Page 27 - MetalForming May 2012

ing sharp edges from stamped parts. 4) Aluminum Star media penetrates hard-to-reach corners and blind holes, and finds use for light burnishing and
deburring.
5) Aluminum-oxide and silicon-car-
bide abrasive media is used to color hardened steels and other ferrous alloys, exotic metals, brass and alu- minum. A preformed version enhances luster on a stainless steel and exotic nonferrous materials. Shape and close- ly controlled sizing eliminate lodging in recessed areas. Other applications include burr removal and final surface finishing. Unlike aluminum oxide, sil- icon carbide does not impregnate soft, ductile materials. Therefore, this media proves ideal for parts that will be weld- ed or braised, for bearing surfaces and parts that will be machined after deburring.
The Dyers note that they’ve more often been recommending steel media to metal stampers in recent years. Ceramic media—long the popular choice—tends to leave a residue on parts and may require a post-wash process. Steel, on the other hand, wears little if at all—“it’s great for edge break, light deburring and burnishing,” says Tim Dyer. “And, the parts come out very clean, safe to handle and cosmet- ically appealing.”
Steel media also maintains its shape and size—“if you size it correctly,” con- tinues Dyer, “it won’t become lodged in part crevices and contours.”
The switch from ceramic to steel media doesn’t come without some planning and investment. Steel media costs more, and the finishing equip- ment must be robust enough to handle the heavier steel media (300 lb./ft.3 vs. 90 lb./ft.3 for ceramic), but the cost is easily justified, say the Dyers. Due to media density, ceramic is not as effec- tive removing sharp edges in continu- ous-flow line as is steel media.
“The upgrade to a continuous-flow system with steel media often can result in a return on investment of less than one year, under the right circum- stances,” Tim Dyer says. MF
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