Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 107 of 707

cleaning capability of the system. It is the combination of part movement, immersion, high-pressure spray, and high-volume solution delivery that is more effective than spray alone in dis- lodging contaminants and soils from all areas of the parts. Parts do contact one another in a Fig. 3. Rotary drum system, wash, rinse, dry with soak, and spray zone. rotary drum system. If no part contact is permitted this would not be a system of choice. Soak with Turbulation Turbulation is, in essence, exciting the cleaning bath; that is, causing fluid movement within the bath. This is accom- plished by using either aerators or impellers to cause the cleaning solution to become a fluidized bed of continuous movement. When parts are introduced to a turbulated bath, the solution moves around areas of the components. This rapid movement of solution has the ability to emulsify oils and dislodge soils. In turbulated systems care should be taken to ensure that parts do not mask one another. Turbulation moves tremendous volumes of solution but lacks any driving force to penetrate a basket or a layer of parts. This masking is sometimes offset by ensuring that there is part movement in the turbulated bath. Part exposure to turbulation is accomplished by either rotating or articulating the part. Small components placed in baskets require this rotation movement. The basket itself and the parts in a basket will act as a mask for the turbulation solution. By rotating the basket, parts in the interior of the basket may eventually be drawn or positioned at the exterior of the basket where they may be somewhat engaged by the turbulated solution; therefore, full baskets or even baskets three quarters full of parts cannot be effectively cleaned with turbulation due to no or minimal part movement. Similar to a rotary drum system there is some part-to-part con- tact due to partially full baskets that are typically rotating. Turbulated systems like spray are not effective for cleaning ID or blind hole areas. Vertical Agitation and Rotation Vertical agitation develops the highest degree of mechanical interaction between parts and chemistry. The ver- tical agitation movement produces a natural hydraulic cleaning action, gen- erating cavitation in the tank, which forces the cleaning solution between parts and in/out of recesses and cavities. This vertical agitation movement of parts in an aqueous solution generates a flushing action that scrubs all parts surfaces, crevasses, holes, and recesses clean. The agitation movement forces solution between components and 106 Fig. 4. Rotary drum system with top drum enclosure cover totally removed. Solid drum section is used for soak and spray. Perforated sections for spray and drain.

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