Metal Finishing Guide Book

2012 Organic Finishing Guidebook Issue

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Page 190 of 331

gent controls on emissions from all manufacturing operations. Waste stream com- pliance is forcing many manufacturing companies to invest in waste treatment plants. Understanding your local laws and knowing your process will determine your direc- tion. If you are not familiar with either, outside help must be sought. COMPONENT DESIGN Material Handling Selection of the material handling method varies directly with production volume and desired cleanliness. In general the monorail is the most economical, flexible, and re- liable method of handling product,but it is not the ideal solution for all cases. If you handle product in batches/baskets a belt internal to the machine can provide an excellent and consistent means of transporting product through the washer. If your product can tolerate "bumping," such as nuts or bolts, a drum ma- chine is a cost-effective means of conveying high volumes with excellent results. There are also situations where combinations of belt and monorail are appro- priate. Rather than having two machines you can easily assimilate dual lines into one washer. Conveyor systems are discussed in further detail in a separate section of this Guidebook. System size is a function of conveyor speed, which is actually based on part density rather than raw production rate. As an example, to determine the line speed for a given production shift divide the number of parts desired by the num- ber of parts per rack times the rack spacing divided by the number of minutes available per shift. Washers/Pretreatment The choice of a spray wand, three-stage, or five-stage machine is based on a number of variables: incoming soil loads, space available, results required, energy consump- tion, total initial cost, estimated total operating cost, production volume, size of part, etc. The initial cost of a five-stage machine (clean, rinse, phosphate, rinse, rinse) is somewhat higher than a three-stage type but operating economies and higher quality quickly offset the investment. The five-stage machine ensures longer chemical life. The high-pressure heated spray wand is an excellent choice for low-volume, hard-to-handle parts. This approach is a cost-effective technology with a great deal of flexibility and versatility. From experience and the recommen- dation of various chemical companies, to remove shop dirt and light machine oil a three-stage machine is adequate. The typical process would be a one-minute wash stage (heated), 30-second rinse (am- bient), and a 30-second rinse/inhibit (am- bient or heated). If you have a more critical cleaning Figure 2. Entrance profile for sample monorail conveyor washer design. specification or phosphating require- ment a five-stage washer with one- minute wash (heated),30-second rinse 189

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