An electric actuator is a device that can create movement of a load, or an action requiring a force such as clamping, using an electric motor to create the necessary force.
An electric motor will create rotary motion as the spindle, or rotor, rotates. The motor spindle is directly coupled to a helical screw, via the drive shaft, which in turn rotates in a ball screw nut.
As the spindle rotates the ball screw nut is driven forwards, or backwards, along the helical screw.
A hollow piston rod is attached to the ball screw nut and this creates the linear motion out of, or into the linear actuator as the motor rotates clockwise or anti-clockwise.
The motor is controlled by an electric drive, which allows the rotation speed to be varied and, hence, the linear speed of the actuator. A feedback mechanism gives positional information and the linear actuator can be programmed to move to a certain position, stop and then move on, or return to its rest position.
The power of the motor will determine the torque that can be generated and hence the force that can be put to useful motion through the actuator.
The actuator will be required for an application requiring force. In a pneumatic linear actuator the force is created by pressure acting on the surface area of a piston. In electric actuators, the force is generated from the torque capability of the motor. The load to be moved, any frictional forces of a surface and the angle of elevation, or declination, of the load will all be critical parameters to consider.
For pneumatic actuators, the load will be required to move a certain distance which determines the stroke of the actuator. The same is true for an electric actuator with some subtle differences. To protect against over-run, the 'usable' stroke is the maximum stroke less four times the pitch of the helical screw. An electric actuator may be used for a number of positions; therefore the stroke required will need to take account of the total movement. Different screw pitches are available, dependent on bore, allowing component combinations to meet many application requirements.
It is also useful to consider when an electric actuator would be preferable to a pneumatic solution. In a situation where a compressed air supply is not available, electric is the only alternative (if hydraulic solutions also are not available).
A key advantage of electric linear actuators is the requirement for multiple positions in an application. Other advantages are: higher axial force; high accuracy; low noise; flexibility through control characteristics; load stiffness and overall lower operating costs.
Electric actuators are available rod-style, or rodless, with or without motors and drives. Motors can be mounted axially behind the actuator body, or parallel to the actuator in four positions.
Electric actuators are found in a wide variety of industrial applications.
In the automotive industry for driverless transport vehicles, dispensing and a selection of jointing methods – gluing, welding and riveting.
In the food and beverage industry, for production of PET bottles, filling and labelling systems and robotic applications such as milking robots.
They are used in materials handling for operations such as servo presses and clamping and widely used in the packaging sector.
Their benefits in accuracy, flexibility and low operating costs lead to use in robotics, electronics and electronic assembly, machine tools and many other industrial sectors.
A suitable electrical supply and the associated cabling to the equipment is essential. Cabling will be required for power and control signals between the motor and drive. Actuators may need to be mounted and, switches can be used to identify position.
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