Effect of Powder Mixed Dielectric on Material Removal Rate,Tool Wear Rate and Surface Properties in Electric Discharge Machining

Abstract

In the process technology, as there are numerous advances at rapid rate, a large number of new materials are being developed everyday. These materials have the combination of properties, like light weight, corrosive resistance, high strength etc., which is not easy to obtain in general. The important aspect is that they satisfy the demands of today’s industry, but the major problem is that it is very difficult to machine the newly developed materials. So, in order to manipulate them, newer machining methods have been developed. These methods are more efficient than the conventional ones. Electric discharge machining (EDM) is one of the most widely used methods among the new techniques. The main reason behind the popularity of the EDM is that its capability of machining the hard to machine materials and intricate shapes. EDM has been employed to effect/change the surface properties such as roughness and hardness of the die steels by varying the electrode material and by adding the various powders in the dielectric. In this thesis work the literature available in the area of Surface modification by PMEDM (Powder Mixed EDM), EDM in general and effect of PMEDM on Tool Wear Rate and Material Removal Rate has been reviewed. Experiments were designed using Taguchi method so that effect of all the parameters could be studied with minimum possible number of experiments. Using Taguchi method, Appropriate Orthogonal Array has been chosen and experiments have been performed as per the set of experiments designed in the orthogonal array. Signal to Noise ratios are also calculated to analyze the effect of PMEDM more accurately. From the point of view of industrial applications, die steel is a very important material and that’s why for the purpose of experimentation EN31 die steel with copper electrode and kerosene as dielectric has been used. Graphite and copper powders were suspended in the dielectric kerosene. The effect of the powder mixed dielectric was studied by selecting peak current, Pulse on-time, Pulse off-time and Dielectric as factors and MRR, TWR, Micro-hardness and Surface roughness as responses. Three levels of each of the factors were taken and experiments were designed by Taguchi methodology. L27 Orthogonal Array was used and experiments were performed as designed by Taguchi method. Results of the experimentation were analyzed analytically as well as graphically using ANOVA and main effect-interaction plots, respectively. ANOVA has determined the percentage contribution of all factors upon each response individually. From the experimental results it is clear that the powders had changed the surface properties like surface roughness, micro hardness and improves the material removal rate and tool wear rate. Responses like Material removal rate, Tool wear rate, surface roughness and micro hardness were also optimized in the study and the optimal value of each of the above response was calculated using their signal to noise ratio values.