Ultrasonic Cleaner Frequency and Power - Tovatech

Selecting an ultrasonic cleaner for any cleaning and sample preparation operation requires careful consideration of many factors before making a purchasing decision.  We offer useful guidelines in our post How to Pick the Best Ultrasonic Cleaner.  This post focuses on two points in particular, frequency and power. Ultrasonic frequency is relatively easy to understand; understanding power is a bit more complicated.  So let’s begin.

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How to Specify Ultrasonic Frequency

Frequency is measured in thousands of cycles per second (kilohertz or kHz). 

These frequencies are generated by transducers most commonly affixed to the bottom of the cleaning tank. Some ultrasonic units have transducers bonded to tank sides; others may have immersible transducers.

Wherever they are placed ultrasonic transducers are excited by the unit’s ultrasonic generator to produce millions of microscopic vacuum bubbles in the solution that implode on contact with parts being cleaned. 

The implosions, called cavitation, remove contamination faster and more thoroughly than mechanical scrubbing using wash tanks or aerosol sprays.

(Note that this process is also used for fast, safe sample preparation in the lab.)

Ultrasonic frequency also determines cavitation bubble size. 

Low frequencies such as 25 kHz produce relatively large bubbles that implode more violently than those created at higher frequencies that produce comparatively gentle cleaning action.  Visually the size is virtually impossible to distinguish.  For example a 25 kHz bubble has about 3 times the approximately 40 micron radius of 80 kHz. 

Widely used Ultrasonic Frequencies and Applications

Here are some widely used ultrasonic frequencies and applications for Elmasonic units available from Tovatech:

So, what does this mean?

If you are removing gross contaminants from robust parts such as fabricated or cast metals specify a lower frequency ultrasonic cleaner. 

If you are cleaning delicate items such as printed circuit boards, a higher frequency is recommended.

You will get efficient and thoughtful service from RedCrown.

Popular benchtop ultrasonic cleaners for simple ultrasonic cleaning jobs are the 37 kHz Elmasonic E+ series in 9 tank sizes from .25 to 7.5 gallons.  Models with additional useful features are exemplified by the 37 kHz Elmasonic Select line in 11 tank sizes.  

Softer metals, plastics, and products with polished surfaces should be cleaned at higher ultrasonic frequencies.  The smaller bubbles are less likely to cause surface damage.  They are also better able to penetrate tight areas such as seams, crevices and blind holes.

If you are cleaning a variety of products consider a dual-frequency ultrasonic cleaner.  An example is the Elmasonic P series that operates at 37 or 80 kHz.

The Role of Ultrasonic Power

Power has several definitions when discussing ultrasonic cleaning and is described in different ways by equipment manufacturers.  In terms of cleaning power it is calculated as the power delivered to the transducers and expressed as watts per gallon (or liter) of cleaning solution. Most cleaners operate at 50 to 100 watts per gallon. 

As power increases so do the number of bubbles, so increased power yields faster cleaning action but only up to a point. Beyond that you are not only wasting energy you also risk damaging parts being cleaned.

Total Power

Another definition is total power or the amount needed to drive everything in the unit including generators and heaters (if supplied).  It should not be confused with power. 

Peak Power

Peak power is defined as the ultrasonic power generated at the summit (or peak) of the vibration amplitude.  In many cases the peak power equals 2X the average power. 

But in some models peak performance may be 4X or 8X the average power depending on the wave shape. 

You don’t need to understand the physics but you do need to understand that while it makes sense to compare the average power of two different units of the same size, it’s not meaningful to compare peak power of one unit to average power of a different unit. You would be comparing apples with oranges.   

Variable power is offered on certain units such as the P series mentioned above. Another useful feature on the Elmasonic P series ultrasonic cleaners is a pulse mode that provides bursts of power to remove tenacious contaminants.

Still Have Questions About Frequency and Power?

This post does not answer all questions on frequency and power but should give you an idea of the importance of these features when purchasing an ultrasonic cleaner. 

Call or chat with the ultrasonic professionals at Tovatech for guidance through the process and to recommend the correct equipment for your requirements.

Contact us to discuss your requirements of Laboratory Ultrasonic Cleaner. Our experienced sales team can help you identify the options that best suit your needs.

Caz: Just a quick remark; I have a HF cleaner and it has been fine. I wish the timer could be set for a longer time and I would like it to be physically larger, but that said, it has performed okay for small clocks. I'm thinking that maybe an additional $100 would have been wiser for something larger, etc.. Hindsight is always 20-20 and at the time I really didn't know what to do and hated to make the additional investment. It seems to be the story of my life, because I've made the same mistake when purchasing other type items. Good Luck and Best Regards: Larry

Here's a link to one that's sold just a few miles away from me and this company makes many sizes and variations.

http://www.ebay.com/itm/COMMERCIAL-...847?pt=LH_DefaultDomain_0&hash=item461cf

My question is pretty much expressed in the title. I have been using a cheapo ultrasonic cleaner from Harbor Freight, and it has been working well for me. I mean, it has never failed to get small parts clean. So what's so good about a better, more expensive machine? I see that I could spend hundreds of dollars for a high-quality one. I have heard (I forget where) that the better ones operate at a higher sound frequency, making smaller bubbles in the cleaning fluid, and somehow smaller bubbles. I don't see why that would make it better. First, is that true? Can someone explain the difference between high & low quality ultrasonics, besides the obvious added features like drain plugs and heating units?
Thanks,
...Doug

Doug
There is a vast difference between inexpensive and quality ultrasonic units, but it must be demonstrated to be understood since the difference will not be obvious from a naked eye glance.
Since you are happy with the unit you have, I assume that you have disassembled parts that are normally assembled when cleaning such as winding arbors etc. to check its effectivness.
Proper cleaning will have penetrated even the tightest moving part areas and even more important will have removed any trace of cleaning fluid when in the rinse cycle. If not, you run the risk of parts prematurely gumming up and possible corrosion.
If by chance you are not happy, you can attend any of the larger machine tool shows, where differences can be demonstrated and discussed especially if you bring samples of what you are trying to do.

Jerry Kieffer

Doug
There is a vast difference between inexpensive and quality ultrasonic units, but it must be demonstrated to be understood since the difference will not be obvious from a naked eye glance.
Since you are happy with the unit you have, I assume that you have disassembled parts that are normally assembled when cleaning such as winding arbors etc. to check its effectivness.
Proper cleaning will have penetrated even the tightest moving part areas and even more important will have removed any trace of cleaning fluid when in the rinse cycle. If not, you run the risk of parts prematurely gumming up and possible corrosion.
If by chance you are not happy, you can attend any of the larger machine tool shows, where differences can be demonstrated and discussed especially if you bring samples of what you are trying to do.

Jerry Kieffer

Ditto. One easy objective" test the user can do to check the effectiveness of the cavitation of US machines is the "aluminum foil test...You suspend a strip of aluminum foil in the bath and run the machine for say 1 or 2 minutes, then examine the foil for the size and pattern of the "dents" made by the cavitation bubbles. You can check this at different positions and orientations in the tank to see if there are "hot" and "cold" spots. You can then label the strips and keep them to compare with previous tests to see if performance changes and you can also compare how different machines (e.g. the HF and other machines) perform on this test. I don't know enough about the different Hz or all that other technical jargon, but when I bought my first Ultrasonic, I bough one of the cheaper models. It worked fine and did the job, but as I got busier and was cleaning more movements, I quickly realized it was too small. I bought a larger one and that is when I discovered some of the differences.

The first one had a heater, but it would take all day to warm it up. The temp was set with a dial that did not indicate the actual temp, but just hi-lo. The new one has a digital temperature setting and also the actual temperature readout. It really does make a difference if the cleaning solution is hot, and now with the new machine, I know what temp I'm working with. The new one heats up much faster, too.

The new one does clean much more thoroughly. I usually peg out the bushings after coming out of the cleaner just to make sure nothing was left behind. With this new cleaner, I rarely find any dirt on the peg.

As far as other features, the new one has a drain which helps a lot. Now, I hook up a hose and run the dirty solution through a sieve before tossing it. No more little washers and pins being thrown out... It also helps to extend the life of the cleaning solution since the sieve gets a lot of the gunk out of the solution. Usually all I have to do is add a little more concentrate and I'm good to go again.

Except for the size, I was satisfied with the smaller cleaner because I didn't realize what the advantages were over the larger models. I will agree, however that if you are not doing a lot of cleaning, you do not need to spend a lot of money.

My question is pretty much expressed in the title. I have been using a cheapo ultrasonic cleaner from Harbor Freight, and it has been working well for me. I mean, it has never failed to get small parts clean. So what's so good about a better, more expensive machine? I see that I could spend hundreds of dollars for a high-quality one. I have heard (I forget where) that the better ones operate at a higher sound frequency, making smaller bubbles in the cleaning fluid, and somehow smaller bubbles. I don't see why that would make it better. First, is that true? Can someone explain the difference between high & low quality ultrasonics, besides the obvious added features like drain plugs and heating units?
Thanks,
...Doug

CAZ, I have two. One is a cheaper model bought off the Internet. I also found a Gesswein at a local auction a year or so ago, and I almost exclusively use it because it works so much better than the other one. Here's a link:
http://www.gesswein.com/c-44-ultrasonic-cleaners.aspx
I have the three quart sweep model. I have not looked at a wide range of ultrasonics in a few years. In years past the "better" grades of ultrasonics may have had more transducers, thicker stainless steel, better electronics, built in drains, a range of accessories, and at least in the recent past some of the best rated were still made in America. Don't know if any of that holds today, my last new ultrasonic was about 10 years ago. By the way, some of the industrial grade ultrasonics can be had be had surplus from time to time, I had one with a 6'x2'x'2' tank and the power supply was 3 phase.....and it would disintegrate a sheet of aluminum foil in seconds....not of much use in clocks, but the real power the unit supplies does make a big difference in cleaning......and as others have mentioned not all companies use the same formula for determining "power",they advertise. Reputable company, heated tank, good history of offering repair, highest power is desired, good usable sized tank, built in drain, are the attributes I would look for. Another huge limitation of the 2.5 liter HF ultrasonic is something an owner made mention of on Harbor Freight's own website. Between the outer plastic shell (it might be a tad thicker than an eggshell, but not by much) and the inner stainless steel liner is a seam where the two come together. Unfortunately the seam is in the INSIDE of the tank, about 1/2" from the top lip. Since there is no drain, you have to tip the tank over and pour the liquid out...so liquid can easily seep into the seam where you pour, and travel between the inner and outer shell and settle where the electronics are, and maybe burn the unit out. I saw that review before I plugged mine in for the first time, so I just ran a bead of JB-Weld along the seam and let it dry. It's still a cheap crappy ultrasonic, but at least it won't burn out prematurely from infiltrating liquid!
I also wish the unit came with a timer with working times longer than 6 minutes, but I just run mine multiple times.

Thanks guys, I've gotten a lot out of this thread. Especially the photo posted by davefr - I can see clearly that you get what you pay for. At some point the HF ultrasonic will cease being sufficient for me - I guess it's been a good starter unit, though. It's certainly cheap.
...Doug

8 transducers! I'm sure there is a reason for that, but for watch/clock cleaning I think 2 ought to be sufficient for up to a 1 gallon tank. How large is the bath in that machine and for what use was it intended?

I've got an Ottosonic T4.4, which has been working quite well for several years. It is rated at 120W, has a heater, and uses two transducers.

L&R claims the 8 transducers eliminate any hot spots and dead zones in the bath. It's a 400 watt/3.1 gallon unit.

It's really overkill for what I use it for but I stumbled across it super cheap. (It was surplus from a medical lab that I found at a garage sale.)

I like it because it's fairly quiet. My previous unit was a Crest and I just couldn't stand the sound.