Electric discharge milling of insulating ceramics

Abstract

Ceramics have been used widely in modern industry. However, the manufacture of ceramic blanks is not an efficient process. The shaping of ceramic blanks with conventional machining methods (such as grinding) is a long, labour-intensive, and costly process. Electromachining processes promise to be effective and economical techniques for the production of tools and parts from ceramic blanks. Wire electric discharge machining (WEDM) is able to slice ceramics effectively. Electrical discharge machining (EDM) and electrical discharge grinding (EDG) shape ceramic blanks at a lower cost. With the help of some assisting methods, WEDM, EDM, and EDG can be used to machine insulating ceramics. However, WEDM, EDM, and EDG of insulating ceramics show lower efficiency, especially for a large surface area on insulating ceramics. This paper presents a new process of machining insulating ceramics using electrical discharge (ED) milling. ED milling uses a thin copper sheet fed to the tool electrode along the surface of the workpiece as the assisting electrode, and uses a water-based emulsion as the machining fluid. This process is able effectively to machine a large surface area on insulating ceramics, as well as other advanced non-conductive materials such as cubic born nitride (CBN) and polycrystalline diamond (PCD). The machining principle and characteristics of the technique are introduced. The effect of pulse on-time, pulse off-time, and peak current on the process performance has been investigated.