current research trend in wire edm: an overvie · current research trend in wire edm: an overview...

Current Research Trend in Wire EDM: An Overview

Abstract: Wire electric discharge machining is a non-conventional metal removal process as well as one of the best manufacturing processes available for hard material for producing jigs, fixtures and dies. This paper projects the main research areas of WEDM machine. Whenever there is a need of high precision in dimensions WEDM is used. WEDM is influenced by many variables, the effect of different variables on MRR, cutting speed (CS) and surface roughness (SR) is presented in this paper. The present paper also projects the major current research areas in field of WEDM and the application area of WEDM.

Key Words: Surface roughness (SR), Wire electro discharge machining (WEDM),Material removal rate (MRR),Cutting speed (CS).

Chanchala,P.G Student

Mechanical Engineering Department,YMCAUST, Faridabad 121006

Email: [email protected]

Navdeep Malhotra,Professor,

Mechanical EngineeringDepartment, YMCAUST, Faridabad 121006Email:[email protected]

1. INTRODUCTION

The rapid developments in the field of materials have given an impetus to the non-conventional manufacturing (NCM) technology to develop, modify and discover newer technological processes with the view to achieve results that are far beyond the scope of conventional manufacturing processes. Needs of future manufacturing technology is sustained productivity in face of rising strength barrier, Higher accuracy consistent with the increasing demand for better tolerances, versatility of automation. Advanced material have attractive properties i.e. high strength, high bending stiffness, good damping capacity, low thermal expansion, better fatigue characteristics which make them more reliable for defence, aero-space and nuclear industry. It is difficult to machine the advanced material. It has become a challenge to manufacturing engineers to develop new processes and tool materials that are necessary for meeting the desire higher metal removal rate, better surface finish and greater dimensional accuracy, with less tool wear [1].

The conventional machining processes normally involve the use of energy from electric motors, hydraulics, gravity, etc and rely on the direct physical contact between tools and work piece. On the contrary, NCM processes utilize energy such as that from electromagnetic force, electrochemical reactions, high temperature plasma, high velocity jets and loose abrasives mixed in various carriers etc. According to the type of energy used to remove material NCM processes are classified. The various forms of energy have been identified to classify these processes, such as mechanical, thermal, electrochemical and chemical. Based upon these types of energy, a large number of NCM processes have been developed in the past.

Wire-electrical-discharge machining (WEDM) is one of the modification of electro-discharge machining (EDM) and has been widely used for cutting punches, dies, shaped pockets and other machine parts on conductive materials. WEDM erodes work piece materials by a series of discrete electrical sparks between the work piece and dielectric performs the flushing

action The WEDM process is particularly suitable for machining hard materials as well as complex shapes.

2. HISTORICAL BACKGROUND

Year Development made

1943 Boris and Natalya Lazarenko invention of EDM principle and developed the first EDM machines

1950 industries produced the first EDM machines but performances of the machines were limited at this time due to the poor quality of Electronic components.

1960 wire-cutting machines were at their very beginning

1970 Computer numerical control (CNC) system was initiated into WEDM that brought a major evolution of the machining process

1974 D.H. Dulebohn applied the optical line follower system to automatically control the shape of the component to be machined by the WEDM process1980Applications in micro-machining

1990 EDM process control arose by using fuzzy control, neural networks response surface methodology, Taguchi optimization etc.

3. PRINCIPLE OF WIRE ELECTRICAL DISCHARGE MACHINING

The Spark Theory on a wire EDM is basically the same as that of the vertical EDM process. In wire EDM, the conductive materials are machined with a series of electrical discharges (sparks) that are produced between an accurately positioned moving wire (the electrode) and the work piece. High frequency pulses of alternating or direct current are discharged from the wire to the work piece with a very small spark gap through an

July 2013 Vol.1(II)YMCAUST International Journal of Research ISSN: 2319-9377

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insulated dielectric fluid. Fluid is continuously flowing in the machining zone.

Many sparks can be observed at one time. This is because actual discharges can occur more than one hundred thousand times per second with discharge sparks lasting in the range of 1/1,000,000 of a second or less. A plasma channel exist between cathode and anode due to supplied electric current, that get finally converted into thermal energy of range 80,000- 12,000°C [3] that melt the metal. The volume of metal removed during this short period of spark discharge depends on the desired cutting speed and the surface finish required.

The heat of each electrical spark, estimated at around 15,000° to 21,000° Fahrenheit, erodes away a tiny bit of material that is vaporized and melted from the work piece. (Some of the wire material is also eroded away) These particles (chips) are flushed away from the cut with a stream of de-ionized water through the top and bottom flushing nozzles. The flushing process occurs as pulsating DC power supply occurring between 20,000 and 30,000Hz [4] is turn-off, then plasma channel break down. Due to this sudden break down temperature reduction occurring between the work piece and electrode allows circulating dielectric fluid to enter the zone and flush the removed particles from the machining zone in the form of small debris. From the machine zone ejected material is flushed away whereas portion of molten material resolidify on to the work surface which is termed as recast layer. The dielectric used also prevents heat build-up in the work piece. Without this cooling, thermal expansion of the part would affect size and positional accuracy. Keep in mind that it is the ON and OFF time of the spark that is repeated over and over that removes material, not just the flow of electric current. In WEDM deionised water is used as dielectric but in conventional EDM process it cannot be used because of its low viscosity and faster cooling rate.

4. FACTORS EFFECTING PERFORMANCE MEASURE OF WEDM

Fig 1.1: Factors Effecting PerformanceMeasure of WEDM

4.1 EFFECT OF ELECTRICAL PARAMETERS

1. Pulse on time - During this time the voltage, VP, is applied across the electrodes.

2. Pulse-off time - The voltage is absent during this part of the cycle.

3. Peak current - The peak current is represented by IP and it is the maximum value of the current passing through the electrodes for the given pulse.

4. Spark gap set voltage -The spark gap set voltage is a reference voltage for the actual gap between the work piece and the wire used for cutting.

5. Servo feed - Servo feed setting decides the servo speed; the servo speed, at the set value of SF, can vary in proportion with the gap voltage (normal feed mode) or can be held constant while machining (with constant feed mode).

Table 2: Effect of Electrical Parameters

S. NO

1

2

3

4

5

Electrical Parameters

Pulse on time

Pulse off time

Peak current

Servo feed

Spark gap set voltage

Effect on cutting speed

Increases with increase in peak on time

Increases with decreases in pulse off time

Increases with increase in peak current

Decreases with increases in servo feed

No variation is recorded with increase in spark gap set voltage

4 . 2 E F F E C T O F N O N E L E C T R I C A L PARAMETERS

1. Wire feed - Wire feed is the rate at which the wire-electrode travels along the wire guide path and is fed continuously for sparking.

2. Wire tension - Wire tension determines how much the wire is to be stretched between upper and lower wire guides.

Table 3: Effect of Non Electrical Parameters

S. NO

1

2


Wire feed

Wire tension


No variation with increases in wire feed

No variation with increase in wire tension


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4.3 EFFECT OF WORK PIECE RELATED PARAMETERS

1. Height – Height of work piece show the thickness of work piece.

2. Material – Material properties like its melting point, electrical properties, magnetic condition of material is considered under material properties.

Table 4: Effect of Work Piece Related Parameters

4.4 EFFECT OF ELECTROD PROPERTIES

1. Wire tension – The wire tension force between the two wire guides present on WEDM machine.

2. Wire size – The wire diameter show the wire size used.

3. Wire feed – Feed of wire shows the speed with which wire is supplied for cutting operation.

4. Wire material – The wire composition is considered in wire material.

Table 5: Effect of the Electrode

S. NO

1

2

3

4


Wire tension

Wire size

Wire feed

Wire material


With increase in wire tension cutting speed increases

Not much variation is observed

With increase in feed not much variation in speed

On greater the wire tension a wire can work higher the cutting speed

5. Advantages of Wire EDM

Here is the list of advantages of WEDM. [6]

• No electrode fabrication required

• No cutting forces

• Unmanned machining

Fig 1.2: Major Research Areas of WEDM

Some of the research work done by various authors is studied and listed below along with the techniques and material used in table 6.


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Parameters

• Die cost reduced by 30-70%

• Cuts hardened material

• Intricate shapes can be cut with ease

6. MAJOR AREAS OF WEDM RESEARCH

OPTIMIZATIONOF PROCESSVARIABLE

MONITORING &CONTROL THE

PROCESS

IMPROVING PERFORM-ANCE MEASURE

WEDMDEVELOP-MENT

ProcessParameter

Design

ProcessModelling

Pulse Duration,

Discharge Current

Intensity, Discharge

Frequency Etc.

FUZZYCONTOL

FUZZY LOGIC, WIRE

BREAKAGE, SELF

TURNING ADAPTIVE

CONTROL

UltrasonicvibrationAssisted,

WECT, WECG,WEDG

Research work done by the various authors in the area of wire EDM some of the authors had done in the field of optimization of process variables and some are worked on monitoring and control of the process of wire EDM. Many of the authors also completed their research work on the performance measures to improve the performance of the process. A few of the authors also did their research work in the field of development of wire EDM to enhance its applications to meet the industrial requirements. Figure 1.2 shows the major research are of wire EDM.

Table 6: List of Experiment Down on WEDM

YEAR

Authors MATERIAL USED

TECHNIQUE USED

OUTPUT PARAMETE-RS STUDY

2012 S.Y. Martowibowo, A. Wahyudi [7]

ASSAB 760

Taguchi L18 MRR,SR

2012 S Sivakiran, et. al. [8]

En31 Taguchi L16 MRR,

2011 Ignacio Puertas Carmelo J. Luis [9]

WC-CO, B4C,SiC

Multiple linear regression

SR, MRR,EWR

2011 D.V Ghewade, S.R Niparka [10]

Inconel 718

Taguchi MRR, EWR,ROC

2011 Chao-LiehYang [11]

Glass fiber Taguchi and grey relation analysis

Cutting speed, cutting load

2010 N.G.Patil Brahmankar [12]

Reinforced aluminium matrix composite

Taguchi Cutting speed,SR, kerf width

2010 M. N. Islam,et. al. [13]

Mild steel 1040

Taguchi and pareto ANOVA

Study three different accuracy characteristics

2010 Kapoor, S. Singh and J. S. Khamba [14]

---- ---- MRR, SR

2009 M.G. Xua.,et. al., [15]

Cemented carbide material

---- Analyzing microstructure of machined surface

2009 Jin Yuan, Kesheng Wang [16]

High speed steel

Regression model

MRR, SR

2009 Susanta Kumar Gauri ,Shankar Chakrabort [17]

High speed steel

Taguchi and weighted principle component processes (WPC)

Comparison of methods

2009 H. Siddhi Jailani, et. al. [18]

Al-Si (12%)alloy/fly ash composite

Taguchi L , 9

grey relational analysis

Sintering parameters

2009 A. Noorul Haq,et. al. [19]

Co casting 2

component Taguchi Casting

defects

2009 Esme.U, et.al. [20]

Neural Networks

SR

2008 Aminollah Mohmmadi [21]

Taguchi L18 MRR

2008 Aminollah Mohmmadi [21]

Taguchi L18 MRR

2008 R. Ramakrishnan, L.Karunamoorthy [22]

Inconel 781

Taguchi L9 MRR

2008 Aminollah Mohammadi, et. al. [23]

Taguchi L18 SR, TWEDM

2008 Gauri, S. K.Chakraborty [24]

Process Applied Weighted Principal Component

Multi-Response Optimization

2007 S.Sarkar, et. al. [25]

Gamma – titanium aluminide

RMS SR, dimensional shift, cutting speed

2007 Kanlayasiri K. and S.Boonmung [26]

Dc53 ANOVA technique

SR

2006 Aminollah Mohammadi, et.al. [27]

Taguchi L18 SR

2006 S.S. Mahapatra, Amar Patnaik [28]

Taguchi L27 MRR,surface finish and cutting width for a rough cut


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2006 A.Manna B.Bhattacharyya [29]

Pt-Al-SiC MMC

Taguchi L18

Gauss elimination mathod

Compariso-n

2006 R. Ramakrishnan, L. Karunamoorthy [30]

Taguchi L16 MRR,SR,Wire wear ratio

2006 A.Manna, B. Bhattacharya [31]

Al/SiC MMC

Taguchi 18

Gauss elimination method

MRR, SR

2006 Hari Singh, Pradeep Kumar[32]

En24 Taguchi MRR, SR

2005 Sarkar, S. et al [33]

γ-titanium aluminide alloy

Mthematical model

Parametric analysis

2005 Hewidey, et.al. [34]

Inconel 601

Mathematical model

Modeling the Machining Parameters

2005 Kuriakose, S. Shunmugam [35]

Genetic algorithm,

Multi objective optimization

2004 K.H.Ho, et. al. [36]

Taguchi L27 Cutting speed , SR, geometricalInaccuracy due to wire lag

7. CONCLUSION

Based on the study carried, it has been observed that process

parameters viz, voltage, current and pulse related parameters

(viz. pulse on time, pulse off time) are the most important

parameters in WEDM. They are affecting the output parameters

viz., MRR, surface roughness, etc. The depth of crater,

temperature generated and the resultant surfaces obtained are

result of pulse energy applied. Study also reveals that which

parameter is actually affecting the cutting speed. This paper also

show the various advancement made in the field of WEDM

research.

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Biographical of Author(s)

CHANCHALA received B.E. from Jabulpur Engineering College,Jabalpur, M.P India in 2010 and P..G (Manufacturing Technology and automation) from YMCAUST, Faridabad, Haryana India in 2013.

Navdeep Malhotra has obtained his B.E (Production Engineering) Degree from NMU, Jalgaon in 1996, PGdMM from NMU in 1998, M.P.M. from NMU in 1999, PGdPE (Plastics Engineering) from CIPET Mysore, India in 2000, M.E (Industrial Engineering) from Thapar University (TIET) 2002, Patiala, India

and Ph.D, from NIT, Kurukshetra, Haryana, India 2011. The major field of interest is Plastics Engineering, Advanced Manufacturing Processes, Optimization, Composites, Fibre Reinforced Plastics and Engineering Graphics. He worked as faculty incharge Central workshop, Shri Mata Vaishno Devi University, katra (J&K)

He has more than 15 years of Teaching Experience. Presently he is working as Professor in Mech. Engg. Department of YMCA university of Science & Technology.

Dr. Malhotra is life member of various technical societies like SME, ISTE, IE, FRPI, ISAMPE, MRIS. He also organized various International and National Conferences. He has published more than 30 papers in Journals and conferences.


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current research trend in wire edm: an overvie · current research trend in wire edm: an overview...

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