Ultrasonic Cleaning Explained

Ultrasonic cleaning is a complex process that involves using ultrasound, usually ranging from 20-400 kHz, (which is above the human hearing limit), along with the right solvent to get rid of a wide range of stubborn contaminants to clean items. This process can help clean a wide range of items, ranging from watches to even fuel injectors.

Metals, glass, ceramics and so on are just some of the materials that can be cleaned using this process. They would be cleaned of pretty much everything, including dirt, oil, bacteria, grease, and many more.

Although this process can even work with using water, it turns out to be much more effective when an appropriate solvent is used. The right solvent to be used usually depends on the item to be cleaned and the type of contaminants.

As far as the time the process takes is concerned, it varies quite a bit. For some items, it may take just around 3 minutes or so, while for some other more complex ones, the time taken may turn out to be around 20 minutes. However, the process is still very fast and effective compared to some of the other ways of cleaning such items.

One of the biggest advantages of ultrasonic cleaning is that the process it follows allows maximizing the use of the things being used, meaning minimal pollution and wastage. Similarly, it’s considered to be powerful enough to get rid of almost everything, including some otherwise extremely stubborn contaminants, yet gentle enough to usually not cause any damage to the item.

The first ultrasonic cleaner was put to use in 1950. However, back then, it was apparently a very expensive product, and hence not used on a wide scale. From the 1970s, however, it became relatively inexpensive, and as of today, it’s widely used in various industries as well as other fields.

Ultrasonic cleaning process overview

To put simply, ultrasonic cleaning uses high frequency (sound) waves to create an agitation in the liquid used in the ultrasonic cleaner. This agitation forces the contaminating agents to lose their hold on the item being cleaned, which is otherwise quite a challenging task. So basically, the process revolves around getting rid of all the contaminating agents without ending up damaging the item.

The process actually uses cavitation, which leads to the formation of millions of small vapour cavities known as ‘voids’. It occurs when the liquid is put under pressure that changes rather rapidly during the process.

Now, as mentioned earlier, you can even use water for this process. In fact, for some particular items, water may turn out to be a good choice.

However, most of the times, it would probably be a better idea to go with an appropriate solvent. Choosing the right solvent would come down to the type of contaminants you want to get rid of as well as the item to be cleaned.

You can use an ultrasonic cleaning for cleaning a wide range of items, irrespective of their size, shape, and such factors, However, the process may obviously differ slightly, especially in terms of the solvent you would need to use and the time it would take to get the item cleaned.

Furthermore, an ultrasonic cleaner doesn’t even require the item to be dissembled in any way to be put in and cleaned. This is usually a huge plus, as apparently, some other similar processes don’t seem to be offering such a level of convenience.

Finally, while using an ultrasonic cleaner, you also need to ensure that the item to be cleaned isn’t allowed to rest at the bottom. This is due to the fact that the process requires the item to be completely exposed in order to clean it thoroughly. So if it’s left completely exposed while the process takes place, it may also be able to clean the item completely, by letting the action penetrate through even the smallest of holes and cracks.

How does ultrasonic cleaning works?

Although this information is a bit too complicated and very technical, we will try putting it as simply as we can to make it easier for you to understand.

The item to be cleaned is simply placed in the chamber of the ultrasonic cleaner along with the suitable solvent. It’s also ensured that the item is completely exposed and is not resting at the bottom. Then a transducer, which may be either built in or lowered into the liquid, starts generating ultrasound waves.

The ultrasonic waves result in the production of compression waves in the liquid, which causes the liquid to “break” apart. This leads to the production of millions of bubble-like particles known as ‘voids’. However, this process also gives out a huge amount of energy, and takes place at an extremely high temperature, with the pressure being up to 500 atm.

With the help of the enormous energy generated, these millions of extremely tiny particles hit the hard surface of the item, causing the contaminants and other dirt particles to leave the surface of the item. However, despite the huge amount of energy this process produces, it usually doesn’t harm the item being cleaned. It’s due to the fact that the particles are so tiny in size that they are incapable of doing anything more than just getting rid of the dirt and contaminants.

Ultrasonic cleaning process infographic

Ultrasonic cleaning process infographic

Understanding more about the transducers used

Coming to the transducers used, which are probably the most important components of ultrasonic cleaners, they are usually of two types, piezoelectric and magnetostrictive. While both are pretty similar as far as the functionality is concerned, they do tend to differ quite a bit when it comes to the performance. Let us take a look at how exactly they differ from each other.

  • Piezoelectric transducers

    Without going into a lot of technical details, we will simply cover what you would actually want to know about them.

    The piezoelectric transducers consist of several different components. They require an aluminum block to be used as an intermediate as there is a little mismatch between the mass of their crystal and their steel diaphragm.

    One of the biggest disadvantages of the piezoelectric transducers is that their performance tends to deteriorate over time. It’s primarily due to the crystal working less effectively due to being used for a long time.

  • Magnetostrictive transducers

    These transducers are known for their durability and ruggedness. Again, without talking about components you would probably understand nothing about, let us simply tell you that they have got a few advantages over their counterparts.

    Firstly, as you guessed it, they are more durable compared to the piezoelectric transducers. Besides that, some of the other advantages they offer include production of more energy, less load sensitivity, offering a consistent performance over a long period of time, and more.

A final word

Ultrasonic cleaning has apparently turned out to be quite a useful process for various industries, as well as cleaning medical and surgical equipments.
However, it’s also probably worth noting that there are a few items that may end up being damaged when made to go through this process, including some electronic components, microphones, gyroscopes, and more.

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