Ultrasonic Cleaners: Working, Types, Uses and Advantages

What is an Ultrasonic Cleaner?

Ultrasonic cleaners are devices which use mechanical vibrations to create sound waves in a liquid medium. These mechanical sound waves generate microscopic bubbles in the liquid medium that grow and collapse in a process called cavitation.

This cavitation produces a ‘scrubbing action’ which aide in the removal of dirt and contaminates on the object being cleaned. Ultrasonic cleaners utilize cavitation in addition to sonic agitation, on the object being cleaned, and require specialized cleaning solutions.

This cleaning method is particularly beneficial to precision instruments, delicate objects and sensitive applications as it is a uniquely complete cleaning method.

The ultrasonic cleaning process compresses and decompresses the cleaning solution and releases energy in a focused or generalized manner throughout the liquid medium, producing cleaning action from encapsulation and large area coverage of the cleaning solution.

The effectiveness of ultrasonic cleaning is primarily based on the historical design of the ultrasonic cleaning system and the frequency and power density at which the cleansing application operates.

The components that define the performance and cleansing process of an ultrasonic cleaning system are important to systematic identification for choosing an appropriate ultrasonic cleaner because these components affect the overall efficiency and outcomes.

How Does Ultrasonic Cleaner works?

Cavitation is a physical process that occurs when regions of high pressure are rapidly fluctuating between high and low pressure levels within a very short interval of time.

In an ultrasonic cleaner, these pressure drops and increases are created by the high frequency sound waves introduced into the cleaning media.

The sound waves induce small bubbles or cavities that change in pressure rapidly resulting in a bubble that will inertially collapse to establish a cavity which emanates small but intense shockwaves.

The tiny shock waves created by cavitation are effective at displacing matter and removing debris from the surfaces of the objects being cleaned even at a microscopic level.

In a number of industrial applications, cavitation is a damaging process and increases wear rates on metal parts including pump impellers and casings.

The need for cleaning protocols to manage the cleaning parameters used for cavitation is also needed as an intense level of cavitation will also damage the objects being cleaned.

An ultrasonic cleaner is mainly composed of three distinct components to operate; generator, transducer and tank. The first and the most important part of the ultrasonic cleaner is the ultrasonic generator because it changes utility power into an electrical signal oscillating at frequency used for cleaning.

where utility power is either 50 or 60 Hz, the generator frequency increases to a much higher frequency, typically between 20 kHz to 80 kHz, continued advances in technology have introduced even higher frequencies known as megasonic frequencies described as 100 kHz and higher.

The second part of an ultrasonic cleaner is the ultrasonic transducer , which changes the electrical signal into mechanical vibrations.This conversion takes place because of the inverse piezoelectric effect, or magnetostrictive effect.

When we apply an electrical signal, the dimensional change on piezoelectric or magnetostrictive materials can range from 1 to 0.1 microns.

The magnetostrictive transducer works because ferrous metals will expand and contract continuously when placed in a magnetic field.

The motions created generate mechanical ultrasonic waves within the ultrasonic cleaners containers. The ultrasonic waves produced in the cleaner will take an elipsoid shape.

Piezoelectric transducers contain crystals with specific electrical properties. When electrical current is utilized through the crystal, it alters its shape, which creates linear oscillations. Piezoelectric transducers are primary in use throughout Europe and Asia.

By considering your transducer, it is important to consider how it will affect the ultrasonic cleaning process. Historically speaking, mechanical vibrations were created and produced through the use of metal transducers.

The issue with metal transducers were they produced waves that were overall too strong, injuring the delicate instruments.

Today, ultrasonic cleaners operate; by utilizing ceramic transducers which produced a more controlled cleaning action, than its predecessors, thus protecting sensitive materials from damage.

The last primary component that comprises an ultrasonic cleaner is the tank. The tank is where the cleaning solution, and the items to clean will be placed. The tank is also the mounting location for the transducers.

Most tanks are made from corrosion resistant materials like stainless steel, but could be plastic and ceramic as well. Tank sizes vary based on the capacity of solvent it can hold, however it should be built to have longevity.

Some ancillary components that are included with ultrasonics cleaners are the heater and strainer basket. The heater may keep the cleaning solution maintained at temperature, which is critical as vapor pressure of the cleaning solution are also related to the temperature factors of cavitation.

While cleaning, it is important to monitor the process temperature, to maximize cleaning ability and ensure that proper care is being maintained on the pieces of interest.

The strainer basket works to keep the pieces submerged in the cleaning solution. In most systems, it will hold your pieces securely and prevent the parts from hitting the bottom or sides of the tank, as this could affect the vibration that propagated through the cleaning solution.

How To Use Ultrasonic Cleaner Machine?

Ultrasonic cleaning is a fairly simple process actually, as the major portion of the work consists of setting up the cleaning bath and machine. While cleaning does require operator interaction very little operator action is involved.

Aditionally, further action can be taken with parts after cleaning if needed. Below is a summary of the standard ultrasonic cleaning procedure.

Pre-Rinsing.

Prior to putting a part into an ultrasonic cleaner, it is recommended to flush or brush the part to remove any loose dirt, soil, and large particles to enhance efficiency of ultrasonic cleaner operation.

This will aid in removing a large quantity of contaminants. This can be accomplished with at least lukewarm water. Using a pre-rinse with parts will help and enhance efficiency.

Solution Preparation.

This can be defined as everything you do in advance of cleaning, including formulizing the cleaning solution and transferring the prepared cleaning solution to the cleaner tank.

There are many ready-to-use ultrasonic cleaning formulations in the marketplace and you can often avoid trial and error.

Just remember to consider the type of contaminant to be removed, as different contaminants have different cleaning solution components and/or additives.

Also, pay attention to the solution components or additives that are added to the solution, as they may not be compatible with the item to be cleaned. For instance, some acidic solutions can corrode metallic objects if rinsing is not done and/or corrosion inhibition is not used.

Setting the Bath Temperature.

Most ultrasonic cleaners in industrial settings will have a heater mounted to heat the bath to a controlled temperature.The temperature has a direct effect on a machine’s ability to produce cavitation efficiency.

In addition, temperature also affects many other fluid properties, including surface tension, viscosity, and density. More importantly, a higher temperature results in increased chemical reactions in the solution.

Setting the Generator Parameters.

This portion is typically carried out when dealing with commercial ultrasonic cleaners. Adjusting the generator parameters grants the operator the ability to adjust the strength of cavitation.

This is important when washing parts of different diameters and weights. Off-the-shelf tabletop ultrasonic cleaners do not have this capability and are pre-programmed with a preset generator

Solution Degassing.

Dissolved gases have an adverse effect on the intensity of the cavitation in the cleaning solution. Gases are dissolved in the solution in the form of gas bubbles. When the displacement or pressure involved in cavitation, the cavitation voids move towards the gas bubbles.

This extra volume will prevent the voids from collapsing, greatly dampening the shock waves created by cavitation.

To degas the solution, the ultrasonic cleaner is first utilized without load for a few minutes. The dissolved gasses will eventually rise toward the surface of the fluid. This rising motion can be seen by the naked eye, as the gases congregate at the surface and form larger bubbles.

Ultrasonic Washing.

Once everything has been set, it is time to start the washing process. Ultrasonic washing is as simple as dropping the piece to be cleaned into the cleaning solution.

Strainer baskets are used to hold the part, avoiding contact with the walls of the tank to a distance of about two or more inches. The washing requires about 10 minutes, give or take depending on the amount and nature of contaminants to be removed.

Rinsing.

Rinsing is an optional process of removing cleaning solution from the part surface. This is an essential step when using acidic solutions. Rinsing baths use pure deionized water or deionized water with additives such as corrosion inhibitors.

Secondary Processes.

Secondary processing is optional and may include polishing and lubricating. Polishing and lubrication use dissimilar solvents that impart positive surface properties to the material.

An additional polishing step is typically applied in cleaning pieces of jewelry. The lubricating step is completed in servicing firearms.

Drying.

This step is the process of exposing the cleaned part to either hot air or simply using room air. A fan or blower is commonly used to speed up this process, which is desirable in manufacturing lines that must dry parts quickly.

Types of Solutions That Are Used For Ultrasonic Cleaning

Cleaning effectiveness depends not only on the efficacy and precision of the ultrasonic machine but also on the type of cleaning solution as well. Simply water will not suffice for optimal cleaning. It is important that cleaning solutions:

• Do not attack what you are cleaning
• Do not foam improperly
• Will actively assist cavitation
• Wet all surfaces that are submerged
• Easily rinse

Ultrasonic cleaning solutions usually consist of alkaline detergents, surfactants, acid, and enzymes diluted in deionized water. The solution composition will vary depending on the debris or contaminant being removed.

Deionized Water.

Deionized water is the principal solvent in which all other ultrasonic cleaning products are diluted. It has been created from common water, which had been ultrafiltered and softened to remove almost all minerals, salts, metals, and other contaminants.

Due to its purity, it can fairly easily absorb contaminants of all types, making the cleaning process extremely quick and efficient.

Alkaline Detergents.

Alkaline detergents are the generally described method for the removal of organic and petroleum based contaminants, oil, grease, and waxes. They will generally exhibit pH numbers of 10 and above. Alkaline detergents are almost entirely interchangeable with caustic solutions and surfactants.

Alkaline detergents’ principal action is to reduce the surface tension of water. This simply allows oil to dissolve into the solution. The action of lowering surface tension improves the wettability of the part and then allows for better immersion into the solution.

Acids.

Acids are recognized for aggressively removing mineral deposits, scale, fouling, rust, and small metal shavings, and burrs. In contrast to alkaline detergents, acid products have a pH of six or lower.

Ultrasonic cleaning applications of acidic solutions are prevalent in automotive, aerospace, or metal fabrication industries. After the ultrasonic cleaning process, a rinsing or corrosion inhibition procedure is immediately required to prevent corrosion. Acid residue will be reactive to the surface of the part, causing damage, tarnishing, and corrosion.

Enzymes.

Enzymes are particularly useful cleaning compounds used in medical and dental ultrasonic cleaners. Enzymes are compounds that act catalytically and are made up of active long chain proteins, and they are used to break down biological matter. Enzymes are safe to use because they are biodegradable and have a pH neutral.

Enzymes are useful to remove blood, bone, tissue, fats, and soils that cannot be removed by conventional detergents. Enzymatic cleaning agents take many forms they may be concentrated solutions or dissolvable tablets or powder.

EDTA (Ethylene Diamine Tetra Acetic Acid).

EDTA is a cleaning chemical compound neutralizes or removes metal ions present in cleaning solution to prevent the metal ion impurities to discolor that material being cleaned.

EDTA also helps to stabilize the cleaning solution for multiple cleaning cycles because it prevents metal ions from reacting with the solution.

Corrosion Inhibitors.

Corrosion inhibitors are chemicals effective at reducing significant oxidation attack to the cleaned material surface. They are used in the cleaning of metallic objects most notably jewelry, electronics, automotive, aerospace items etc.

Given that some ultrasonic cleaning solutions may contain acids, a rinsing bath with corrosion inhibitors may be applied to the part as a protective layer to the material being cleaned. These chemical additives will protect and maintain the cleaner tank from corrosion as well.

Ammonia:

Ammonia is a popular compound in most homemade cleaning solutions. Ammonia, similar to detergents will remove the bulk of dirt, grime, and residues originating from oil based cleaning agents.

It is inexpensive since a small amount of ammonia is all that is required in a cleaning solution. Ammonia is commonly used to clean pieces of jewelry.

Types Of Ultrasonic Cleaning Machines

There are many types of ultrasonic cleaning machines that are designed to clean specific parts or materials. Many of these ultrasonic cleaning machines differ in certain aspects to meet different cleaning applications.

Medical and Dental Ultrasonic Cleaners:

Ultrasonic cleaners will remove blood, tissue and protein-based contaminants while preserving the delicate surface of the medical or dental instrument.

Because ultrasonic cleaning destroys most contamination, ultrasonic machines can prepare instruments for sterilization.

Some common medical or dental items prepared for sterilization include: surgical instruments, implants, surgical screws and fasteners, needles, blades, labware, and more.

Jewelry Ultrasonic Cleaners:

Ultrasonic cleaning is often a common part of the jewelry making. The precision and gentle cleaning that ultrasonic cleaners provide is a benefit. Ultra sonic cleaners can produce cavitation on messenger inner surface of the jewelry.

Ultrasonic cleaning does not damage or scratch the jewelry; this is beneficial from a making standpoint. Furthermore, ultrasonic cleaning can be used with ultrasonic polishing, which can provide a better luster than other forms of cleaning.

Ultrasonic Gun Cleaners:

Guns are made of multiple pieces of metal; they contain multiple hollow areas, cavities, and more. Brushes and polishers can only reach so much. Even in disassembly, there are some areas that cannot be accessed for hand washing, brushing, or polishing.

Additionally, traditional gun cleaning uses solvents to clean; this can also harm the environment. Ultransonic gun cleaners do not have this problem.

If correctly wetted with the cleaning solution, ultrasonic gun cleaners, or ultrasonic firearm cleaners, will reach all parts of the gun. They can also be used with ultrasonic gun lubricants.

The two processes are essentially the same; they both use cavitation. Because ultrasonic cleaning and lubrication happens completely, gun cleaning and lubrication eliminates the process of having to completely dismantle the gun for maintenance every time.

Electronics Ultrasonic Cleaner:

Ultrasonic cleaners are used in circuit boards and electronics cleaning because they are simple to operate, have high throughput, and clean precisely.

The electronics ultrasonic cleaners can remove various types of debris found in semiconductors and electronics manufacture processes.

Small metal chips and burrs can be eliminated while keeping the small features of the electronics intact, allowing the creation of a defect free product that performs reliably.

Industrial Ultrasonic Cleaners:

Industrial ultrasonic cleaners clean various machine parts, automotive parts, and aviation parts. These are very large cleaning machines designed to hold pieces like compressors, radiators, pumps, valves, and gear cases.

They are efficient at removing oils and grease. Also, while cleaning is being done to large components, part cycle times are only a few minutes longer than those of the smaller ultrasonic cleaning machines. Most importantly, cleaning is evenly performed on all wetted surfaces of the component.

Medical Parts Cleaning During Manufacturing:

Sanitation and sterilization go a long way to eliminate harmful microorganisms from medical devices. The component parts of medical instruments must also be cleaned to remove debris and particulates before assembly and sterilization.

Cleaning medical devices prior to sterilization is intended to rid devices of contaminants, including particulates and fluids that might have adhered during machining and assemblies.

When specific devices, such as joint implants made of stainless steel and titanium, are machined and assembled, there is a likelihood metal shavings will adhere to holes or connections.

Likewise, the fluids used to cut and shape the implants also need to be removed prior to proceeding with the next steps of production.

Medical instrumentation products undergo multiple degrees of cleaning if they had been assembled and later prior to sterilization. Ultrasonic precision-cleaning is the industry standard when cleaning medical devices during manufacture.

An ultrasonic precision-cleaning bath is optimal for cleaning complexly designed components and in cleaning areas of components that can be hard to reach or are blind holes, and will further enhance subsequent surface treatments.

It has proven to be an ideal, and in most cases the best solution, for the precision cleaning of everything from surgical instruments, implants, surgical screws and fasteners, needles, blades and cannulae, to catheters, stents, hospital/laboratory ware, and test instruments.

Ultrasonic Mold Cleaners:

Ultrasonic cleaners utilized in cleaning molds for plastics, and other materials, benefit from the fact that their system delivers non contact cleaning cleaning benefits, which do not change, damage, modify, or alter mold cavity detail designs.

A very specific design detail of a mold includes careful consideration of mold geometry and naturally virtual vertical dimensions, therefore strict adherence to mold tolerances is critical in making sure the molded product is made to the quality requirements.

Unlike other cleaning techniques that involve harmful toxic chemicals, ultrasonic cleaning never touches the surface of a mold, but it can still accomplish precision cleaning of a mold’s most complex and detailed areas.

Ultrasonic cavitation turbulence enhances the cleaning action by exposing surfaces to a fresh chemical cleaning. In addition, with the help of heat and cleaning solvents, the process establishes a cleaning action that enters blind holes, small crevices, and the complexity of the contours of a mold.

Residual burnt polymers and mold releases from mold components are cleaned away; extending the useful life of a mold’s surface without damaging or harming the surface. Buildup from cooling ports and channels are also cleaned away, which helps to improve the polymer flow.

Side mounted immersible transducers are a new innovation in ultrasonic cleaning, and they produce a more intense and precise cavitation than transducers that are mounted to the bottom of the tank.

Plastic injection molds are rectangular in shape and have design features on their surfaces that face the side of the tank. Side mounted transducers provide a more efficient and concentrated cleaning action for the orientation of the mold’s most complex features.

The turbulence of ultrasonic cavitation enhances cleaning action by presenting surfaces with fresh chemical cleaning.

Coupling heat and chemical cleaners with the process develops a cleaning action that travels into blind holes, tiny crevices, and the iterated complexity of the contours of a mold.

Residual burnt polymers and mold releases from mold components are cleaned away; extending the mold’s surface useful life while decreasing or destroying the surface. Buildup from cooling ports and channels collect being cleaned away helps improve polymer flow.

A recent innovation in ultrasonic cleaning are side mounted immersible transducers, which produce more intense and directed cavitation, than transducers mounted onto the tank bottom.

Plastic injection molds are rectangular in shape, having design features oriented on their surfaces that face the side of the tank. Side mounted transducers clean more effectively and direct more cleaning action for the orientation of the mold’s most complex features.

Immersible Ultrasonic Cleaners:

Immersible ultrasonic cleaners sometimes referred to as submersible cleaners, consist of only two components: the ultrasonic generator and transducer. The transducer is attached to the generator by a cord and it is submersible in the cleaning solution.

Any type of container can act as a tank as long as it holds the sufficient amount of cleaning solution. Immersible ultrasonic cleaners are designed to be portable; though this brings some advantages the performance of the machine is poorly cleaning products.

Advantages Of Ultrasonic Cleaners

Ultrasonic cleaners are gaining more and more popularity as an overall cleaning procedure in many industries.

They are frequently utilized in healthcare, dental care, electronics, plastics, metalworking, and machinery manufacturing industries. Below are benefits of using ultrasonic cleaning equipment.

Highly Effective for Fragile Parts

In contrast to traditional cleaning techniques including brushing, polishing, scrubbing, cleaning jets or sprays, compressed air cleaning, and chemical cleaning, ultrasonic cleaning will not damage the part during cleaning.

Aside from contamination, mechanical and chemical techniques can usually remove some surface material from the part being cleaned. This can create unwanted surface imperfections, scratches, corroded spots, and discoloration.

Hence, ultrasonic cleaners are highly effective for cleaning delicate and sensitive items such as jewelry, dental and surgical instruments, microelectronics, and small intricate fabricated parts.

Uniformity and Accuracy of Cleaning

Ultrasonic cleaners operate by applying the energy of vibrations to the whole cleaning medium. This means that all wetted surfaces are cleaned at the same speed. This also helps limit the chance of excessively cleaning a certain section and damaging the part.

In addition, using proper wetting, virtually inaccessible areas will reach and clean every corner no matter how hard to reach it appears (including crevices and cavities).

Faster and More Thorough Cleaning:

Ultrasonic cleaners are both effective and quick. Normal cleaning cycle time is only 10 to 15 minutes, even for the most delicate items. Cleaning is completed in only one cycle; more than one cycle is generally not necessary for the cleaning process to be effective.

Cleaning speed can also be attributed to multi-tank installations where multiple parts can be cleaned concurrently. Cleaning parts are submerged in various tanks that comprise only one ultrasonic cleaner unit.

Able to Remove Most Contaminants:

Ultrasonic cleaning is not just limited to dirt but also other unwanted materials. To name a few, ultrasonic cleaning is capable of removing mineral deposits, rust, oil and grease, carbonized material, plastic and elastic residues, pigments, molds, and proteins.

This makes ultrasonic cleaning units a piece of cleaning equipment/broad-spectrum cleaning tool. Ultrasonic cleaning can easily target various types of debris by merely changing the machine parameters and the cleaning solution as necessary.

Relatively High Power Efficiency:

Compared to the power consumption of other mechanical cleaning processes, ultrasonic cleaning is relatively low power. Other cleaning methods use motors, pumps, and compressors which consume a considerable amount of power while converting only a small amount of that power into useful mechanical cleaning action.

Ultrasonic cleaning has the potential to readily convert electrical energy to vibrations. The ultrasonic generator itself is designed to have an efficiency of 95%, while the transducer is somewhere between 65% to 70%.

Total ultrasonic cleaner efficiency of ultrasonic cleaners, primarily piezoelectric types, can be estimated at 70% or greater.

Requires minimal space:

Ultrasonic cleaners require relatively little space/compact size. An ultrasonic cleaner only requires a tank to contain the cleaning bath and the item/part to be cleaned. There are no other pieces of equipment or accessories that are required. Some typical arrangements have another tank used to rinse the solution.

This is completely different from other cleaning methods such as the chemical cleaning method that requires several chemical baths, or water spray and compressed air cleaning methods that requires pumps and compressors to pressurize the cleaning medium.

Easy to Operate:

Most ultrasonic cleaners are equipped with digital controls, and in some cases, automatic control. Most tabletop machines only require a cleaning time input from the user.

Industrial and manufacturers ultrasonic cleaners allow operator modification of the operating parameters of the cleaning process by adjusting temperature, power density, wave amplitude, and frequency.

After the cleaning parameters are established, the operator is only required to drop the item that needs to be cleaned in the tank. After that the ultrasonic cleaner does the cleaning work. Depending on the application rinsing is completed afterwards.

This simple action is in contrast with cleaning methods that demand an operator to be in continual attendance throughout the cleaning process.