Actuators that use electrically-powered rods are starting to replace fluid powered actuators across many industries for high-force applications. Tasks like holding, pressing, spot welding and lifting used to be limited to just pneumatic and hydraulic cylinders, but they can now be carried out by electric actuators, partly because of their decreased life cycle costs. Furthermore, electric actuators possess better accuracy, flexibility and speed and this will increase production speed and integrate more flexibility and adaptability into machines.

Benefits of electric actuators

Electric actuators bring many advantages to engineers and designers over their fluid powered counterparts. Let’s go through some of the main advantages:

Energy efficiency

Electric actuators generally operate from 75% to 80% efficiency range. By contrast, pneumatics usually are in the 10% to 25% range, and hydraulics generally range from 40% to 55%. There are many different factors that contribute to the efficiency of fluid powered systems, including pressures, seal integrity, temperature, system leaks and compressor design.

Another big factor that impacts the efficiency of electric actuators is that they only use current in the drive motors when it is needed. Electric actuators at rest consume very little (or no) current to stay in their hold position. Fluid powered actuators constantly need a pressurized fluid, which is not an efficient use of power.

Compact and quiet

Electric actuators are not just great for your pocket, that are also smaller that fluid powered actuators which is very useful in crowded factory floors or in tight spaces. Hydraulic systems need a power unit, control valves, a cylinder, filters and other components. Electric systems just need the motor and actuator itself, and a small control space for the drive, which is typically located near the point of use for convenience.

Power units that run fluid cylinders are usually noisy, have the potential to damage the hearing of a person if they work or walk too near to them, and are generally a nuisance. Electric actuators are known to be a lot quieter.

Accuracy and repeatability

Typical fluid powered actuators are pretty good for end-to-end stroking applications, however mid-stroke positioning is quite complex and needs operator assistance and a control valve. Servo hydraulic controls are more advanced and can give increased repeatability and precision, but the complexity and cost of the system also increases. Electric actuators provide infinite positional flexibility, are much less complicated, and need much less interference once they are programmed to maintain their consistency and accuracy.

Clean and green

Dangerous messes in factories are created by hydraulic system leaks. As well as general leaks, hydraulic fluid can also get into key processes and contaminate them, any food products, medical devices, pharmaceuticals, as well as the environment. Within pneumatic systems, if there are any air leaks it can create unwanted noise, waste energy and impact air quality. Fortunately, electric actuators do not have any of these disadvantages.

As an example, if a lumber processing company wanted to replace their hydraulic cylinder in the log cutting setup to get rid of any potential hazardous leaks into the environment, they could choose an electric ball-screw to actuator to move the saw blade. This type of actuator comes with an IP67 water resistance rating and can also be lubricated with high/low temperature grease in order to keep its performance reliable and consistent in any weather conditions.

Minimal maintenance

Electric actuators that are properly sized need very little maintenance, and in most cases none at all. If they are used in a high-performance application, they might need to be re-greased, but this is a low-cost, easy procedure that will not need to be done very often. Fluid powered actuators are generally quite rugged and easy to install and use, but do need a good amount of maintenance to keep them running consistently. Oil and air maintenance are two of the main tasks required on a regular basis to ensure that contaminants and humidity do not destroy their seals and other parts of the system.

A steel mill could choose to replace hydraulic actuators with electric models due to the intense amount of maintenance that the hydraulic actuators needed. However, the actuators secured as replacements must still carry a lot of power, as it can take up to 15,000 pounds of force to pull a hot casting out of a mold, and almost three times that if the casting cools in the mold! Again, rod-style electric actuators could be used here with high-capacity roller screws, which will meet the thrust requirements, but also keep maintenance to a minimum. These types of actuators are strong enough and carry an IP65 rating so they will be able to last as long as possible in a dirty, hot foundry.

Improve productivity

Electric actuators can increase the general productivity within their application over their fluid powered competitors. Their advantages in positioning help them to be much more efficient, and they are fully programmable, allowing them to do runs of various lengths. In contrast fluid power actuators can only be set up to do one run length, so if the required run length is shorter, energy and time are wasted on every run.

Automotive wheel bearing manufacturers have used hydraulic actuators in the past which need to be adjusted for every different sized wheel that came down the line. This was a slow process and led to more time and money wasted. With electric actuators they can be changed over to different sized wheels using control program procedures operated with a simple push of a button.

Low costs over life cycle

Electric actuators are known to be at least twice as efficient as hydraulic systems, but they do cost more upfront. When the increased performance, lower maintenance, lower energy costs, system flexibility and process improvements are taken into account, they end up being much cheaper than hydraulic systems over the course of their life cycle.

What do you think of electric actuators? Are they really better the fluid powered actuators in every way?

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