Electric discharge milling of silicon carbide ceramic with high electrical resistivity

Abstract

Silicon carbide (SiC) ceramics have been widely used in modern industry. However, the manufacture of SiC ceramic blanks is not an efficient process. The shaping of SiC ceramic blanks with conventional machining methods (such as grinding) is a long, labour-intensive and costly process. Wire electric discharge machining (WEDM) and electrical discharge machining (EDM) promise to be effective and economical techniques for the production of tools and parts from conducting ceramic blanks that their electrical resistivity is below of 100 Ω cm. However, these electrodischarge-machining methods of machining a large surface area on ceramics that their electrical resistivity is higher than 100 Ω cm shows low efficiency. This paper employs a steel toothed wheel as the tool electrode to machine SiC ceramics with specific resistivity of 500 Ω cm using electrical discharge milling. The process employs the pulse generator used in EDM, and uses a water-based emulsion as the machining fluid. It is able to effectively machine a large surface area on SiC ceramics with electrical resistivity of 500 Ω cm. The effects of tool polarity, peak voltage, pulse on-time, pulse off-time, and peak current on process performance have been investigated.