An ultrasonic cleaner is a cleaning device that uses ultrasound (usually from 20–400 kHz) and an appropriate cleaning solvent (sometimes ordinary tap water) to clean delicate items. The ultrasound can be used with just water, but use of a solvent appropriate for the item to be cleaned and the soiling enhances the effect. Cleaning normally lasts between three and six minutes, but can also exceed 20 minutes, depending on the object to be cleaned.
Ultrasonic cleaning penetrates even microscopic openings to provide complete cleaning of the objects treated. This makes it one of the most effective, economical and powerful cleaning methods available. It has applications in laboratories, dental and medical technology, microelectronics, precision engineering, cosmetics, optics and the automotive industry. Ultrasonic cleaners are used to clean many different types of objects, including jewellery, lenses and other optical parts, watches, dental and surgical instruments, tools, coins, fountain pens, golf clubs, window blinds, firearms, musical instruments, industrial parts and electronic equipment. They are used in many jewellery workshops, watchmakers’ establishments, and electronic repair workshops
Modern baths tend to have a heavy duty ultrasonic generator which ensures that the ultrasonic output remains constant, regardless of the bath temperature, fill level and cleaning material. This feature guarantees consistent and reproducible cleaning results. ‘Frequency sweeping’, a frequency modulation of the ultrasonic output generated, prevents ‘standing waves’ from being generated and ensures extremely homogeneous energy distribution in the cleaning bath.
Ultrasonic cleaning uses Cavitation bubbles induced by high frequency pressure (sound) waves to agitate a liquid. The agitation produces high forces on contaminants adhering to substrates like metals, plastics, glass, rubber, and ceramics. This action also penetrates blind holes, cracks, and recesses. The intention is to thoroughly remove all traces of contamination tightly adhering or embedded onto solid surfaces. Water or other solvents can be used, depending on the type of contamination and the workpiece.
There are various ways to test the level of ultrasonic activity within an ultrasonic bath..
There are a number of recommended tests for establishing levels of ultrasonic activity in the bath.
The foil test involves suspending a strip of foil into various locations around the tank. The foil should not touch the base of the tank and should be held in position for around 1 minute. It should then be removed and there should be an even distribution of perforations and small holes on the surface of the foil.
Another test requires the use of Brownes soil test strips. These are plastic strips which have been contaminated to simulate the contamination which might affect surgical instruments. After running an ultrasonic cycle the strips should be taken from the bath and all contamination should have been removed.
An ultrasonic energy meter can also be used to test the level of ultrasonic activity within the tank.
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