Metal Finishing Guide Book

2012-2013

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Applications: Pressure deburring of steel parts, ball burnishing (or ball polishing) of mainly stainless steel parts, occasionally also aluminum parts. ORGANIC MEDIA Material: Mostly corn cob or walnut shell granules. Applications: For drying of parts after vibratory finishing. Also used for highgloss polishing of metal parts, mainly stainless steel, aluminum, titanium, etc., in combination with a mixed-in polishing paste. SELECTION CRITERIA: MEDIA SHAPE, SIZE, AND ABRASIVE CONTENT Media shape, size, and abrasive content are crucial for achieving the optimum surface finish. MEDIA SHAPE The geometry of the parts to be finished generally determines the shape of the media to be used. A simple rule of thumb is: Figure 14: Round and compact media. Round and compact media (Fig. 14): Use for standard applications. There is less danger of media lodging in the part; lower danger of chipping (in the case of ceramic media); and lower wear rate. Typical shapes include: cylinder, cone, ball. Media with sharp edges (Fig. 15): For parts with complex geometry and difficult-to-reach surfaces. Danger of chipping; higher wear rate. Typical shapes include: tri-star, triangle, arrowhead. Figure 15: Media with sharp edges. Figure 16: Small and large media. MEDIA SIZE The required finish usually determines the media size (Fig. 16): Small media size: Produces a smoother surface by having more contact with the part surface; usually requires longer processing times and more gentle processing. Large media size: Faster removal of burs and radiusing of sharp edges on the parts; produces a rougher surface than small media; more aggressive grinding required. ABRASIVE TYPE Silica: For deburring/deflashing of relatively soft metals, such as aluminum, brass, and zinc. Silicon carbide: For aggressive grinding on difficult-to-machine metals. This abrasive produces dark surfaces. Aluminum oxide: Characteristics are similar to silicon carbide. Zirconium: Used in plastic media for adding weight. Mainly used for fine grinding of all kinds of metals. HOW DO YOU SELECT THE CORRECT MEDIA? BY ASKING THE RIGHT QUESTIONS! Selecting the right media requires much experience and possibly, as mentioned 16

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