For successful commercial adaptation of the ß-EDM (micro electro-discharge machining) process, there is a need to increase the process efficiency by understanding the process mechanism. This paper presents a model of the plasma discharge phase of a single discharge ß-EDM event in deionized water. The plasma discharge is modeled using global model approach in which the plasma is assumed to be spatially uniform, and equations of mass and energy conservation are solved simultaneously along with the dynamics of the plasma bubble growth. Given the input discharge voltage, current and the discharge gap, complete temporal description of the ß-EDM plasma during the discharge time is obtained in terms of the composition of the plasma, temperature of electrons and other species, radius of the plasma bubble and the plasma pressure. Eor input electric field in the range of 10-2000 MVIm and discharge gap in the range of 0.5-20 ßm, timeaveraged electron density of 3.88 x 10^' 'm^^ -30.33 x 10^''m~^ and time-averaged electron temperature of 11,013-29,864 K are predicted. Experimental conditions are simulated and validated against the spectroscopic data from the literature. The output from this model can be used to obtain the amount of heat flux transferred to the electrodes during the ß-EDM process.

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High-aspect-ratio arrayed structures find application in the creation of deep blind holes used in ink-jet nozzles, air-bearings, etc. This paper focuses on the use of reverse microelectric discharge machining (micro-EDM), to generate high-aspect-ratio micro-rod arrays. A micro-rod of 60 mm in diameter and a high-aspect-ratio of 33 is successfully fabricated using the process. An L8 orthogonal array is used to study the effect of gap voltage, capacitance, threshold, and feed rate on the process response variables. The measured process responses are dimensional accuracy (measured at various locations along the length of the micro-rod), zero error length, and surface roughness. Furthermore, the surface morphology and chemical composition at the root and tip of the generated structure are studied. Analysis of variance studies show that the statistically significant factors that influence response variables are the gap voltage and capacitance. The gap voltage is identified as the single most important factor governing the accuracy of the micro-rods at almost all locations. Analysis of surface morphology reveals that there are more craters at the tip of machined rods whereas, the area around the base is relatively smooth. Value of surface roughness varies from 1.6 mm Ra to 6.3 mm Ra under different experimental conditions. A variation in chemical composition is observed along the length of the rod. Plausible explanations are presented for the various phenomena observed during the reverse micro-EDM process. Downloaded from * indicates that these factors are significant of 95% confidence level. JEM1745Proc. IMechE Vol. 224 Part B: J. Engineering Manufacture Experimental characterization of the reverse micro-EDM process

Die casting is a type of metal casting in which a liquid metal is solidified in a reusable die. In such a complex process, measuring and controlling the process parameters are difficult. Conventional deterministic simulations are insufficient to completely estimate the effect of stochastic variation in the process parameters on product quality. In this research, a framework to simulate the effect of stochastic variation together with verification, validation, and uncertainty quantification (UQ) is proposed. This framework includes high-speed numerical simulations of solidification, microstructure, and mechanical properties prediction models along with experimental inputs for calibration and validation. Both experimental data and stochastic variation in process parameters with numerical modeling are employed, thus enhancing the utility of traditional numerical simulations used in die casting to have a better prediction of product quality. Although the framework is being developed and applied to die casting, it can be generalized to any manufacturing process or other engineering problems as well.

This paper presents a micro-electrodischarge machining (EDM) melt-pool model to predict workpiece (anode) material removal from a single discharge micro-EDM process. To model the melt-pool, heat transfer and fluid flow equations are solved in the domain containing dielectric and workpiece material. A level set method is used to identify solid and liquid fractions of the workpiece material when the material is molten by micro-EDM plasma heat flux. The plasma heat flux, plasma pressure and the radius of the plasma bubble have been estimated by a micro-EDM plasma model and serve as inputs to the melt-pool model to predict the volume of material removed from the surface of the workpiece. Experiments are carried out to study the effect of interelectrode voltage and gap distance on the crater size. For interelectrode voltage in the range of 200–300 V and gap distance of 1,2 μm, the model predicts crater diameter in the range of 78–96 μm and maximum crater depth of 8–9 μm for discharge duration of 2 μs. The crater diameter values for most of experimental craters show good agreement with the simulated crater shapes. However, the model over-predicts the crater depths compared to the experiments.