Ultrasonic cleaning. Theory and practice. The principle of operation of an ultrasonic cleaner. Which cleaning solution should not be used

It allows you to quickly and efficiently process a variety of parts, remove the most durable contaminants, replace expensive and unsafe solvents and mechanize the cleaning process.

When ultrasonic vibrations are communicated to the liquid, variable pressures arise in it, changing with the frequency of the exciting field. The presence of dissolved gases in the liquid leads to the fact that during the negative half-period of oscillations, when a tensile stress acts on the liquid, ruptures in the form of gas bubbles form and increase in this liquid. Impurities from microcracks and micropores of the material can be sucked into these bubbles. Under the action of compressive stresses during the positive half-period of pressures, the bubbles collapse. By the time the bubbles collapse, they are affected by the fluid pressure reaching several thousand atmospheres; therefore, the collapse of the bubble is accompanied by the formation of a powerful shock wave. This process of formation and collapse of bubbles in a liquid is called cavitation... Usually cavitation occurs on the surface of the part. The shock wave crushes the dirt and transports it into the cleaning solution (see Fig. 1.10).

Rice. 1.10. Diagram of the suction of contaminants from surface microcracks into a growing gas bubble

The separated dirt particles are captured by bubbles and float to the surface (Fig. 1.11).

Rice. 1.11. Ultrasonic cleaning

An ultrasonic wave in a liquid is characterized by a sound pressure P sound. and vibration intensity I. Sound pressure is determined by the formula:

P stars = . C. . . Cos (t-k x) = p m. Cos (t-k x),

where p m = . C. .  - amplitude of sound pressure,

. C - wave impedance,

 - vibration amplitude,

 - frequency.

With an increase in the sound pressure to the optimal value, the number of gas bubbles in the liquid increases, and the volume of the cavitation region increases accordingly. In ultrasonic devices for cleaning, the sound pressure at the “emitter-liquid” interface is in the range of 0.2 ÷ 0.14 MPa.

In practice, the intensity of ultrasonic vibrations is taken to be the power per unit area of ​​the emitter:

1.5 ÷ 3 W / cm 2 - aqueous solutions,

0.5 ÷ 1 W / cm 2 - organic solutions.

Cavitation destruction reaches its maximum when the collapse time of the bubbles is equal to the half-period of oscillations. The formation and growth of cavitation bubbles is influenced by the viscosity of the liquid, the vibration frequency, static pressure and temperature. A cavitation bubble can form if its radius is less than a certain critical radius corresponding to a certain hydrostatic pressure.

Ultrasonic vibration frequency lies in the range from 16 Hz to 44 kHz.

If the vibration frequency is low, then larger bubbles with a small pulsation amplitude are formed. Some of them simply float to the surface of the liquid. Low-frequency ultrasound propagates worse due to absorption, so a high-quality cleaning process takes place in an area close to the source. At a low frequency, microcracks, the dimensions of which are less than the ultrasound wavelength, are not cleaned well enough.

An increase in the vibration frequency leads to a decrease in the size of gas bubbles and, consequently, to a decrease in the intensity of shock waves at the same power of the installation. To start the cavitation process with an increased frequency, a high intensity of vibrations is required. An increase in the frequency of an ultrasonic cleaning installation usually leads to a decrease in the efficiency of the installation. However, increasing the frequency of ultrasound has a number of positive aspects:

Cleaning is carried out by hydro streams with significantly less vibration of the part;

The density of ultrasonic energy increases in proportion to the square of the frequency, which makes it possible to introduce high intensities into the solution or, at a constant intensity, to reduce the amplitude of oscillations;

With increasing frequency, the amount of absorbed ultrasound energy increases.

Due to the absorption of energy of higher density, particles of oils, fats, fluxes, etc. surface contaminants, parts become more fluid when heated, and easily dissolve in the cleaning liquid. The water (as the base of the cleaning solution) does not heat up;

As the frequency increases, the wavelength decreases, which contributes to a more thorough cleaning of small holes;

When ultrasound oscillates at a sufficiently high frequency (40 kHz), the ultrasonic wave propagates with less absorption and acts effectively even at a large distance from the source;

The dimensions and weight of ultrasonic generators and transducers are significantly reduced;

The risk of erosive destruction of the surface of the part being cleaned is reduced.

Fluid viscosity during ultrasonic cleaning, it affects energy loss and shock pressure. An increase in the viscosity of the liquid increases the losses due to viscous friction, but the collapse time of the bubble is reduced, therefore, the force of the shock wave increases. Technical contradiction.

Temperature has an ambiguous effect on the ultrasonic cleaning process. An increase in temperature activates the cleaning medium and increases its dissolving power. But at the same time, the viscosity of the solution decreases and the pressure of the vapor-gas mixture increases, which significantly reduces the stability of the cavitation process. Here again we face the situationtechnical contradiction.

The engineering approach to resolving this contradiction is to optimize the temperature (viscosity) of the solution depending on the nature and type of contamination. To clean the parts from chemically active contaminants, the temperature should be increased, and to remove poorly soluble contaminants, it is necessary to choose a temperature that creates the conditions for optimal cavitation erosion.

Alkaline solutions 40 ÷ 60 ° C,

Trichloroethane 38 ÷ 40 ° C,

Water emulsions 21 ÷ 37 ° C.

In addition to the cavitation dispersion of contaminants, acoustic liquid flows have a positive value during cleaning, i.e. vortex flows formed in the sonicated liquid in the places of its inhomogeneities or at the “liquid-solid” interface. The high level of excitation of the liquid in the layer adjacent to the surface of the part reduces the thickness of the diffusion layer formed by the reaction products of the cleaning solution with contaminants.

Ultrasonic cleaning media

Cleaning is carried out in aqueous washing solvents, emulsions, acidic solutions. When using alkaline solutions, the temperature and concentration of alkaline components can be significantly reduced, while the cleaning quality remains high. This reduces the etching effect on the part. The composition of alkaline solutions most often includes caustic soda (NaOH), soda ash (Na 3 CO 3), trisodium phosphate (Na 3 PO 4.12H 2 O), water glass (Na 2 O. SiO 2), anionic and nonionic surfactants ( sulfanol, tinol).

Surfactants significantly increase cavitation erosion, i.e. intensify the cleaning process. However, the risk of cavitation destruction of the surface of the material with the addition of surfactants also increases. A decrease in surface tension in the presence of surfactants leads to an increase in the number of bubbles per unit volume. In this case, the surfactant reduces the strength of the surface of the part (technical contradiction).

To prevent erosion of metals, it is necessary to choose the optimal surfactant concentration, the minimum duration of the process, and place the parts away from the emitter (engineering solution).

Ultrasonic cleaning in organic solvents is used when cleaning in alkaline solvents can lead to corrosion of the material or to the formation of a passive film, and also if it is necessary to shorten the drying time. The most convenient are highly reactive chlorinated solvents; they dissolve a wide variety of contaminants and are safe to use.

Chlorinated solvents can be used neat or in azeotropic mixtures (distilled without changing the composition). For example, mixtures of freon-113, freon-30. Azeotropic solvent mixtures react with many contaminants to increase cleaning efficiency.

Gasoline, acetone, alcohols, alcohol-gasoline mixtures are also used for ultrasonic cleaning.

For ultrasonic etching of parts when cleaning from oxides, concentrated acidic solutions are used (see table 1.6).

Table 1.6.

Composition of solutions (mass fractions) and modes of ultrasonic etching

Ultrasonic cleaning process control methods .

Fluid pressure change. The method is implemented in the form of creating a vacuum or, conversely, overpressure. When the liquid is evacuated, the formation of cavitation is facilitated. Excessive pressure increases erosional destruction, shifts the maximum of cavitation erosion to the zone of high sound pressures, and affects the nature of acoustic flows.

Application of electric or magnetic fields to the cleaning medium. With electrochemical ultrasonic cleaning, the cavitation area can be localized directly at the workpiece; bubbles of gases released on the electrodes contribute to the destruction of pollution films; reduced oil wettability of the polarized surface of the part.

The imposition of a magnetic field on the cavitation region causes the movement of gas bubbles with a negative surface charge, which increases the cavitation erosion of parts.

The introduction of abrasive particles into the cleaning solution. Solid abrasive particles participate in the mechanical separation of impurities and stimulate the formation of cavitation bubbles, as they disrupt the continuity of the liquid.

What is ultrasound?

Ultrasound (US) - elastic vibrations and waves, the frequency of which is higher than 15 ... 20 kHz. The lower boundary of the region of ultrasonic frequencies, separating it from the region of audible sound, is determined by the subjective properties of human hearing and is conditional. The upper limit is due to the physical nature of elastic waves, which can propagate only in a material environment, that is, provided that the wavelength is much greater than the mean free path of molecules in gases or interatomic distances in liquids and solids Oh. Therefore, in gases, the upper limit of ultrasonic frequencies is determined from the condition of approximate equality of the sound wavelength and the free path of molecules. At normal pressure, it is 10 9 Hz. In liquids and solids, the decisive factor is the equality of the wavelength to the interatomic distances, and the cutoff frequency reaches 10 12 -10 13 Hz. Depending on the wavelength and frequency, ultrasound has specific features of radiation, reception, propagation and application, therefore, it is convenient to subdivide the region of ultrasonic frequencies into three sub-regions:

Low - 1.5–10 ... 10 5 Hz;

Average - 10 5 ... 10 7 Hz;

High - 10 7 ... 10 9 Hz.

Elastic waves with frequencies of 1 · 10 8 ... 1 · 10 13 Hz are commonly called hypersound.

Sound wave theory

Ultrasound as elastic waves

Ultrasonic waves by their nature do not differ from elastic waves of the audible range, as well as from infrasonic waves.

The propagation of ultrasound obeys the basic laws common to acoustic waves of any frequency range, usually called sound waves. The basic laws of their propagation include the laws of reflection and refraction of sound at the boundaries of various media, diffraction and scattering of sound in the presence of obstacles and inhomogeneities in the medium and irregularities at the boundaries, the laws of waveguide propagation in limited areas of the medium.

Specific features of ultrasound

Although the physical nature of ultrasound and the basic laws governing its propagation are the same as for sound waves of any frequency range, it has a number of specific features that determine its importance in science and technology. They are due to its relatively high frequencies and, accordingly, a small wavelength.

So, for high ultrasonic frequencies, the wavelengths are:

In the air - 3.4⋅10 -3 ... 3.4⋅10 -5 cm;

In water - 1.5⋅10 -2 ... 1.5⋅10 -4 cm;

In steel - 1⋅10 -2 ... 1⋅10 -4 cm.

Such a difference in the values ​​of ultrasonic waves (USW) is due to the different speeds of their propagation in different media. For the low-frequency region, ultrasonic wavelengths do not exceed, in most cases, several centimeters and only near the lower boundary of the range reach several tens of centimeters in solids.

USW decays much faster than low-frequency waves, since the sound absorption coefficient (per unit distance) is proportional to the square of the frequency.

Another very important feature of ultrasound is the ability to obtain high intensity values ​​at relatively small amplitudes of the vibrational displacement, since at a given amplitude the intensity is directly proportional to the square of the frequency. The amplitude of the vibrational displacement is in practice limited by the strength of acoustic emitters.

The most important nonlinear effect in an ultrasonic field is cavitation - the appearance in a liquid of a mass of pulsating bubbles filled with vapor, gas, or their mixture. The complex movement of bubbles, their collapse, merging with each other, etc., generate compression impulses (microshock waves) and microflows in the liquid, cause local heating of the medium, ionization. These effects affect the substance: the destruction of solids in the liquid occurs (cavitation erosion), various physical and chemical processes are initiated or accelerated (Fig. 1).

Rice. one

By changing the conditions for the occurrence of cavitation, it is possible to enhance or weaken various cavitation effects. For example, with an increase in the frequency of ultrasound, the role of microflows increases and cavitation erosion decreases; with an increase in hydrostatic pressure in a liquid, the role of microshock effects increases. An increase in frequency usually leads to an increase in the threshold intensity value corresponding to the onset of cavitation, which depends on the type of liquid, its gas content, temperature, etc. For water in the low-frequency ultrasonic range at atmospheric pressure, it is usually 0.3-1 W / cm 3.

Sources of ultrasound

In nature, ultrasound is found in many natural noises (in the noise of the wind, waterfall, rain, in the noise of pebbles rolled by the sea surf, in the sounds accompanying lightning discharges, etc.), as well as in the world of animals that use it for echolocation and communication.

Technical ultrasound emitters used in the study of RAS and their technical applications can be divided into two groups. The first includes emitters-generators (whistles). Oscillations in them are excited due to the presence of obstacles in the path of a constant flow - a jet of gas or liquid. The second group of emitters is electro-acoustic transducers: they convert already given electrical vibrations into mechanical vibrations of a solid body, which emits acoustic waves into the environment.

Application of ultrasound

Multiple applications of ultrasound, in which various of its features are used, can be conditionally divided into three directions. The first is associated with obtaining information through RAS, the second - with an active effect on the substance, and the third - with the processing and transmission of signals (directions are listed in the order of their historical formation).

Ultrasonic cleaning principles

The main role in the effect of ultrasound on substances and processes in liquids is played by cavitation. The most widely used ultrasonic technological process is based on cavitation - cleaning the surfaces of solids. Depending on the nature of the contamination, various manifestations of cavitation, such as microshock impacts, microflows, and heating, may be of greater or lesser importance. By selecting the parameters of the sound field, the physicochemical properties of the washing liquid, its gas content, external factors (pressure, temperature), it is possible to control the cleaning process within wide limits, optimizing it in relation to the type of contamination and the type of parts to be cleaned. A type of cleaning is etching in an ultrasonic field, where the action of ultrasound is combined with the action of strong chemical reagents. Ultrasonic metallization and soldering are actually based on ultrasonic cleaning (including from the oxide film) of the surfaces to be joined or metallized. Brazing cleaning (Fig. 2) is caused by cavitation in the molten metal. In this case, the degree of purification is so high that compounds of materials that cannot be soldered under normal conditions are formed, for example, aluminum with other metals, various metals with glass, ceramics, and plastics.

Rice. 2

In the processes of cleaning and metallization, the sound-capillary effect is also essential, providing the penetration of the cleaning solution or melt into the smallest cracks and pores.

Cleaning and washing mechanisms

Cleaning in most cases requires that impurities be dissolved (in the case of salt dissolution), scraped off (in the case of insoluble salts) or both dissolved and scraped off (as in the case of insoluble particles fixed in a layer of fatty films). The mechanical effects of ultrasonic energy can be useful both to accelerate dissolution and to separate particles from the surface to be cleaned. Ultrasound can also be effectively used in the rinsing process. Residual detergent chemicals can be quickly removed by ultrasonic rinsing.

When removing contaminants by dissolution, the solvent must come into contact with the contaminating film and destroy it (Fig. 3, a). As the solvent dissolves the contamination, a saturated solution of contamination in the solvent arises at the solvent – ​​contamination interface, and dissolution stops, since there is no delivery of fresh solution to the contamination surface (Fig. 3, b).

Rice. 3

Exposure to ultrasound destroys the saturated solvent layer and ensures the delivery of fresh solution to the contamination surface (Fig. 3, c). This is especially effective when cleaning is performed on “irregular” surfaces with a labyrinth of sinuses and surface relief, such as printed circuit boards and electronic modules.

Some contaminants are a layer of insoluble particles firmly adhered to the surface by the forces of ionic bonding and adhesion. It is enough only to separate these particles from the surface in order to break the forces of attraction and transfer them into the volume of the cleaning medium for subsequent removal. Cavitation and acoustic currents rip off contaminants such as dust from the surface, wash off and remove them (Fig. 4).

Rice. 4

Pollution, as a rule, is multicomponent and may contain both soluble and insoluble components in a complex. The effect of ultrasound is that it emulsifies any components, that is, it transfers them into a washing medium and, together with it, removes them from the surface of products.

To introduce ultrasonic energy into the cleaning system, an ultrasonic generator, a converter of the generator's electrical energy into ultrasonic radiation and an acoustic power meter are required.

An electric ultrasonic generator converts electrical energy from the grid into electrical energy at an ultrasonic frequency. This is done by known methods and does not have any specificity. However, it is preferable to use a digital generation technique, when the output is rectangular pulses of alternating polarity (Fig. 5). The efficiency of such generators is close to 100%, which makes it possible to solve the problem of the energy consumption of the process. The use of a rectangular waveform results in acoustic radiation rich in harmonics. The advantages of a multifrequency cleaning system are that no “dead” zones are formed in the interference nodes in the volume of the cleaning medium. Therefore, multi-frequency ultrasound irradiation makes it possible to locate the cleaning object practically in any zone of the ultrasound bath.

Rice. 5

Another technique for getting rid of the "dead" zones is to use a swept generator (Fig. 6). In this case, the nodes and antinodes of the interference field move to different points of the cleaning system, without leaving any areas for cleaning without irradiation. But the efficiency of such generators is relatively low.

Rice. 6

There are two general types of ultrasonic transducers: magnetostrictive and piezoelectric. They both perform the same task of converting electrical energy into mechanical energy.

Magnetostrictive converters (Fig. 7) use the effect of magnetostriction, in which some materials change their linear dimensions in an alternating magnetic field.

Rice. 7

The electrical energy from the ultrasonic generator is first converted by the winding of the magnetostrictor into an alternating magnetic field. The alternating magnetic field, in turn, generates mechanical vibrations of the ultrasonic frequency due to the deformation of the magnetic circuit in time with the frequency of the magnetic field. Since magnetostrictive materials behave like electromagnets, the frequency of their deformation vibrations is twice the frequency of the magnetic, and, therefore, the electric field.

Electromagnetic converters are characterized by an increase in energy losses for eddy currents and magnetization reversal with increasing frequency. Therefore, powerful magnetostrictive transducers are rarely used at frequencies above 20 kHz. Piezo transducers, on the other hand, can emit well in the megahertz range. Magnetostrictive transducers are generally less efficient than their piezoelectric counterparts. This is primarily due to the fact that a magnetostrictive converter requires a double energy transformation: from electrical to magnetic and then from magnetic to mechanical. Energy losses occur at every transformation. This reduces the efficiency of magnetostrictors.

Piezo transducers (Fig. 8) convert electrical energy directly into mechanical energy through the use of the piezoelectric effect, in which some materials (piezoelectrics) change their linear dimensions when an electric field is applied. Previously, piezoelectric emitters used such piezoelectric materials as natural quartz crystals and synthesized barium titanate, which were fragile and unstable, and therefore unreliable. More durable and highly stable ceramic piezoelectric materials are used in modern converters. The vast majority of ultrasonic cleaning systems today use the piezoelectric effect.

Rice. eight

Ultrasonic cleaning equipment

The range of ultrasonic cleaning equipment used is very wide: from small tabletop modules in dentistry, jewelry stores, the electronics industry, to huge systems with volumes of several thousand liters in a number of industrial applications.

Right choice necessary equipment is of paramount importance to the success of ultrasonic cleaning. The simplest ultrasound cleaning application may require as little as heated washing liquid. More complex purification systems require a large number of baths, the latter of which must be filled with distilled or deionized water. The largest systems use submersible ultrasonic transducers, the combination of which can irradiate baths of almost any size. They provide maximum flexibility and ease of use and maintenance. Ultrasonic baths with heated cleaning solution are most often used in laboratories, medicine, and jewelry.

Lines of ultrasonic cleaning (Fig. 9), used in large-scale production, combine in one building electric ultrasonic generators, ultrasonic transducers, a transport system for moving objects to be treated in the baths and a control system.

In industry, there has always been a task of cleaning parts from all kinds of dirt. The issue of cleaning was especially acute in those industries where cleaning of a complex surface of a part or thin and long channels in datals was required. In metallurgy, after smelting, it was required to free the part from the molded mixture, which adhered during smelting to the entire surface of the part. It was either impossible or laborious to use any mechanical means (grinder) for this operation.

To simplify the operation of cleaning parts from dirt in the 40-50s of the 20th century, the idea was put forward to use ultrasound in a liquid medium to clean parts immersed in this liquid. Most often, the working fluid is water.

Many devices have been designed that generate in solution ultrasonic waves with frequency lying in the area 500 kHz... It was assumed that the energy of sound waves at such frequencies would be sufficient that small particles contained in the solution, accelerated by ultrasonic waves to high speeds, could knock out large particles of dirt, i.e. wash off the dirt. Devices designed to operate at this frequency turned out to be unworkable.

Those devices that were designed to generate sound wave in the range of 20 kHz, proved to be efficient... And mainly due to the fact that a sound wave in a liquid at a given frequency creates cavitation effect, which became the reason for the effective cleaning of the surface from dirt.

Is the process of the formation of bubbles, that is, cavities filled with gas, in a liquid. Such bubbles do not live long, since negative pressure is created in these cavities, and the liquid surrounding them has a positive pressure, the pressure difference leads to the fact that the bubbles "collapse" resulting in the formation of intense shock waves that can destroy even metal structures. At the moment of "collapse", the pressure of the gaseous medium inside the bubble can be several thousand times higher than atmospheric.

A gas-filled bubble may have a longer life span. This is due to the successive compression and expansion processes caused by the passing ultrasonic waves, and as a result of diffusion, the size of the bubbles will grow until the air in them lifts them to the surface of the liquid. There they burst instantly. Such cavitation process usually degassing liquids. This phenomenon began to be applied for degassing liquids.

Products requiring cleaning were immersed in liquid and irradiated with ultrasonic waves. Contaminated objects are immersed in a tank filled with a suitable solvent, ultrasound of such frequency and intensity is applied to the liquid, which forms cavitation with maximum efficiency. The created shock waves hit the surface of objects and clean them very effectively.

It should be borne in mind when designing and setting up an ultrasonic cleaner that the ability of acoustic waves to create cavitation decreases significantly with increasing frequency.

Ultrasonic bath

We figured out the theory, based on the theory, in order to choose an ultrasonic bath or assemble it yourself, you need 3 elements:

• bath- a vessel for a liquid - any shape, but taking into account the volume of the contained liquid. Manufacturing material - stainless steel 08X17 or other.
• ultrasonic wave generator- to generate ultrasonic waves, piezoelectrics are used, rigidly attached to the bath, using epoxy-based glue (you can use acrylic-based glue). Piezoelectric ultrasonic wave generators can be made from different materials, the most widely used material is piezoceramics, quartz-based piezoelectric elements can also be found. The power of the ultrasonic cleaner depends on the size of the crystal of the wave generator. The rule here is that the more, the more powerful.
• electronic circuit- it is necessary to supply energy to the piezo wave generator, it consists of a power transformer and a frequency converter, the frequency of an industrial wire of 50 Hz is converted to the required frequency of the order of 18-20 kHz and then, passing through a step-up transformer (at the output of about 8 kV), it enters the piezoceramic plate.

Ultrasonic cleaning of nozzles

For cleaning automobile injectors, both an ultrasonic cleaner and a specialized station for cleaning injectors can be used. The differences in use are that the post for cleaning nozzles allows you to clean the nozzles during operation and its use, purchase or assembly is justified in the professional field at the stations of those. maintenance, a bath is suitable for cleaning the fuel injectors at home, although there is no possibility of cleaning the injectors during operation, there the entire injector is completely immersed in the cleaning agent and there is no visual confirmation of cleaning the injector either, whether the injector is cleaned or not can be understood only when the engine is running according to the sensations ... But there is also a plus of using a bath, and not a post, there is also a fuel filter in the injector, which retains dirt in the fuel, when it is cleaned in the bath, the dirt crushed by cavitation does not pass the entire fuel path to the injector and does not settle in the irregularities of this path.

Video of the post on cleaning injectors:

Cleansers

The interaction of an ultrasonic wave with a contaminated object takes place in an aqueous medium, since water is a universal solvent, cheap and it is possible to get it everywhere, in addition, the frequency of cavitation creation is known for water of 18-20 kHz, and for other liquids its own cavitation frequency. Therefore, all cleaning agents are made on a water basis, which contains various surfactants and anticorrosive additives, which give the cleaning agent highly effective detergent properties. To prepare a cleaning agent for ultrasonic cleaning, it is enough to add detergents (soap) to the water, for less critical parts, and for more critical metal parts, also anti-corrosion substances.

And the answers to them.

Ultrasonic cleaning: questions and answers

Questions

1. What is ultrasonic cleaning?

Ultrasonic cleaning is a fast and effective environmentally friendly cleaning method that uses ultrasonic energy that passes through a suitable cleaning solution. This provides a high-speed, thorough removal of unwanted contaminants from the cleaning elements located within the ultrasonic penetration fluid container. This cleaning method is one of the most modern and effective ways to remove dirt from various objects, especially in as soon as possible and without possible damage to the elements. The ultrasonic cleaning method is based on cavitation.

2. What is cavitation?

Cavitation is the process of rapidly forming and dispersing micro bubbles in a liquid. The phenomenon of cavitation occurs when ultrasonic waves pass through a liquid. Ultrasound (high frequency sound, typically 20 to 400 kHz) produces alternating high and low pressure waves that produce tiny cavities (bubbles). They start to grow from microscopic sizes in the low pressure phase until they contract and then burst during the high pressure phase. The molecules of the liquid collide, releasing a tremendous amount of energy. The energy instantly increases the local temperature and forms a high energy stream directed to the surface of the object to be cleaned. These bubbles have tremendous energy, which is directed towards cleaning - its release separates dirt from the surface to be cleaned.

3. How to get ultrasound?

The ultrasonic energy of high frequency sound waves is converted from high frequency electrical energy using a transducer. The cleaning capacity of the device depends on the type and capacity of the inverter used.

4. How is the ultrasonic cleaner designed?

Module ultrasonic bath includes an ultrasonic generator and special transducers mounted on the bottom of the stainless steel tank. The reservoir must be filled with liquid to form a cleaning medium. The generator, together with the transducer, generates alternating compression and expansion waves in the fluid at very high frequencies, typically 25 to 130 kHz.

5. What is the ultrasonic heater used for?

The ultrasonic cleaner uses a heating function to keep the solution temperature at the desired level between cleaning cycles. In turn, the heat required for cleaning is generated during the cavitation process.

6. What is degassing and why is it needed?

Degassing is a process of preliminary removal of gases that may be present in the cleaning liquid. Cavitation should only take place after all gases have been removed from the cleaning solution. This provides a vacuum in the bubbles that form. They are destroyed when a high pressure wave hits the wall of the bubble and the released energy helps the detergent to break the bonds between the objects being cleaned and their contaminants.

7. How to get the optimal cleaning result?

You can get the best ultrasonic cleaning result only after following simple steps: choose the right type of ultrasonic cleaner and the right tank size; choose the appropriate cleaning agent suitable for your purposes; set the correct temperature and cleaning time.

8. What is direct and indirect cleaning?

When you place the items to be cleaned in an ultrasonic cleaner tank filled with detergent solution, this is called direct cleaning. The objects are usually placed in a special perforated plastic tray or basket rather than at the bottom of the tank. However, for direct cleaning, you should choose a liquid that will not damage the ultrasonic cleaner tank. Otherwise, you can use a non-perforated tray or glass container, fill it with the cleaning liquid you need, and place the items inside. This method is called indirect cleaning. Keep in mind that the water level inside the tank must reach the fill line during cleaning, that is, about 3 centimeters from the top.

9. Why is a special cleaning solution needed?

You can use a variety of cleaning fluids, even clean running water. However, the water itself does not have cleaning properties, so you will have to use a special cleaning solution to get the desired effect. You place objects to be cleaned in the solution to start this process, and cavitation helps the solution break the bonds between parts and contaminants. Special cleaning solutions contain certain ingredients to enhance the ultrasonic cleaning effect. For example, a decrease in the surface tension of a liquid leads to an increase in the level of cavitation. The liquid contains an effective humectant or surfactant.

10. Which cleaning solution should I use?

You can find a wide variety of ultrasonic cleaners designed for specific applications. Modern solutions contain various detergents, wetting agents and other reactive components. The correct choice of cleaning solution determines the success of the cleaning process and helps to avoid unwanted reactions with the object to be cleaned. Please consult technical experts before choosing a product for your needs.

11. Which cleaning solution should not be used?

Never use flammable solutions or liquids with a low flash point (gasoline, benzene, acetone, etc.). Energy caused by cavitation generates heat, and high temperatures can create a hazardous environment in flammable solutions. Avoid using bleaches and acids. They can damage the stainless steel bath tub. Otherwise, use them carefully if necessary, but only for indirect cleaning. A suitable container for indirect cleaning should be available, glass containers may be used.

12. When should the cleaning solution be replaced?

13. Why is it necessary to maintain the solution level at the level indicator?

Before cleaning, make sure the solution level is in line with the bath level indicator. It should match the level indicator with trays and basket inside. Otherwise, the characteristics of the cleaning process may be affected, the frequency of cleaning may change, the cleaning efficiency may decrease, and your ultrasonic bath may even be damaged. Compliance with this requirement allows for a higher circulation of the solution around the objects to be cleaned and to protect the heaters and transducers of the device from overheating and shock.

14. How long does the cleaning process take?

The cleaning time depends on a number of conditions, the most important of which are: the cleaning solution, the amount and type of contamination on the site, the cleaning temperature and the required level of cleanliness. You can observe the removal of contaminants immediately after starting the cleaning cycle. You can adjust the duration of the cleaning process according to your conditions. Usually, you will have to set the approximate time required, then check the cleaning result, and repeat the cleaning cycle if necessary. The actual use and cleaning result helps the operator determine the optimal time for certain types of objects as well as for specific types of contamination.

Heating helps the bath to make the cleaning process faster and more efficient. Cleaning solutions are usually formulated to provide better results and higher temperatures. You can determine the optimum temperature that suits your needs in order to provide the fastest and most effective results by experimenting with different types of soiling and cleaning items. Typically, you can get the best results in the 50 ° C ~ 65 ° C range.

16. Should I rinse the parts after cleaning?

To remove any harmful or unwanted chemical residues from the cleaning agent, it is recommended to rinse the objects after cleaning. You can rinse in your ultrasonic bath filled with plain tap water, or use tap, distilled, or deionized water and a separate container if needed.

17. Why should you turn off the ultrasound bath if it is not in use?

Continuous operation of the bath increases the evaporation of the cleaning solution. This can cause the liquid level in the reservoir to drop, which could result in serious damage to the bath. Turn off the ultrasonic bath after completing the cleaning cycle and check the solution level before each operation in order to ensure the long life of the device.

18. Can ultrasonic cleaning damage my parts?

This cleaning method, with some caveats, is considered safe for most objects. Although a powerful release of energy occurs during the process of cavitation, this is safe, since the energy is localized at a microscopic level. The first thing you should pay attention to is choosing the right cleaning solution. Ultrasonic power can intensify the effect of the detergent on the items to be cleaned. It is not recommended to use ultrasound to clean the following stones: emerald, malachite, pearl, tanzanite, turquoise, opal, coral and lapis.

19. What are the applications of ultrasonic cleaning?

Typically this cleaning method is used to clean items, parts and other objects with complex surface structures and items that require special care. Ultrasonic cleaning will prove useful in chemistry, automotive, mechanical engineering, polymer manufacturing, scientific research, healthcare, medicine, weapons, jewelry and other industrial applications.

20. What is prohibited when using an ultrasonic cleaner?

• Never place objects on the bottom of the tank for cleaning. This can damage the bath as the ultrasonic energy will be reflected from the items to be cleaned back to the transducers. Always use a cleaning tray or basket with a 30 mm distance between the bottom of the tank and the objects to be cleaned.
• Do not drop the ultrasonic bath and avoid other shock. This can damage the ultrasonic transmitter.
• Never run the bath without liquid inside the tank.
• Never use flammable liquids such as gasoline, benzene, acetone for fire hazard reasons.
• Never use the ultrasonic bath in very dusty places.
• Never use the ultrasonic bath at very high temperatures for extended periods of time.
• Never try to clear explosive objects, ammunition, hand grenades, mines, etc.
• Never put animals or other living things inside the bathtub or use the bathtub to clean your pets.

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