What is a Linear Actuator?

September 11, 2017, by Jimmy Coleman

Block and TackleBlock and Tackle Series Volume 5 - What is a Linear Actuator? 

Question: What is a linear actuator?

Answer: Quite simply, a linear actuator is a device that moves a load in a straight line.  Linear actuators come in many styles and configurations – our blog post today covers those actuators associated with motion control.


Straight Line A to B

Linear actuators are an important piece of the motion control picture.  There are so many methods of creating motion using rotary motors that I won’t go into all of them.  I probably couldn’t even list all of them in one sitting.  But, linear ballscrew, lead screw, and belt drive actuators offer a unique solution to linear motion applications.  The main advantage, other than converting rotary motion into linear motion, is the fact that they are self-contained.

URS Series medium imageThere are a few general types of actuators, commonly specified by their primary mechanical components.  Electric cylinders are those actuators that have a cylinder much like a hydraulic ram, which is controlled by an electric motor.  Rodless actuators are those actuators that don’t have the protruding cylinder or ram.  These have a carriage that traverses the length of the actuator.  And precision tables, although basically the same principal as the rodless actuator, have very high positioning precision.  Precision tables are designed to be mounted to a granite table and hold tight tolerances for straightness, flatness, and axial accuracy and repeatability.

The mechanisms usually consist of a coupling or gear reducer, and a lead screw or belt drive system.  Some actuators have the motor directly coupled to the screw shaft, but more often, there is a gear reduction between the motor shaft and the screw shaft.  This can be performed using a set of gears or a timing belt with pulleys.  The gear ratio is typically a speed reduction, which multiplies the motor’s torque.  The overall speed of the actuator’s motion is limited by this gear ratio.

In Part 2 of our blog post on Linear Actuators, we will explore a variety of the mechanism types which are used most frequently in motion control applications.

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