The main equipment of ultrasonic cleaning
The ultrasonic cleaning equipment is mainly composed of three parts: generator, transducer and cleaning tank. The generator is the power supply, generating electromagnetic oscillation signals and providing energy. The transducer is the vibration plate, is a key part of the ultrasonic cleaning. It converts the electromagnetic vibration generated by the generator into the ultrasonic vibration of the transducer itself and passes into the cleaning tank to generate cavitation, usually at the bottom of the tank. The cleaning tank is used to contain the cleaning fluid and the workpiece to be cleaned.
The principle of ultrasonic cleaning
Ultrasound is a sound wave that frequency exceeds 20 kHz above the human hearing range. Ultrasound is much like electromagnetic waves, it can refract, focus and reflect. However, unlike electromagnetic waves, electromagnetic waves can propagate freely in vacuum, and the propagation of ultrasound depends on elastic medium. When it propagates, it causes the particles in the elastic medium to oscillate, and transmits energy through the medium in the direction of propagation of the ultrasonic wave. This wave can be divided into longitudinal and transverse waves. In solids, both can be transported, while in gases and liquids only longitudinal waves can be transmitted.
Ultrasound can cause particle vibration, and the acceleration of particle vibration is proportional to the square of the ultrasonic frequency. Therefore, when the strong ultrasonic wave propagates in the liquid, it will produce acoustic cavitation due to the nonlinear effect. The shock waves generated by the sudden closure of cavitation bubbles can produce thousands of atmospheric pressures around them. On the one hand, it destroys the adsorption of the surface of the dirt and the cleaning part, on the other hand, it will cause the destruction of the dirt layer and break away from the surface of the cleaning part and disperse them into the cleaning liquid.
The vibration of the bubbles also scrubs the solid surface. Bubbles can also "drill into" cracks to make vibration, so that dirt will fall off. For oily dirt, the two liquids disperse rapidly and emulsify at the interface due to ultrasonic cavitation. When the solid particles are covered with oil and adhere to the surface of the cleaning part, the oil is emulsified and the solid particles fall off. In the process of vibration, the cavitation bubble will cause the liquid itself to produce circulation, so that there is a high velocity gradient and viscous stress on the surface of the vibratory bubble, which causes the destruction and shedding of the dirt on the surface of the cleaning part. The high speed microjets generated by ultrasonic cavitation on the surface of solid and liquid can remove or weaken the boundary layer, corrode the solid surface, increase the stirring effect, accelerate the dissolution of soluble contaminants, and strengthen the cleaning effect of chemical cleaning agent. In addition, ultrasonic vibration causes large particle vibration speed and acceleration in the cleaning fluid, and also causes frequent and intense impact on the surface of the cleaning parts.
According to the ultrasonic cleaning principle mentioned above, any liquid immersed in the place of cavitation will have the cleaning effect, and it will not be restricted by the complex shape of the surface of the cleaning parts. For example, the holes, grooves, slits, deep holes and micropores on the surface of the components can be cleaned, and these parts cannot be cleaned by general brush.