Limits of Die-Sinking EDM for micro Structuring in W300 Steel with pure Copper Electrodes

Abstract

Electrical discharge machining (EDM) is capable of almost force-free 2D and 3D machining of any kind of conductive material. The micro die-sinking EDM process described in this paper uses electrodes with features in the micrometer scale as a working tool. The ability to machine micro features is desirable for many applications, which range from miniaturization to functionalization of large surfaces. To achieve the desired workpiecès final shape, the working gap and the tool wear behavior must be known and minimized or compensated if possible. For an overall understanding, the interaction between process parameters, such as pulse and pause duration, as well as discharge current with resulting gap sizes, wear formation and work piece shape must be displayed. Besides the optimization of the micro-EDM process itself, the entire process chain must be discussed, including the shaping of the electrodes. This paper provides knowledge on micro structuring copper electrodes using wire-EDM. It also includes information about their subsequent use in micro die-sinking EDM when machining large areas with high aspect ratio micro structures in W300 steel of Böhler Edelstahl. On electrodes, micro ribs with heights of 350 µm, widths of 70 µm and pitch distances of 320 µm could be reached. For micro die-sinking, a relative frontal length wear as low as 19% was determined. The limits of minimum structure sizes in W300 have been investigated, and rib widths down to 31 µm, as well as pillar edge lengths down to 80 µm, have been achieved. Surface quality and changes of the chemical surface compounds of W300 were analyzed using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDX). Deposit of copper material from the electrode was identified and a proliferation of carbon was detected on the workpiece.