What’s a Rotary Actuator?

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Rotary actuators produce rotary motion or force through mechanical conversion of linear force. They are powered by hydraulic, pneumatic, or electric systems and used in various applications, including automotive engines, industrial equipment, robotics, and military machinery. Hydraulic systems are the most powerful, while electric systems offer precise control.

A rotary actuator is a type of mechanical switch that produces rotary motion or force, often through mechanical conversion of linear force. A standard electric motor is a form of rotary actuator, but devices designated as actuators usually have finer control over the range and application of motion they provide. The devices perform various functions and are usually powered in three ways: hydraulic power, pneumatic power or electricity. A common example of rotary actuator principles is the system built into automotive engines for converting the linear force of piston motion in a series of mechanical connections into rotary force for the wheels.

The diversity of rotary actuator designs allows them to produce a range of different types of rotary motion. Industrial actuators often produce smooth rotary motion like a basic electric motor to power various types of equipment. If necessary, this motion can be reversed, as well as increased and decreased in speed, as in variable speed saws and heavy duty drills. Often a powerful rotary actuator is not required to produce any significant rotary motion, but instead relies on a torque motor design, where the device applies a controlled rotary force to counteract other forces or to rotate other equipment.

The finely controlled motion by intermittent digital signals is powered by stepper motors, which are usually a miniaturized version of rotary actuators used in control systems made to precisely position a product or tool. Electrical impulses are applied to a stepper motor, which causes rotation in controlled increments of a full step, half step or microstep. They are often compared to another category of precision rotary control devices called servo motors. Stepper motors can be used in high-end applications such as robotics, aircraft controls and factory automation. Common applications for them include clocks, computer disk drives, and printers.

Of the three types of power systems that drive the rotary actuator, the hydraulic system is the most powerful. It produces more rotork, or rotational torque force, than pneumatic systems, but both are employed in production settings. Electric rotary actuators are generally preferred when precise rotation control or variable settings are required. Such control is easier to change by varying the electric power level than by varying the hydraulic or pneumatic force levels.

Hydraulic rotary actuators are used in areas where large amounts of weight need to be moved easily, such as in car lifts in auto repair shops, and are considered essential equipment in many engineering and manufacturing environments. Backhoes used to perform heavy digging in small, confined spaces and factory presses that can apply pressures of up to 300 tons rely on the hydraulic rotary actuator as part of the machinery. They are also essential components of ship power systems and drills used in mines, as well as for military applications such as tank turret rotation.




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