As with nearly any actuation technology in industrial automation applications, there is no shortage of opinions around the use of electric or pneumatic motion control. These predilections tend to get even more precise when you’re talking about multi-axis motion control.
To help better understand the differences between electric and pneumatic multi-axis motion control technologies, we connected with Anthony Leo of Norgren, a supplier of industrial pneumatic and electric motion control, sensors and actuation technologies for a recent episode of the “Automation World Gets Your Questions Answered” podcast series.
Leo first explained that multi-axis motion control is used to perform a task within a 3D plane. This could be robotic pick and place, material handling or even 3D printing. With electric systems, he noted that multiple motors have to be combined and controlled on the machine. “It’s kind of like an etch-a-sketch, where you turn the knobs in different directions to move along the X and Y axes. But you also have motion along the Z axis. With electric systems, it’s easier to have precision control and is generally easier to set up than a pneumatic solution, because you don't need all the compressed air infrastructure. That also means you're going to have a little bit less maintenance than traditional pneumatic solutions, whether with the actuators themselves or with the air lines that supply the air.”
Weight and distance
In terms of weight handling capability, Leo notes that it’s critical to size the appropriate actuator for the application to ensure that it will work as expected. “Because we need to calculate the moment of inertia to appropriately size an actuator, the weights involved in the application will drastically affect the performance and the durability of the product. If the application has an offset load, or if you're pushing or pulling something, that all matters—not just to the design aspects of a multi-axis system but even to single-axis electric actuator solutions.”
As for distance, Leo says this factor isn’t a concern with electric multi-axis motion control. “Some of our longest applications up to 60 meters, which is pretty long,” he said, “but we also have applications where we're moving just 20 millimeters.”
Speed and accuracy
Leo said that Norgren’s multi-axis electric motion control systems can accelerate up to 10 Gs. He notes, however, that achieving such speeds will depend on the guide and drive systems used in the actuator.
For short movements, Leo noted that “pneumatics perform very well and have been used forever for very short, quick actuation,” Leo said. However, there are maintenance and air supply issues to remain aware of with pneumatics that make the decision between electric and pneumatic dependent on the application’s parameters.
While speed is often a critical aspect in automation applications, accuracy is typically the more critical characteristic. Leo noted that accuracy is “probably one of the key reasons why people have been looking at replacing pneumatics with electric, especially when they're designing a new system. Electric allows for much more precision capabilities than pneumatics since you're basically just driving a motor. With pneumatic motion control, there's a lot more effort and time that goes into the setup to get pneumatic [actuators] to go to a specific point and dial that [accuracy] in. And if you have a drop in air pressure or a seal that starts to wear, the accuracy will start to go away. So dependable accuracy is definitely one of the big reasons for choosing electric compared to pneumatics—having that ability to quickly get it exactly where you want it and know that it's going to go back to that same place every single time. Electric is extremely good at that.”