Energetic Characterization of Trim Cut Process Signals in Wire EDM

Abstract

Wire EDM has a high potential for aerospace applications. Particularly the turbine manufacturing with its growing use of difficult to machine materials to meet the increasing demand for turbine efficiency is predestinated for a technology that is independent of mechanical material properties. However, rigorous safety requirements in aerospace necessitate the precise knowledge of thermal rim zone modifications induced by the process and its assessment regarding component (fatigue) strength. Therefore, insight into the effective specific energy dissipation as well as knowledge of external influences on the process is key for a broad application and certification of Wire EDM in turbine manufacture. This information can only be generated by analyzing the process signal during machining. The focus of these analyses should be set to the trim cuts during EDM because they define the resulting surface integrity of the part. However, the trim cuts’ high-frequent nature as well as their pronounced deviation from ideal EDM signal characteristics found in the literature makes energetic signal processing very challenging. In practice, varying machining heights as well as complex geometries cause deviations from the ideal process leading to a variance in geometrical or energetic values. Monitoring and evaluating the characteristic patterns of the process signals this paper aims to present a methodology to characterize different types of trim cuts energetically as a prerequisite for further correlations between process energy and rim zone formation.