What is an Electric Linear Actuator?
An electric linear actuator pushes/pulls a load by converting motor-driven rotational motion into controlled linear motion. Linear actuators are frequently used in automation environment, such as manufacturing or packaging, for precise, repeatable and controlled motion and positioning.
Component Breakdown
Lead Screw
The lead screw connects to the motor’s gearbox and provides a rotating shaft for the nut
As the screw rotates, it drives the screw nut along the lead screw’s axis.
Screw Nut
Located on the screw the nut features internal threads, or a bearing system, that mate with the lead screw.
The threads convert rotational to linear motion.
Motor
The motor gear assembly drives the lead screw rotation.
Motors are usually either externally mounted or integrated directly with the actuator housing.
Coupling
The coupling connects the motor’s output to the lead screw shaft, transferring the motor torque and accounting for any misalignment.
Rod
Connected to the screw nut, the rod extends outside of the housing and allows for the connection of loads and tools via the rod end.
Sensors
Sensors provide feedback to the control system on positions, forces, motion limits and fault conditions.
Common sensors include internal position sensors and encoders.
Housing
The housing protects all internal components from environmental hazards such as moisture, corrosion and particulates.
Housing materials vary depending on actuator use, for example, using stainless steel for increased corrosion resistance.
Simplified CAD Model
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System-Level Description
Electrical Subsystem
Supplying electrical power to the motor drive energizes the motor windings and causes magnets mounted on the shaft to rotate.
Attached to the rotating shaft, a gear system transmits torque to the lead screw.
Mechanical Subsystem
The lead screw and nut are the core of the linear actuator system. The motor applies torque to the screw, which is free to rotate, while the nut is constrained against rotation yet allowed to travel linearly along the screw.
As the screw rotates, the nut and attached rod move linearly. To use the actuator’s output motion, external loads are typically mounted to the rod end.
Control Subsystem
The control subsystem governs how the actuator is commanded and monitored when operated. Control subsystems can range from simple switches that denote the end of travel to programmable logic controllers (PLC) that determine position, speed and motion timing.
Controllers send commands to the motor, receive feedback data such as position, detect faults and enable repeatable, coordinated motion.
Failure Modes and Constraints
Mechanical Wear
When components such as the screw, nut or bearings wear down it can reduce efficiency and increase backlash.
Debris Ingress
If particulates get between mechanical components like gears or bearings, it can cause binding and increase friction during operation.
Corrosion
Corrosive substances or moisture can eat away and degrade mechanical components and reduce electronic component performance.
Misalignment and Side Loads
If the motor, screw and loads aren’t axially aligned, it can cause vibration and increase component wear rate.
Thermal
Extremely high or low temperatures can reduce performance of lubrication and electronic components.
Power Loss
Depending on the actuator design, power failures can prevent actuator motion or keep it from holding position.
Sensor Failure
Failed sensors will provide incorrect or missing feedback data on motion and if faults occurred
Mechanical Animation
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