Electrical discharge milling with oblong tools

Electrical discharge milling (ED-milling) is an emerging technology which entails a rotating cylindrical tool that is traversed along a predefined tool path to machine a cavity. This process configuration offers advantages such as minimal time/cost associated with tool manufacture and improved gap flushing, as compared to traditional die-sinking that involves complex three-dimensional tools. Rotating cylindrical tools, however, inherently preclude the machining of sharp features and correspond to increased relative electrode wear; the reduced machining engagement further restricts the machining power which in turn limits the removal rate. To this end, this paper presents a novel tooling concept that relates to a set of standard prismatic tools of an oblong section, which incorporate the favorable functional characteristics of both ED-milling and die-sinking technologies. Aspects of computer-aided manufacture referring to tool selection, sizing and path planning are discussed. The concepts developed are illustrated through the application of an oblong tool that rotates and translates to machine a sample two-dimensional cavity.