Metal Finishing Guide Book


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Page 77 of 843

Cleaning performance Ultrasonic Transducers—How to 100% Choose the Power Level. It is a 80% human characteristic to believe 60% "more is better." This character40% istic is reflected in the financial 20% advice: "bears make money, 0% bulls make money, and hogs get 0 500 1,500 2,000 1,000 Power Level, watts slaughtered." Another example of this characteristic is the Figure 4. Generalized relationship between cleaning choice by many users of evereffectiveness and power. larger power ratings for sonicpowered transducer systems. There are at least three factors to be considered by a manager when choosing the power level for the ultrasonic transducers in a cleaning system: parts, cycle time, and tank size. POWER TO THE PARTS A generalized relationship between cleaning effectiveness for a properly designed system is illustrated in Figure 4. Note that the relationship is "S-shaped (asymptotic):" • Modest application of ultrasonic power has only minor effects. This is because an adequate number of cavitation bubbles of sufficient size hasn't been produced. • At some level of applied power, the ultrasonic cleaning system performs well, as designed. • When a high level of cleaning performance has been achieved, there is little gain by applying additional ultrasonic power. • In the latter situation, if removal of the small levels of remaining soil is necessary, a secondary cleaning process should be employed rather than force this cleaning process to perform beyond its capability. Without regard to the character of the parts, there is a suitable range of power levels. There is no point to paying for more power, or trying to economize by paying for less. EFFECT OF CYCLE TIME Cycle time (contact time with ultrasonic agitation) should be viewed similarly. Cleaning quality will have the same general ("S-shaped") relationship vs time as seen in Figure 4. • Parts just "dipped" into the ultrasonic tank will not be well cleaned. • Parts "cooked" as some like their steak to be well done will not be cleaned to a premium level. Doubling the cycle time will not double the cleaning quality. For a properly designed cleaning system, if the production rate is raised and the associated cycle time shortened, cleaning quality will suffer only to a modest degree. As benchmarks, a cycle time of 2 minutes contact would be quite short, but perhaps satisfactory. A cycle time of 5 to10 minutes would be quite long, but perhaps necessary. 74

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