Chapter 1: The Principle of Electric Actuators

The purpose of this chapter is to describe what electric actuators are, what their manufacturing and components are, how they function, and how efficient they are.

What are Electric Actuators?

The electric actuators is a device that is capable of moving a load or creating an action that requires a force, such as clamping, using an electric motor.

An electric motor creates rotary motion as the spindle or rotor rotates. An electrical actuator has a helical screw to which the motor spindle is coupled via a drive shaft. A ball screw nut will rotate this.

Manufacturing Electric Actuators

In order to manufacture an electric linear actuator, the manufacturing process begins with the electric motor. Each electric motor is made up of two main components: Stator - a stationary permanent magnet; Rotor - a spinning rotor that is forced to rotate by the magnetic field generated by the stator.

An assembly line within the factory that manufactures electric linear actuators crafts each part carefully. During each step, from winding the copper coils on the rotor to inserting the shaft screw, every step is carefully monitored. Quality assurance experts carefully examine each batch. To optimize the assembly line for each linear actuator, different parts of the motors are produced concurrently.

By using mechanical arms and conveyor belts, raw materials and finished parts are transported to the next production line. When the electric linear actuators have been completed, the final stage of assembly is more hands-on. Professional assembly workers follow a manufacturing document created by engineers to assemble the final pieces. Each step in the quality assurance process is carefully monitored by quality assurance experts, who inspect the finished components before moving on.

Quality Control

For the first article, the actuators are sent to the Quality Control team for inspection after they have been assembled. A first-article inspection verifies the accuracy of the dimensions, ensuring that all parameters are met. To ensure that the IP rating, operating temperature, and duty cycle requirements are met, the first article unit undergoes stress testing.

After the Quality Control team is satisfied with the results, the batch is approved for shipment to the distribution center. Upon arrival at the distribution center, the products are stored in a warehouse. In addition, the unit is then inspected again by the product engineer for a few minutes to ensure that all specifications have been met and that the units have not been damaged during transportation.

As soon as the products are added to the stock units, they can be purchased. Several products are tested again by the logistics team before being packed and prepared for shipping.

The Components of an Electric Actuator

This section discusses the various components of an electric actuator.

Front/Rear Clevis

There are holes at each end of the u-shaped metal piece, through which pins, bolts, or fasteners are run. Front and rear clevis attachments allow the actuator to be mounted to the application.

Outer Tube

It is also known as the cover tube. An extruded aluminum tube protects the linear actuators from the outside and houses all of their inner components.

Inner Tube

The extension tube is also known as the translation tube, piston, or drive tube. Aluminum or stainless steel is usually used for the inner tube. The inner tube is where the spindle is located when it is retracted. The tube is attached to a threaded drive nut that extends and retracts with the rotation of the nut.

Spindle Component

Also known as the rotating screw, lead screw, or lifting screw. It is a long, straight rod that turns into a machine or tool. By rotating this segment of the linear actuator, linear motion is generated by retracting or extending the inner tube. Steel spindle ensures strength and durability. The spindle can be threaded in different ways depending on the speed and load.

Safety Stop

It is located at the end of the spindle. It prevents the inner tube from overextension.

Wiper Sealing Component

A sealing component is attached to the outer tube's end. Contaminants such as dust and liquids cannot enter the spindle area of the actuator. The seal between the inner and outer tubes is also important for the IP rating of the actuator.

Drive Nut

The inner tube is attached to this and travels along the spindle. The inner tube can be retracted or extended using this component. Plastic or metal drive nuts are sometimes keyed to prevent inner tube rotation.

Limit Switches

Electrically cutting the current to the motor controls the position of the fully extended and retracted inner tube. These switches prevent the actuator from overextension or overreaction. In addition to cutting current, limit switches can also send signals.

Gears for Electric Actuators

Plastic or steel gears mate with other gears to alter the relationship between the speed of the driving mechanism and that of the driven part. A drive gear is connected to a power source like a motor.

Motor Housing

The housing contains the gear motor as well as all internal components without exposing anything to external damage. Most motor housings are made of high-quality plastic.

DC Motor

All of the electric actuator's power comes from a direct current motor. DC motors come in a variety of types. Brush motors are the most commonly used motors. Components of a motor include:

Motor Stator

The motor's stationary outside portion. It consists of a motor housing, motor caps, and two permanent magnets. The rotor and stator are surrounded by a stationary magnetic field generated by the stator.

Rotor

It is also known as the armature. The motor's inner part rotates. The commutator, silicon steel laminate, copper windings, and motor shaft make up the motor.

DC Motor Commutator

Attached to the shaft of the motor are these plates. Two connections are provided for the coil of the electromagnet. Motors are kept in rotary motion without losing torque by the commutator, which reverses the polarity of the motor.

Carbon Brushes

A motor's rotor transmits electrical current from its stator by sliding friction.

Motor Shaft

On DC motors, this part connects the gear motor to the stator at the bottom.

Output/Feedback Sensors

These are used to communicate the actuator's stroke position. These components provide feedback to the control box MCU. Position feedback linear actuators are typically used when high level functions such as synchronization and memory positioning are required. A variety of output sensors are available, including:

Hall Effect Sensor

An output signal from this type of sensor is the magnetic field density function around the device. Whenever the magnetic flux density of the sensor exceeds a certain threshold, the sensor detects it and produces a hall voltage as an output. A linear actuator with position feedback is important for accuracy and reliability, exactly what a hall sensor provides.

Potentiometer (POT) Sensor

Sensors of this type consist of a wiper and two connectors for changing an electrical signal output. As the linear actuator lead screw turns, the resistance between the wiper and the two end connections changes. The resistance value corresponds to a position in the actuator's stroke.

Reed Sensor

It is a magnetic positional sensor. An electrical switch is operated by a magnetic field. In a sealed glass envelope, reeds made of ferrous metal make up the contacts. Normally, the contacts are open, but they may close in the presence of a magnetic field (closing the circuit as well as cutting power to the actuator).

How an Electric Actuator Functions

When the spindle or rotor rotates, the electric motor creates a rotary motion. A ball screw nut rotates the motor spindle. Through the shaft of the drive, the motor spindle is directly coupled to a helical screw.

When the spindle rotates, the ball screw nut is driven forward or backward along the helical screw. During the clockwise or anti-clockwise rotary motion of the motor, the hollow piston rod attaches to the ball screw nut and generates linear motion into or out of the linear actuator.

The motor is controlled by an electric drive, which allows the rotation speed and hence the linear speed of the actuator to be varied. Position information is provided by a feedback mechanism, and the linear actuator can be programmed to move, stop, and move again, or return to its resting position.

Motor power determines how much torque can be generated. Therefore, the power will also determine the force that can be applied to the actuator.

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