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The factors that affect the cleaning effect of ultrasonic cleaning machine!

Date: 2022-08-31Number: 187

Ultrasonic cleaning equipment according to the needs of cleaning objects and production capacity, its combination and structure is different, can choose complex, large-scale industrial equipment, but also can be very simple structure. Here mainly by the ultrasonic frequency power supply, vibrator and cleaning tank combination into the key areas of ultrasonic cleaning equipment product quality issues.
Selection of ultrasonic transducer structure
In the low ultrasonic frequency band (20-100KHz) , the sandwich piezoelectric vibrator (compound vibrator) with single screw clamping is mostly used in industry, the main structural differences are in the form of the radiator (aluminum bonded to stainless steel) , a trumpet-shaped shape, and a rod-shaped shape.
The sound radiation efficiency of horn-shaped vibrator is higher than that of rod-shaped vibrator, that is, the same input electric power. A relatively large sound power is obtained in the cleaning tank
In certain places, such as when cleaning very deep screw holes. The vibrator with high radiation intensity should be adopted, at which time the radiant body of the vibrator usually has sharp focus shape to enhance the sound intensity in the radiation range. The vibrator is not usually glued to the cleaning tank, but instead inserted into the liquid to clean.


ultrasonic transducer

The distribution and adhesion of vibrators in the cleaning tank
At present, there are some ultrasonic cleaning machine products, stick to the bottom of the cleaning trough or the wall of the vibrating distribution guarantee, 1 next to a row. The electrical power of the input vibrator reaches 2-3 watts per square centimeter, which not only accelerates cavitation erosion on the surface of the stainless steel plate (the surface in contact with the cleaning fluid) , but also reduces the service life, at the same time because the sound intensity is too high. There will be a lot of larger bubbles around the surface of the steel plate, increasing the effect of sound propagation, and weakening the cleaning effect in the area far away from the vibrator. The output power intensity is generally less than 1.5 watts per square centimeter (converted from the area of the steel plate with the vibrator) . If the cleaning trough is very deep, in addition to the bottom of the groove with shock, in the groove wall should also consider bonding shock. The bonding quality of vibrator and cleaning tank has an effect on the quality of the whole equipment of ultrasonic cleaning machine. Not only to stick firmly, and provide a uniform adhesive layer, no lack of glue and do not allow gaps, so that the maximum extent of ultrasonic energy transfer to the cleaning fluid, in order to improve the efficiency of the entire equipment and the actual cleaning effect. At present, there are some cleaning machines to prevent the vibration from falling off the sink. Take screws and viscose fixed way, although this connection is not easy to fall, but there are many safety hazards. If the screw welding quality is poor, such as not perpendicular to the stainless steel plate surface, then the glue layer is not uniform, and even there are cracks or lack of glue, energy transfer will be weakened; at the same time. If the welding is not very good will also affect the stainless steel surface leveling, causing accelerated cavitation erosion, reduce the service life. One way to determine the bonding quality is to load water in the cleaning tank and run the machine for a period of time to detect the temperature rise of the vibrator. If the temperature of one of the many is rising rapidly, it means that it may not bond well. Because the sound radiation at this time is not very good, most of the electrical energy spent on the vibrator and heat.
The important basic principle of ultrasonic cleaning
The basic principle of ultrasonic cleaning is ultrasonic cavitation effect. The strength and weakness of ultrasonic cavitation are related to the main parameters of acoustics, the physical properties of cleaning agent and the natural conditions. Consideration of sound intensity level or sound pressure negative pressure occurs in cleaning agents only when the amplitude of the sound pressure alternately changes beyond the static pressure of the liquid. The negative pressure must be greater than the compressive strength of liquid can cause cavitation. The lowest sound intensity level or the amplitude of sound pressure caused cavitation by liquid is called cavitation threshold. The ratio of the maximum radius of cavitation bubble to the initial radius increases, and the cavitation compressive strength increases, that is, the higher the sound intensity level, the stronger the cavitation is. Good for cleaning effect. It is necessary to select relatively high sound intensity level for cleaning part of the dirt which is difficult to clean, such as metal oxide on metal surface and dirt in hole of chemical fiber spinneret steel plate. The cleaned surface should be close to the source of the sound, at this time most do not choose trough-type cleaning machine. Therefore, a rod-shaped focusing transducer is used to insert a cleaning agent close to the surface of the cleaning piece for cleaning.
Ultrasonic cleaning agent
The flow rate of the cleaning agent also has a great influence on the ultrasonic cleaning effect. Try to keep the liquid at rest during the cleaning process. At this point the growth and closure of the bubble can be sufficient to carry out. If the flow rate of the cleaning agent is too fast, some cavitation cores will be carried away by the flowing liquid, and some cavitation cores will leave the sound field before the whole process of growth and closure is reached, therefore, the overall cavitation compressive strength decreases. In the specific cleaning link, sometimes in order to prevent the dirt from adhering to the cleaning again. Cleaning agent to continuously liquidity upgrade, at this time to pay attention to the flow rate of cleaning agent can not be too fast, in order to reduce the actual effect of cleaning.
Frequency selection
The ultrasonic cavitation threshold is closely related to the ultrasonic frequency. The higher the frequency, the greater the cavitation threshold, in other words, the greater the sound intensity level or sound power required to cause cavitation in a liquid; There is a long time lag between the compressibility and the sparsity of the liquid. The bubble can grow to a larger size before collapsing, and the cavitation compression strength is improved, which is beneficial to the cleaning effect. At present, the working frequency of the ultrasonic cleaning machine affects the cleaning object, which can be divided into three frequency bands: low frequency ultrasonic cleaning (20-50KHz) , high frequency ultrasonic cleaning (50-200KHz) and megahertz ultrasonic cleaning (above 700KHz-1MHz) . Low frequency ultrasonic cleaning is suitable for large parts of the surface or dirt and cleaning parts surface bonding strength of places.