Machining rate and wire motion in wire EDM of conductive ceramics

摘要

In this study, the machining rate, surface roughness and side gap were investigated to clarify the extremely high machining rate at a special machining condition in the wire electrical discharge machining (EDM) of conductive ceramics, experimentally and theoretically. The experimental results of Sialon ceramics showed that the extremely high machining rate appeared at a special duty factor peculiar to the pulse duration, where the machining rate steeply increased with the peak current. The side gap also increased with pulse duration as well as peak current, but there was no particular machining condition with extremely high side gap and surface roughness. These results suggest that the extremely high machining rate is related to the wire motion in the EDM process. The numerical calculations based upon a mechanical model with the vibration of string showed that a vibration with high frequency mode appears in the wire EDM, and its amplitude becomes extremely high at a special pulse duration. It is seen from the comparison between the experimental and calculated results that the high amplitude in the wire motion is caused from the resonant behavior in the process, which results in the high machining rate in the wire EDM of conductive ceramics.