Experimental Investigation on Nickel Aluminium Alloy by Electric Discharge Machine

Advanced structural ceramics, such as Silicon Carbide (Sic), Silicon Nitride (Si3N4), Alumina (Al2O3) and Zirconia (ZrO2) are attractive materials for many applications ranging from aero engines to dental restoration and is possible due to high hardness and strength, wear resistance, resistance to chemical degradation and low density. Various applications of these ceramic materials demand shaping to a high degree of surface finish and dimensional accuracy. These materials difficult to machine because of high hardness and abrasive nature of reinforcing elements like alumina particles. In this study, homogenized (4%, 6%, and 8%) by weight of alumina aluminum metal matrix composite materials were fabricated and selected as work piece for experimental investigations of surface roughness and metal removal rate. Among the machining processes used for shaping advanced ceramics, grinding is the most widely used machining process as it gives reasonably good rate of material removal. However, the high cost of diamond grinding and difficulty in machining complex shapes and 3D surfaces have promoted research into alternative methods of ceramics machining like ultrasonic machining, abrasive water jet machining, electrical discharge machining and laser beam machining. Electrical-discharge machining (EDM) is an unconventional, non-contact type machining process where metal removal is based on thermal principles. In this process, the material removal mechanism is based on the conversion of electrical energy into thermal energy through a series of discrete electrical discharges that occur between the electrode and work piece immersed in an insulating dielectric liquid. The concentrated heat of spark generates a channel of plasma between the cathode and anode at a temperature in the range of 8000 to 12,000 °C, initializing a substantial amount of heating and melting of material at the surface of each pole. When the direct current supply is turned off and the potential reaches above the breakthrough voltage of dielectric, the plasma channel breaks down. This causes a sudden reduction in the temperature Allowing the circulating dielectric fluid to implore the plasma channel and flush the molten material from the pole surfaces in the form of microscopic debris. EDM does not make direct contact between the electrode and the work piece whereby it can eliminate mechanical stresses chatter and vibration problems of conventional machining. Despite all the advantages, the EDM process is not free from drawbacks. In EDM, the tool wear problem is very critical since the tool shape degeneration directly affects the final shape of the die cavity. The machinability of a material is a factor of its thermal and electrical properties in EDM. Material’s electrical resistivity is dependent on its temperature. In addition, the cost of a part manufactured by the EDM is determined mainly by the tool cost, which consists of the raw material cost of the tool, the tool production cost and the number of tools required for operation. In most of the EDM operations, the contribution of the tool cost to the total operation cost is more than 70%. It is also known that during the cut by EDM the material removal rate (MRR) decreases, which is due to process instability. However, the decrease of MRR is due to the change of metallurgic constituent in the machining zone. The quality of the surface machined plays an important factor in evaluating the productivity. Surface Roughness is a significant design factor which has a considerable influence on properties such as fatigue, strength, and wears resistance. It is one of the most important measures also in machining operations. It is, therefore, imperative to target for good surface finish. Other drawbacks include difficulty in reproducing sharp corners on the work piece due to electrode wear, surface and subsurface damage and creation of thin and brittle heat-affected zone. This work has attempted to overcome some of the drawbacks of the EDM process. It has been observed that the rapid electrode wear can be reduced and better surface quality obtained by An efficient cooling strategy. The present work correlates the inter-relationships of various EDM machining parameters namely discharge current, pulse-on time, duty cycle and gap voltage on the material removal rate (MRR) and surface roughness (SR) in EDM process using c). Regression models have been developed to predict MRR and SR by correlating the input parameters. The significance of EDM parameters on the selected responses has been evaluated using Taguchi Method with copper electrode. Confirmation experiments were also conducted at various test conditions to show that the developed models for EDM process can predict MRR and SR values accurately within 94% confidence interval an attempt has been made to optimize the EDM conditions to obtain maximum MRR and minimum SR. A trust-region based optimization method has been used to obtain optimum solution. The objective of this research study is to investigate the optimal Process parameters of Electric Discharge Machining on Nickel aluminum composite work piece with copper as a tool electrode. The effect of various process parameters on machining performance is investigated in this study. The input parameters considered are impulse current, Pulse on time and pulse off time, voltage gap are used for experimental work and their effect on Material Removal Rate, Tool and Surface Roughness. The Central competitive method is used to formulate the experimental layout, Taguchi Method is used to analysis the effect of input process Parameters on the machining characteristics and finds the optimal Process parameters of Electric Discharge Machining. The results of the Present work reveal that proper selection of input parameters will play a significant role in Electric Discharge Machining.