The process for selecting an electric actuator is similar to one for hydraulic or pneumatic actuators, with a few differences. Here are the essentials.
A good place to start is the motion profile itself. This will spell out the demands for velocity and time as well as force (or torque) and the required travel distance. This is also the place to determine the maximum stroke needed as well as maximum and minimum speed requirements.
Another critical factor is calculating the load. This can have many different components including inertial load, friction load, the external applied load as well as the gravitational load. Load calculations will also depend upon the orientation of the actuator itself; that is, whether it’s horizontal or vertical.
Duty cycle is another important factor. This is defined as the ratio of operating time to resting time and is usually expressed as a percentage. The cycling rate may be in seconds, minutes, hours or even days, and knowing the operating hours per day may also be necessary. Knowing the duty cycle will help in estimating the life requirements of the system and can also eliminate problems such as overheating and faster wear and premature component failure due to an incorrectly sized actuator.
The positional accuracy and precision demanded by the application also needs to be known. Make sure that the precision of the actuator meets or exceeds the application’s requirements for accuracy, backlash, and straightness and flatness of linear motion. This directly impacts the cost of the system because if the application doesn’t demand high accuracy or precision, then there is no need to buy a more expensive actuator when a less expensive one will satisfy the demands of the application.
Aside from the technical specifications mentioned above, there is also the need to select the proper configuration for the actuator in the final design. This includes mounting considerations and the need for any other external components such as holding brakes and communication and power cables.
Lastly, consider the operating environment for the actuator. What are the temperature requirements? Are there any contaminants such as water, oil or abrasive chemicals? Contaminants can affect seals and impact the working life of the actuator. In such cases, selecting the appropriate IP rating for an application can guard against the affects of contaminants.
Filed Under: Motion Control Tips
