OCTOBER 19-20, 2012 - YMCA University of Science & Technology

Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
Investigation of the effect of Process Parameters on Surface Roughness
in Wire Electric Discharge Machining of En31 Tool Steel
Dharmender 1 , Rajeev Kumar 2 and Anmol Bhatia 3
1 Research Scholar, YMCA University Of Science & Technology,Faridabad., Haryana
2 Assistant Professor, IIMT College of Engineering, Greater Noida,UP
3 Sr.Lecturer, Echelon Institute of Technology, Faridabad, Haryana
Abstract
Modernization of mechanical industry has lead to the increase in demand for hard and tough materials
and thus various non traditional methods have been developed in order to machine such hard and tough
materials. Wire Electric discharge machine is one of the most commonly used machine which is employed in
machining of conductive metals of any hardness or that are difficult or impossible to cut with traditional
methods. WEDM is one of the most popular machining methods in present industry which specializes in
cutting complex shapes or geometries. The literature survey has revealed that very less work has been done in
order to achieve optimal levels of process parameters for Tool Steel-En31 using Brass wire electrode.
This paper deals with the study the effect of different process parameters viz. peak current, pulse on time, pulse
off time, Wire Tension on the response variable- Surface roughness using Brass wire electrode (0.25 mm
diameter). Taguchi design methodology has been chosen for design of experiment and L 9 orthogonal array
has been selected for present study. In this study MINITAB software was used to find the effect of each
parameter on response characteristic and to predict the setting of control parameters. ANNOVA and main
effect plot have been used to find the significant process parameters and their effect on the response
variables. The predicted optimal value of Surface Roughness is further verified by confirmation experiments.
Keywords: WEDM, Process parameters, ANNOVA, En-31 tool steel.
1. Introduction
Wire Electrical discharge machining (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. Melting and vaporization due to electrical discharge removes minute amounts of the work
material, which are then ejected and flushed away by the dielectric. The schematic representation of the WEDM
cutting process is shown in Figure 1.Wire electrical discharge machining (WEDM) is a specialized thermal
machining process capable of producing accurately machined parts with different hardness or complex shapes,
which have sharp edges that are very difficult to be machined by conventional machining processes. At present,
WEDM is a widely used technique in industry for high-precision machining of all types of conductive materials
such as metals, metallic alloys, graphite, or even some ceramic materials, of any hardness [1-3]. Many Wire-
EDM machines have adopted the pulse generating circuit using low power for ignition and high power for
machining. However, it is not suitable for finishing process since the energy generated by the high-voltage subcircuit
is too high to obtain a desired fine surface, no matter how short the pulse-on time is assigned [4].As newer
and more advance as well as exotic materials are developed, and demand of more complex shapes ,conventional
machining operations will continue to reach their limitations[5].
WEDM is considered as variants of the conventional EDM process, which uses an electrode to initialize the
sparking process. However, WEDM utilizes a continuously travelling wire electrode made of thin copper, brass
or tungsten of diameter 0.05-0.30 mm, which is capable of achieving very small corner radii. The wire is kept in
tension using a mechanical tension providing device reducing the tendency of producing inaccurate parts.
Fig (1):Schematic representation of WEDM cutting process
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