The Grain Size Effect of Polycrystalline Diamond on Surface Integrity by Using Micro EDM

In this study, the optimization of machining parameters and the effect of polycrystalline diamond (PCD) grain sizes on machining characteristics in micro electrical discharge machining (μEDM) are analyzed. There are four experimental factors, each parameter is set at three levels: current (0.5A, 2A and 4A), pulse-on time (2 μs, 4 μs and 8 μs), pulse-off time (2 μs, 4 μs and 8 μs) and PCD grain size (1.7 μm, 4 μm and 6 μm). Voltage is fixed at 140 V. Base on L9 orthogonal array and signal to noise ratio through Taguchi method, analysis of variance (ANOVA) is used to validate the significant experimental parameters. The results suggest that the PCD in grain size of 6 μm is the best choice for maximum material removal rate and minimum for electrode wear ratio, meanwhile, the optimum condition of surface roughness is obtained at 1.7 μm. The current and pulse on-time play as significant roles that affect machining performance. The discharge energy (current and pulse on-time) increases leading to the decrease of the material removal rate and the increase of the electrode wear ratio and the surface roughness. In addition to, the PCD grain size has a minor influence on electrode wear ratio and material removal rate and relatively affects surface roughness. The surface roughness increases as increasing the diamond particle size.