◆　Transducer and generator


The most important part of the ultrasonic cleaning system is the transducer. There are two kinds of existing transducers, one is a magnetic transducer, which is made of nickel or nickel alloy, and one is a piezoelectric transducer, which is made of lead zirconate titanate or other ceramics. When a piezoelectric material is placed in an electric field with a varying voltage, it will deform, which is called the'piezoelectric effect'. Relatively speaking, magnetic transducers are made of materials that deform in a changing magnetic field.


No matter what kind of transducer is used, the most basic factor is usually the intensity of the cavitation effect. Ultrasound, like other sound waves, is a series of pressure points, that is, a wave that alternates compression and expansion (as shown below). If the sound energy is strong enough, the liquid is pushed away in the expansion phase of the wave, thereby generating bubbles; while in the compression phase of the wave, these bubbles burst or implode in the liquid instantaneously, generating a very effective impact force, especially Suitable for cleaning. This process is called cavitation.


Compression and expansion of sound waves

Theoretically, a burst cavitation bubble will generate a pressure of more than 10,000 psi and a high temperature of 20,000 °F (11,000 °C), and the shock wave will radiate outward quickly at the moment of its burst. The energy released by a single cavitation bubble is very small, but millions of cavitation bubbles burst at the same time every second. The cumulative effect will be very strong, and the powerful impact force will peel off the dirt on the surface of the workpiece. This is the characteristic of all ultrasonic cleaning.


If the ultrasonic energy is large enough, cavitation will occur everywhere in the cleaning fluid, so ultrasonic waves can effectively clean tiny cracks and holes. Cavitation also promotes chemical reactions and accelerates the dissolution of surface films.


However, cavitation occurs in a region only when the liquid pressure in the region is lower than the gas pressure in the bubble, so this condition can be satisfied when the amplitude of the ultrasonic wave generated by the transducer is sufficiently large. The minimum power required to produce cavitation is called the cavitation critical point. Different liquids have different cavitation critical points, so the ultrasonic energy must exceed this critical point to achieve the cleaning effect. That is to say, only when the energy exceeds the critical point can cavitation bubbles be generated for ultrasonic cleaning.


◆　Maintenance


○ If the power supply is automatically shut down during the operation of the power supply, there may be two situations: one is an instant overload, and the other is a cleaning machine failure. Usually it is caused by overload. In this case, just turn off the power, stop and then turn it on again; if you encounter repeated overload, you should check the load, such as: whether the output is short-circuited, whether the transducer is wet or immersed in water. If the transducer is wet or immersed in water, use an electric hair dryer to dry the transducer before turning it on. If the washing machine can not work, after careful inspection, it is confirmed that the washing machine power failure or transducer damage should be repaired by professional technicians. Do not disassemble it casually to avoid greater losses.


○ After starting, pay attention to whether the fan is working normally. If the fan is faulty, it should be stopped immediately to replace the fan.


○ Observe regularly whether there is leakage in the cleaning tank, if there is any leakage, it should be repaired immediately


◆　Precautions


○ Electricity should be stable and not exceed ±5%.


○ The ambient temperature of the ultrasonic power supply (signal generator) during long-term operation should be kept below 37 degrees Celsius, and the ambient temperature during short-term operation (more than 40 minutes) should be less than 40 degrees Celsius. If the ambient temperature exceeds 40 degrees Celsius, it should be shut down immediately


○ If you find that the power fan is not rotating, you should stop


○ The power supply should be avoided in the environment of high temperature, humidity, dust and corrosive gas


◆　Operating regulations


○ Fill the cleaning tank with cleaning fluid


○ Requirements:


(1) For the tank type (transducer is bonded to the bottom of the tank), the water depth should be greater than 5 cm


(2) For intrusive cleaning machines, the transducer box should be fully immersed in the cleaning solution


○ Put into the work to be cleaned


○ Check whether the power connection is correct, if there is no problem with the power supply, turn on the power switch and the washing machine starts to work


○ Take out the work piece after the cleaning is completed, there is no need to release the cleaning liquid