Abstract: A continuous wire EDM machine is configured to form blind holes by using a track member to carry the EDM wire into the cut. The track member has a thickness that is less than the diameter of the EDM wire. The EDM wire is retained, for example, in a shallow groove formed in the arcuate outer peripheral edge of the thin planar track member. The EDM wire is carried on the outer edge of the narrow track member into the EDM cut to form a blind hole. The EDM wire is received in the shallow groove to a depth that is less than the radius of the EDM wire. The EDM wire can be advanced into a workpiece to a depth that is slightly less than the depth at which a spark forms between the workpiece and the broader base of the track support member that supports the thin track member. The radial length of the track member is measured in a direction generally normal to the longitudinal axis of the EDM wire and to the thickness of the track member.

Abstract: A method of electrical discharge machining a workpiece, while maintaining the desired size, shape and surface finish of the cut. After an initial machining operation at an initial power setting forms a cut of the desired size and finish in the workpiece to some initial depth, a multi-phase machining cycle is established to carry the cut deeper. Machining is carried out for most of this multi-phase cycle at a reduced power setting, which results in the reduction of at least the rate of particulate debris production. If reduced on-time power settings are employed, the average particle size of the debris is also reduced. At the very end of the multi-phase machining cycle, the power setting is abruptly increased to a level which is sufficient to cause substantial agitation of the dielectric fluid in the spark gap. If the on-time power level has been reduced, the cut is enlarged to the desired size by the terminal power pulse.