In Ultrasonic Cleaning, an Historical Perspective, author Timothy J. Mason notes “The development of ultrasonic cleaning dates from the middle of the 20th century and has become a method of choice for a range of surface cleaning operations.” This helps explain why, according to a Fortune Business Insights report, “the global ultrasonic cleaning equipment market was $604.8 million and projected to reach $783.1 million by 2027.”
The Basics of Ultrasonic Cleaning
A way to describe how ultrasonic cleaners work is likening them to an automatic dishwasher, but with some added refinements. An automatic dishwasher, much the same as an ultrasonic cleaner, combines water and a detergent to remove grease, grime and other contaminants from objects being cleaned.
But instead of cleaning pots and pans and bowls, ultrasonic cleaners most often are used to clean various other metal and plastic products difficult or impossible to clean by other methods. Applications for ultrasonic cleaners include cleaning greasy engine components, newly machined and fabricated components, medical and surgical instruments, precision optics and laboratory glassware.
Unlike high-pressure water sprays used in automatic dishwashers, ultrasonic cleaners work by using the power of imploding (not exploding) microscopic bubbles in a process called cavitation.
Ultrasonic Cleaning Unit Size and Features
Understanding how ultrasonic cleaning works calls for an understanding of equipment size and features. A Google search for these cleaners will reveal that models and pricing range all over the map. The basic features to consider consist of the following:
- Tanks to hold the cleaning solution. Tanks should be of stainless steel; their size (volume) depends on the size of objects being cleaned. Ultrasonic cleaning equipment ranges from small tabletop units to huge, multi-gallon industrial cleaners.
- Ultrasonic transducers that create the cavitation and that are bonded to the bottom of the tank.
- A generator to power the transducers
- Controls that range from a simple on-off switch to sophisticated microprocessors that govern cleaning time, sweep, pulse, degassing, temperature, ultrasonic frequency, ultrasonic power, auto safety shutoffs and other more.
Read more about selecting ultrasonic cleaner features.
What Do Ultrasonic Transducers Do?
There are two basic types of transducers; piezoelectric (a.k.a. electrostrictive) or magnetostrictive, but their function is the same.
They are excited by electric current provided by the ultrasonic cleaner’s generator to vibrate at ultrasonic frequencies that cause the bottom (and sides as the case can also be) of the tank to vibrate and serve as a membrane.
This vibration forms the vacuum bubbles that implode, (not explode) on contact with items in the ultrasonic cleaner tank thereby blasting loose and carrying away contaminants.
Check this post on piezoelectric and magnetostrictive transducers for more information on the differences.
How to Choose an Ultrasonic Cleaning Frequency
Ultrasonic is typically defined as sound above the human range of hearing. Ultrasonic frequency is defined as kilohertz (KHz) or thousands of cycles per second.
Low frequencies such as 25,000 cycles per second or 25 kHz produce relatively large bubbles that implode more violently than those created at higher frequencies such as 37, 80 or 130 kHz that produce progressively gentle cleaning action.
As an example, the radius of a cavitation bubble produced at 37 kHz is approximately 88 microns. At 80 kHz it is 41 microns.
As a bit of digression, the implosion of cavitation bubbles produces shock waves radiating from the site of the collapse and create temperatures in excess of 10,000°F and pressures in excess of 10,000 psi at the implosion site.
Yet the process is so fast that there is little heat buildup and no damage to parts being cleaned. That said, one should never reach into an operating ultrasonic cleaner to check, reposition or remove parts for examination.
Removing gross contaminants from robust parts such as fabricated or cast metals requires lower frequency cleaners.
Softer metals, plastics, and products with polished surfaces should be cleaned at higher frequencies. In addition to protecting polished surfaces smaller bubbles are better able to penetrate tight areas such as seams, crevices and blind holes.
Find out more about how to select the right ultrasonic frequency and power.
Baskets for Ultrasonic Cleaning
Ultrasonic cleaners work best when cavitation bubbles access all surfaces immersed in the cleaning solution. This is best accomplished when parts are suspended in the solution, not reposing on the cleaning tank floor (a bad practice).
In the majority of instances, ultrasonic cleaning baskets are used to hold the parts at the proper distance from the tank bottom. Baskets typically are of stainless-steel mesh with mesh or solid stainless-steel walls.
Small parts such as screws can be placed in fine mesh baskets that either rest in the tank basket or are suspended in the solution. Very large parts can be suspended from overhead supports to the correct depth for cleaning.
Find out how baskets and accessories can boost ultrasonic cleaning efficiency.
What Solutions Can You Use with Your Ultrasonic Cleaner?
Ultrasonic Cleaners use biodegradable cleaning solution concentrates specially formulated for the cleaning tasks at hand. The ultrasonic cleaner solution you select plays a major role in successful ultrasonic cleaning operations. Cleaning solutions, chemicals or soaps are available in a wide variety of formulations. <
For details on selecting the right cleaning solution, visit our Ultrasonic Cleaner Solution Selection Tips blog.
Additional Resources for Selecting and Using Ultrasonic Cleaners
Read our tips on how to pick the best ultrasonic cleaner.
Check out these real-life examples of how folks use ultrasonic cleaners to:
- Clean and restore vinyl phonograph records
- Remove contaminants from plastic injection molds
- Clean scuba diving regulators
- Clean jet engine fuel injectors
If you need a cleaner for industrial use, refer to our 101 on selecting an industrial ultrasonic cleaner.
If you prefer video, watch our ultrasonic cleaning learning center videos to learn everything you need to know to get the most out of your ultrasonic cleaners.