Electric discharge machining apparatus

Abstract

In a three dimensional generic electric discharge machining (EDM) apparatus the positionable driver assembly (,) houses a discharge electrode (,) that is in the form of a continuous wire, exposing only a predetermined length, the working portion, of that wire for discharge machining. Additional portions of that wire are incrementally advanced (,) from the housing as needed. In one embodiment, that need arises from electrode erosion, and, as an incremental portion of the electrode's working portion is eroded away, an additional increment of wire is advanced from the housing to restore the working portion to the desired length. For automatic control of the working portion's length, a novel sensor (,) monitors the virtual location of the discharge spark that occurs off the tip of the electrode during machining; and a significant shift in position of the spark, indicative of electrode wear, is detected and acted upon by the apparatus (,) to automatically replenish the spent electrode portion. In another embodiment (FIG.,), wire (,) is automatically advanced (,, FIG.,) under control of a computer (,, FIG.,) programmed to predict the progress of workpiece cutting in which the electrode acts as a scoop. The continuous wire, in the form of a flat ribbon, is extruded (,) in increments to form continuous segments of semi-torroidal shape as the ribbon is automatically advanced over a period from the electrode housing for discharge machining that “scoops” material from the workpiece.