80kHz Ultrasonics / Evenly Distributed Cleaning Action for
Late in 1992, Zenith demonstrated the ULTRAPROBE Ultrasonic Testing Instrument
at the IMTS show at McCormick Center in Chicago, IL. At this time,
customers purchasing ultrasonic cleaning equipment were being told that the
scrubbing action being produced in ultrasonic cleaners was completely evenly
distributed, and that Standing Waves were overcome by the inclusion of
Sweep Frequency Circuits which were added to the generators to sweep the output
frequency to the transducers, thereby eliminating the gaps between standing
waves. They could not have been more incorrect.
The ULTRAPROBE clearly indicated that standing waves are NOT eliminated by
Sweep Frequency Circuits. In fact, this circuit made NO VISIBLE CHANGE to
the standing wave positions in an ultrasonic cleaning tank, and the same thing
applies today. No one in 1992 had ever seen a device such as this, or how
ultrasonic cleaning action was distributed in an ultrasonic tank. After
all, other vendors claimed that standing waves did not exist. Yet, every
competitive system tested demonstrated the same standing waves regardless of the
design of their Sweep Frequency Circuits. Soon after the 1992 show, all
major manufacturers of ultrasonic cleaning systems were offering frequencies
above 40kHz, finally realizing the benefits of 80kHz that Zenith had promoted
cleaning systems, regardless of manufacturer or frequency, produce a scrubbing
action which is distributed as a series of an equidistant bands known as
Standing Waves which begin at the transducer mounting location, which is
typically the bottom of the tank. The frequency of the ultrasonic cleaner
will determine the distance between these bands of activity. The higher
the ultrasonic frequency, the closer these bands will be to one another, but the
less powerful the activity will be at any one location. High-frequency
ultrasonic systems generally produce a very evenly distributed cleaning effect,
but a less powerful one, while low-frequency ultrasonic systems produce a
cleaning effect with large areas of inactivity, but the cleaning action is more
powerful at standing wave locations.
The photograph at the right depicts Zenith's ULTRAPROBE Ultrasonic Testing
Instrument, which visually displays the ultrasonic scrubbing action distribution
in an 80kHz ultrasonic cleaning system. This patented device is composed of
a quartz test tube which is filled with a colored detergent mixture, and
precious metal particles of a specific size. When the tip of the
instrument is inserted into an ultrasonic cleaning system, the metal particles
migrate to areas of intense ultrasonic activity. Note that there are light
colored bands spaced roughly 1/4 inch apart in this instrument. This is
the scrubbing pattern that an 80 kHz ultrasonic system will produce. As
you can see, almost no areas of inactivity exist, and ultrasonic cleaning energy
is very evenly distributed in this tank.
Although the 80kHz frequency produces a more evenly distributed cleaning
effect, the scrubbing action that is produced is less powerful than lower
frequencies, which can be positive or negative. If parts being cleaned
have contaminants which are highly bonded, the 80kHz frequency may not remove it
from the parts without the use of a detergent or cleaning fluid which can loosen
the bond of the contaminants to a level where existing scrubbing action can
remove it. In other words, cleaning fluid effectiveness becomes more
important when removing highly-bonded contaminants in an 80kHz cleaning system
80kHz systems are perfect when the parts include a high level of detail, such
as threaded areas, small holes, folded metals, or other similar features, and
when the contaminants are lightly bonded. These contaminants can include
machining oils, coolants, lubricants, particles, metal chips, and similar
contaminants. However, with the proper cleaning agents, an 80kHz system
can remove highly-bonded contaminants such as burned carbon, rust, and others.
80kHz ultrasonic systems are very quiet during operation since the frequency
is well above the human hearing range. The sound is composed of a gentle
buzz that can barely be heard when the cover of the tank is closed.
80kHz ultrasonic cleaners are non-destructive to the ultrasonic cleaning tank.
Cavitational Tank Erosion, the slow deterioration of the
cleaning tank at the transducer mounting locations, hardly exists at 80kHz, and
systems have been operated for decades, every day, without a single tank
Here is an example of how frequency can make the difference between success
and failure when cleaning fine detail in a part. A recent customer had
purchased 4 table-top ultrasonic cleaner through McMaster Carr with
Multiple Frequency Ultrasonics operating at
40kHz. The objective
was to clean a hole the size of a human hair that was used to manufacture nylon
strands. The customer contacted Zenith directly after the system failed to
clean successfully, and the recommendation was made to submit parts to Zenith
for our Ultrasonic Testing Service. Upon receipt of the parts, Zenith
test-cleaned the items using a 40/80kHz
CROSSFIRE system, and returned the
samples for evaluation. The higher-frequency system cleaned the item
successfully, and all 4 systems were converted to 40/80kHz as a result.
80kHz systems also have an improved ability to remove particles of a smaller
size. Testing which was performed a few years ago indicated that
40kHz ultrasonics performed better at removing particles larger than .7 microns in
size, while 80kHz performed better at removing particles down to .2 microns and
Today, Zenith rarely delivers an ultrasonic system with all 80kHz ultrasonic
components. The customer typically purchased a
CROSSFIRE 40/80kHz system
for improved performance. Although 80kHz alone could more-than-likely
address the application, the
CROSSFIRE option increases system capabilities, and
is currently our best-selling equipment frequency. By combining the 2
frequencies together, one does not sacrifice power for penetration, and the
range of particles addressed by the system is greater than either frequency
When to Use 80kHz Ultrasonic Cleaners:
- When Cleaning Light-weight, Detailed Parts.
- When Removing Lightly-bonded Contaminants.
- When Lower Frequencies Fail to Clean a Part.
- When Cleaning Thin Contaminant Layers.
- Particles Being Removed are Possibly Sub-micron in Size.
For additional information,
85 Oak St.
Norwood, NJ 07648-0412