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

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Proceedings of the National Conference on
Trends and Advances in Mechanical Engineering,
YMCA University of Science & Technology, Faridabad, Haryana, Oct 19-20, 2012
MACHINING CHARACTERISTICS OF BOROSILLICATE GLASS
USING TRAVELLING WIRE ELECTRO-CHEMICAL SPARK
MACHINING (TW-ESCM) PROCESS
Basanta Kumar Bhuyan 1 , Vinod Yadava 2
Mechanical Engineering Department, Motilal Nehru National Institute of Technology, Allahabad, India
E-mail: bkbhuyan@mnnit.ac.in
2 Mechanical Engineering Department, Motilal Nehru National Institute of Technology, Allahabad, India
E-mail: vinody@mnnit.ac.in
Abstract
Machining of borosilicate glass is a challenging task for manufacturing engineers from the quality and accuracy
point of view. Traveling Wire Electro-Chemical Spark Machining (TW-ECSM) is an emerging technique in the
field of non-conventional machining to machine electrically non-conductive materials. It is a hybrid process
which combines features of Electro Chemical Machining (ECM) and Wire Electro Discharge Machining
(WEDM). An experimental setup has been developed and employed for machining of borosilicate glass which
was used as workpiece. In the present paper only the machining characteristics of non-conductive material is
reported. Experiments were also conducted to analysis the effects of supply voltage, pulse on-time and
electrolyte concentration on the material removal rate (MRR) and surface roughness (R a ). Material removal
rate and surface roughness are found to increase with increase in supply voltage and pulse on-time. But
MRR and R a increase with increase in electrolyte concentration at certain value (20%), beyond that value it
decreases.
Keywords : TW-ECSM, Borosilicate Glass, MRR and R a
1. INTRODUCTION
At the present time, borosilicate glass is gaining increasing importance in precision engineering application
owing to its high strength to weight ratio, heat resisting capacity and high corrosion resistance. The main limiting
factor for growing usage of this material is its limited structuring possibility. Chemical etching technologies are
well established, though this process remains very slow and expensive for many industrial applications. Other
processes like ultrasonic machining, abrasive jet machining, laser beam machining and electron beam machining
are some of the advanced machining processes that can be used for machining these materials, but dimensional
accuracy and good surface quality of the machined surfaces are the major concern. ECM and WEDM are also
being used for electrically conductive materials and failed to machine non-conductive materials. A possible
answer to machine this material with good surface quality is Traveling Wire Electro-Chemical Spark Machining
(TW-ECSM). It is a new and potential process developed to machine non-conductive materials like glass,
ceramic and composite etc. In this process also sparks are generated across the hydrogen bubbles evolved at
cathode. Thermal energy of spark is utilized for cutting non-conducting materials such as glasses and ceramics
[1]. TW-ECSM principle is based on electro-chemical spark machining (ECSM) process.
Electro-chemical spark machining (ECSM) which combines the features of electro chemical machining and
electro discharge machining, has stemmed from its ability to remove metal at high rates, as much as five and fifty
times faster than ECM and EDM, respectively under the same parameter setting. A simple electro chemical cell
consists of two electrodes dipped in the electrolyte. When an external potential is applied between the electrodes,
electric current flows through the cell resulting in electrochemical reactions such as anodic dissolution, cathode
deposition and electrolysis. This is known as Electro-Chemical Discharge (ECD) phenomenon. The electrochemical
spark machining process uses ECD phenomenon for generating heat for the purpose of removing work
material by melting and vaporization. This was presented for the first time in 1968 by Kurafuji as
“Electrochemical Discharge Drilling” for microholes in glass [2]. Several other names of ECSM are used in
literature by different researchers, such as Electro chemical arc machining (ECAM), Electro chemical discharge
machining (ECDM) and Spark assisted chemical engraving (SACE) [3]. The diversity of name illustrates the
complexity of the process. Various researchers have put forth explanations of ECD phenomenon based on their
experimental studies.
Bhattacharya et al. [4] conducted experiments on alumina and concluded that the most effective parametric
combination for moderately higher machining rate and dimensional accuracy are 80Vand 25% NaOH
concentration. Tool tip geometry was also found to play an important role in a controlled spark generation in
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