Metal Finishing Guide Book


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treatment volume and associated chemistry consumption. The result is less water purchased and treated because there is no rinse water flow between cycles. Similar to water replenishment techniques, recipe-driven chemistry addition reduces usage and improves bath quality by eliminating saw-tooth fluctuations common with less frequent manual additions. This precision is available only by an integrated PC/HMI, needed to recognize and manage parts, select recipes, and adjust for rack or barrel fill variation. Advanced controls allow local and/ or remote adjustment of replenishment at any time during machine operation. Generation of RO water costs floor space, energy, water, and money. Discussion with your chemistry supplier (water analysis report in hand) will determine if RO water is recommended or needed for a plating or coating process. Use may be recommended because of unsuitable local water quality, or required for a specific chemistry, regardless. Makeup, addition, and replenishment for evaporative losses can sometimes be accomplished with rinse waters, reducing the need for fresh water. Careful consideration should be given to plating and coating barrel design. Cylindrical plating and coating barrels offer a 17% increase in capacity compared to hex style barrels. Further, more consistent anode-to-work relationship improves efficiency for plating systems. Part-specific tumbling rib and perforation configuration contributes to efficient rollover, quicker drainage, and reduced drag-out. Recipe-driven, up-barrel rotation drains directly to the process tank, a feature especially important for parts known to cup solution. Up-barrel rotation should be considered mandatory in today's highly competitive finishing environment. WASTEWATER TREATMENT BASICS Critical to resource reduction strategy is a basic understanding of water consumption drivers. Water use begins with total purchased and ends the total water discharged, a variable expense that directly affects operating cost. Metrics are discussed in terms of loads per hour, parts per hour, gallons per hour, etc. Consumption is almost purely a function of surface area. A crude rule-of-thumb indicates approximately one gallon of drag-out is generated for every 1,000 square feet of surface area processed, including work, rack, barrel, or basket. The total will vary depending on the shape, size, and orientation of parts in process. It is critical to know the surface area and the number of parts required per hour. Fortunately, most parts are designed in CAD, so area is easily found. Figure 2. Enclosed ventilation system in action. (Photo credit: Photography by Colleen Sadlik, 699

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