Selecting Ultrasonic Cleaner Frequency
Ultrasonic frequency is a key selection criterion when operating an ultrasonic cleaner. The correct frequency yields superior results in terms of efficiency, thoroughness, and in certain cases avoiding damage to parts being cleaned. Moreover, there are projects where more than one frequency is recommended, or when you are cleaning a variety of products calling for different ultrasonic frequencies.
Ultrasonic Frequency Defined
Ultrasonic frequency is defined as sound waves above the range of hearing, nominally 20,000 cycles per second, or 20 kilohertz (KHz).
In an ultrasonic cleaner sound waves are created by transducers bonded to the underside or sides of cleaning tanks. (There are also immersible transducers.) Transducers are powered by ultrasonic generators designed to operate at a specific frequencies – or in some models dual frequencies.
When activated transducers vibrate at their assigned frequency causing the bottom of the tank to vibrate as a membrane and create billions of microscopic vacuum bubbles pulsing through the solution.
When the bubbles contact objects being cleaned they implode, releasing powerful jets of liquid (the cleaning solution) that blast loose and carry away contaminants.
The process is called ultrasonic cavitation. Ultrasonic frequency governs the cavitation bubble size, which directly affects the cleaning process.
What Ultrasonic Frequency Should I Use?
In a sentence, the lower the frequency the larger the bubbles and the more vigorous the cleaning action – although the relative size of bubbles is not observable by the naked eye.
Frequency selection usually depends on what you are cleaning.
A low frequency such as 25 kHz produces (relatively) large cavitation bubbles that implode vigorously and therefore are favored for cleaning heavily soiled parts such as fabricated and cast metals.
Delicate and highly polished surfaces should be cleaned at higher frequencies such as 80 or 130 kHz. Higher frequencies are also recommended when cleaning parts of complex shape and those with cracks, crevices, blind and machined holes. That is because the smaller bubbles are better able to penetrate these difficult-to-reach areas.
The vast majority of cleaning operations can be performed with equipment operating at 37 or 45 kHz.
Dual-frequency ultrasonic cleaners are a good choice if you clean a variety of products with differing characteristics.
A Guide to Ultrasonic Cleaner Selection
Here’s a representative guide to help you select Elmasonic ultrasonic cleaners delivering the right ultrasonic frequency for your cleaning tasks. Please check the links for added details including multi-frequency options.
| Cleaning Task | Suggested Equipment |
| Remove coarse and tenacious contaminants; pre-cleaning robust surfaces such as stainless steel and cast iron | Benchtop Transsonic TI-H, Floor-mounted X-tra ST at 25 kHz |
| Industrial-scale cleaning jobs | Benchtop Transsonic TI-H, Floor-mounted X-tra ST at 45 kHz |
| Common benchtop cleaning jobs | E Plus, Select and P units at 37 kHz |
| Heavy-duty benchtop cleaners for long cleaning cycles | X-tra TT at 37 kHz |
| Heavy-duty industrial large part cleaning | Shirclean units at 40 kHz |
| Laboratory and sanitary cleaning jobs | Benchtop Transsonic TI-H at 45 kHz |
| Fine cleaning sensitive surfaces | Transsonic TI-H; floor-mounted X-tra ST at 45 kHz |
| Highly sensitive surfaces such as micro-electronics and optics | Transsonic TI-H; floor-mounted X-tra ST at 130 kHz |
Points to Consider Beyond Frequency
Ultrasonic “Noise”
While “ultrasonic” is defined as sound above the hearing range, ultrasonic cleaners, especially those operating a low frequencies, are not silent. Noise emanates from vibrations in tank walls and products being cleaned. This can be reduced by having staff wear hearing protectors and by options including sound deadening lids and noise protection boxes.
Ultrasonic Cleaning Chemicals
Cleaning solution chemistry is as important as frequency when it comes to getting the best results from your ultrasonic cleaner.
Most commonly used ultrasonic cleaning solutions fall into three categories: alkaline, acidic and neutral and are briefly described in our post on ultrasonic cleaning chemistries.
These cleaning formulas are usually supplied as concentrates so a little goes a long way. When formulated with non-toxic biodegradable ingredients disposal concerns are eased. Manufacturers provide dilution and cleaning temperature recommendations.
Because most ultrasonic cleaning solutions are water based there may be a concern about rusting when cleaning ferrous parts. Rust inhibitors such as elma KS can be added to address this.
Ultrasonic Cleaner Capacity
When purchasing an ultrasonic cleaner consider the size of the parts you are cleaning.
Most parts are placed in cleaning baskets, the dimensions of which are less than tank dimensions.
You’ll want to specify an ultrasonic cleaner tank size based on the corresponding basket size that will accommodate the parts to be cleaned.
Added to that, parts to be cleaned must be totally immersed in the cleaning solution.
Because of this you must consider what is called the working depth of the cleaning solution.
This is defined as the distance from the inside bottom surface of the basket to the surface of the liquid in a filled tank.
If the working depth of the equipment you are considering is not provided or unclear from the specs, ask the manufacturer.
Rather than go into more detail here, please check our post on selecting ultrasonic cleaner size.
Final Thoughts on Ultrasonic Cleaner Frequency
We hope this post is helpful when it comes to choosing the correct ultrasonic frequency for your cleaning challenges. You’ll find additional important information by viewing our informational video in our ultrasonic cleaning learning center.
When it comes to selecting the right unit, frequency and other important specification details for your tasks please contact our scientists for unbiased recommendations.
