Ultrasonic cleaning is powerful enough to remove tough contaminants, yet gentle enough not to damage the substrate. It provides excellent penetration and cleaning in the smallest crevices and between tightly spaced parts in a cleaning tank. The use of ultrasonic cleaning machines has become increasingly popular due to the restrictions on the use of chlorofluorocarbons. The use of ultrasonics enables the cleaning of intricately shaped parts with an effectiveness that corresponds to that achieved by vapor degreasing, but in a more comprehensive, high-tech, and ecologically friendly manner.
How does ultrasonic cleaning work? In a process termed cavitation, micron-size bubbles form in the ultrasonic cleaning fluid and grow due to alternating positive and negative pressure waves in a solution. The temperature inside a cavitating bubble can be extremely high, with pressures up to 500 atm. Ultrasonic cleaning systems create an implosion event, which, when it occurs near a hard surface, changes the bubble into a jet about one-tenth the bubble size, which travels at speeds up to 400 km/hr toward the hard surface. With the combination of pressure, temperature, and velocity, the jet frees contaminants from their bonds with the substrate. Because of the inherently small size of the jet and the relatively large energy, ultrasonic cleaning can reach into small crevices and remove entrapped soils very effectively.
In order to produce the positive and negative pressure waves in the ultrasonic cleaning fluid, a mechanical vibrating device is required. Ultrasonic cleaning systems manufacturers make use of a diaphragm attached to high-frequency transducers. The transducers, which vibrate at their resonant frequency due to a high-frequency electronic generator source, induce amplified vibration of the diaphragm. This amplified vibration is the source of positive and negative pressure waves that propagate through the solution in the tank. The operation is like the operation of a loudspeaker except that it occurs at higher frequencies. When transmitted through water, these pressure waves create the cavitation processes for ultrasonic cleaning solutions.
The basic components of an ultrasonic cleaning system include a bank of ultrasonic transducers mounted to a radiating diaphragm, an electrical generator, and a tank filled with aqueous solution. A key component is the transducer that generates the high-frequency mechanical energy. There are two types of ultrasonic transducers used in the industry, piezoelectric and magnetostrictive. Both have the same functional objective, but the two types have dramatically different performance characteristics.
Piezoelectric Transducers have an assembly that is inexpensive to manufacture due to low material and labor costs. This low cost makes piezoelectric technology desirable for ultrasonic cleaning. For industrial cleaning, however, piezoelectric transducers have several shortcomings, the most common problem being that the performance of a piezoelectric unit deteriorates over time.
Magnetostrictive Transducers are known for their ruggedness and durability in industrial applications. Zero-space magnetostrictive transducers consist of nickel laminations attached tightly together with an electrical coil placed over the nickel stack. When current flows through the coil it creates a magnetic field. This is analogous to deformation of a piezoelectric crystal when it is subjected to voltage. When an alternating current is sent through the magnetostrictive coil, the stack vibrates at the frequency of the current.
Ultrasonic cleaning is a technology that has revolutionized the way in which various items are cleaned. This process involves the use of high frequency sound waves to agitate a liquid, creating tiny bubbles that remove impurities from surfaces in a matter of minutes.
Ultrasonic cleaning can be used in a variety of industries, including healthcare, aerospace, manufacturing, automotive, and semiconductor. While this technology has been around for decades, it continues to be refined and improved, making it an increasingly popular choice for those seeking efficient and effective cleaning solutions.
To begin with, an ultrasonic cleaner generates ultrasonic waves by passing an electric current through a transducer. This creates high-frequency sound waves that are transmitted through the cleaning solution.
These waves create a vibration in the liquid that produces small bubbles known as cavitation. The cavitation bubbles oscillate and implode, generating energy that is then transferred to the surrounding liquid. This energy is what ultimately removes dirt and other contaminants from the surface being cleaned.
Water molecules play a critical role in the cavitation process. They are constantly imploding and generating energy, which leads to the evolution of energy water waves that constantly impact the surface of the object to be cleaned. This impact is what strips away attached dirt from the object.
One of the primary benefits of ultrasonic cleaning is its ability to effectively remove contaminants from complex shapes and hard-to-reach areas. Items such as medical instruments, aerospace components, etc. can all be thoroughly cleaned using ultrasonic technology. In addition, ultrasonic cleaning is more efficient than traditional cleaning methods because it requires less time and fewer chemicals.
Frequency is used to measure cycles per second or vibrations per second. The unit used to measure frequency is Hertz (Hz). For example, if a sound wave vibrates 1 cycle per second, then its frequency is 1 Hz. If it vibrates 20 cycles per second, then its frequency is 20 Hz. Our ears can detect changes in frequency based on the pitch of the sound. Higher frequency sound waves have a higher pitch, while lower frequency sound waves have a lower pitch.
In ultrasonic cleaning, frequencies are used to create high-frequency sound waves that agitate a liquid to produce tiny bubbles known as cavitation. These bubbles implode, releasing energy that removes dirt and other contaminants from surfaces being cleaned. The frequency used in ultrasonic cleaning can range from 15 kHz to 400 kHz. However, frequencies below 20 kHz are usually not effective for cleaning, and frequencies above 100 kHz are typically reserved for delicate parts.
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The typical frequency used in ultrasonic cleaning applications falls around 40 kHz. This frequency is chosen because it is effective at removing dirt and other contaminants from surfaces without damaging the item being cleaned. Higher frequencies are used for delicate parts or those that require a gentler cleaning process, while lower frequencies are used for heavy-duty cleaning applications.
One of the main benefits of using ultrasonic technology is that it is incredibly efficient. Ultrasonic cleaning can clean items in a matter of minutes, while traditional cleaning methods may take hours and require harsh chemicals that can damage the item. Additionally, ultrasonic cleaning can effectively remove contaminants from complex shapes and hard-to-reach areas.
When it comes to ultrasonic cleaning, frequency matters. Different frequencies are used for different purposes and can have a significant impact on the effectiveness of the cleaning process.
At the lowest end of the ultrasonic cleaning frequency range is 25 kHz. This frequency is used with larger mass items that require a little more power to remove surface grime. Examples include cleaning cast iron blocks for injection molding, massive steel cutting tools, and large stainless steel plates.
The vast majority of ultrasonic cleaning machines feature a 40 kHz transducer, which produces mid-sized cavitation bubbles. This frequency is the middle-of-the-road standard and is commonly used for a wide range of cleaning applications. It has enough power to shake contaminants loose without causing damage to the item being cleaned. Common uses for 40 kHz ultrasonic cleaning include removing oils and metal chips from general machine shop applications, soot removal from items damaged in fires, and cleaning ceramics used in high technology fields.
For delicate cleaning applications, higher frequency generators are used. These include 68 kHz, 132 kHz, and 170 kHz ultrasonic cleaning. Such frequencies provide a delicate and thorough cleaning, and are employed in cases where cavitation bubbles need to reach even closer to the substrates being cleaned. Although less common, these ultrasonic cleaning are highly effective at removing the tiniest particles.
The success of the cleaning process depends largely on the cleaning solution used.
It is also important to note that HFE should never be used to fill an ultrasonic tank due to its high solvent loss. It can damage surfaces and cause a risk to the person using the equipment.
It is essential to use ultrasonic cleaning carefully to avoid causing damage to the items being cleaned. Here are some tips on how to avoid damage during ultrasonic cleaning:
Additionally, it is advisable to use baskets and jigs to reduce damage and optimize the cleaning process. These tools keep the items separated, ensuring there is no contact between them, and allow for maximum exposure to the cleaning solution.
In conclusion, ultrasonic cleaning technology has revolutionized the cleaning process across various industries. By utilizing high-frequency sound waves, ultrasonic cleaning generates cavitation bubbles that remove impurities from surfaces in a matter of minutes. Ultrasonic cleaning frequencies can range from 15 kHz to 400 kHz, but the common frequency utilized in most ultrasonic cleaning applications is around 40 kHz. Lower frequencies are ideal for heavy-duty cleaning, while higher frequencies are suitable for delicate items.
Ultrasonic cleaning offers numerous benefits, including the ability to clean complex shapes and hard-to-reach areas, reduced cleaning time, and the use of fewer chemicals. However, it is essential to use appropriate cleaning solutions, follow best practices, and take precautions to avoid damage to the items being cleaned.
With ongoing advancements, ultrasonic cleaning continues to evolve as a popular choice for efficient and safe cleaning solutions.
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