Motion: major actuator types
Electric, hydraulic, and pneumatic motion are three major actuator technologies. Which you use depends on your application’s characteristics. Electric control excels when absolute accuracy of movement is required or when continuous motion is needed. Electric servo control is useful in diverse applications: CNC (computer numerical control) for spindles in machining centers and in lift̵...
Electric, hydraulic, and pneumatic motion are three major actuator technologies. Which you use depends on your application’s characteristics.
Electric control excels when absolute accuracy of movement is required or when continuous motion is needed. Electric servo control is useful in diverse applications: CNC (computer numerical control) for spindles in machining centers and in lift—and locate—applications in assembly operations.
Hydraulics is the choice for heavy loads when fast response is required. Forces are the highest of the three—upwards of 100 tons.
Pneumatics is reliable and intrinsically safe in adverse conditions, and insensitive to high and low temperatures, dirt, mechanical vibration, moisture, and electrical noise.
Since they use cylinders, hydraulic and pneumatic applications achieve linear motion simply and easily. Electric control, by virtue of being motor driven, is based on rotating motion and requires a conversion from rotary to linear motion—such as ball screw. Key operating parameters can affect selection:
Accuracy and repeatability: Electronic servo control offers the highest levels of precision. Today’s hydraulic and pneumatic valves provide greater control than previous generations. Fluid power excels in its ability to apply constant pressure efficiently, like holding a load in position.
Complexity: Hydraulic servo-based digital control is ideal for complex multi-axis applications. Servo-based electric control is ideal for tight synchronization. Pneumatics offers fine performance and simple application.
Productivity: Improving system productivity relies on increasing throughput and decreasing machine cycle time. A practical working speed for simple linear motion is 10 m/s for electric, double those of hydraulics and pneumatics.
Life cycle costs: When evaluating each technology, cost should not be the sole criteria. Balance acquisition costs with a life cycle cost analysis for a true picture.
—Rodney Rusk, Dan Warmus, Brian Rogers, and Thomas Dwyer are pneumatic, hydraulic and electric technology specialists from Bosch Rexroth Corp.,
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