Ultrasonic cleaning is a process that uses ultrasound (usually from 20-400 kHz) and proper cleaning solution (sometimes ordinary tap water) to clean the goods. Ultrasound can be used only with water, but the proper use of solvents for items to be cleaned and the type of impurities present will increase the effect. Cleaning usually lasts between three and six minutes, but can also exceed 20 minutes, depending on the object to be cleaned.
Ultrasonic cleaners are used for cleaning various types of objects, including jewelry, lenses and other optical parts, watches, dental and surgical instruments, equipment, coins, pens, golf clubs, fishing reels, window curtains, firearms, fuel injectors, music, gramophone , industrial parts and electronic equipment. They are used in many jewelry workshops, watchmakers, and electronic repair shops.
Video Ultrasonic cleaning
History
Ultrasonic cleaners began to be used in industry since 1950, and began to be used as relatively inexpensive home appliances around 1970.
Maps Ultrasonic cleaning
Process characteristics
Ultrasonic cleaning uses cavitation bubbles induced by high pressure waves (sound) to vibrate the fluid. Agitation produces high strengths on contaminants attached to substrates such as metals, plastics, glass, rubber, and ceramics. This action also penetrates the blind holes, cracks, and niches. The goal is to remove all traces of contamination that are firmly attached or attached to a solid surface. Water or solvents may be used, depending on the type of contamination and workpiece. Contaminants may include dust, dirt, oils, pigments, rust, fat, algae, fungi, bacteria, lime scales, polishing compounds, flux agents, fingerprints, sooty wax and mold release agents, biological soils such as blood, Ultrasonic cleaning can be used for various forms of workpieces, sizes and materials, and may not require parts to be disassembled before cleaning.
Objects should not be left at the bottom of the device during cleaning, as this will prevent cavitation on parts of the object that are not in contact with the solvent.
Design and operation principles
In ultrasonic cleaners, the object to be cleaned is placed in a space containing the appropriate solution (in an aqueous or organic solvent, depending on the application). In an aqueous cleaner, surfactants (eg, laundry detergents) are often added to allow the dissolution of nonpolar compounds such as oils and fats. Transducers that produce ultrasound built into space, or lowered into a liquid, produce ultrasonic waves in the liquid by resizing in concert with an electric signal oscillating at ultrasonic frequencies. This creates a compression wave in the tank fluid that 'rips' the liquid apart, leaving many millions of microscopic 'voids' or 'partial vacuum bubbles' (cavitation). These bubbles collapse with tremendous energy; temperature and pressure on the order of 5,000 K and 135 MPa achieved; However, they are so small that they do not over clean and remove dirt and surface contaminants. The higher the frequency, the smaller the vertex between the points of cavitation, which allows more complex details to be cleaned.
Transducers are usually piezoelectric (eg made with lead zirconate titanate (PZT), barium titanate, etc.), but are sometimes magnetostrictive. Chemicals often used as cleaners in many industries are not needed, or used in much lower concentrations, with ultrasonic agitation. Ultrasonic is used for industrial cleaning, and is also used in many medical and dental techniques and industrial processes.
Cleanup solution
Ultrasonic activity (cavitation) helps the solution to perform its task; ordinary water usually will not be effective. The cleaning solution contains ingredients designed to make ultrasonic cleaning more effective. For example, a reduction in surface tension increases the cavitation level, so the solution contains a good wetting agent (surfactant). Aqueous cleaning solutions contain detergents, wetting agents and other components, and have a major effect on the cleaning process. The correct composition of the solution depends on the goods being cleaned. The solution is mostly used warmly, about 50-65 ° C (122-149 ° F); however, in medical applications it is generally accepted that cleaning should be at temperatures below 45 ° C (113 ° F) to prevent coagulation of proteins.
Water-based solutions are more limited in their ability to remove contaminants by chemical action alone rather than solvent solutions; for example for fine parts coated with thick oil. The effort required to design an effective water purification system for a particular purpose is much greater than that of a solvent system.
Some machines (which are not too large) are integrated with steam degreasing machines using hydrocarbon cleaning fluids: Three tanks are used in cascades. The lower tank containing the dirty liquid is heated causing the liquid to evaporate. At the top of the engine there is a cooling coil. The liquid condenses on the coil and falls into the upper tank. The top tank eventually overflows and clean fluid flows into the work tank where the cleaning takes place. The purchase price is higher than the simpler one, but such machines are economical in the long term. The same liquid can be reused many times, minimizing waste and pollution.
Carbon tetrachloride was used in the past, but is now banned as a health hazard.
Usage
The hardest, non-absorbing material (metal, plastic, etc.) Not chemically attacked by a cleaning fluid suitable for ultrasonic cleaning. The ideal materials for ultrasonic cleaning include small electronic components, cables, rods, cables and detail items, as well as objects made of glass, plastic, aluminum or ceramics.
Ultrasonic cleaning does not sterilize the cleaned objects, as the spores and viruses will remain in the object after cleaning. In medical applications, sterilization usually follows ultrasonic cleaning as a separate step.
Industrial ultrasonic cleaners are used in automotive components, sports, printing, marine, medical, pharmaceutical, electroplating, disk drives, engineering and weapons industries.
Limitations
Ultrasonic cleaners are widely used to remove flux residue from soldered circuit boards. However, some electronic components, especially MEMS devices such as gyroscopes, accelerometers and microphones can become damaged or destroyed by the high intensity vibrations imposed during cleaning. Piezoelectric buzzers can work in reverse and generate voltage, which can pose a danger to their drive circuits.
See also
- Cleaning section
- Acoustic cleanup
- Washing machine
- Macroonik
- Sonication
References
Source of the article : Wikipedia
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