Complex taper profile machining of WC-Co composite using wire electric discharge process: analysis of geometrical accuracy, cutting rate, and surface quality

Abstract

Complex profiles, comprising curved features and inclined surfaces, are an inherent attribute of tungsten carbide (WC-Co) tooling applications like dies, molds, and cutting tools. Such profiles are difficult to machine by conventional processes due to high hardness of WC-Co. Wire electric discharge machining (WEDM) is a frequently employed non-traditional machining process for producing intricate shapes and complex geometries in difficult-to-cut materials. However, this process offers its own challenges regarding machining accuracy of arced profiles such as undercutting or overcutting of material. Machining task becomes more complicated if arced profiles are to be machined at a certain taper angle. Keeping in view the stringent requirements of productivity and geometrical accuracy for WC-Co tooling, current research is focused on comprehensively evaluating the performance of WEDM process for producing complex tapered profiles in WC-Co composite. Furthermore, instead of using simple brass wire, a zinc-coated wire electrode is employed to enhance cutting rate. The impact of WEDM control variables namely, pulse-on/off time, servo voltage, and wire tension, in conjunction with workpiece taper, is studied on geometrical accuracy, cutting rate, and surface quality of complex tapered profile. Results of experimentation are analyzed using various statistical techniques. Scanning electron microscopy (SEM) and energy-dispersive X-ray (EDX) analysis are carried out for in-depth evaluation of machining results. Experimental results show that a complex tapered profile can be generated with as small as 0.16° angular error and 6-μm radial error using optimal parameter settings. Optimal settings of process parameters result into 33.3% reduction in angular error, 14.3% reduction in radial error, 12% increase in cutting speed, and 14.4% reduction in surface roughness of workpiece.