Metal Finishing Guide Book


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bling can be ideal for a drum washer; baskets of parts that cannot be tumbled can be immersed and agitated. The same situation is true with paint application. Smooth, flat parts can be easily automated, while complex shapes may require additional, manual reinforcement for complete coverage. Material Composition of Parts Knowing the base materials will allow compatibility with selected cleaners, subsequent waste treatment requirements, operating temperature, method of handling, and process specifications. Desired Material Handling Methods Selecting the appropriate material handling method should be done based on the principles of increasing productivity. The method selected must incorporate reliability, economy, flexibility, and ease of installation. For example an overhead monorail-type conveyor system is relatively low in cost but not very flexible, while a power-and-free system is very flexible but higher in cost. Understanding Soils and Cleanliness Contaminants determine chemical selection and spray or immersion selection, and ancillary equipment for handling the effluent (chips, oil, or heavy metals) will impact the waste treatment stream. If the cleaning process is not defined it is important to get contaminated parts to the chemical and equipment suppliers and have the parts tested in a laboratory. While in the laboratory your suppliers can simulate conditions and test the different variables. Minimizing or avoiding contamination is the key to keeping your factory and parts clean. Know where your soils are coming from and why. This allows you to take steps to contain soils in the area where they occur. Effective and inexpensive means to check for clean parts are the ���water-breakfree surface test��� and ���white towel test.��� If organic soil has been effectively removed a uniform sheeting of the rinsewater will occur as parts exit the last pretreatment stage. If the surface has beaded water standing you have not adequately removed organic soils. Inorganic soils can be checked by using a white towel after they have passed through the dry-off oven. If the towel is dirty you have not adequately removed the inorganic soils. More sophisticated is the millipore test. This test requires a vacuum pump, flask, funnel, filter papers, isopropyl alcohol, oven, and scale. This test can detect micron particle size and weight in milligrams. Facilities and Utilities Available A floor layout with height clearance is important for design considerations. Often, space constraints dictate process times. Although it may not be the optimum process it may achieve acceptable results. Availability of electrical service, heating preference, and plant conditions (such as availability of truck dock, building door size,floor and roof construction, distance from unloading site to erection site, and whether there is a clear path) must also be considered. Environmental Considerations Local, regional, and federal regulations are continually being added and changed. The recent Clean Air Act Amendments of 1990 established procedures for a national permit system for air pollutante missions, as well as establishing a basis for more stringent controls on emissions from all manufacturing operations. Waste stream com808

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