We propose an additive manufacturing (AM) method using electrical discharge with twin electrodes. Today, inexpensive three-dimensional (3D) modeling machines for fused deposition modeling (FDM) with resin fibers are used in various fields. On the other hand, laser sources and electron beam guns as heat sources for the powder bed fusion (PBF) method with metal powder are generally expensive. This impedes the wide use of modeling machines. In the proposed AM method, part of the powder layer is selectively solidified by electrical discharge from the twin electrodes through the surface of a metal powder layer. It is expected that the use of a discharge circuit as an inexpensive heat source will reduce the total machine cost and the overall machine size. A three-dimensional shape with overhangs was successfully fabricated by laminating thin layers.
Sintered polycrystalline diamond (PCD) is widely employed for cutting tools because of its excellent hardness and high wear resistance. However, it is extremely difficult to shape PCD tools by conventional machining methods. We describe the truing of a PCD tool by electrical discharge machining (EDM). Although EDMing of PCD is possible under PCD positive polarity, the removal rate is relatively low. In this paper, we discuss the possibility of applying a bipolar pulse for the EDMing of PCD. It is confirmed that the removal rate of PCD using a bipolar pulse is higher than that using a normal pulse (electrode positive or negative polarity). Moreover, the electrode wear ratio is also improved.