Article Contents

1. Introduction
2. What is "Ultrasonics?"
3. Nature of Sound Waves
4. Cavitation and Implosion
5. Benefits of Ultrasonics
6. Ultrasonics Speeds Cleaning
7. Complex Contaminants
8. Ultrasonic Generators
9. Pulse and Frequency Sweep
10. Frequency and Amplitude
11. Magnetostrictive Transducers
12. Piezoelectric Transducers
13. Ultrasonic Cleaning Equipment
14. Maximizing the Cleaning Process
15. Maximizing Cavitation
16. Minimizing Dissolved Gas
17. Maximizing Overall Cleaning Effect (1)
18. Maximizing Overall Cleaning Effect (2)
19. Conclusion

Ultrasonic Cleaning: Fundamental Theory and Application
(p. 18)

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Maximizing Overall Cleaning Effect (continued)

Degassing of cleaning solutions is extremely important in achieving satisfactory cleaning results. Fresh solutions or solutions which have cooled must be degassed before proceeding with cleaning. Degassing is done after the chemical is added and is accomplished by operating the ultrasonic energy and raising the solution temperature. The time required for degassing varies considerably, based on tank capacity and solution temperature, and may range from several minutes for a small tank to an hour or more for a large tank. An unheated tank may require several hours to degas. Degassing is complete when small bubbles of gas cannot be seen rising to the surface of the liquid and a pattern of ripples can be seen.

The Ultrasonic Power delivered to the cleaning tank must be adequate to cavitate the entire volume of liquid with the workload in place. Watts per gallon is a unit of measure often used to measure the level of ultrasonic power in a cleaning tank. As tank volume is increased, the number of watts per gallon required to achieve the required performance is reduced. Cleaning parts that are very massive or that have a high ratio of surface to mass may require additional ultrasonic power. Excessive power may cause cavitation erosion or "burning" on soft metal parts. If a wide variety of parts is to be cleaned in a single cleaning system, an ultrasonic power control is recommended to allow the power to be adjusted as required for various cleaning needs. Part Exposure to both the cleaning chemical and ultrasonic energy is important for effective cleaning. Care must be taken to ensure that all areas of the parts being cleaned are flooded with the cleaning liquid. Parts baskets and fixtures must be designed to allow penetration of ultrasonic energy and to position the parts to assure that they are exposed to the ultrasonic energy. It is often necessary to individually rack parts in a specific orientation or rotate them during the cleaning process to thoroughly clean internal passages and blind holes.

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