Evaluation of Advanced Wire-EDM Capabilities for the Manufacture of Fir Tree Slots in Inconel 718

This paper deals with a technological evaluation of wire electrode material and machining technologies for the production of fir tree slots by Wire-EDM to compete with the conventional broaching process. Meeting the high requirements on surface integrity and precision, new electrodes in combination with machining technologies have been developed in order to increase the productivity of this machining process. In particular three wire electrodes including a standard brass wire, a coated high-speed-cutting wire and a Ni-coated wire for zero contamination of Cu and Zn in combination with standard and specifically developed machining technologies for cutting Inconel 718 are presented. Evaluation criteria for the comparison are the demanding requirements on fir trees in turbine engine production like precision, surface roughness, minimization of white layer formation and contamination. Finally, an energy consumption analysis of the electrode/machining technology combination is shown. The analyzed processes show that Wire-EDM is a capable process for the fir tree slot production.