Ultrasonic cleaners provide excellent cleaning of a wide variety of parts and objects. However, there are certain conditions that can lead to erosive damage of these parts. Besides this, ultrasonic cleaning tends to cause erosion damage to the cleaner tank in the long term. Knowledge of these various conditions allows the modification of treatment methods to minimize such damage. This helps in better, safer cleaning of susceptible parts and longer tank life.

The core cleaning action of ultrasonic cleaners is the generation and rapid implosion of microbubbles at the interface between the solvent liquid and solid parts. This process, or cavitation, is the driving force for the cleaning action. Lower operating frequencies generate larger bubbles that produce a more vigorous cleaning action. Higher frequencies generate smaller microbubbles with a gentler cleaning action.

Each frequency creates a particular sonic power distribution with evenly spaced energy-level bands across the tank – a standing wave formation. The parts to clean, and portions of the tank or transducer joints, will be exposed to higher energies if they fall in a higher energy band of this standing wave, or sonic resonance. This can cause highly undesirable erosion of these parts or objects. One of the ways to reduce this effect is to use sweep frequencies. The sweep frequency function continuously varies the frequency by a certain amount above and below a base value, shifting the sonic energy bands back and forth.

All transducers have a fixed natural frequency that will tend to resonate inside the tank volume – this has a tendency to cause resonance damage. Delicate objects such as glass, plastics, aluminum parts, silicon or quartz, and the area where the transducer is attached to the tank, are susceptible to erosion. Even with the usage of sweep frequencies, this erosion is likely to occur. One solution to this problem is to select a transducer with sufficiently high frequencies for cleaning. For sensitive materials, oscillate the parts to reduce the time spent in overlap with these resonance bands.

Given the option, choose a cleaner that switches between two frequencies. This keeps the high-energy bands shifting around, reducing the erosion effect. Otherwise, choose a cleaner that uses as high a frequency as is practical – too high a frequency is gentler, but has a longer cleaning time.

Erosion will inevitably eventually damage the area where the transducer bonding or brazing lies. To extend the usable life of the cleaner, take several precautions. Clean and dry the unit after each run. This will remove particles energized by the ultrasonic waves, and cause erosion. Low pH acids with chloride ions may cause considerable damage on the stainless steel tank wall, as will strong alkali solutions of potassium or sodium hydroxide. Determine alternative liquids where feasible and use them. Ensure that objects do not physically touch the tank floor – always use a stainless steel immersion basket. See that the liquid level never drops past a lower limit.

Following these suggestions and prior preparations will ensure a long operating life for the ultrasonic cleaner, as well as good, high-quality, fast and efficient cleaning of a set of delicate objects.

Author Bio: Dr. Pramit Sarma is a consummate geek with an abiding love for technology innovation! At Tovatech he indulges in his passion for high precision engineering & scientific equipment. Tovatech is a leading North American supplier of ultrasonic cleaners. For more details on this article please visit the ultrasonic cleaner section of Tovatech’s website.

Category: Medical Business
Keywords: ultrasonic cleaner,ultrasonic cleaning,cavitation erosion,ultrasonic cleaner frequency