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productionmachining.com :: 47 ?????? Cleaning Ultrasonic Cleaning by dividing 3.28 by the frequency of the ultrasonic cleaner in Hertz (determining the radius), then multiplying by 2. For example, an 80-kHz frequency = 80,000 Hertz or cycles per second; 3.28 divided by 80,000 = 0.000041 m, or a cavitation bubble radius of about 41 microns. For the higher frequency 130-kHz cleaners, the cavitation bubble radius is approximately 0.000025 m or 25 microns. Ultrasonic cleaner frequency should be selected based on what is being cleaned. Machined, welded and stamped steel or alloy parts are safely cleaned at lower frequencies. Parts with complex confgurations, softer metals and highly polished surfaces should be cleaned at higher frequencies. If a shop produces or fnishes a variety of products, a dual-frequency ultrasonic cleaner such as the Elmasonic X-tra basic, operating at 25 or 45 kHz, can be used. Some dual-frequency models can be set to automatically switch frequencies at 30-second intervals. Tank and Basket Dimensions Cleaning tank dimensions must be larger than the largest part(s) being cleaned. Parts cleaning baskets, used in the majority of cases, are smaller than the tank internal dimen- sions. Another important consideration is the working depth of the cleaning solution. Working depth is the distance from the inside bottom surface of the basket to the surface of the liquid in a flled tank. Parts being cleaned must be fully immersed in the liquid. Working depth data are available on equipment spec sheets or can be obtained from the equip- ment manufacturer. Some basket upper rims are immersed in the solution while others may not be. Still others may be equipped with rubber-coated feet positioned near the corners of the tank bottom, where there is minimal vibration. Fine mesh baskets for small parts can be positioned in beakers or standard baskets. Industrial tanks may be equipped with a bottom rack to support large parts. In these cases, the working depth is the distance from the surface of the rack to the surface of the liquid. An alternative to using baskets or racks is suspending parts in the solution from an overhead support. In such cases, parts must not contact the tank's internal surfaces, which could lead to equipment damage. Operating Modes Ultrasonic cleaners range from those with a simple on-of switch to highly sophisticated programmable units with features contributing to efciency and thoroughness. Te following variations can provide distinct advantages in the right applications. • Degas mode is engaged to quickly drive of cavitation- inhibiting trapped air from fresh cleaning solutions. Tis step can be accomplished in a unit without a degas mode by operating a cleaner without a load, but in large capacity cleaners, it can require an excessive amount of time. :: Explosion-proof ultrasonic cleaners encase internal electronics in high-density foam. :: Elma's P series of 37/80 kHz benchtop cleaners display user-set power; set and remaining time; set and current temperature; and activate degas, sweep and pulse modes. :: This photomicrograph shows stages of an imploding cavitation bubble.