40kHz is the most popular single-frequency ultrasonic system found in the industry today, and has been for some time.  If you have an ultrasonic cleaner in your facility, chances are it is a 40kHz system.  This ultrasonic frequency has a good combination of power, penetration, and even energy distribution, and can successfully address most cleaning applications when combined with a properly-engineered cleaning system.

All ultrasonic 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 a 40kHz 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 1/2 inch apart in this instrument.  This is the scrubbing pattern that a 40 kHz ultrasonic system will produce.  As you can see, there are a large areas of inactivity, but these areas are NOT as large as those found in a 25kHz system.  Cleaning is more consistent when using 40kHz ultrasonic cleaners, but penetration into very find detailed areas, and completely even energy distribution is still not present.  As such, these systems are considered "general purpose" ultrasonic cleaners.

40kHz ultrasonic cleaners are quieter in operation than a 25kHz system, and produces a more gentle cleaning action.  It is appropriate for the removal of common contaminants from parts, but may not consistently remove contaminants from tight tolerance areas.  40kHz also has a tendency to remove particles which are smaller than 25kHz, but not quite as small as an 80kHz system can remove.

40kHz ultrasonic cleaners are less destructive to the cleaning tank than 25kHz systems. 

When to Use 40kHz Ultrasonic Cleaners:

• When Cleaning Medium to Heavy Parts
• When Removing Most Contaminants Found in Manufacturing Environments
• When Parts have Some Detail, but Not ultra-fine Detail, such as small blind holes, threaded areas, and Similar Details
• When Higher Frequencies Fail to Clean a Part.

Common Customer Complaints:

• Cleaning is Not Consistent in Very Fine Detailed Areas.  Sometimes it Works, Other times is Doesn't.

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