Metal Finishing Guide Book


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Fig. 2. Access covers from Fig. 1 removed to view spray headers. For this reason parts in baskets in cabinet cellular washers are rarely filled more than 60%. This allows parts in the middle of the basket to eventually migrate to the exterior of the basket, if the basket is rotated. Spray systems can also be used as inline manufacturing cleaning systems. The same belt that it used to transport the parts through the washer can transport parts from one location to another location, thus acting as a material han- dling unit. Spray systems should also be designed to ensure that the various spray chambers are shrouded with baffles, both before and after spray zones, to minimize overspray and solution drag-over. A belt can act as a natural pump and adequate drain area is necessary on belt systems to minimize carryover of wash solution to rinse zones, or as the belt returns, from rinse to wash zone. In all instances where spray systems are employed, sufficient drain area or drain cycles are required to allow the parts, belt, and baskets to adequately drain to minimize contamination of subsequent spray zones or to maintain rinse tank clarity. Soak and Spray Belt or monorail systems can be equipped with soak zones, these being areas where the part is drawn through a soak stage prior to being sprayed. The soak area will ensure that all areas of the component are exposed to chemistry and can initially loosen and emulsify some soils and oils as parts are drawn through the soak zone, prior to spray impingement. This greatly assists the ability of the spray to flush and remove soils. Rotary drum systems also typically employ soak and spray. Rotary drums are designed to move parts through various operations in a horizontal cylinder, the interior of the cylinder equipped with a helix (see Figs. 3 and 4). This automatically advances parts forward as the drum rotates and allows a large quantity of parts to be effectively engaged by the mechanical interaction generated by the machine; this a combination of soak and spray impingement, as well as high volume of solution delivery. The parts are soak cleaned and spray cleaned simultaneously. Spray headers are positioned so that the spray engages the parts as they are lifted out of the soak solution. After the soak section, the parts continue to be engaged by spray. The spray typically uses a combination of spray impingement and high-volume solution delivery. The soak section loosens contaminants. The high-pressure spray impingement is generated by directed stainless steel spray nozzles and is designed to dislodge contaminants from the parts. In short the combination of soak and spray impingement dislodges soils; the high-volume delivery flushes the soils, oils, and other contaminants away. In a rotary drum system the mass of parts is gently tumbled in the aqueous cleaning and rinsing solutions. This gentle tumbling action provides an effective method of completely exposing all edges and surfaces of components to the action of the soak, impingement spray, high-volume solution delivery, rinsing solutions, and to the drying action. The rotation of the drum causes parts to rotate and move. The movement within the drum causes all surfaces and edges to be exposed to the cleaning action; therefore, all areas of parts are engaged by the 75

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