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Fundamentals of Ultrasonic Cleaning Technology2004#2
- Cavitation control is the basis of ultrasonic cleaning technology.It is not advisable to skip over this understanding and move on to the next step.Without an understanding of the basics, there can be no success in applied technology.
Importance of cavitation control.
The author refers to early ultrasonic cleaning systems in which ultrasonic cleaning is possible by placing the object to be cleaned above the ultrasonic transducer as the first generation of ultrasonic cleaning systems.In response to the importance of cavities in ultrasonic cleaning, devices with ultrasonic designs that attempt to control cavitation in the ultrasonic cleaning tank are called second-generation ultrasonic cleaning devices.Cavitation control in second-generation ultrasonic cleaners is briefly described here.This is the basis of all ultrasonic cleaning system design, and I am convinced that ultrasonic cleaning design in the new era cannot be achieved without understanding and practising this.
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Control of cavitation generation position.
In ultrasonic cleaning baths (also ultrasonic sprays), it is an extremely important basic technology where and how cavitation is generated in a stable manner.The position and shape of the cavitation distribution are determined by the frequency, type of liquid, temperature, depth of liquid, transducer arrangement, direction of liquid flow, temperature distribution, etc., and the type of material to be cleaned.The basic distribution of cavitation can be designed to suit the purpose, such as horizontal, vertical, grid, even or cylindrical distribution.The ultrasonic cleaning engineer and the user must be clear about the purpose of each ultrasonic bath and share the cavitation distribution for each bath and the method of checking it.If the liquid depth is unstable or not theoretically supported, it can be assumed that the basics of cleaning design have not been established.
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Control of cavitation generation density.
Cavities in ultrasonic cleaning do not occur on a surface.They occur at points.There is a distance between the cavities and several do not occur attached to each other.In general degrease cleaning, but not in so-called precision cleaning, the space between cavities is the cause of defects.Therefore, efforts are made to increase cavity density in various ways.Or, efforts are made to increase the distance travelled by the cavities.A series of detailed efforts are made to improve the ultrasonic waveform, oscillation efficiency, liquid input efficiency, output per unit area, the method of attaching the vibrating elements, reducing the amount of wasted liquid, etc.The latest idea of ultra-compact, high-speed, high-density ultrasonic cleaning is an extension of this concept.
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Cavitation impact force control.
If the positive and negative impact forces of the cavities are too weak, they cannot clean, and if they are too strong, they damage the object to be cleaned, resulting in defective products.Naturally, if the impact force of the cavity cannot be controlled, it is impossible to design ultrasonic cleaning.Recently, ultrasonic cleaning objects have become more and more precise and delicate, and the range of cavity selection has become narrower.However, if you have a better understanding of cavities in ultrasonic cleaning, you will have a better understanding of the control of impact force.In general, the impact force of a cavity is proportional to the pressure of the liquid and inversely proportional to the frequency, vapour pressure of the liquid and the amount of dissolved air.Since the impact force of the cavity is proportional to the mass of liquid that the cavity eliminates (suctions) in unit time, once the principle is understood, it is clear what should be controlled.Cavitation control in ultrasonic cleaning systems is an important basic technology in ultrasonic cleaning design.It is impossible to introduce new ultrasonic cleaning technologies without neglecting these, i.e. neglecting cavity control.
The concept of cavitation control is necessary to stabilise this horizontal distribution and ensure efficient use.However, compared to the cavity enhancement systems described in the following paragraphs, they are far inferior in cleaning power and we do not recommend them.However, it is impossible to use the next generation of ultrasonic cleaning without clearing this state of the art technology.If you try to use the most advanced technology while neglecting the basics, you will run into a lot of trouble.
In non-water ultrasonic cleaners without measures to reduce dissolved air, more than 99% of the ultrasonic energy is lost on the vibrating surface!(measured by the author) The reason this was not a problem in non-water cleaning is that the cleaning agent itself had a certain amount of cleaning power, which was overlooked, but these are not rough times.Cavities generated by ultrasound are a high-speed phenomenon that repeats generation and disappearance more than 20 000 times per second, and are not a phenomenon visible to the human eye as bubbles?The bubbles are not a phenomenon visible to the human eye as bubbles, etc.When visible bubbles are observed during ultrasonic oscillation, the ultrasonic tank should be considered to have disappeared, as most of the ultrasonic energy is not used.
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