An ultrasonic cleaning is a process that uses ultrasound (usually
from 20–400 kHz) and an appropriate cleaning solvent (sometimes
ordinary tap water) to clean items.
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.Ultrasonic cleaners are used to clean many different types of objects, including dental and surgical instruments, jewellery, lenses and other optical parts, watches, tools, coins and other.
The ultrasound can be used with just water, but use of a solvent appropriate for the item to be cleaned along with 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.DESCRIPTION OF CAVITATION PROCESS
In a process named cavitation, micron-size bubbles form and grow due to alternating positive and negative pressure waves in a solution. The bubbles subjected to these alternating pressure waves continue to grow until they reach resonant size. Just prior to the bubble implosion there is a tremendous amount of energy stored inside the bubble itself.
Temperature inside a cavitating bubble can be extremely high, with pressures up to 500 atm. The implosion event, 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 has the ability to reach into small crevices and remove entrapped soils very effectively.