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Frontiers of Mechanical Engineering

ISSN 2095-0233

ISSN 2095-0241(Online)

CN 11-5984/TH

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Front. Mech. Eng.    2016, Vol. 11 Issue (4) : 374-387    https://doi.org/10.1007/s11465-016-0388-8
RESEARCH ARTICLE
Assessing the effects of different dielectrics on environmentally conscious powder-mixed EDM of difficult-to-machine material (WC-Co)
Jagdeep SINGH(),Rajiv Kumar SHARMA
Department of Mechanical Engineering, National Institute of Technology, Hamirpur, Himachal Pradesh-177005, India
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Abstract

Electrical discharge machining (EDM) is a well-known nontraditional manufacturing process to machine the difficult-to-machine (DTM) materials which have unique hardness properties. Researchers have successfully performed hybridization to improve this process by incorporating powders into the EDM process known as powder-mixed EDM process. This process drastically improves process efficiency by increasing material removal rate, micro-hardness, as well as reducing the tool wear rate and surface roughness. EDM also has some input parameters, including pulse-on time, dielectric levels and its type, current setting, flushing pressure, and so on, which have a significant effect on EDM performance. However, despite their positive influence, investigating the effects of these parameters on environmental conditions is necessary. Most studies demonstrate the use of kerosene oil as dielectric fluid. Nevertheless, in this work, the authors highlight the findings with respect to three different dielectric fluids, including kerosene oil, EDM oil, and distilled water using one-variable-at-a-time approach for machining as well as environmental aspects. The hazard and operability analysis is employed to identify the inherent safety factors associated with powder-mixed EDM of WC-Co.
Keywords WC      hazard and operability analysis (HAZOP)      discharging      aerosol concentration      dielectrics      powders     
Corresponding Author(s): Jagdeep SINGH   
Online First Date: 20 June 2016    Issue Date: 29 November 2016
 Cite this article:   
Jagdeep SINGH,Rajiv Kumar SHARMA. Assessing the effects of different dielectrics on environmentally conscious powder-mixed EDM of difficult-to-machine material (WC-Co)[J]. Front. Mech. Eng., 2016, 11(4): 374-387.
 URL:  
https://academic.hep.com.cn/fme/EN/10.1007/s11465-016-0388-8
https://academic.hep.com.cn/fme/EN/Y2016/V11/I4/374
Author and year Work done Remarks/gaps
EDM of tungsten carbide Lee and Li [16] The effects of machining parameters on machining characteristics in electrical discharge machining of tungsten carbide • In the literature, only Kung et al. [18] performed PM-EDM for WC-Co.
• According to Refs. [3,16], all the input parameters, such as current, pulse-on time, and flushing pressure have different effects on the EDM of WC-Co. All these parameters are contradictory in nature and require detailed investigation.
• Jahan et al. [19] concluded that PM-EDM is a well-established method to machine the DTM material, namely, WC-Co.
• Shayan et al. [20] performed the modeling and optimization of the dry WEDM process of WC-Co. According to authors, EDM is a potential electro-thermal process among non-traditional machining methods useful for machining, such as difficult-to-cut materials.
• Assarzadeh and Ghoreishi [21] concluded in their study that pulse-on time and current are extremely significant for the EDM of WC-Co.
Mahdavinejad and Mahdavinejad [3] EDM of WC-Co
Lin et al. [17] EDM characteristics associated with electrical discharge energy on machining of cemented tungsten carbide
Kung et al. [18] The material removal rate and electrode wear ratio on the powder mixed electrical discharge machining of cobalt-bonded tungsten carbide
Jahan et al. [19] Modeling and experimental investigation on the effects of nano powder-mixed dielectric in micro-electro discharge machining of tungsten carbide
Shayan et al. [20] Parametric study of the selection of optimal solutions in dry wire cut machining of cemented tungsten carbide (WC-Co)
Assarzadeh and Ghoreishi [21] Statistical modeling and optimization of process parameters in electro-discharge machining of cobalt-bonded tungsten carbide composite (WC/6%Co)
Green EDM Tan et al. [22] A decision-making framework model of cutting fluid selection for green manufacturing and a case study • In literature, no author has studied the green PM-EDM of DTM materials, especially WC-Co.
• According to Refs. [23,24], environmental factors, such as aerosol concentration and dielectric consumption, require immediate attention.
• Fard and Baseri [26] and Teimouri et al. [27] emphasized the thorough investigation of green machining methods to address high wastage and the production of toxic substances during manufacturing.
Jose et al. [23] Analysis of aerosol emission and hazard evaluation of the EDM process
Kellens et al. [24] Preliminary environmental assessment of electrical discharge machining
Sivapirakasam et al. [25] Multi-attribute decision making for green electrical discharge machining
Fard et al. [26] Experimental investigation, intelligent modeling and multi-characteristics optimization of dry WEDM process of Al-SiC metal matrix composite
Teimouri and Baseri [27] Experimental study of rotary magnetic field-assisted dry EDM with ultrasonic vibration of workpiece
Tab.1  Literature survey
Fig.1  Experimental setup and equipment details
Properties Details Tungsten carbide (workpiece)
Material Cobalt-bonded tungsten carbide

Chemical Composition W-65.50%, Ti-15.47%, Co-10.07%,
Nb-4.69% and Cu-3.66%
Size of the workpiece 90 mm × 60 mm × 10 mm
Density 15.1 g/cm3
Hardness 1800 HVN
Melting point 2597 °C
Tensile strength 179 kg/mm2
Compressive strength 410 kg/mm2
Toughness 50 kg/mm2
Tab.2  Properties and specifications of workpiece material
Properties Details Electrolytic copper (tool)
Material Electrolytic copper

Composition 99.9% copper
Density 8.914 g/cm3
Melting point 1083 °C
Electrical resistivity 9 µW·cm
Hardness HB 100
Diameter 17 mm
Tab.3  Properties and specifications of tool
Parameter Value
Grain size 55 µm
Density 2.25 g/cm3
Thermal conductivity 1.50 W/(m·K)
Electrical conductivity 3 × 10−3 µW−1·cm−1
Melting point 3652 °C
Specific heat 710 J/(kg·K)
Tab.4  Properties of used graphite powder
Medium Dielectric strength/(MV·m−1) Dynamic viscosity/(g·m−1·s−1) Thermal conductivity/(W·m−1·K−1)
EDM oil 45 2 to 5 0.954
Distilled water 13 0.92 0.606
Kerosene 14 to 22 1.64 0.149
Tab.5  Details of dielectric fluids used in the work
Level Pulse-on time/ms Dielectric level/mm Current/A Flushing pressure/(kg·cm−2)
Level-1 15 40 3 0.2
Level-2 50 60 6 0.4
Level-3 100 80 9 0.6
Tab.6  Selection of input processing parameters
Fig.2  Effect of input parameters and dielectrics on MRR. (a) Pulse-on time; (b) dielectric level; (c) current; (d) flushing pressure
Sl. No. Pulse-on time/µs Dielectric level/mm Current/A Flushing pressure/(kg·cm−2)
1 100 80 9 0.6
2 100 80 9 0.4
3 100 80 9 0.2
4 100 80 6 0.6
5 100 80 3 0.6
6 15 40 9 0.2
7 15 40 6 0.2
8 15 40 3 0.2
9 100 60 9 0.6
10 100 40 9 0.6
11 50 80 9 0.6
12 15 80 9 0.6
Tab.7  Experimental design to perform experimentation
Sl. No. MRR/(mm3·min−1) TWR/(mm3·min−1)
EDM oil Distilled water Kerosene oil EDM oil Distilled water Kerosene oil
1 8.136 7.832 6.981 1.326 1.509 1.664
2 7.541 7.215 6.743 1.449 1.648 1.743
3 6.739 6.425 6.324 1.548 1.695 1.885
4 6.433 6.214 6.118 0.474 0.672 0.824
5 5.332 4.988 4.860 0.329 0.582 0.678
6 2.689 3.139 1.774 0.485 0.594 0.694
7 2.311 3.554 1.569 0.882 1.042 1.443
8 1.482 1.993 1.238 1.136 1.436 1.589
9 9.119 8.746 8.723 1.267 1.438 1.664
10 8.671 8.263 7.506 1.944 2.121 2.267
11 6.754 6.248 6.532 0.887 0.940 1.266
12 5.136 4.532 3.883 0.694 0.780 1.184
Tab.8  Experimental results for the machining factors
Sl. No. PM-EDM with EDM oil PM-EDM with distilled water PM-EDM with kerosene oil
Aerosol concentration/(mg·m−3) Dielectric consumption/cm3 Aerosol concentration/(mg·m−3) Dielectric consumption/cm3 Aerosol concentration/(mg·m−3) Dielectric consumption/cm3
1 5.641 0. 404 4.650 0.398 5.924 0.414
2 5.822 0.519 5.151 0.506 6.026 0.536
3 6.688 0.612 5.442 0.581 6.981 0.621
4 4.263 0.244 3.780 0.230 4.542 0.262
5 3.329 0.149 2.756 0.128 3.728 0.158
6 1.024 0.270 0.783 0.256 1.126 0.276
7 0.986 0.184 0.591 0.172 1.082 0.192
8 0.862 0.272 0.801 0.256 0.982 0.290
9 2.470 0.388 2.144 0.363 2.668 0.396
10 1.423 0.392 1.228 0.384 1.603 0.404
11 2.303 0.271 2.040 0.269 2.480 0.283
12 1.296 0.220 0.988 0.205 1.497 0.227
Tab.9  Experimental results for the environmental factors
Fig.3  Effect of input parameters and dielectrics on TWR. (a) Pulse-on time; (b) dielectric level; (c) current; (d) flushing pressure
Fig.4  Effect of input parameters on the aerosol concentration. (a) Pulse-on time; (b) dielectric level; (c) current; (d) flushing pressure
Fig.5  Effect of input parameters on the dielectric level. (a) Pulse-on time; (b) dielectric level; (c) current; (d) flushing pressure
Fig.6  HAZOP performing procedure for each selection
Fig.7  HAZOP worksheet for the green-PM-EDM of WC-Co. (a) Effect of input parameters and dielectrics on the material removal rate; (b) effect of input parameters on the tool wear rate; (c) effect of input parameters on the aerosol concentration; (d) effect of input parameters on the dielectric consumption; (e) operator and environmental conditions
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