CDM2B25-25 | SMC Pneumatic Cylinder

What is an linear actuator?

A linear actuator is a mechanical device for converting electrical energy into mechanical energy in the form of linear motion. It consists mainly of an electric motor, a worm or rack system and a nut which moves along the screw, thus driving the movement of the piston. The electric cylinder offers several advantages over hydraulic and pneumatic cylinders, including lower energy consumption, reduced maintenance and better adaptation to different industrial environments.

How does a linear actuator work?

The operation of an linear actuator is based on the conversion of electrical energy into mechanical energy. For this, the cylinder uses an electric motor which must be supplied with electric current. When the motor turns, it rotates a worm or rack, which moves a nut attached to a piston forward (or backward).
As the nut moves along the screw, it drives the piston in a linear motion. This movement can be precisely controlled depending on the motor rotation speed and the screw pitch used. This allows the electric actuator to achieve highly variable speeds and thrust forces, as well as high positioning accuracy.

What are the different types of linear actuators?

There are several types of linear actuators, which can be classified according to their operating principle, their components or even their performance.

Electric worm screw jacks

Electric worm screw actuators are the most common and mechanically simple. They use an electric motor to turn an endless screw, on which a nut secured to a piston slides. The linear movement of the latter is directly proportional to the rotation speed of the screw and the pitch of the threads which compose it.
These cylinders can reach relatively high speeds and forces, but their performance depends largely on the friction between the nut and the screw. To improve this performance, certain technologies use ball bearings located between the screw and the nut.

Electric rack and pinion cylinders

Electric rack and pinion actuators use another mechanical principle to convert the rotary motion of the motor into linear motion. A motorized pinion is housed in the teeth of a rack fixed on the piston rod, and thus moves the latter forward or backward when the engine is running.
This type of cylinder is generally more robust than worm screw cylinders, and offers better resistance to radial loads. However, their cost and size can be higher, which makes them less suitable for certain industrial applications.

Toothed belt electric cylinders

Finally, some electric actuators use a toothed belt to transmit the movement of the motor to the piston. The belt winds around two pulleys, one of which is motorized and the other is attached to the piston. When the engine turns, the belt moves around the pulleys, thus driving the movement of the piston.
Toothed belt electric actuators are particularly suitable for applications requiring high speeds and long strokes, as well as those requiring very precise position control. On the other hand, they are not recommended for significant efforts or demanding environments (heat, humidity, etc.).

What are the components of a linear actuator?

To better understand how different electric actuators work, it is important to know their main components.

Electric motor

This is the heart of the actuator. The electric motor can be a direct or alternating current motor, and its power must be adapted to the needs of the application (speed, force, precision, etc.). Motor characteristics directly influence cylinder performance.

Transmission system

The conversion of rotary energy into linear energy passes through a mechanical transmission system: endless screw, rack or toothed belt. Choosing the right transmission medium is essential to ensure optimal performance in terms of speed, strength and durability.

Linear guidance

Linear guidance is provided by rails or bearing systems that keep the piston moving in a straight path and absorb radial forces during movement. The quality of the guidance has a direct impact on the precision of the positioning of the cylinder.

In short, the electric actuator is a key element of modern mechatronics and has many advantages over traditional hydraulic and pneumatic systems. There are several types of electric cylinders, such as worm screw cylinders, rack and pinion cylinders and toothed belt cylinders. The choice of a type of cylinder depends on the specifics of the application, the desired performance and environmental constraints.

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