Ultrasonic cleaning tooling is one of the most demanding applications for ultrasonic cleaning equipment. We need heavy-duty equipment that can withstand a lot of abuse. Operating temperatures are high (ideally180°F), loads are heavy (which absorb ultrasonic energy), cleaning solutions are typically alkaline in chemistry for best cleaning performance,

and ultrasonic cycle times are longer than in typical ultrasonic cleaning applications (typically 10 to 30 minutes as opposed to 1 to 5 minutes for the typical parts cleaning application).

Ultrasonic Transducers
For these reasons, it is important to understand that there are two different types of ultrasonic transducers used in ultrasonic cleaning tanks: magnetostrictive and piezoelectric . The transducers are the heart of the ultrasonic cleaner and the basis for the tank design. Both types of transducers do the same thing—vibrate a wall in the tank at an ultrasonic frequency—but they are completely different in design and durability.

Most manufacturers use piezoelectric transducers in their systems. They are inexpensive to manufacture, cheap to buy, lightweight and can be attached to the tank (or face of an immersible transducer) by simply bonding them on with epoxy. Because they are lightweight, they are attached to a thin tank diaphragm.

Piezoelectric systems have the following problems over the long term when it comes to heavy-duty applications, such as tool cleaning:

Susceptibility to cavitation erosion—pitting through the tank wall where the transducers are attached (can happen in as little as six months to two years in an aggressive application and is not warranted by the manufacturer).

Deterioration of the output of the piezoelectric transducer, which reduces cleaning performance over time.

Detachment from the tank due to epoxy bond failure.

Inability to operate at higher temperatures (typical recommended maximum temperature for a piezoelectric cleaning system is 160°F)—the higher the operating temperature, the faster the deterioration of the piezoelectric transducer.

The other type of transducers are magnetostrictive transducers, which are manufactured of a pure nickel alloy and utilize an inherent property in the material (magnetostriction) to create the vibration in the tank wall. While this technology is more expensive to manufacture, it offers the following benefits when operating in a heavy-duty environment:
Consistent performance over time, as the magnetostrictive property in the nickel never deteriorates; it is part of the chemical structure of the material.

Ability to operate at high temperatures (180°F-200°F) for extended periods with no degradation of the material or cleaning performance.

In addition, there are several methods of assembling and attaching magnetostrictive transducers. One is using flat nickel laminations formed into a stack (resembling a small transformer), which is known as zero-spaced. The other method uses corrugated laminations so that when formed into a stack, it resembles a honeycomb from the end view. The zero-spaced method uses more nickel (added cost), but allows for several additional benefits:
The zero-spaced stack is silver brazed directly to the radiating face, creating a solid all-metal joint that provides improved energy transmission.

The zero-spaced stack has much more mass, which drives a more powerful pressure wave into the tank bath; therefore providing better cleaning power and less load sensitivity.
Because there is more mass, the radiating diaphragm that the transducers are brazed to is much thicker, eliminating the routine problem of cavitation erosion.