The ultrasonic cleaner for parts has become a major industry to itself. By using an electrical generator that puts out a high frequency signal [20 to 250 kHz] the transducer rapidly induces compression and rarefaction waves in the liquid. During the rarefaction cycle the liquid is torn apart, creating a vacuum in the liquid. The vacuum grows as the ultrasound frequency is continued. The vacuum reaches a certain size and the cavity cannot maintain its shape and collapses in a violent reaction that can produce temperatures of 5000 degrees centigrade and the plasma produced is in the form of millions of bubbles collapsing each second in the tank. It can cause an increase in mass transfer, heat transfer, fluid degasification, chemical rates and yields and improvement of polymeric and metallic surfaces, due to very efficient ‘stirring’ and cleaning. The effects are known to cause local ‘hotspots’ of high energy and leading to the ability to clean and degrease surfaces. Sonoelectrochemical and ultrasonic techniques have been used to modify metallic surfaces and other conductive substrates in views of preparing them for plating, for example, in the degreasing and plating industries. The use of ultrasound has allowed us to move away from more dangerous chemicals that were carcinogenic, mutagenic, toxic and polluting such as trichlorophenol, Trichloroethylene, Perchloroethylene, and Methylene Chloride.
The ultrasonic cleaner is simply a metal tank , usually stainless steel, that has piezo ceramic transducers bonded to the bottom or side. Jewelry cleaners and other types used in the home operate at the low range of the frequencies between 20 and 50 KHZ. Industrial cleaners at the higher ends of the range [up to 250]. When a alternating pulse of energy is introduced to the tank, the ceramic transducer at the bottom changes shape rapidly and makes the bottom of the tank move. This movement creates a vibration, and compression waves do the cleaning.
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