Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 100 of 707

Table I. Typical Applications for Ultrasonic Cleaning Diesel fuel nozzles Turbine engine blade and vanes Bearings, races, and rings Aircraft fuel nozzles Flatware (buffing compound) Stamped parts (pieces or strips) Pistons Piston rings Valve lifters Battery cans Die castings (buffing compound) Textile spinnerettes Rachet handles (buffing) Valve plates, refrigeration Continuous strips, up to 200 fpm Golf club heads (buffing) Computer disk drive hubs ABS valve bodies line is doubled. These examples are only two of hundreds like them that illustrate the benefits of applying the proper type of mechanical energy to a process. Table I provides a list of parts typically cleaned in ultrasonic processes. When trying to determine if ultrasonic cleaning can help you keep these few things in mind: 1. Is the part a complex shape? 2. Does the part have small crevices, blind holes, or deep recesses? 3. Is the part delicate? Will strong agitation damage it? 4. Will strong chemistry damage the part? (Example—you cannot use high pH on aluminum). 5. Will high temperature affect the part? 6. Is the cleaning cycle time limited because of part volume? If the answer to most of the questions is "yes" then you are a candidate for ultra- sonic cleaning. Future trends are dictating cleaner parts, better quality, and a safer environment. Ultrasonics can be a tool to help you. SIZING THE SYSTEM Once you have determined that ultrasonics is right for your application the next question is "How do I choose the right power level, tank, configuration, etc.?" It takes a certain amount of energy to achieve the "threshold of cavitation," i.e., the level of energy required to achieve cavitation. The problem is that when you put a load in the tank, you attenuate or absorb energy. If you do not have a good Watt density (power level) you can fall below the threshold, and cavitation ceases. In other words the heavier your load, the more power or Watt density you will need. Some ultrasonic manufacturers calculate in terms of Watt density per area of radiating face such as 5 to 7 W/in2 . Others recommend power levels in terms of volume, typically in 40 to 75 W/gal. Because the displacement of the ultrasonic transducer is a mass relationship a volumetric determination seems more realistic. It is desirable to have the transducer/diaphragm moving mass exceed the mass of the cleaning load. This usually assures sufficient driving 99

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