is passed through them. These are less common as 12-volt linear actuators since most of the materials need high voltages. However, piezoelectric linear actuators offer fine positioning resolution and are handy where short motion ranges are needed. Again, when piezoelectric materials exhibit hysteresis, it becomes challenging to control how much they expand.
Electro-Mechanical Linear Actuators
These are applied in miniature 12-volt linear actuators where the lead nut forms part of the motor. Here, the lead screw is stationary and as the lead nut is rotated, the lead screw extends or retracts.
Electro-mechanical actuators are more or less like mechanical actuators. However, instead of the control knob or handle, an electric motor is used. The rotary motion of the electric motor is converted to linear displacement. Manufacturing varies from one company to the next, bringing into the market different forms of actuators. Most electro-mechanical linear actuators seem to have a proprietary construction.
Advantages of 12-volt Linear Actuators
For a long time, hydraulic, pneumatic and manual linear actuators have been used for industrial applications. In the recent past, 24 and 12-volt actuators have been gaining traction. A volt linear actuator is used to raise, lower, push, pull, rotate, position, lift, shift or move. Electric actuators operate swiftly, efficiently and with less noise. Again, they have fewer components and thus act up less and also wear out less. They are exceptionally durable.
They Save Money
Though 12-volt linear actuators are comparatively expensive, they require less maintenance. Unlike their hydraulic counterparts, no hydraulic fluid replacement is needed, no leak repairs, and there are fewer components on the system to maintain.
Users will only need to lubricate bearing and change cables semi-annually.
Ease of Installation
Volt DC actuators' components are much less costly compared to hydraulic and pneumatic components. The systems are easy to install, which leads to savings in OEM assembly situations. Again, these systems are easy to fine tune to meet different applications.
They Improve Productivity
Unlike the hydraulic and pneumatic systems, 12-volt linear actuators offer improved control over machine operations thanks to the variety of analog and digital feedback options. There are multiple limit switches offered for teach and repeat positions. There are low voltage switching options that allow users to interface them directly with programmable controllers. The pulse width can be modulated for variable speed control.
12-volt linear actuators offer great accuracy and repeatability thanks to their controllable nature. With these units, users can link and even automate different processes.
They offer users reduced downtime thanks to longer component life, reduced maintenance and redundancy through a manual override.
12-volt linear actuators are for engineers looking for compactness, lightweight, energy efficiency, quiet operation, ruggedness and reliability. Besides these benefits, the 12-volt linear actuator has found its use in a variety of applications in different industries. It offers different load speed and can be used in homes.
12-Volt Linear Actuator Accessories
Different accessories can be used with DC linear actuators either to vary speeds, operate, automate operations, mount, control power, and supply power. Some of the common accessories used with these units include:
- Remote transmitters
- Mounting brackets
- Power adapters
- Motor rate of rotation controllers
- Automatic direction switches
- Steel rack gears
- Rocker switch harnesses
- Rubber boots
- Momentary switches
While some of the accessories are offered together with the actuator, some have to be bought separately online or from the producer. This is the same case with the spare parts for dc actuators.
How To Install 12-Volt Linear Actuators
Installing a 12-volt linear actuator is done in two steps; connecting the mounting bracket to the application and wiring the actuator. In most cases, users will only need a rocker switch, a power adapter and the actuator.
Actuator producers will offer the installation manual for the 12-volt linear actuator. Normally, it involves connecting the actuator to power supply using the power adapter provided and connecting the rocker switch terminals.
12-volt linear actuators are low maintenance units. To ensure that they work optimally, users only need to ensure that the bearing and other moving parts are well lubricated. This can be done after a few weeks based on the frequency of use, the load speed and load capacity. When the unit starts producing sounds, it is a clear indication that lubrication is needed.
The cables will need replacement twice every year while screws and bolts will work efficiently for more than a year. When the unit's general performance subsides, there are normally parts that require replacement. Parts can be purchased from producing companies.
Most of the actuators have an IP rate and meet ISO and NFPA standards. This makes it easy to convert an existing hydraulic or pneumatic linear actuator to a 12-volt linear actuator.
Choosing Actuators and Manufacturers
The motor of a volt linear actuator is already pre-selected and fitted into the actuator. This makes it easy for users to choose the unit size. The thrust of the actuator will directly influence its size. Therefore, this is the first parameter that most people consider when shopping for an actuator. The stroke length is another aspect that determines the overall size of the unit.
After choosing the size, users can go on and choose the rate of rotation and the duty cycle of an actuator. Producers will normally indicate the allowed force and rate of rotation combo. This is offered in form of performance curve or as a chart. Another factor to be considered is the duty cycle since heating can limit the performance of an actuator.
However, when good actuator producing company are chosen for the job, 12-volt linear actuator users can have custom units to meet their needs. Good actuator producers will offer a wide range of actuator types, different construction materials, sizes, and designs. This allows users to choose just what they need. However, the right manufacturer will allow users to request for custom units. This, like earlier explained, can involve users, in most cases engineers, presenting designs of the units they need to be produced.