Multi-frequency ultrasonic cleaners are systems that allegedly include more-than-one ultrasonic frequency in the same cleaning bath.  The inclusion of multiple frequencies benefits the cleaning process by:

• Increasing the range of particles addressed by the system:  Lower frequencies remove larger particles more effectively while higher frequencies remove smaller particles more effectively.  By including multiple frequencies, the range of particles addressed is significantly greater than a single frequency system.
• Providing power and penetration:  Lower frequencies provide a more aggressive scrubbing action that is less evenly distributed while higher frequencies provide a less aggressive scrubbing action that is more evenly distributed and has better penetration into detailed part areas.  By including multiple frequencies, the cleaning tank has the properties of all included frequencies.  This leads to faster cleaning  as well.
• Preventing damage:  Zenith customers have confirmed that a multiple frequency CROSSFIRE system produces 16x less damage potential when compared to single-frequency ultrasonic systems.  When cleaning machined aluminum or other parts sensitive to ultrasonic attack, this is crucial.

While there are a few vendors who claim to provide multiple-frequency ultrasonic systems, the truth is that Zenith’s patented CROSSFIRE system is the only true multi-frequency system available.

What types of multi-frequency ultrasonic cleaners are available?

There are generally 4 different types of multiple frequency ultrasonic systems which include the following:

• Theoretical Bar-type Ultrasonics: Some manufacturers claim that mounting transducers to a thick bar of aluminum creates multiple frequency output even though only single frequency transducers and generators are included. However, simple tests using a patented Zenith Ultraprobe or aluminum foil proves this as completely false. The signal being produced by these systems is very clearly the frequency of the transducers installed, and this is easily proven. This is NOT a multiple-frequency ultrasonic system.
• Switching Generator: A switching generator system is one where transducers of a single frequency are driven by an ultrasonic generator that switches between 2 or more frequencies. While this system does provide multiple frequency output, only 1 frequency (the natural resonance frequency of the transducer) operates at high efficiency. At all other frequencies, efficiency drops off to less than 30% when compared to 95% when driven at transducer resonance frequencies. Furthermore, since the generator operates only 1 frequency at a time, the parts receive a fraction of the cleaning cycle time at each frequency. For example, if 4 frequencies are included and the cycle time is 10 minutes, the parts actually receive only 2.5 minutes at each frequency. We have also seen systems from Europe that SOUND like the frequencies are changing but the cleaning action remains exactly the same. These systems are typically sold as 25kHz and 40khz systems and include a selector switch that allows operators to select which frequency is used.
• Separated Transducer Arrays: In these systems, transducers of a more-than-one frequency are mounted to different radiating surfaces or areas of the cleaning tank. For example, an array of 40kHz transducers may be mounted to one side of the tank, and 25khz on the opposite side of the tank. All transducers are powered by generators that drive them at their natural resonance frequencies. This design IS a multiple frequency ultrasonic system and is significantly better than either of the 2 designs mentioned above since the transducers are operating at over 95% electrical/mechanical efficiency and all included frequencies are operating at the same time. However, since transducer arrays are separate from each other, the cleaning action is different depending upon the location of the parts in the tank. Using the example above, the surface of the parts which face the 40khz array would be cleaned at 40kHz and the surfaces facing the 25khz array would be cleaned at 25kHz with very little activity at 40kHz. This, however, depends upon a number of factors which include part mass, material of construction, the number of parts being cleaned in the batch, and others..
• CROSSFIRE Multiple Frequency Ultrasonics: Manufactured and patented by Zenith, this system mounts 2 or more frequencies of transducers onto the SAME radiating surface. This is at the heart of the Zenith patents. The arrays are not separated, but rather combined. Therefore, parts are cleaned at all included frequencies regardless of their orientation, and all transducers are operated at natural resonance with over 95% electrical/mechanical efficiency. This IS a true multiple frequency ultrasonic cleaner that eliminates the shortcomings of all of the above technologies. Parts received multiple-frequency scrubbing effects from all sides.

Don’t the sound waves of different frequencies cancel each other out?

Zenith has more experience manufacturing and applying true multiple frequency ultrasonic systems than any manufacturer in the world.  Based on tests of thousands of customer-submitted parts and feedback from our customers who have purchased both competitive single-frequency ultrasonic systems as well as Zenith CROSSFIRE systems, the answer is that there is no destructive cleaning interference created.  What we have seen is that when combining frequencies, the destructive properties of the lower frequency transducers with regards to damaging parts being cleaned are reduced.

After testing thousands of parts of virtually every material of construction and design, we can say that in our experience, no single frequency ultrasonic system has ever out-performed the results produced by a CROSSFIRE multi-frequency ultrasonic cleaning system.

How did Zenith develop the first true multi-frequency ultrasonic cleaner?

Before the advent of multi-frequency ultrasonics, many customers had requested an ultrasonic cleaner that had the power of low-frequency ultrasonics with the penetration and even energy distribution of higher frequencies. Unfortunately, it did not exist at the time, but Zenith never stopped working on creating such a system. At the time, the Separated Transducer Array design was available, but had the shortcomings that were detailed earlier on this page. Just as Zenith had manufactured its first CROSSFIRE system and applied for its patent, many major manufacturers were approached by Seagate Magnetic Media for a new project. They requested that each manufacturer send in a small system for side-by-side testing for a large upcoming order for 100’s of disk cleaning systems. Based on this side-by-side testing, Zenith was awarded the contract since the CROSSFIRE system out-performed all other competitive single-frequency systems with regards to particle removal. 1 year after Zenith was awarded the contract, the 3 largest competitors had developed their own versions of our CROSSFIRE systems that side-stepped our patents and claimed superiority.

Is a Zenith CROSSFIRE multi-frequency ultrasonic system the best for my application?