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What Is a Rotary Actuator?

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  • Written By: Ray Hawk
  • Edited By: E. E. Hubbard
  • Last Modified Date: 31 August 2016
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A rotary actuator is a type of mechanical switch that produces rotary motion or force, often through the mechanical conversion of linear force. A standard electrical motor is a form of rotary actuator, but devices designated as actuators usually have finer control of the range and application of motion that they deliver. The devices serve several different functions and are powered in usually one of three ways: by hydraulic force, pneumatic force, or by electricity. A common example of rotary actuator principles is the system built into automotive engines to convert the linear force of piston movement in a series of mechanical connections to 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 rotational motion like a basic electrical motor to power various types of equipment. As needed, this motion can be reversed as well as increased and decreased in speed such as in variable-speed saws and heavy-duty drills. Powerful rotary actuator equipment is often not required to produce any significant rotary motion, but is instead based on the torque motor design, where the device applies controlled rotary force to counteract other forces or to cause another piece of equipment to rotate.

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Motion that is finely controlled by intermittent digital signals is powered by stepper motors, which are usually a miniaturized version of rotary actuator used in control systems made to precisely position a product or tool. Electrical pulses are applied to a stepper motor, which causes rotation in controlled increments of a full-step, half-step, or micro-step. They are often compared to another category of fine rotary control devices called servo motors. Stepper motors can be used in high-end applications like robotics, aircraft controls, and factory automation. Common applications for them include in watches, computer disc drives, and printers.

Of the three types of power systems that run 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 manufacturing settings. Electrical rotary actuators are usually preferred where precise control of the rotation or variable settings are required. Such control is easier to change by varying the level of electrical power than it is by varying hydraulic or pneumatic force levels.

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

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