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)

Electrical discharge machining (EDM) is one of the earliest non-traditional machining processes. EDM process is based on thermoelectric energy between the work piece and an electrode. A pulse discharge occurs in a small gap between the work piece and the electrode and removes the unwanted material from the parent metal through melting and vaporising. The electrode and the work piece must have electrical conductivity in order to generate the spark. There are various types of products which can be produced using EDM such as dies and moulds. Parts of aerospace, automotive industry and surgical components can be finished by EDM. This paper reviews the research trends in EDM on ultrasonic vibration, dry EDM machining, EDM with powder additives, EDM in water and modeling technique in predicting EDM performances.

A review on current research trends in electrical discharge machining (EDM)

Advancing EDM through fundamental insight into the process

This paper provides a roadmap of development in the thermal and fabrication aspects of microchannels as applied in microelectronics and other high heat-flux cooling applications. Microchannels are defined as flow passages that have hydraulic diameters in the range of 10 to 200 micrometers. The impetus for microchannel research was provided by the pioneering work of Tuckerman and Pease [1] at Stanford University in the early eighties. Since that time, this technology has received considerable attention in microelectronics and other major application areas, such as fuel cell systems and advanced heat sink designs. After reviewing the advancement in heat transfer technology from a historical perspective, the advantages of using microchannels in high heat flux cooling applications is discussed, and research done on various aspects of microchannel heat exchanger performance is reviewed. Single-phase performance for liquids is still expected to be describable by conventional equations; however, the gas flow may...

Evolution of Microchannel Flow Passages-Thermohydraulic Performance and Fabrication Technology

Wire electrical discharge machining (WEDM) is a specialised thermal machining process capable of accurately machining parts with varying hardness or complex shapes, which have sharp edges that are very difficult to be machined by the main stream machining processes. This practical technology of the WEDM process is based on the conventional EDM sparking phenomenon utilising the widely accepted non-contact technique of material removal. Since the introduction of the process, WEDM has evolved from a simple means of making tools and dies to the best alternative of producing micro-scale parts with the highest degree of dimensional accuracy and surface finish quality. Over the years, the WEDM process has remained as a competitive and economical machining option fulfilling the demanding machining requirements imposed by the short product development cycles and the growing cost pressures. However, the risk of wire breakage and bending has undermined the full potential of the process drastically reducing the efficiency and accuracy of the WEDM operation. A significant amount of research has explored the different methodologies of achieving the ultimate WEDM goals of optimising the numerous process parameters analytically with the total elimination of the wire breakages thereby also improving the overall machining reliability. This paper reviews the vast array of research work carried out from the spin-off from the EDM process to the development of the WEDM. It reports on the WEDM research involving the optimisation of the process parameters surveying the influence of the various factors affecting the machining performance and productivity. The paper also highlights the adaptive monitoring and control of the process investigating the feasibility of the different control strategies of obtaining the optimal machining conditions. A wide range of WEDM industrial applications are reported together with the development of the hybrid machining processes. The final part of the paper discusses these developments and outlines the possible trends for future WEDM research.

State of the art in wire electrical discharge machining (wedm)

In this paper, a new prototyping method called a dot-matrix electrical discharge machining (EDM) with scanning motion is proposed, and a prototype of a machining unit by the dot-matrix method is developed. The machining process by the dot-matrix method is similar to printing motion with a dot impact printer. This method can be applied to not only EDM but also electrochemical machining and forming. A prototype of the machining unit has six feeding devices for thin wire electrodes. The electrodes of 300 /spl mu/m in diameter are arranged with the pitches of 760 /spl mu/m. To obtain smooth surface, a planetary motion in the xy plane is added to the feeding of the machining unit in the z direction, the same area is machined repeatedly or the machining unit is moved with fine feed. By compensating the wear of the electrode during the scanning EDM, various shapes with the accuracy of micrometers order can be obtained without a formed tool electrode. The surface modification by EDM with thin wire electrodes is also investigated.

Dot-matrix electrical discharge machining for shaping fine structure

Displacement Monitoring of Stacked Piezoelectric Actuator by Observing Induced Charge

Condition Monitoring in Concurrent Micro-hole Electrical Discharge Machining with Electrode Feeding Devices Employing AZARASHI (Seal) Mechanism☆

This paper deals with a fabrication method of a wire saw by electrical discharge machining (EDM). Hard bumps were discretely patterned on the surface of a thin stainless steel wire by EDM with titanium powder suspended in working oil. With an increase of the machining time, the average of the bump height was increased and no removal was observed. The bumps were deposited from four directions in an orthogonal sequence by manually turning the wire. A soda lime glass rod could be cut with the wire saw. The bumps tightly adhered on the wire.

Fabrication of Wire Saw with Patterned Hard Bumps by Electrical Discharge Machining with Powder Suspended in Working Oil

In this paper, we deal with the performance of electrochemical discharge machining (ECDM) with multiple electrodes. ECDM has been used to machine grooves and holes on insulated materials such as glass. However, many cracks are often observed around a machined hole because of the accumulation of discharge heat. While some holes were being machined by ECDM on glass, the discharge current was forced to disperse by switching the electrodes to decrease the number of cracks (divided power). The performance of ECDM was compared with those of multiple electrodes connected electrically in parallel (equipotential power) and of a single electrode. Then hole shapes were observed. The hole entrance was round because of the divided power. In the cases of equipotential power and a single electrode, cracks were frequently generated around the hole entrance by heat expansion. The cracks were the origins of protrusions by erosion. Eventually, long protrusions were formed. Because bubbles collapse during pulse intervals because of the divided power, the hole diameter was not enlarged.

Katsushi Furutani

Papers

Dot-matrix electrical discharge machining for shaping fine structure

Displacement Monitoring of Stacked Piezoelectric Actuator by Observing Induced Charge

Condition Monitoring in Concurrent Micro-hole Electrical Discharge Machining with Electrode Feeding Devices Employing AZARASHI (Seal) Mechanism☆

Fabrication of Wire Saw with Patterned Hard Bumps by Electrical Discharge Machining with Powder Suspended in Working Oil

Performance of Electrochemical Discharge Machining by Forced Discharge Dispersion