Effect of Complex Electrodischarge Grinding for Electrically Conductive PCD

Abstract

Polycrystalline Composite Diamond (PCD) is excellent in chipping resistance despite its very high hardness. However, it is not easy to EDM or grind PCD. To realize high efficiency and high quality processing of PCD simply and at low cost, the authors devised new PCD (EC-PCD) by using electrically conductive diamond particles and applied a complex electrodischarge grinding method. In this study, investigation is made on effective grinding condition to realize high efficiency, low and stable grinding force and low wheel wear in complex electrodischarge grinding. As a result, superior grinding property was obtained when the grinding wheel was set at minus polarity, and set peak current of iP = 4 and 6 A was applied. Furthermore it also became clear that additional conventional grinding process followed after complex electrodischarge grinding improved the surface condition.

Electrical discharge machining of polycrystalline diamond: A review

“…Usually, reverse polarity is used to constrain the heating of work material to minimize HAZ and associated defects. Experimental work showed that negative polarity was more suitable for EDM, 70,75,76 and EDG 77,78 due to the protection of the electrode caused by the adhesion of workpiece material (Figure 8), which results in minor surface wear. However, this coverage effect may adversely affect the machining accuracy; and the reduction in the effectiveness of electron action may weaken the material removal effect when using negative polarity with long pulse duration.…”

Electrical Discharge Machining of Polycrystalline Diamond Using Copper Electrode - Finishing Condition

“…The investigation on the machinability of PCD would greatly important as it plays important role in several aforementioned extreme applications. Since 2010 extensive research has been initiated to increase PCD machining efficiency and tool quality [1,2] But no significant breakthrough was achieved due to the lack of innovative approaches and new theories to solve the two fundamental problems in machining PCD: the ultra-hardness of diamond particles and the low electrical conductivity of PCD material. Despite improvements of various levels were achieved, the increase in machining efficiency was limited.…”

“…However, it suffers with high wheel wear (G ratio of 0.01 to 0.05) and extremely low material remove rate [1,5] This leads to the high manufacturing cost caused by the long machining time that becomes a major impediment to the implementation of PCD tools: a brazed PCD tool is about 10 times expensive than a tungsten carbide tool, and the price of a vined PCD tool is about 20 times higher than the carbide ones Electrical Discharge Machining (EDM) is a noncontact thermal erosion process in which the metal is removed by a series of recurring electrical discharges between the electrode and the electrically conductive workpiece, in the presence of a dielectric fluid. The electric conductivity of PCD caused by the conductive binding material (Cobalt) makes it possible to machine PCD tools with EDM.…”