Technically inclined people in the baby boom generation no doubt remember the crystal (more properly known as piezoelectric) phonograph cartridge or microphone. Often temperamental, these devices put out a voltage when the crystal was stressed by mechanical motion such as a phonograph stylus or a microphone diaphragm. But the piezoelectric effect also works in reverse: Apply a voltage to a piezoelectric substance, and it contorts, producing motion.

This effect has worked well for Parker Hannifin’s Pneumatic Division North America; its engineers learned how to use it to open and close pneumatic valves. The effect takes little power and can move an actuator up to one-eighth of an inch. That may not sound like much, but 1.5mA of current at 6.8VDC can exert a force up to seven pounds.

So, why not harness this capability to work a robot arm gripper? Well, that was Richard (Rich) McDonnell’s idea, and he, with the help of Parker’s engineering staff, has come up with a gripper with a light touch—one that can pick up light and fragile food products without turning them into crumbs. McDonnell, market development manager for his group, has been experimenting with the gripper, but would love some real-world applications to give it a try.

Using robots for pick-and-place applications can save a lot of time compared to a human doing the same jobs. FE caught up with McDonnell at PACK EXPO and asked him about Parker’s new device, how it works and how compares it with other technologies.

FE: Parker acquired intellectual property and patents a few years ago for piezoelectric technology that can be applied to actuators. Could you explain the history in a little more detail?

McDonnell: Parker acquired the intellectual property around a transducer/actuator from a company based in Florida approximately seven years ago. Immediately after that, Parker established a center for excellence for the technology at the division level. During that time, numerous divisions investigated how the technology could be leveraged to serve their current or emerging markets.

FE: How did you think of applying the piezoelectric valve actuator technology as a gripper for end-of-arm tooling (EOAT) for robotics?

McDonnell: As part of an extensive market research project, a wide range of potential application areas were identified. As it happens, the piezo gripper idea was born out of some internal discussions and in-the-field observations with customers while researching a related application area in factory automation. During these discussions, it became clear to me that there were some unique application areas in the fast-moving consumer goods industry that could benefit from a piezoelectric gripper.

FE: Has Parker applied for a patent for the gripper technology?

McDonnell: Yes, we have taken the necessary steps to protect it.

FE: What kind of engineering support has your group provided?

McDonnell: We have a dedicated business development/engineering team responsible for the commercialization of our piezoelectric products. To date, we have commercialized an ultra-low-power piezo 3/2 pneumatic pilot valve. Our “intrinsically safe” piezo valve is scheduled for launch around the time your audience reads this article.

FE: What are some of the gripper’s capabilities?

McDonnell: In the confectionery product business, we believe our piezo gripper offers unique capabilities for handling high-value chocolates. In such a setting, an end-user would want to ensure the gripper not only precisely grasps and transports the chocolate without marring it, but also releases it into its final container prior to closing. In this situation, the final release of the product can be the trickiest function of all. That’s why, at this stage, our technology provides a short high-frequency vibratory pulse to ensure the product is released into its container.

FE: How does the gripper compare with other gripper technologies?

McDonnell: First, it’s energy efficient. The power consumption of the gripper is less than 2W, which is up to 10 times less than some other solutions on the market. Second, the way the voltage is applied enables our technology to “shake” residual product off the gripper, as I previously described.

FE: In what food applications could the gripper be used?

McDonnell: Here again, I believe our piezo gripper differentiates itself by its precise controllability. By that, I mean its ability to accelerate quickly to a position, slowly move into a final position and then apply only the necessary gripping force for that product’s proper handling and transport. The vibratory pulse comes in, when necessary, to enable the item’s release into a container.

FE: Is anyone testing the gripper now?

McDonnell: No, but we have been working with a leading robot manufacturer that shares our vision for the gripper. In parallel with that, we are open to exploring its use further with food machinery manufacturers or processors that might like to test it in their applications. During such trials, we would optimize the gripper’s design and capabilities to fit their particular requirements.

FE: Would it be possible to develop a parallel gripper with more than one pair of “fingers?”

McDonnell: Yes. Our two-stage actuator design incorporates a unique linkage that provides movement on the same axis as our piezo stack. Because of its forward/backward movement, this could easily be integrated into a gentle-touch multi-finger (three to four) gripper.

FE: How easy is it to adjust the gripper to the size or texture of a product?

McDonnell: Thus far, we have successfully experimented with a variety of items including razors, razor blades and other odd-shaped plastic products. But, here again, I would stress that we would need to work on an engineer-to-engineer basis with clients to optimize the gripper’s functionality for a specific product.

FE: Since the gripper is pretty much an off/on device, how do you control the force of the grip?

McDonnell: That’s just it; our piezo gripper isn’t just discrete (on/off) in its operation. Because it is piezoelectric, its position and speed can be varied by a controller. Its gripping force can also be variable and monitored by a variety of sensors, if the customer wants either of these options.

FE: Would the gripper most likely be used with a vision-guided system?

McDonnell: Yes, in most cases, it would be.

FE: Since the gripper is “looking for work,” is it available for testing?

McDonnell: We do have a gripper available for testing. To learn more or to discuss how we can work together, your readers should contact me via email at