DEVELOPMENT AND EXPERIMENTAL INVESTIGATIONS INTO ELECTRIC DISCHARGE MACHINING USING RAPIDLY
MANUFACTURED COMPLEX SHAPE ELECTRODE WITH COOLING CHANNEL
JAGTAR SINGH
DEPARTMENT OF MECHANICAL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2020
©Indian Institute of Technology Delhi (IITD), New Delhi, 2020
DEVELOPMENT AND EXPERIMENTAL INVESTIGATIONS INTO ELECTRIC DISCHARGE MACHINING USING RAPIDLY
MANUFACTURED COMPLEX SHAPE ELECTRODE WITH COOLING CHANNEL
by
JAGTAR SINGH
DEPARTMENT OF MECHANICAL ENGINEERING Submitted
in fulfilment of the requirements of the degree of Doctor of Philosophy to the
INDIAN INSTITUTE OF TECHNOLOGY DELHI
OCTOBER 2020
DEDICATED TO
almighty
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Certificate
This is to certify that the thesis entitled ‘Development and Experimental Investigations into Electric Discharge Machining using Rapidly Manufactured Complex Shape Electrodes with Cooling Channel’ submitted by Mr. Jagtar Singh to the Indian Institute of Technology Delhi, for the award of the degree of Doctor of Philosophy is a record of the original bonafide research work carried out by him under my guidance and supervision. The results contained in it have not been submitted in part or full to any other institute or university for the award of any degree/diploma.
(Dr. Pulak Mohan Pandey)
Professor Department of Mechanical Engineering
Indian Institute of Technology Delhi
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Acknowledgements
This thesis symbolizes an important milestone in the journey of my life. I express my deep sense of gratitude and sincere thanks to my thesis supervisor Prof. Pulak M. Pandey. His excellent guidance, constant encouragement and optimistic outlook have been a source of motivation for me throughout this work. His knowledge of the subject and wealth of experience steered me to complete the work. My last three years of interaction with him has been a great learning experience. I am immensely benefited by his devotion for the research, his ability to see things that are not obvious and their perseverance to pursue creative leads in research. Besides being a source of immense knowledge and experience, Prof. Pulak M.
Pandey is very kind and caring with great compassion and love for the students. I will forever cherish my close association with him.
I express my deep sense of gratitude to Prof. P. V. Rao, Prof. Sudarshan Ghosh, Prof. Jyoti Kumar, for being part of my student research committee and thankful for their constructive criticism and valuable guidance during the course of presentations. I am thankful to lab staff members Mr. Tulsiram, Mr. Ayodhya Prasad, Mr. Jitendra Prasad, Mr.
Ramchandar and Mr. Subash Chand for providing me essential aids to complete experimentation work for the thesis.
I am also thankful to the office staff members Mr. Kishan Kumar and Mr. Pratap Singh Negi for their support in the day to day activities. I am thankful to my friends and research scholars at IITD Dr. Gurminder Singh, Dr. P. K. Jain, Dr. Jatinder Pal Singh, Dr.
Vineet Srivastava, Dr. Varun Sharma, Dr. Vishal Gupta, Dr. Girish Chandra Verma, Dr.
Pawan Sharma, Dr. Hardikkumar S Beravala, Dr. Vipin C. Shukla, Dr. Kheelraj Pandey, Dr. Harsha Goel, Mr. Dayanidhi K. Pathak, Mr. Ravinder Pal Singh, Mr. Jasvinder Singh, Mr. Ajit Kumar, Mrs. Usha Rani, Mr. Dipesh Mishra, Mr. Rudranarayan Kandi, Mr.
Mayank Srivastava, Mr. Abhishek Pandey, Dr. Dilpreet Singh, Mr. Tanuj Joshi, Mr. Gaurav
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Tripathi, Mr. Shitanshu Arya, Mrs. Garima Dixit, and co-research scholars/ friends at IIT Delhi who were always there to lend a helping hand when it mattered most and for the camaraderie that took away all the pressures and made research work more enjoyable.
I am indebted to my parents, Mrs. Joginder Kaur & Mr Ajmer Singh for their blessings, motivation and constant support throughout this period. I am gratified, with the love & support of my wife Mrs. Manpreet Kaur for her inspiration, cooperation & taking care of family. Virtuous activities of my twins made me joyful and stress free. I am thankful to everyone who helped me directly or indirectly to complete this work. I am also grateful to Almighty, for having blessed me to rise and take up this challenge.
(Jagtar Singh)
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Abstract
Rapid manufacturing techniques permit tools and die to be fabricated in a short duration of time with complex geometry. The significant contribution of the present research was to fabricate copper complex geometry electric discharge machining (EDM) electrode by using an amalgamation of 3D printing along with pressure-less loose sintering. Response surface methodology was employed to study the effect of sintering parameters (sintering temperature, heating rate and soaking time) effect on EDM electrodes essential characteristics such as density, shrinkage and electrical conductivity. ANOVA was used to investigate the significant contribution of the parameters on the responses. Density and electrical conductivity of fabricated EDM electrode was revealed to increase with respect to the rise in soaking time and sintering temperature. The interaction between the heating rate and sintering temperature for density and electrical conductivity responses signified the lesser effect of the heating rate at high temperatures. Further, multi-objective optimization was used to maximize density and electrical conductivity and to minimize volumetric shrinkage. Different shapes of EDM electrodes were fabricated at optimized parameters. In addition, the fabricated electrodes were tested on EDM of D2 steel for 5 mm depth. The dimensional analysis was carried out between the CAD model, fabricated EDM electrode and obtained cavity by EDM process. The results depicted the high efficacy of the process to fabricate complex geometry EDM electrodes.
An investigation on the machining outcome of electric discharge machining (EDM) using a rapid manufactured complex shape copper electrode was carried out. Developed rapid manufacturing technique using an amalgamation of polymer 3D printing and pressure- less sintering of loose powder as rapid tooling have been used to fabricate copper electrode from the CAD model of the desired shape. The fabricated electrode was used for the EDM of the D-2 steel workpiece. Central composite design (CCD) was employed to study the
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EDM parameters (pulse duration, duty cycle and peak current) effect on the EDM characteristics such as material removal rate (MRR), electrode wear rate (EWR) and cavity dimensional deviation (DD) as overcut from electrode CAD model. ANOVA was executed to attain significant parameters along with interactions. Peak current was found to be the utmost dominating parameter for three responses. The high percentage of carbon was observed on the electrode surface after EDM at the high level of pulse duration and resulted in low EWR. The high percentage of DD was noticed at the maximum duty cycle and maximum peak current by the substantial interactions. Genetic algorithm-based multi- objective optimization was employed for the EDM parameters optimization to maximize MRR, minimize EWR, and DD. The multi-feature complex copper electrode was fabricated and used for EDM as the case study to check the efficacy of the optimized process. It was witnessed that the process was capable of fabricating complex shape cavity as per the desired CAD model shape with efficient MRR and EWR.
Moreover, a rapid manufacturing process based on the combination of polymer 3D printing and pressure-less loose sintering was explored for the fabrication of complex shape electric discharge machining (EDM) copper electrodes with the cryogenic cooling channel. The fabricated electrodes were used to EDM D-2 steel workpiece. The comparative study was performed on material removal and electrode wear rates between the solid copper electrode, rapid manufactured electrode without cryogenic cooling (RME) and with cryogenic cooling (RMECC). Also, the surface characteristics of the worn electrode and the machined workpiece were studied with and without cryogenic cooling. The significant effect of the cryogenic cooling on the electrode wear rate and the surface roughness was observed. Better surface finish, small cracks and less debris were notified on the workpiece surface machined with RMECC due to rapid dissipation of the heat from the surface of the electrode after machining. Similarly, few cracks and low carbon deposition was observed on the RMECC
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surface after machining as compared to RME. The sharp corner edges of the complex shape tool in RMECC was retained after machining due to low melting and vaporization of the electrode material. The dimensional deviation of the machined surface with respect to computer-aided design (CAD) model design was compared. The RMECC was found to machine the more accurate complex shape features in terms of dimensions on the workpiece as compared to RME.
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सार
रैपिड प्रोटोटीपििंग तकनीक उपकरणों की अनुमतत देती है और जटिल ज्यातमतत के साथ कम समय में गढी
जाती है। वततमान अनुसंधान का महत्वपूणत योगदान दबाव-कम ढीले तसन्िररंग के साथ 3 डी प्रंरिंग के
एक समामेलन का उपयोग करके तांबे के जटिल ज्यातमतत तवद्युत तनवतहन मशीप्नंग (ईडीएम) इलेक्ट्रोड का तनमातण करना था। रततक्रिया की सतह कायतरणाली को ईडीएम इलेक्ट्रोड पर तसन्िररंग मापदंडों
(प्संिररंग तापमान, हीरिंग दर और तिगोने के समय) के रिाव का अध्ययन करने के तलए तनयोतजत क्रकया
गया था, जैसे घनत्व, संकोचन और तवद्युत चालकता जैसी आवश्यक तवशेषताओं का इलेक्ट्रोड। एनोवा
का उपयोग रततक्रियाओं पर मापदंडों के महत्वपूणत योगदान की जांच करने के तलए क्रकया गया था। हीटटिंग रेट और प िंटटरिंग टेम्िरेचर में वृति के संबंध में तनर्मतत ईडीएम इलेक्ट्रोड की घनत्व और तवद्युत चालकता
का पता चला था। घनत्व और तवद्युत चालकता रततक्रियाओं के तलए हीरिंग दर और प िंटटरिंग तापमान के
बीच बातचीत ने उच्च तापमान पर हीरिंग दर के कम रिाव को दशातया। इसके अलावा, बहु-उद्देश्य अनुकूलन का उपयोग घनत्व और तवद्युत चालकता को अतधकतम करने और वॉल्यूमेटरक संकोचन को कम करने के तलए क्रकया गया था। ईडीएम इलेक्ट्रोड के तवतिन्न आकार अनुकूतलत मापदंडों पर गढे गए थे।
इसके अलावा, 5 तममी की गहराई के तलए डी 2 स्िील के ईडीएम पर गढे गए इलेक्ट्रोड का परीक्षण क्रकया
गया था। आयामी तवश्लेषण सीएडी मॉडल के बीच क्रकया गया था, ईडीएम इलेक्ट्रोड गढा और ईडीएम रक्रिया द्वारा गुहा राप्त की। पटरणामों ने जटिल ज्यातमतत ईडीएम इलेक्ट्रोड बनाने की रक्रिया की उच्च रिावकाटरता को दशातया।
तेजी से तनर्मतत जटिल आकार के तांबे के इलेक्ट्रोड का उपयोग करके इलेतक्ट्रक तडस्चाजत मशीप्नंग (ईडीएम) के मशीप्नंग पटरणाम पर एक जांच की गई। बहुलक 3 डी प्रंरिंग और दबाव के एक समामेलन का उपयोग करके तेजी से तनमातण तकनीक तवकतसत की गई है - वांतित उपकरण के सीएडी मॉडल से
तांबा इलेक्ट्रोड बनाने के तलए रैतपड िूप्लंग के रूप में ढीले पाउडर की कम तसन्िररंग का उपयोग क्रकया
गया है। डी -2 स्िील वकतपीस के ईडीएम के तलए गढे गए इलेक्ट्रोड का उपयोग क्रकया गया था। केंद्रीय समग्र तडजाइन (सीसीडी) का अध्ययन करने के तलए तनयोतजत क्रकया गया था EDM मापदंडों (पल्स अवतध, कततव्य चि और तशखर वततमान) EDM तवशेषताओं पर रिाव जैसे सामग्री हिाने की दर (MRR), इलेक्ट्रोड पियर रेट (EWR) और इलेक्ट्रोड CAD मॉडल से ओवरकि के रूप में गुहा आयामी तवचलन (DD)। बातचीत के साथ महत्वपूणत मापदंडों को राप्त करने के तलए एनोवा को क्रियातन्वत क्रकया गया था।
पीक करेंि को तीन रततक्रियाओं के तलए सबसे अतधक वचतस्व वाला पैरामीिर पाया गया। EDM के बाद पल्स अवतध के दौरान इलेक्ट्रोड सतह पर काबतन का उच्च रततशत देखा गया और इसके पटरणामस्वरूप तनम्न EWR था। डीडी का उच्च रततशत अतधकतम ड्यूिी चि और अतधकतम तशखर वततमान पर पयातप्त
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अंतर द्वारा देखा गया था। एमआरआर को अतधकतम करने, ईडब्लल्यूआर को कम करने, और डीडी के तलए ईडीएम मापदंडों के अनुकूलन के तलए आनुवंतशक एल्गोटरथ्म आधाटरत बहु-उद्देश्यीय अनुकूलन को
तनयोतजत क्रकया गया था। अनुकूतलत रक्रिया की रिावकाटरता की जांच के तलए मल्िी-स्िडी कॉम्प्लेक्ट्स कॉपर इलेक्ट्रोड का तनमातण क्रकया गया था और इसका उपयोग ईडीएम के तलए क्रकया गया था। यह देखा
गया क्रक यह रक्रिया कुशल एमआरआर और ईडब्लल्यूआर के साथ वांतित सीएडी मॉडल के आकार के
अनुसार जटिल आकार गुहा बनाने में सक्षम थी।
इसके अलावा, बहुलक 3 डी प्रंरिंग और रेशर-लेस लूज तसन्िररंग के संयोजन पर आधाटरत एक तेजी से
तनमातण रक्रिया को िायोजेतनक कूप्लंग चैनल के साथ जटिल आकार के इलेतक्ट्रक तडस्चाजत मशीप्नंग (ईडीएम) कॉपर इलेक्ट्रोड के तनमातण के तलए खोजा गया था। गढे हुए इलेक्ट्रोडों का उपयोग EDM D-2 स्िील वकतपीस के तलए क्रकया गया था। तुलनात्मक अध्ययन सामग्री को हिाने और ठोस तांबे इलेक्ट्रोड,
िायोजेतनक कूप्लंग (आरएमई) के तबना तेजी से तनर्मतत इलेक्ट्रोड और िायोजेतनक कूप्लंग (आरएमईसीसी) के बीच इलेक्ट्रोड पहनने की दरों पर क्रकया गया था। इसके अलावा, पहना इलेक्ट्रोड और मशीनी वकतपीस की सतह तवशेषताओं का अध्ययन िायोजेतनक शीतलन के साथ और तबना क्रकया गया
था। इलेक्ट्रोड पहनने की दर और सतह खुरदरापन पर िायोजेतनक शीतलन का महत्वपूणत रिाव देखा
गया था। मशीप्नंग के बाद इलेक्ट्रोड की सतह से गमी के तेजी से अपव्यय के कारण RMECC के साथ बेहतर वकतपीस सतह पर बेहतर सतह खत्म, िोिी दरारें और कम मलबे को अतधसूतचत क्रकया गया था।
इसी तरह, RMECC पर कुि दरारें और कम काबतन जमाव देखा गया RME की तुलना में मशीप्नंग के
बाद सतह। RMECC में जटिल आकार के उपकरण के तेज कोने क्रकनारों को इलेक्ट्रोड सामग्री के कम तपघलने और वाष्पीकरण के कारण मशीप्नंग के बाद बनाए रखा गया था। कं्यूिर एडेड तडजाइन (सीएडी) मॉडल तडजाइन के संबंध में मशीनीकृत सतह के आयामी तवचलन की तुलना की गई थी। आरएमईसीसी
को आरएमई की तुलना में वकतपीस पर आयामों के संदित में अतधक सिीक जटिल आकार सुतवधाओं को
मशीन करने के तलए पाया गया था।
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Contents
Certificate ... i
Acknowledgements ... ii
Abstract ... iv
सार...
viiList of Figures ... xiii
List of Tables ... xvi
Abbreviations ... xvii
Chapter 1 Introduction ... 1
1.1 Introduction ... 2
Electric discharge machining (EDM) ... 2
Rapid Manufacturing (RM) ... 3
1.1.3 Sintering ... 4
1.2 Cryogenic EDM ... 5
1.3 Motivation of the work ... 6
1.4 Overview of the thesis ... 7
Chapter 2 Literature review ... 10
2.1 Introduction ... 11
Rapid manufacturing of EDM electrode ... 11
Parametric analysis and process optimization for MRR, EWR and cavity dimensions ... 12
x
Electric discharge machining using rapid manufactured complex shape copper
electrode with cryogenic cooling channels ... 13
2.2 Research gap ... 14
2.3 Proposed research work and objectives ... 15
Chapter 3 Process optimization for rapid manufacturing of complex geometry electrical discharge machining electrode ... 16
3.1 Introduction ... 17
3.2 Methodology ... 17
Materials ... 17
Fabrication Procedure ... 18
Measurement of Response ... 20
3.3 Statistical modelling ... 21
3.4 Results and Discussion ... 25
Process parameters effect on sintering density ... 25
Process parameters effect on electrical conductivity ... 29
Process parameters effect on volumetric shrinkage ... 34
3.5 Multi-objective optimization ... 35
3.6 EDM by fabricated copper electrodes ... 37
3.7 Conclusions ... 39
Chapter 4 Parametric analysis and process optimization for MRR, EWR and cavity dimensions ... 42
4.1 Introduction ... 43
xi
4.2 Materials and method ... 43
Materials ... 43
Electrode fabrication... 44
4.3 EDM machining and characterizations... 46
4.4 Planning of experiments ... 47
4.5 Statistical modelling ... 48
4.6 Results and Discussion ... 52
Process parameters effect on MRR ... 54
Process parameters effect on electrode wear rate (EWR) ... 57
Process parameters effect on dimensional deviation (DD) ... 62
4.7 Multi-objective optimization ... 66
4.8 EDM by fabricated copper electrodes ... 67
4.9 Conclusions ... 71
Chapter 5 Electric discharge machining using rapid manufactured complex shape copper electrode with cryogenic cooling channel ... 73
5.1 Introduction ... 74
5.2 Materials and method ... 74
Materials ... 74
Rapid Manufacturing of electrode with cooling channels and EDM setup ... 75
5.3 Characterizations ... 78
5.4 Results and Discussion ... 79
5.5 Conclusions ... 91
xii
Chapter 6 Summary, conclusions and future scope ... 93
6.1 Summary ... 94
6.2 Conclusions ... 96
6.3 Future scope ... 98
References... 99
Appendices ... 107
List of Publications ... 115
Biodata ... 117
xiii
List of Figures
Figure 3.1: (a) Schematic diagram and (b) actual image of ultrasonic assisted sintering setup.
... 18
Figure 3.2: Methodology to fabricate customized EDM electrodes. ... 19
Figure 3.3: Parameters effect and percentage contribution for density. ... 26
Figure 3.4 Optical microscope images of sintered sample at sintering temperature ... 27
Figure 3.5: Optical microscope images of sintered sample at heating rate (a) 100 ℃ /hr and (b) 500 ℃/hr. ... 28
Figure 3.6: Optical microscope images of sintered sample at soaking time (a) 30 min and (b) 150 min. ... 28
Figure 3.7: Interaction plots between sintering temperature and heating rate for density. 29 Figure 3.8: Parameters effect and percentage contribution for electrical conductivity. ... 31
Figure 3.9: Interaction plots between sintering temperature and heating rate for electrical conductivity. ... 32
Figure 3.10: Interaction plots between sintering temperature and soaking time for electrical conductivity. ... 33
Figure 3.11: Parameters effect and percentage contribution for volumetric shrinkage. ... 35
Figure 3.12: Optical micrograph image of sintered specimen at optimized parameters. ... 36
Figure 3.13: (a) Dimensions and (b) CAD model of complex shape EDM electrode and (c) fabricated EDM electrode at optimized parameters. ... 37
Figure 3.14: (a) EDM machining with three different shape electrodes: square, circle and complex shape and (b) dimensional analysis of the machined surfaces... 38
Figure 4.1: Adopted rapid manufacturing technique flow. ... 45
Figure 4.2: Experimental setup for EDM of D-2 steel using rapid manufactured electrodes. ... 46
xiv
Figure 4.3: (a) Fabricated copper EDM electrode using developed rapid manufacturing technique, (b) SEM image and (c) EDX analysis of the fabricated electrode (red arrows indicating closed pores). ... 53 Figure 4.4: Process parameters (a) main effect and (b) percentage contribution for MRR.
... 55 Figure 4.5: Interaction between peak current and pulse duration for MRR. ... 56 Figure 4.6: (a) Parameters effect and (b) percentage contribution for EWR. ... 57 Figure 4.7: EDX analysis of worn electrode at (a) 100 µs and (b) 500 µs pulse duration with a duty cycle of 60% and peak current of 8 A. ... 58 Figure 4.8: : SEM analysis of worn electrode at (a) 40% and (b) 80% duty cycle with pulse duration of 300 µs and peak current of 8 A (with higher magnification)... 60 Figure 4.9: Interaction between peak current and duty cycle for EWR. ... 61 Figure 4.10: (a) Parameters effect and (b) percentage contribution for dimensional deviation.
... 63 Figure 4.11: DD analysis of workpiece at (a) 100 µs and (b) 500 µs pulse duration with duty cycle of 60% and peak current of 8 A. ... 63 Figure 4.12: DD analysis of workpiece at (a) 4 A and (b) 12 A peak current with duty cycle of 60% and pulse duration of 300 µs. ... 63 Figure 4.13: Interaction between peak current and duty cycle for DD. ... 65 Figure 4.14: Pareto front from the optimization result. ... 67 Figure 4.15: (a) Dimensions of complex shape electrode with (b) CAD model, (c) polymer printed part and (d) fabricated copper complex shape electrode at optimized parameters (dimension in mm). ... 68 Figure 4.16: (a) EDM electrode over the cavity, (b) workpiece after EDM and (c) customized electrode after EDM. ... 69
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Figure 4.17: Dimensional of cavity features obtained by EDM using rapid manufactured complex shape tool (at 15.8x Magnification). ... 70 Figure 5.1: XRD of workpiece. ... 75 Figure 5.2: Flow chart for the rapid manufacturing of copper electrodes with cooling channel. ... 76 Figure 5.3: CAD model and drawing of the EDM tool. ... 77 Figure 5.4: Cryogenic EDM setup. ... 78 Figure 5.5: Fabricated (a) rectangular, (b) complex shape RMECC electrodes, (c) cross- section view of the electrode and (d) microscopic image of the sintering electrode at optimized sintering cycle. ... 80 Figure 5.6: EWR using solid copper electrode, RME and RMECC with rectangular and complex shape for machining of D2 steel workpiece... 81 Figure 5.7: SEM images of the solid copper electrode, RME and RMECC after machining.
... 83 Figure 5.8 (a) side view and EDX analysis and (b) worn edges of RME and RMECC after machining. ... 84 Figure 5.9 MRR using a solid copper electrode, RME and RMECC with rectangular and complex shape for machining of D2 steel workpiece... 85 Figure 5.10 : SEM images of (a) surface morphology, and (b) cracks of the workpiece machined by Solid Copper, RME and RMECC. ... 86 Figure 5.11: Optical surface profile of workpiece machined by solid copper, RME and RMECC. ... 87 Figure 5.12: XRD analysis of workpiece machined by RME and RMECC. ... 88 Figure 5.13: Dimension analysis of the complex shape features on the workpiece machined by RMECC. ... 90
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List of Tables
Table 3.1: Sintering parameters levels. ... 20
Table 3.2: Experiments runs with responses. ... 22
Table 3.3: ANOVA table for Density. ... 23
Table 3.4: ANOVA table for electrical conductivity. ... 23
Table 3.5: ANOVA table for volumetric shrinkage. ... 24
Table 3.6: Confirmatory experiments for statistical models. ... 25
Table 3.7: Optimized parameters with statistical and experimental response. ... 36
Table 3.8: Comparison between geometries... 39
Table 4.1: Composition of D2 steel. ... 44
Table 4.2: EDM machining parameters levels. ... 48
Table 4.3: Experiments runs with responses. ... 49
Table 4.4: ANOVA table for MRR. ... 50
Table 4.5: ANOVA table for EWR. ... 50
Table 4.6: ANOVA table for dimensional deviation. ... 51
Table 4.7: Confirmatory experiments for statistical models. ... 52
Table 4.8: Dimensional measurements of the complex shape electrode CAD model, fabricated electrode and obtained cavity after EDM. ... 71
Table 5.1: Dimensional measurements of the complex shape electrode CAD model, fabricated electrode and obtained cavity after EDM. ... 91
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Abbreviations
ANOVA Analysis of Variance
ASTM American Society for Testing and Materials
BCC Body Centered Cubic
CAD Computer Aided Design
CPS Conventional Pressure-less Sintering CSP Copper Spherical Particles
DF Degree of Freedom
EBM Electron Beam Melting
EDX Electron Diffraction X-ray
FEM Finite Element Method
HIP Hot Isostatic Processing
HCL Hydrochloric Acid
IACS International Annealed Copper Standard
MS Mean of Squares
RM Rapid Manufacturing
SC Simple Cubic
SLS Selective Laser Sintering SLM Selective Laser Melting
SEM Scanning Emission Microscopy
SLA Stereolithography
SS Sum of Squares
