Investigation and process optimization for different machining characteristics during die cutting with wire EDM

Abstract

With the development of high strength temperature resistant, non-conductive and special application materials which have wide applications in aerospace, automobile, medical etc., demand for powder metallurgy alloying methods has grown tremendously. Using modern compacting techniques more complex parts can be sintered in larger sizes and quantities with high quality and precision. The compacting dies are the mid-point of this powder metallurgy technique which influences the quality of finished components and hence affect the economies of producing a large number of assemblies and subassemblies. Therefore, aim of the manufacturing engineers is to produce the dies which run for a longer time and produce the components of desired quality. For efficient working, in long run, these compacting dies must possess some key qualities like good surface finish and precise dimensional tolerance. Good surface finish significantly affects the die release characteristics, durability and finished product quality. Precise dimensional tolerance can eliminate the additional machining and finishing of sintered components. Material for these compacting dies must possess high strength, wear resistance and long term reliability. Cemented carbide, primarily those of WC have been commonly used in tool and die industries because of their excellent hardness and strength. They are formed by sintering of WC powder with the binder (typically Co or Ni) at temperature near the melting point of the metal. Hardness and strength of WC composite is determined by the percentage of binder and the grain size of the particles. WC Co composite is very difficult to machine with conventional machining methods.Die performance is a function of umpteen numbers of factors such as percentage and grain size of material constituents, machining parameters, tool electrode, geometry of die and type of machining operation. Wire Electrical Discharge Machining (wire EDM/WEDM) is a special form of Electrical Discharge Machining (EDM) which has the capability to produce