Metal Finishing Guide Book

2011-2012 Surface Finishing Guidebook

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Page 32 of 707

mechanical surface preparation BUFFING WHEELS AND EQUIPMENT BY DAVID J. SAX STAN SAX CORP., DETROIT; WWW.STANSAXCORP.COM Three elements to a successful buffing operation are the buff wheel, the buffing compound, and the buffing machine. It is necessary to understand all of these ele- ments and how they interact to achieve desired quality, productivity, cleanabil- ity, corrosion resistance, reject elimination, and overall cost-effectiveness. WHAT IS BUFFING? Buffing is a mechanical technique used to bring a workpiece to final finish. It also can be used to prepare the surface of a machined, extruded, or die-cast part for plating, painting, or other surface treatment. The objective is to generate a smooth surface, free of lines and other surface defects. Buffing is not a process for removing a lot of metal. Deep lines and other more severe surface defects should be removed before buffing by polishing with a polishing wheel or abrasive belt. Buffing usually involves one, two, or three steps: cut buffing, intermediate cut, and color buffing. These operations normally are performed by what is referred to as either "area" buffing or "mush" buffing. Cut Buffing A harder buff wheel and, generally, a more abrasive buffing compound, are used to start the buffing process. In cut buffing, the buff wheel and workpiece are usually rotated in opposite directions to remove polishing lines, forming marks, scratches, and other flaws. Color Buffing When a mirror finish is specified, a color buff step may be required. Color buff- ing may be performed with a softer buff wheel and less aggressive abrasive com- pounds. In color buffing, the buff wheel and workpiece are usually rotated in the same direction. This enhances the cut buff surface and brings out the maximum luster of the product. Area Buffing For localized finishing, narrow buffing wheels, positioned tangentially to the workpiece, are used. This is often is referred to as "area buffing." Mush Buffing To finish larger parts or parts having several surface elevations, mush buffing may be used. This involves the use of one or more wide buff wheels. In mush buffing, a part is rotated or cammed through the buffing wheel. This technique is also used to finish multiple products simultaneously. BUFFING COMPOUNDS Buffing compounds are the abrasive agents that remove minor surface defects dur- ing the buffing phase of the finishing cycle. Buffing compounds are available in paste or solid form. There are thousands of products from which to choose. The prime consideration in selecting a buffing compound is the substrate being buffed and the surface to be provided. 31

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