Recently, aluminium alloy has partially been developed as a metal mold for plastic injection molding in place of steel which has conventionally been used. It is expected that the demand of aluminium alloy mold will increase, since lightening of large mold is necessary. However, study on EDM of aluminium alloy has not yet been carried out sufficiently.
In this study, electrical discharge machining (EDM) performances of aluminium alloy are experimentally investigated. Furthermore, the effects of high speed polarity changing on EDM performance are also discussed. Main conclusions obtained in this study are as follows:
(1) The removal rate in EDM of aluminium alloy is larger than that of steel because of its low melting point.
(2) In EDM of aluminium alloy, the removal rate decreases and the appearance of machined surface becomes worse with machining time. These deteriorations can be improved using high speed polarity changing method.
(3) In the high speed polarity changing EDM of aluminium alloy, the removal rate takes the maximum when the reversed polarity discharge is a little mixed into the normal polarity EDM.
(4) In the high speed polarity changing EDM of aluminium alloy, the electrode wear takes the minimum when the normal polarity discharge is a little mixed into the reversed polarity EDM.
(5) The removal rate, the electrode wear and the surface finish in the EDM depend on the ratio of normal polarity discharge to the reversed polarity one regardless of the number of each polarity discharge in a cycle.
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