Method of electrical discharge machine with simultaneous relative advance and cyclic translational movement of the electrodes

Claim 1

In a method of machining by electrical discharges the surfaces of a recess in a workpiece electrode to substantially the same shape as a tool electrode, said method comprising controlling the relative displacements of the electrodes which are translationally movable relative to one another both in the direction of an axis of penetration of one electrode into the other and in a plane perpendicular to said axis and displacing one of the electrodes along said axis of penetration to produce sparking in a machining zone comprised between corresponding surfaces of said electrodes, said machining zone extending on frontal and lateral portions of said surfaces, the improvement comprising simultaneously relatively moving the electrodes in translation in said perpendicular plane with a predetermined amplitude, and progressively increasing said amplitude as a function of the penetration along said axis to provide a combined oblique relative translational movement along at least one generatrix of a surface of revolution of increasing section in said direction of penetration, while controlling said oblique relative translational movement to maintain given sparking conditions in the machining zone comprised between said electrodes at said frontal and lateral portions of said surfaces, wherein the amplitude of said relative translational movement in said plane increases linearly with the penetration along said axis whereby said oblique relative translational movement is along a generatrix of a cone coaxial to said axis of penetration and said generatrix is substantially at 45° to said axis of penetration.