Insights into process innovation through ultrasonically agitated concentric flow dielectric streams for dry wire electric discharge machining

1. MATERIALS AND MANUFACTURING PROCESSES
https://doi.org/10.1080/10426914.2017.1415442
Insights into process innovation through ultrasonically agitated concentric
flow dielectric streams for dry wire electric discharge machining
Bharat C. Khatria
, Pravin P. Rathodb
, Janak B. Valakic
, and C. D. Sankhavarad
a
Mechanical Engineering Department, L. D. College of Engineering, Ahmedabad, Gujarat, India; b
Mechanical Engineering Department,
Government Engineering College, Bhuj, Kutch, Gujarat, India; c
Mechanical Engineering Department, Government Engineering College,
Bhavnagar, Gujarat, India; d
Mechanical Engineering Department, School of Engineering, RK University, Rajkot, Gujarat, India
ABSTRACT
Application of gaseous dielectric in place of liquid dielectric for wire electric discharge machining
(WEDM), popularly known as dry wire electric discharge machining (DWEDM), offers technological
solutions to some environmental and metallurgical issues pertaining to process. However, conventional
side jet stream of dielectric in dry WEDM renders ineffective debris removal from sparking gap to cause
unwanted arcing. Moreover, side thrust on the wire surface tends to induce wire vibrations and results
into uneven geometrical profiles. To harness full potential of DWEDM technology, it is imperative to
improve cutting characteristics of process by minimizing the adverse impacts of side jet stream of
dielectric. In this research work, the authors have conceptualized and demonstrated the idea of using
concentric flow pattern of gaseous dielectric as a novel technological solution to limitations of DWEDM
process by introducing ultrasonic-agitated concentric dry wire electric discharge machining (UCDWEDM).
Experiments have been performed on Ti–6Al–4V material. Ultrasonically agitated pressurized air streams
were supplied through indigenously developed concentric and side flow nozzles mounted on
experimental set up. The experimental results showed that concentric flow mode of dielectric supply
has outperformed the conventional side flow mode with 42% higher CV, 22% lower SR, and 8% lesser KW.
Process mechanism of UCDWEDM is based on high velocity of air in concentric flow and ultrasonic-
agitation in spark gap and suggested that UCDWEDM has potential to replace conventional dielectric
supply system in DWEDM.
ARTICLE HISTORY
Received 4 February 2017
Accepted 14 November 2017
KEYWORDS
Concentric; dielectric; dry;
flow; side; Ultrasonic; WEDM
Introduction
Wire electric discharge machining (WEDM) is a highly
popular variant of spark erosion process. The process utilizes
series of high frequency discrete electrical discharges
applied between workpiece and thin wire, which facilitates
dielectric breakdown in the sparking gap, hence results in
8000–12,000 K temperature in that zone. The high tempera-
ture generated favor localized melting then vaporization of
both material. Since its introduction in 1960s, WEDM process
satisfied demand in precision machining industries for making
variety of components economically and at faster production
rate.[1–3]
Deionized water is generally used as dielectric fluid for
WEDM process. However, hazardous emissions and toxic
fumes, such as CO, N2O, O3, and aerosols are produced
due to decomposition of water, which are injurious to
operator health. Moreover, recycle, reuse, nonbiodegradabil-
ity of debris mixed contaminated deionized water is a serious
concern pertaining to environmental impact.[4]
Dielectric
liquids contribute to 23.1% in total environmental impact
of WEDM process.[5]
In addition, there is a chance of
bacteria growth in dielectric water tank, which tend to cause
bacterial hazard.
Dry wire electric discharge machining (DWEDM) is a
green and environment friendly technology variant of WEDM,
wherein, liquid dielectric is replaces by gaseous medium with a
view to minimize the severity of the generation of hazardous
gas and waste from the dielectric liquid. DWEDM was first
practiced in 2000 by Furudate and Kunieda[6]
and the
fundamental characteristics of process for finish cutting were
investigated using pressurized air instead of deionized water
or hydrocarbon oil. DWEDM produced significantly better
accuracy, narrower gap length, and straight finished surface,
due to lesser vibration, and deflection of the wire because
of negligible process reaction forces compared to forces in
conventional WEDM.[7]
However, DWEDM produce poor material removal rate
(mm3
/min) (MRR) compare to conventional WEDM because
of frequent short circuits due to poor exclusion of debris from
spark gap.[8]
Ineffective debris evacuation from the gap and
wire vibration due to impact of high velocity side jet, wire
breakage occurred, and resulted in low material removal rate
and poor shape accuracy.[9]
For the prevention of debris
stagnation and smooth exclusion of debris, high discharge rate
from the nozzles was used but it may cause breakage of
wire.[10,11]
In addition, unsteady flow field by side flow jet of
none defined
CONTACT Bharat C. Khatri khatribharat752@yahoo.com Mechanical Engineering Department, L. D. College of Engineering, Ahmedabad,
Gujarat 380016, India.
Color versions of one or more of the figures in the article can be found online at www.tandfonline.com/lmmp.
© 2017 Taylor & Francis
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