Ultrasonic Cleaning
Transducer

Available frequencies range from about 25 kHz to the megahertz range but commonly used industrial frequencies are around 25 kHz, 40 kHz, 80 kHz and 130 – 160 kHz. The exact frequencies may differ slightly but below are the common uses for these four frequencies:

25 kHz - the lowest ultrasonic frequency used is for removing heavy contamination from parts with very hard surfaces. Fragile parts could be damaged and soft surfaces could suffer pitting. A typical use is to clean engine parts such as valves or other steel components that have heavy deposits of grease or carbon.

33 kHz & 40 kHz - this intermediate frequency is suitable for many common cleaning applications because its bubbles are smaller and clean less roughly than the lowest frequency. Despite the reduced bubble size, cleaning is still intense enough to remove almost all contaminants. Typical applications are the cleaning of glass, jewellery and machined parts.

80 kHz - this higher frequency is used for more delicate parts and parts that have a fragile surface finish. The cleaning action is gentle enough to avoid pitting or roughening of smooth surfaces but still removes moderate amounts of dirt. Typical applications are hard disc drives, LCDs and aluminium parts.

100 kHz to 200 kHz - the highest ultrasonic frequencies are used for very fragile parts or parts with soft surfaces. The cleaning action is light but effective while avoiding damage to components. Typical applications include electronic components, semiconductors and delicate medical instruments.

While the ultrasonic cleaning process is a simple one, selecting the right operating frequency is important for avoiding damage to the parts to be cleaned and for rapid and complete removal of contaminants. An ultrasonic cleaning generator produces the frequency for the system. When the ultrasonic waves pass through the cleaning solution, they produce tiny cavitation bubbles that form and collapse constantly. When they collapse, they produce a powerful jet that dislodges foreign matter from the surface of the parts to be cleaned. The jets result in a continuous scrubbing action that cleans the part surfaces.

The frequency used for the cleaning application is produced by the ultrasonic generator. Low frequencies produce larger bubbles, stronger jets and a powerful cleaning action. Higher frequencies generate smaller bubbles and gentler cleaning. The choice of the generator and the frequency depends on the type of cleaning needed and the type of parts to be cleaned. Powerful cleaning from low frequencies removes dirt quickly but may damage fragile components by pitting or roughening the part surface. Gentle cleaning from high frequencies won’t damage the parts but may not remove tough grime. Choosing the right ultrasonic generator strikes a balance between cleaning power and the possibility of part damage.