Q: How to use Piezo Actuators?

A: While piezo actuators can be reliable actuators, they are often kept to the smallest dimensions possible, driven near their limits, and/or implemented improperly in a system. Piezo actuators are sometimes viewed as the weakest link in a mechanical system, particularly because improper use can cause cracking or failure in the piezo actuators. Failure modes in piezo actuators may not be immediately observable but can affect long-term reliability and reproducibility.

Mounting PZT Devices

Piezo ceramics are brittle and have low tensile strength. Avoid loading conditions that subject the actuator to lateral, transverse, or bending forces. When applied incorrectly, an external load that may appear to be compressive can, through bending moments, cause high tensile stresses within the piezo device. Improperly mounting a load to the piezo actuators can easily result in internal stresses that will damage the actuator. To avoid this, the piezo actuators should be interfaced with an external load such that the induced force is directed along the actuator's axis of displacement. The load should be centered on and applied uniformly over as much of the actuator's mounting surface as possible. When interfacing the flat surface of a load with an actuator capped with a flat mounting surface, ensure the two surfaces are highly flat and smooth and that there is good parallelism between the two when they are mated. If the external load is directed at an angle to the actuator's axis of displacement, use an actuator fitted with a hemispherical end plate or a flexure joint to achieve safe loading of the piezo element. PANT can also design custom mounting options to meet various user requirements.

One of the most common mistakes in mounting a PZT actuator is a mismatch in the mating faces, particularly in applications that do not use a floating axis. It’s important to note that when mounting flat-face to flat-face, even slight misalignments between the two faces will produce edge squeezing and high pressures at localized spots. Edge squeezing often results in damage to the ceramic PZT.