Electrical discharge machining (EDM) is a well-established machining option for manufacturing geometrically complex or hard material parts that are extremely difficult-to-machine by conventional machining processes. The non-contact machining technique has been continuously evolving from a mere tool and die making process to a micro-scale application machining alternative attracting a significant amount of research interests. In recent years, EDM researchers have explored a number of ways to improve the sparking efficiency including some unique experimental concepts that depart from the EDM traditional sparking phenomenon. Despite a range of different approaches, this new research shares the same objectives of achieving more efficient metal removal coupled with a reduction in tool wear and improved surface quality. This paper reviews the research work carried out from the inception to the development of die-sinking EDM within the past decade. It reports on the EDM research relating to improving performance measures, optimising the process variables, monitoring and control the sparking process, simplifying the electrode design and manufacture. A range of EDM applications are highlighted together with the development of hybrid machining processes. The final part of the paper discusses these developments and outlines the trends for future EDM research.

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State of the art electrical discharge machining (EDM)

Application of response surface methodology in describing the performance of coated carbide tools when turning AISI 1045 steel

Manufacturing and measurement of freeform optics

Advances in engineered surfaces for functional performance

Surface modification by electrical discharge machining: A review

This paper evaluates the performance of a relatively new type of drill called an endrill which is a cross between a drill and an endmill. Investigations into the effects of its cutting conditions on the drilling forces, surface finish, drill wear and hole oversize were carried out. It was found that endrills produced better quality holes than conventional twist drills, better surface finish and less oversize of the holes. Hence, with proper feed, speed and flow rate of the pressurized flushing coolant, a good finish of about Ra = 1 μm can be attained without reaming. Thus, the productivity of finished holes can be remarkably improved. Compared to twist drills, lower torque and thrust were observed which yielded improved tool life and reduced power consumption. No “walking phenomenon” was observed when this kind of drill was used and the amount of hole oversize was found to average about 0.7% of the drill diameter as compared to 1.6% when twist drills were used. Finally, general equations for the drill torque and thrust were derived from the experimental results.

Performance evaluation of endrills

Wear mechanisms in coated carbide tools

Surface integrity studies on the grinding, lapping and polishing processes for optical products

Bore finishing—The ballizing process

A judicious choice of insert material, tool geometry and cutting conditions can make hard turning produce better surfaces than grinding. AISI D2 is the most extensively used cold work tool steel in the tool and die industry. This steel of 60 HRC hardness was turned with PVD TiN coated ceramic tools (Al2O3/TiCN). Intragranular cracks were observed with single pass turning, while transgranular cracks occurred with multiple pass turning that was also accompanied by an increase in compressive stresses. In both passes, the white layer was observed, but in single pass, there was no subsurface deformed grain orientation, whereas in multiple passes, there was a distinct orientation.

V.C. Venkatesh

Papers

Performance evaluation of endrills

Wear mechanisms in coated carbide tools

Surface integrity studies on the grinding, lapping and polishing processes for optical products

Bore finishing—The ballizing process

The effect of multiple pass cutting on surface integrity when hard turning of AISI D2 cold work tool steel