A review of the current understanding and technology of powder mixed electrical discharge machining (PMEDM)
This paper reviews the current understanding of powder mixed electrical discharge machining (PMEDM), highlighting particularly the mechanisms proposed for PMEDM under the influence of additive of powders in the dielectric fluids. Generally, the mirror surface phenomenon in PMEDM can be explained by the enlarged gap widths which can expand the discharge channel and thereby reduce the electrical power density since lower power density can yield large and shallow craters that evenly distributed on the machined surface. Moreover, the increment of the inter electrodes distance will limit the capacitive effect and enable a small surface roughness even in a large area. Another possible mechanism, multi-discharge model was also presented in this paper. More investigations on the fundamental mechanism in power mixed EDM are highly desirable since it has not been understood clearly. In this paper, the traditional and some recent development technology for PMEDM is also reviewed. Historically, PMEDM was invented to improve the surface quality of the machined components. Nowadays, some new applications of this technology, such as micro machining, rough machining and surface modification were proposed; some novel variations that based on power mixed EDM, such as PMEDM combined with ultrasonic or abrasive, powder mixed near-dry EDM and powder mixed electrical chemical discharge machining (ECDM) were also developed.
Characteristics of plasma channel in powder-mixed EDM based on monopulse discharge
Electrical discharge machining (EDM) was developed over 70 years ago, but the knowledge of plasma channels that form during this process remain understudied. Therefore, this study systematically investigated the breakdown process and impedance characteristics of plasma channels through singe-pulse discharge experiments. The influence of discharge current and gap distance on the breakdown process and impedance characteristics of plasma channels was also analyzed. The results of this work can contribute to the existing body of knowledge of the physical nature of EDM.
Automatic Process for Manufacturing Free-form Surface by Electrical Discharge Machining.
In this paper, a new process for finish machining on free-form surfaces is proposed. This process consists of generating CL data, milling an electrode and a work by a machining center, removing cusps of the electrode and the work by electrical discharge machining (EDM) and finish EDM for the work. In the cusp removing process, EDM with planetary motion under high wear conditions is carried out. Powder suspended working fluid is used in finish EDM in order to break through the roughness limit. Since the planetary motion in EDM process decreases geometrical accuracy, the electrode shape is manufactured to compensate its planetary motion. A geometrical tracing method generates tool paths for the work and the electrode without any cutter interference. A shape with mirror-like free-form surfaces has been realized through a series of automatic processes without sacrifice of geometrical accuracy and without any manual works.