ELECTRIC SPARK MACHINING ELECTRODE AND METHOD OF PRODUCTION THEREOF.

摘要

An electrode for engraving electric spark machining which is produced by using a mixture of gypsum hemihydrate powder serving as both a principal material and a binder with a conductive metal powder as a filler, transferring, shaping and hardening the mixture into a desired shape to form electrode material and plating the electrode with the conductive metal. Gypsum hemihydrate powder, gypsum dihydrate powder of less than 1 vol % on the basis of the former and the conductive metal powder are kneaded in a vacuum. Water is added to the kneaded matter, which is again kneaded in a vacuum, poured into a mold to which a predetermined shape is transferred, shaped and hardened by hydration to obtain an electrode material. Then the electrode material is dried and plated with the conductive metal so as to reinforce electrical connection with the metal powder. Since the electrode is made of gypsum as the principal material, even an electrode for electric spark machining to which a precise and complicated shape is transferred can be produced easily, economically, and precisely by the use of a simple mold of, e.g. a silicone rubber, and hence it is particularly suitable for producing dental crowns one by one. Furthermore, gypsum hemihydrate as the principal body of the electrode material and the conductive metal film increase the strength of the electrode by virtue of their synergistic effect. The present invention makes possible machining of a hard material such as titanium for which precise electric spark machining at a desired speed has been difficult by the use of a conventional electrode subjected to impregnation treatment of a conductive solution in which graphite or the like is dispersed in place of plating treatment.