Optimization of Wire EDM Process Parameters of ...

International Review of Mechanical Engineering (I.RE.M.E.), Vol. 6, N. 3 ISSN 1970 - 8734 March 2012

Optimization of Wire EDM Process Parameters of Aluminium Alloy/Flyash/Boron Carbide Hybrid Composites J. Udaya Prakash1, J. Milton Peter2, T. V. Moorthy3 Abstract – The objective of the present investigation is to analyze the influence of Wire Electrical Discharge Machining (WEDM) process parameters like Pulse on time, Pulse off time, Wire feed and Gap voltage on the responses surface roughness (SR) and material removal rate (MRR) during the machining of aluminium alloy (LM 6) flyash boron carbide hybrid composites using Taguchi method. Aluminium alloy (LM 6) was reinforced with flyash particles of 75 µm and boron carbide of 20 µm in 3%, 6% and 9% by weight. Analysis of variance (ANOVA) is done to find the significance of machining parameters which affects the quality characteristics of WEDM process and also to find the relative contribution of machining parameters in controlling the responses of the WEDM process. The parameter with the strongest influence on the response is determined by signal to noise (S/N) ratio response analysis. However, as a final step, confirmation experiment has also been conducted with the optimum combination to predict and verify the improvement of the observed values. Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved. Keywords: Wire Electrical Discharge Machining, Hybrid Composites, Taguchi Method, Analysis of Variance, Signal to Noise Ratio, Material Removal Rate, Surface Roughness

I.

DOE approach using Taguchi technique is devised for process optimization and identification of optimal combination of the factors for a given response. Taguchi designs provide a powerful and efficient method for designing products that operate consistently and optimally over a variety of conditions. Taguchi technique creates a standard orthogonal array to consider the effect of several factors on the target value and defines the plan of experiments. Experiments are designed and conducted to study the parameters that affect the response. This method employs a generic S/N ratio to quantify the present variation. These S/N ratios are meant to be used as measures of the effect of noise factors on performance characteristics. ANOVA is used to determine the design parameters or their interactions significantly influencing the response. It is a computational technique that quantitatively estimates the relative contribution of control factor on the overall measured response and expresses it as a percentage.

Introduction

Aluminium matrix composites (AMC) have become increasingly important in modern industrial world. Since AMCs contain certain amount of hard and abrasive ceramic reinforcements, they are considered to be one of the most difficult materials to machine. The addition of hard reinforcements makes machining of AMCs using conventional machining processes significantly more difficult and leads to severe tool wear and work piece damage. In view of the difficulties such as high tool wear, high tooling cost and poor surface finish, encountered during machining of AMCs with conventional methods nonconventional machining process such as WEDM is extensively used to perform the precision machining of AMCs. WEDM is a nontraditional, thermoelectric process which erodes material from the work piece by a series of discrete sparks between a work and tool electrode immersed in a liquid dielectric medium. These electrical discharges melt and vaporize minute amounts of the work material, which are then flushed away by the dielectric. It is typically used to cut plates as thick as 300mm and to make punches, tools, and dies from hard metals that are difficult to machine with other methods. At present, WEDM is a widespread technique used in industry for highprecision machining of all types of conductive materials such as metals, metallic alloys, graphite, or even some ceramic materials, of any hardness. Design of Experiment (DOE) is a powerful analysis tool for modeling and analyzing the influence of multiple control factors on the performance output.

A large number of components are made of AMCs due to their useful properties such as high strength, light weight, good wear resistance and elevated temperature capabilities. An aluminium alloy with discontinuous ceramic reinforcement is rapidly replacing the conventional materials in automotive, aerospace, automobile industries and electronic packaging.

Manuscript received and revised February 2012, accepted March 2012

Copyright © 2012 Praise Worthy Prize S.r.l. - All rights reserved

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Experiments Selection of Materials

J. Udaya Prakash, J. Milton Peter, T. V. Moorthy

TABLE I CHEMICAL COMPOSITION OF LM6 ALLOY Contents Composition

%Si 11.05

%Fe 0.19

%Mg 0.06

%Cu 0.042

%Mn 0.04

%Ti 0.013

%Ni 0.004

%Pb 0.002

%Zn