What’s the Difference Between Pneumatic, Hydraulic, and Electrical Actuators? An overview electrical machine design pdf download the differences between powered actuators and their benefits. A linear actuator moves a load, which can be an assembly, components, or a finished product, in a straight line. It converts energy into a motion or force and can be powered by pressurized fluid or air, as well as electricity.
Here is a breakdown of common linear actuators, their advantages and their disadvantages. Pneumatic linear actuators consist of a piston inside a hollow cylinder. Pressure from an external compressor or manual pump moves the piston inside the cylinder. As pressure increases, the cylinder moves along the axis of the piston, creating a linear force. The piston returns to its original position by either a spring-back force or fluid being supplied to the other side of the piston. Hydraulic linear actuators operate similarly to pneumatic actuators, but an incompressible liquid from a pump rather than pressurized air moves the cylinder.
An electric linear actuator converts electrical energy into torque. An electric motor mechanically connected turns a lead screw. A threaded lead or ball nut with corresponding threads that match those of the screw is prevented from rotating with the screw. When the screw rotates, the nut gets driven along the threads. The direction the nut moves depends on which direction the screw rotates and also returns the actuator to its original position. Download this article in .
This file type includes high resolution graphics and schematics when applicable. The benefits of pneumatic actuators come from their simplicity. Pneumatic actuators generate precise linear motion by providing accuracy, for example, within 0. 1 inches and repeatability within . Pneumatic actuators typical applications involve areas of extreme temperatures. In terms of safety and inspection, by using air, pneumatic actuators avoid using hazardous materials.
They meet explosion protection and machine safety requirements because they create no magnetic interference due to their lack of motors. In recent years, pneumatics has seen many advances in miniaturization, materials, and integration with electronics and condition monitoring. The cost of pneumatic actuators is low compared to other actuators. Pneumatic actuators are also lightweight, require minimal maintenance, and have durable components that make pneumatics a cost-effective method of linear motion. Pressure losses and air’s compressibility make pneumatics less efficient than other linear-motion methods. Compressor and air delivery limitations mean that operations at lower pressures will have lower forces and slower speeds.
A compressor must run continually operating pressure even if nothing is moving. To be truly efficient, pneumatic actuators must be sized for a specific job. Hence, they cannot be used for other applications. Accurate control and efficiency requires proportional regulators and valves, but this raises the costs and complexity. Even though the air is easily available, it can be contaminated by oil or lubrication, leading to downtime and maintenance.
Companies still have to pay for compressed air, making it a consumable, and the compressor and lines are another maintenance issue. The top image shows a spring return actuator. The maximum spring compression pushes back on the piston and the hydraulic fluid exits the cylinder and returns to its starting position. The bottom image is a double-acting cylinder where fluid enters either side of the piston depending on the desired motion. Hydraulic actuators are rugged and suited for high-force applications. They can produce forces 25 times greater than pneumatic cylinders of equal size. They also operate in pressures of up to 4,000 psi.