The core principle of ultrasonic cleaning is to utilize the powerful impact force generated by the formation and violent collapse of numerous tiny bubbles (cavitation bubbles) in a liquid, which impacts dirt on surfaces and in crevices, achieving efficient and thorough cleaning. This process can be broken down into the following key steps and concepts:
I. Core Principle: Cavitation Effect
1. Ultrasonic Wave Generation: A transducer at the bottom of the cleaning machine converts high-frequency electrical energy (typically 20-40 kHz or even higher) into mechanical vibrations of the same frequency (i.e., ultrasonic waves).
2. Sound Wave Transmission: These high-frequency mechanical vibrations are transmitted to the cleaning liquid (water or organic solvent) through the cleaning machine's inner tank.
3. Formation of Density-Sparseness Waves: Ultrasonic waves propagate through the liquid in a pattern of alternating density and sparseness. In the sparse areas (negative pressure zones), the liquid is stretched, increasing the distance between molecules; in the dense areas (positive pressure zones), the liquid is compressed.
4. Cavitation Bubble Generation and Collapse:
a. Generation: During the dispersion stage, the liquid is torn apart, forming tiny, near-vacuum microbubbles (called "cavitation bubbles"). These bubbles are extremely small, but extremely numerous.
b. Growth: These microbubbles rapidly expand and grow in the negative pressure zone.
c. Collapse: When the sound waves enter the positive pressure zone, these already-grown bubbles are instantly compressed. Unable to withstand the external pressure, they violently collapse (implode) at extremely high speeds (approximately over 400 km/h).
5. Cleaning Effect: The moment the bubbles collapse, they generate extremely intense localized high pressure (up to thousands of atmospheres) and high-speed microjets (jet streams). These microjets precisely impact every surface and pore of the object being cleaned, acting like countless tiny "high-pressure water guns," blasting, stripping, and tearing away stubborn dirt, such as oil, dust, oxides, and microbial biofilms.
II. Key Components and Functions of Ultrasonic Cleaners
1. Ultrasonic Generator: The power source and brain. It converts mains electricity into a high-frequency electrical signal that matches the transducer, controlling the frequency and power of the ultrasonic wave.
2. Transducer: The core component. It converts the high-frequency electrical energy from the generator into mechanical vibrations. Common types include piezoelectric ceramic (bonded to the bottom of the cleaning tank) and magnetostrictive (mostly used in large industrial equipment).
3. Tank: The container that holds the cleaning fluid and the objects being cleaned. Its material (usually stainless steel) and design must effectively transmit vibrations to the liquid.
4. Cleaning Solution: The crucial medium. Pure water cannot effectively produce cavitation and produces poor cleaning results. The cleaning solution's functions include:
a. Conducting Ultrasonic Waves: It is the medium through which cavitation occurs.
b. Dissolving dirt: Selecting a cleaning agent (such as a degreaser or rust remover) based on the type of dirt (oil-based or water-soluble) can chemically break down and dissolve the dirt.
c. Wetting the surface: Reducing surface tension allows cavitation to penetrate deeper into tiny crevices.
In summary, ultrasound provides the physical "violent" force for removal, while the cleaning fluid assists with the chemical "softening" and decomposition. The combination of these two is incredibly powerful.