ultrasonic generator application for cleaning and welding

The most important part of ultrasonic cleaning system is transducer. There are two kinds of transducers, one is magnetic transducer, made of nickel or nickel alloy; the other is piezoelectric transducer, made of lead zirconate titanate or other ceramics.

When a piezoelectric material is put into an electric field with varying voltage, it will deform, which is called "piezoelectric effect". In contrast, magnetic transducers are made of materials that are deformed in a changing magnetic field. No matter what transducer is used, the most basic factor is the intensity of cavitation produced by it.

Ultrasound, like other sound waves, is a series of pressure points, a wave of alternating compression and expansion (shown below). If the sound energy is strong enough, the liquid is pushed away in the expansion phase of the wave, which produces bubbles; while in the compression phase of the wave, these bubbles burst or implode instantaneously in the liquid, producing a very effective impact force, especially for cleaning. This process is called cavitation. Theoretically, the compression and expansion of sound waves indicate that the bursting cavitation bubble will produce pressure exceeding 10,000 psi and high temperature of 20,000 degrees F (11,000 degrees C), and the shock wave will rapidly radiate outward at the moment of its burst. The energy released by a single cavitation bubble is very small, but there are millions of cavitation bubbles bursting at the same time every second, the cumulative effect will be very strong, resulting in a strong impact on the surface of the workpiece to peel off dirt, which is the characteristics of all ultrasonic cleaning. If the ultrasonic energy is large enough, cavitation will occur everywhere in the cleaning fluid, so the ultrasonic can effectively clean tiny cracks and holes. Cavitation also accelerates the chemical reaction and accelerates the dissolution of the surface film. However, cavitation occurs only when the liquid pressure in a certain region is lower than the gas pressure in the bubble, so the ultrasonic amplitude generated by the transducer is large enough to satisfy this condition. The minimum power required to generate cavitation is called the critical cavitation point. Different liquids have different cavitation critical points, so ultrasonic energy must exceed this critical point to achieve cleaning effect. That is to say, only when the energy exceeds the critical point can cavitation bubbles be generated for ultrasonic cleaning.

Importance of frequency

When the working frequency is very low (within the range of human hearing), noise will be generated. When the frequency is lower than 20 kHz, the working noise not only becomes very high, but may exceed the limits of the safety noise stipulated in the Occupational Safety and Health Care Act or other regulations. In applications requiring high power to remove dirt without considering damage to the surface of the workpiece, low cleaning frequencies ranging from 20 kHz to 30 kHz are usually chosen. Cleaning frequencies in this frequency range are often used to clean large, heavy, or high-density parts. Jiekang provides 20 KHz magnetic transducers and 25 KHz piezoelectric transducers Cavitation Strength Relative to 40 kHz high frequencies, which are often used to clean smaller, more sophisticated parts or remove tiny particles. High frequency is also used in applications where surface damage is not allowed. High frequency can improve cleaning performance from several aspects. As the frequency increases, the number of cavitation bubbles increases linearly, resulting in more and more intensive shock waves that can enter smaller cracks. If the power remains unchanged, the cavitation bubble will become smaller, and the energy released will be reduced accordingly, thus effectively reducing the damage to the surface of the workpiece. Another advantage of high frequencies is that they reduce the viscous boundary layer (Pournoulli effect), allowing ultrasound to'detect'tiny particles. This is similar to the small stones in the bottom of the Qingxi river when the water level is lowered. Jie Kang provides a series of intermediate frequency products, including 40kHz, 80kHz, 120kHz and 170kHz. When cleaning tiny particles, you can choose products with a frequency of 350kHz. Jie Kang recently launched a MicroCoustics system for such occasions, with a frequency of 400kHz.