There’s no doubt ultrasonic cleaning is simple, versatile and effective. No other method can deliver the same spotless cleaning in the same short timeframe while offering an equal level of safety for your parts and employees. But even though you’re dealing with a simple process, an adjustment in the frequency your ultrasonic cleaner operates at can make a noticeable difference in performance.
Why does “hitting the right note” matter? It comes down to the details of cavitation. When ultrasonic waves travel through a liquid, they form bubbles on the surface of submerged items. But the waves also cause the bubbles to collapse, and as they do so, they create a powerful jet of liquid that strikes the surface and any contaminants clinging to it. This creates a constant scrubbing action.
Different frequencies will produce larger or smaller bubbles. The higher the frequency, the smaller the bubbles are. The smaller they are, the more gentle the scrubbing action will be, and the more evenly the bubbles will be distributed across the surface. Smaller bubbles also penetrate cracks, crevasses and other narrow and/or deep recesses more effectively. The larger bubbles produced by lower frequencies create a far more powerful cleaning action, but don’t penetrate as well.
Let’s take a look at the available frequency ranges, what they can accomplish and what the best items to clean them with are:
This frequency is quite low, just above the top of the human hearing range, which is 18kHz. It produces relatively large, powerful bubbles, which strike the part being cleaned with a powerful jet. This makes it the ultimate scrubbing tool for contaminants which are thick and/or tenaciously sticky. This frequency is ideal for cleaning large, durable metal parts—such as engine blocks, radiators, dies—and any parts for which finish isn’t a critical consideration. The main disadvantage is that the bubbles produced won’t penetrate narrow crevices.
This is the most commonly used frequency in industrial applications because it hits the “sweet spot” for scrubbing power and penetration. It can be used for about 95% of ultrasonic cleaning applications. The bubbles it produces are about a micron in diameter, and can deliver excellent cleaning results in all but the smallest spaces. It’s gentle enough for almost all materials and the bubble size also provides good coverage on wide surfaces.
For some materials, 40kHz is too aggressive and can leave damage behind. Those parts—such as hard drive components, electronics, buffed soft metal parts and precision optics—call for the gentler scrubbing action of a higher frequency. As you’ve probably guessed, this frequency also penetrates into even smaller spaces than 40kHz.
132kHz to 170kHz
This is the highest frequency range commonly used in industrial ultrasonic cleaning, and offers the ultimate in gentle cleaning and penetration of even the tiniest crevices. It’s commonly used to clean pharmaceutical products, medical implants, titanium components and unusually delicate electronic parts.
With the right frequency and our Vibra-bar® Simultaneous Multi-Frequency® transducers, you can clean nearly anything, and do it with a healthier bottom line. To see how our customers used our cleaners to reduce costs and deliver a cleaner product, click here to learn about Ushers Machine and Tool.