The micro-cracks generated by EDM (RCL circuit) were studied experimentally under various machining conditions. The results are as follows:
(1) The crack length is more largely affected by the source voltage than by both the condenser capacity and the inductance in the discharge circuit, but it is almost unaffected by the charging resistance.
(2) The cracks observed on cemented carbide S2 are always longer than the ones on G2 under the same machining condition.
(3) By a reversed polarity (workpiece: cathode, tool-electrode: anode) the shorter cracks are generated than by a straight polarity.
(4) It can be inferred by the statistical analysis that the distribution of crack length fits the gamma distribution.
(5) The generation mechanism of cracks can not be perfectly explained from a viewpoint of the thermal shearing stress.

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The electrochemical machining in stagnant electrolyte (ECMSE) was realized with the use of pulse currents. The examples of drilling, deburring, and wire cutting were shown. One example showed that a carbon steel plate (S45C) of 30mm thickness was cut with a wire electrode of 0.2mm∅ diameter at a feed rate of 0.28mm/min. The advantages of the ECMSE are that the machine and the tool electrode can be simplified as the forced electrolyte flow is unnecessary and that a feeble tool electrode such as curved wire can be used as little force acts on it. A three dimensional wire cutting method with the curved wire electrode was proposed and an example was shown. The disadvantage of the ECMSE is that the feed rate as well as the electrode area is limited to be relatively small at present stage.

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