Copper alloy MS46 has recently been developed as a metal mold material for shell mold core in place of cast iron FC which has conventionally been used. In this paper, the electrical discharge machining performances of copper alloy MS46 are experimentally investigated, analyzing the crater shape generated by a single pulse discharge, the metal removal rate, the electrode wear rate, the surface finish and so on. Then the surface integrity of MS46 for metal mold is evaluated. Main conclusions obtained in this study are as follows:
(1) The metal removal rate in EDM of MS46 is the same as that in cast iron FC.
(2) No electrode wear EDM of MS46 is difficult because of less material adhesion to the surface of electrode than that in case of cast iron.
(3) EDMed surface of MS46 has some excellent properties for metal mold such as better surface finish than that of cast iron, no crack on the machined surface and harder recast layer than base material.

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It has been thought that the wear ratios of copper electrode in the machining of carbon steels are the same. In this paper, the difference of wear ratio of copper electrode is discussed through machining of several kinds of carbon steels comparing with pure iron and brass (Bs) as the work pieces. And the influence of duty factor (Df) on electrode wear ratio is investigated in the machining of the carbon steel S45C. Electrode wear ratio is very large with small Df. In these cases, electrode wear ratio is strongly affected by not only the structure but also the quantity of carbon layer which covers the electrode. If a turbostratic carbon layer can be generated much sufficiently thick on the surface of the electrode, it will be possible to realize a lower wear ratio.

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A maximum cutting speed of WIRE EDM is restricted by a wire rupture during WIRE EDM. Normally it is said that too high machining speed supplies high temperature on the wire and causes the wire breaking. But it was difficult to measure the wire temperature during EDM because the wire is moving and surrounded by a workpiece material. Only a mathematical analysis is tried to obtain a temperature distribution assuming a heat transfer coefficient, but not considering a effect of water flow.
We already found that a discharge concentration occurs just before the wire breaking. Then the discharge concentration may be the main reason of the wire rupture. In this case a local wire temperature may increases so high but not a averaging wire temperature. But it depends on machines. If an ON/OFF control in power supply was so fine as to avoid the discharge concentration, the averaging wire temperature may be already so high, and the prevention of discharge concentration may be a fruitless effort for the machining speed. Then it is important to know the real wire temperature to develop the machining speed on WIRE EDM.
In this report we describe an attempt to measure the wire temperature distribution from discharging currents and voltages during WIRE EDM. Results show that the averaging wire temperature may be 100°C or less.

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This paper deals with micro-electrodischarge machining which enables three-dimensional machining of micromechanical systems.
In a relaxation type pulse generator, the minimum discharge energy depends on the stray capacitance. A small stray capacitance was achieved by using ceramic material for the mechanical components such as the bearing and machining table base.
Adhesion of the electrode and workpiece tends to occur for small discharge energies. The rotation of the electrode is indispensable in micro-electrodischarge machining since the adhesion is avoided by applying it. An accurate rotation was achieved by laying the mandrel, which installs the electrode, directly on the V-shaped block. This modification realized an accuracy of rotation better than 0.51μm.
Since the bending and runout were too large for small-size electrodes, it was necessary to form electrodes under the same setup as in machining. The formation was realized on the machine using the reverse discharge method.

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