Tolerance-Based Optimization of Sinking Electrical Discharge Machining for Industrial Seal Slot Manufacture

Journal of Engineering for Gas Turbines and Power, vol. 144

Abstract

Abstract Seal plates for turbine vanes significantly reduce gap losses and thus play a major role in increasing the efficiency of turbines. The industrial production of seal slots, which position the seal plates in the turbine vanes, is driven by the need for high productivity in combination with a reliable processing of necessary geometrical and surface integrity features. A machining technology that is able to machine hard-to-cut materials such as nickel-based alloys is electrical discharge machining. Due to its electrothermal working principle, it is able to machine materials independently from their mechanical properties even at high aspect ratios. Achievable removal and wear rates as well as the resulting surface properties strongly depend on the discharge energy. Furthermore, the discharge energy affects the working gap sizes and therefore flushing efficiencies when machining high aspect ratio cavities. This relationship is investigated taking into account various contemporary generator technologies and graphite grades from both published literature and own experimental investigations. Their effect on machining performance focusing on productivity, recast layer thickness, and crack formation is quantified. Based on these data, a novel empirical model for tolerance-based optimization is developed. The model is used to perform an optimization on an existing serial production, and implementation has been proven successful.

Authors 3

1. Timm Petersen corresponding Aachen Laboratory for Machine Tools and Production Engineering (WZL)

   RWTH Aachen University

   Affiliation as printed

   Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Aachen 52074, Germany

2. Markus Zeis

   MTU Aero Engines (Germany)

   Affiliation as printed

   MTU Aero Engines AG, Munich 80995, Germany

3. Thomas Bergs Aachen Laboratory for Machine Tools and Production Engineering (WZL) Fraunhofer Institute for Production Technology

   RWTH Aachen University · Fraunhofer Institute for Production Technology IPT

   Affiliation as printed

   Laboratory for Machine Tools and Production Engineering (WZL) of RWTH Aachen University, Aachen 52074, Germany; Fraunhofer Institute for Production Technology (IPT), Aachen 52074, Germany

   Fraunhofer Institute for Production Technology (IPT), Aachen 52074, Germany