Following on from our article about hydraulics v pneumatics, I got a question via Facebook asking “what about electrical actuators?”
Now, it’s a bit off-piste for us, but our aim is to please, and as a discussion about the differences between them, it’s actually worth putting the work in, so I have, and here it is!
What are actuators?
The primary purpose of an actuator is to move a load which can compose an assembly or some finished products. It is also meant to control mechanisms and is powered using energy in the form of air, pressurized fluid, or electricity sourced through a hydraulic, pneumatic, or electric pump. Energy conversion takes place and the force or motion makes movement and control possible.
By the way, if you’re interested in the physics of how energy is moved around, it’s worth checking out Why Does E=MC2.
Hydraulic Vs. Electrical Power
The obvious difference between a hydraulic versus an electrical actuator is in how each one derives its power.
Just like pneumatics, hydraulic actuators comprise a piston that moves in the inside of a hollow cylinder. Incompressible liquid coming from a pump moves the cylinder. As the pressure is increased, the cylinder is likewise moved along the axis of that piston and creates a linear force. Through fluid supplied on the piston’s other side or via a spring back force, the piston is returned to its original positioning.
The mechanics of an electrical actuator is quite different as it entails conversion of the energy into torque. What takes place is that a mechanically-connected electric motor turns a lead-screw. What prevents the screw from rotating, is either a ball nut with matching threads or a threaded lead. As the screw rotates, the nut is driven along those threads. The direction by which the nut moves is dependent upon the direction where the screw rotates which likewise allow the actuator to return to the original position.
Both hydraulic and electrical systems have their own advantages, but you can count on hydraulic actuators to be more suited for high force applications. These rugged actuators can produce force that is 25 times more powerful than pneumatic cylinders of the same size. They can operate in pressures as high as 4,000 psi. They can even hold torque and force constant without the need for a pump to supply more fluid or pressure because it makes use of incompressible fluids. You can put the motors and pumps away at a certain distance without much power loss.
Meanwhile, electrical actuators are the kind of systems you can rely on for precision control positioning at the highest level. The range of accuracy is at +/- 0.000315 in. while repeatability is less than 0.0000394 in. They are set up to be scalable for any type of force requirement or purposes. They are smooth, network-friendly, reprogrammable, repeatable, and quieter compared to hydraulics. They can give you diagnostics or maintenance feedback almost immediately.