PURPOSE: To produce uniform aventurine surface by controlling frequency of inter- pole detection according to the rotation speed of the roll.
CONSTITUTION: A low voltage pulse and a high voltage pulse are impressed in the machining space between an electrode 2 and a roll 1. A high voltage pulse and a low voltage pulse exist in mixture between the poles due to the same signals of an oscillating circuit 12, but the machining current is detected at a detector circuit 13 at time of low voltag pulse impression, whose detecting signal is distinguished at a distinguishing circuit 14 to determine the electrode feeding amount, and the electrode feeding device is operated by the driving dircuit 15. Thus, as the length of the inter-pole space is most appropriate at time of low voltage pulse impression, it is narrow enough for high voltage pulse discharge, letting most of the impressed high voltage pulse be discharged. In this way, even at time of vibration or highest rotation rate of the roll, the change of the machining space causes no machining amount, eliminating the generation of stripe patterns on the machined surface.
URATA TETSUO
NAKAYAMA TAKEO
KAMIUMA TERUMASA
KAWANO MITSUGI
KAMIBAYASHI TAKEO
NIPPON KOKAN KK