Influence of short-circuitng on machined surface quality in electrical discharge machining of carbon fiber reinforced plastics

Abstract

This paper investigates the influence of a short circuit on machined surface quality in the electrical discharge machining (EDM) of carbon fiber reinforced plastics (CFRP) in order to obtain a machined surface with good quality. In the EDM of CFRP, short circuits caused by the attraction of frayed carbon fibers on the machining surface to the tool electrode frequently occur and has adverse effects on the quality of the machined surface. In this study, die-sinking EDM of CFRP using deionized water was carried out, and the influence of duration of stable state in which short circuit does not occur on quality of machined surface was investigated. The occurrence of short circuits was determined from the fluctuation of the z-axis position. The machined surface was investigated using an optical microscope and the quality of the machined surface was judged on the basis of the presence or absence of frayed carbon fibers. The experimental results show that each stable state continues for 50 seconds or less when elapsed time is from 0 to 20 minutes. On the other hand, when the elapsed time is from 20 to 40 minutes, the duration of each stable state becomes longer than 50 seconds. It was found that when the machining process was stopped during unstable state in which short circuits occur, the quality of the machined surface was poor. On the other hand, when the machining process was stopped after stable states for a certain amount of time, the quality of the machined surface was good.