An ultrasonic cleaning machine is a cleaning device that uses ultrasonic waves (usually 20-400 kHz) and an appropriate cleaning solvent (sometimes common tap water) to clean fragile objects. Ultrasound can be used only with water, but solvents suitable for cleaning items and stains can enhance the effect. Cleaning usually lasts three to six minutes.

Process characteristics

Ultrasonic cleaning uses cavitation bubbles caused by high-frequency pressure (sound) waves to stir liquids. Agitation exerts a powerful force on contaminants that attach to substrates such as metals, plastics, glass, rubber and ceramics. This action can also penetrate blind holes, cracks and grooves. The aim is to completely remove all traces of contaminants that adhere or are embedded in the solid surface.

Water or other cleaners can be used, depending on the type of contaminant and the material being ultrasonic treated. Contaminants may include dust, dirt, oil, pigments, rust, grease, algae, fungi, bacteria, scale, polishing compounds, flux, fingerprints, soot and mold release agent, biological dirt (such as blood) , etc. .

Ultrasonic cleaning can be used on workpieces of all shapes, sizes, and materials, and may not require disassembly prior to cleaning. During the cleaning process, objects should not be left at the bottom of the equipment as this will prevent corrosion of parts of the object that are not in contact with water, so shelves or baskets are needed to hold objects above the bottom.

Frequency?

Today, ultrasound systems are available in the frequency range of 20 to 950 kHz, depending on what you clean, the type of dirt to remove and how clean your components need to be. In fact, most systems today contain ultrasonic waves of more than one frequency. They may use 40/70/170 for the graded cleaning process.

20-40khz heavy duty cleaning, such as engine block heavy metal, heavy oil.

40-70khz equipment parts such as optics are very good at cleaning the general removal of small particles. Industrial cleaning tank with dual-frequency and sweep function, can achieve the best cleaning effect.

70-200khz ultra-fine temperature and clean optical devices, semiconductor wafer disk drives, etc. .

How should the correct power level be selected for the ultrasonic trough?

For critical cleaning applications, the average wattage per gallon of ultrasound should be between 70 and 100 watts. This is the average rating and can be adjusted for cleaning applications. To calculate the power requirement, use the following formula;

It is important to remember that ultrasonic can rate the Watt of ultrasonic energy in two ways, peak and average. Peak Watt is the starting requirement, average Watt is the wattage of continuous operation.

When using very large tanks, power levels can be reduced to 50 watts per gallon.

Most companies offer power intensity control options. This control reduces the wattage of the ultrasound to any desired level at the top of the power curve. Below 50% , there is not enough power to activate the sensor.

Power Intensity control is a good option for cleaning precision components that may be subject to corrosion, or for the use of ultrasound in electroplating operations or other chemical processes.

What are the effects of different frequencies and multiple frequencies?

For a given cleaner, lower frequencies are much stronger because they concentrate available power in fewer cleaning bands. The higher the frequency, the more evenly the available power is distributed throughout the tank area. Most companies that claim to have multiple frequencies change the power of the converter to push it away from its natural frequency. This only works to a limited extent, because any transducer has a natural frequency at which it resonates optimally. If pushed away from their natural frequencies, they dissipate energy in the form of heat and do not create cavitation bubbles. Any ultrasonic unit produces more than one frequency; in addition to the basic low frequencies, most devices produce enough high frequencies to provide a useful balance for general cleaning applications. Higher frequencies such as 65-70 or 170 kHz produce smaller cavitation bubbles and remove smaller particles more evenly than lower frequencies. When you run a 40 kHz transducer at a 170 kHz resonant point, there is a loss of efficiency. The loss is only about 5% of the total power of the system and is immaterial for all practical purposes.

It is important to remember that the power of an ultrasonic cleaner is usually expressed as a total watt/average rating. Or Peak Watt. The average wattage is the power consumed by a vacuum cleaner during continuous operation. Peak wattage is the amount of power a vacuum cleaner consumes at startup. The average wattage is a good measure of cleanliness.

In some specific cases, the tank consists of two or three types of transducer, so as to achieve true multi-frequency operation. Some sensors work on more than one frequency. These transducers have natural harmonics at higher frequencies, such as 40 kHz and 170 kHz, and slots can be switched from one frequency to another by including two drive plates of different frequencies in a single generator.