ELECTRIC-DISCHARGE MILLING OF POLYCRYSTALLINE DIAMOND

Polycrystalline diamond (PCD) has been used widely in modern industry. However, the manufacture of PCD blanks is not an economical and effic ient process. The shaping of PCD blanks with conventional machining me thods (such as grinding), is a long, labour-intensive and costly proce ss. Electromachining processes promise to be effective and economical techniques for the production of tools and parts from PCD blanks. Wire electric discharge machining is able to effectively slice PCD. Electr ical discharge machining (EDM) and electrical discharge grinding (EDG) shape PCD blanks at a lower cost. However, EDM and EDG of a large sur face area on PCD show lower efficiency. This paper presents a new proc ess of machining PCD using electrical discharge (ED) milling. ED milli ng employs a DC source instead of the pulse generator used in EDM, and uses a water-based emulsion as the machining fluid. This process is a ble to effectively machine a large surface area on PCD, and effectivel y machine other advanced conducting materials such as cubic born nitri de (CBN), and ceramics. The effect of pulse on-time, peak current, and polarity on the process performance has been investigated.