Abstract
Cemented carbide P20 was worked by electrical discharge machining (EDM) using a transistor-type machine with a jet-type copper electrode. The occurrence of abnormal discharge which causes extremely deep cracks could be suppressed under a condition of large flow amount of fluid (kerosene) Q, large discharge time τon and small duty factor D. Furthermore, increasing peak value of current Ip for a given τon and decreasing τon for a given D were effective in raising stock-removal rate V without introducing deep cracks onto the machined surface. Analysis of the results on EDM of several kinds of cemented carbides showed that depth of surface crack l was uniquely related to the discharge energy of one pulse by the equation l = 3.92 (Ip × τon)0.37 [l : μm, Ip : A, τon : μs], within a factor of two.
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