Metal Finishing Guide Book

2012-2013

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tion for a successful cleaning process. Other forms of mechanical energy used in cleaning would be simple immersion, spray, turbulation, agitation, and rotation of the part. The selection of the type of mechanical energy depends to a great extent on the relationship of the heat applied to the process and the type of chemistry used. Many times companies only consider the chemical aspects when converting a vapor degreaser, trading the solvent for another chemical. A more successful approach considers all of these parameters, which maximizes the investment. Ultrasonics is not a magic force, nor is it right for every application. It is just another form of mechanical energy to enhance a chemical process. Thermal Energy: (1) Acts as a catalyst to enhance chemical energy. (2) Raises the energy level in any type of process. (3) Can condition a contaminant to be acted upon by chemical and mechanical energies, especially ultrasonic applications. Chemical Energy: (1) Provides a method to break molecular bonds. (2) Acts primarily on organic contamination. (3) Provides many properties to do many jobs, i.e., degreasing, pickling, phosphating, etc. (4) Can be polar (water soluble) or nonpolar (water insoluble). Mechanical Energy: (1) Provides energy to physically remove contamination from the part surface. (2) Is used to enhance chemical and thermal energy. (3) Is available in many forms, including spray, agitation, turbulation, and ultrasonics. Using a combination of these energies, and finding the balance for your application, can be a challenging project. The relationship of the chemistry, the temperature of the bath, and the degree of mechanical motion the part can withstand are all critical factors in choosing your cleaning method. Examples If your part is not complex, made of steel, is not susceptible to mechanical damage, and only contaminated with cutting oil, you probably will not need ultrasonic cleaning. A typical process might look like this: Temperature, 160��F Chemistry, pH neutral Agitation bath with oil separation Cycle time, 5 min. Take the same part and add blind holes 2 in. deep by in. in diameter. The process might look like this: Temperature, 160��F Chemistry, pH neutral Turbulation, parts fixtured with a rotating basket and oil separation Cycle time, 5 min. If this same part has been sitting around in storage and has corroded, the process might look like this: Temperature, 180��F Chemistry, pH 12.5 Turbulation with rotation, no oil separation Cycle time, 10 min. At this point one might need to introduce ultrasonics as the mechanical catalyst in the equation. The cycle is getting long and the temperature is getting high. By introducing a high degree of mechanical action it may be possible to reduce both: 67

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