(EDM) of TI-6AL-4V Alloy

131 Pages·2016·7.04 MB·English

by  Farshid Alavi

Western Kentucky University
TopSCHOLAR®
Masters Theses & Specialist Projects Graduate School
Spring 2016
Optimization of Process Parameters in Micro
Electrical Discharge Machining (EDM) of
TI-6AL-4V Alloy
Farshid Alavi
Western Kentucky University, [email protected]
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Recommended Citation
Alavi, Farshid, "Optimization of Process Parameters in Micro Electrical Discharge Machining (EDM) of TI-6AL-4V Alloy" (2016).
Masters Theses & Specialist Projects.Paper 1568.
http://digitalcommons.wku.edu/theses/1568
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OPTIMIZATION OF PROCESS PARAMETERS IN MICRO ELECTRICAL
DISCHARGE MACHINING (EDM) OF TI-6AL-4V ALLOY BASED ON FULL
FACTORIAL DESIGN

A Thesis
Presented to
The Faculty of the Department of Architectural and Manufacturing Sciences
Western Kentucky University
Bowling Green, Kentucky

In Partial Fulfillment
Of the Requirements for the Degree
Master of Science

By
Farshid Alavi

May 2016

I dedicate this thesis to my loving wife, Mahshid Molaei, who supported me, and all this
while bearing us a son. I am most grateful for her love, patience, and faith in me.
I am thankful to my adorable and wonderful son, Nick, for his shower of happiness in my
life.
ACKNOWLEDGMENTS
I would like to thank my advisor Professor, Dr. Muhammad Jahan, for giving me
an opportunity to work with him in the micro-machining laboratory. His guidance and
directions on micro-EDM has inspired me to broaden my knowledge and complete my
thesis.
I am deeply indebted to Dr. Mark Doggett for his valuable advice and
encouragement. He has been a supportive and inspirational force during my time at
WKU. I express my sincere gratitude to Dr. Daniel Jackson who always helped me with a
cheerful attitude. I appreciate his advice, direction, and patience throughout the study.
I would like to thank Dr. John Andersland from Biology Department. He
selflessly imparted knowledge and we had several excellent discussions on the SEM
images that I am greatly appreciative of. I would also take this opportunity to thank Dr.
Gregory Arbuckle for all the support that he has extended to me, and for providing a
friendly working atmosphere.

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CONTENTS
Introduction ..........................................................................................................................1
Problem Statement ......................................................................................................2
Significance of the Research .......................................................................................3
Purpose of the Research ..............................................................................................4
Research Questions .....................................................................................................4
Assumptions ................................................................................................................5
Limitations ..................................................................................................................5
Delimitations ...............................................................................................................6
Review of Literature ............................................................................................................7
EDM Power Supply ....................................................................................................7
The Electrode ..............................................................................................................8
The Servo Control System ..........................................................................................9
The Process Parameters in Micro-EDM ...................................................................11
The Response Variables in Micro-EDM...................................................................15
Methodology ......................................................................................................................24
Equipment and Tools ................................................................................................24
Material .....................................................................................................................28
Procedures .................................................................................................................29
Results and Analysis ..........................................................................................................34
Machining Time ........................................................................................................38
Tool Wear (Δl) ..........................................................................................................48
Surface Microhardness..............................................................................................58
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Crater Size .................................................................................................................67
Element Characterization - EDS Analysis on the SEM ............................................76
The Micro-EDM Machined Surface Topography Using SEM .................................89
The Optimal Process Parameters ..............................................................................92
Conclusion .........................................................................................................................95
Suggestions for Further Research .............................................................................98
Appendix A: Abbreviations .............................................................................................100
Appendix B: Published literature .....................................................................................101
Appendix C: Full Factorial Design Settings ....................................................................104
Appendix D: ANOVA Tables for Insignificant Parameters ............................................106
References ........................................................................................................................111

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LIST OF FIGURES
Figure 1. The volume of electrode wear ............................................................................17
Figure 2. Crater diameter versus energy input ..................................................................19
Figure 3. The micro-EDM set-up. .....................................................................................24
Figure 4. The tungsten carbide electrodes coated with titanium nitride ............................25
Figure 5. The micro-hardness tester set-up. ......................................................................26
Figure 6. The SEM and EDS set-up. .................................................................................27
Figure 7. The sample of SEM images and EDS data. .......................................................28
Figure 8. The resulting machined area on three workpieces .............................................35
Figure 9. The general structure of the results and analysis. ..............................................36
Figure 10. Element characterization - The structure of the results and analysis. ..............37
Figure 11. The scatter plot - the discharge energy and machining time. ...........................42
Figure 12. The effect of TN coating on machining times .................................................43
Figure 13. The effect of electrode rotational speed on machining times ..........................44
Figure 14. The main effects plot for machining time. .......................................................45
Figure 15. The interaction effects plot for machining time. ..............................................46
Figure 16. The scatter plot - the discharge energy and tool wear. .....................................52
Figure 17. The effect of the TN-coating on tool wear .......................................................53
Figure 18. The effect of electrode rotational speed on tool wear ......................................54
Figure 19. The main effects plot for tool wear. .................................................................55
Figure 20. The interaction effects plot for tool wear. ........................................................56
Figure 21. The scatter plot – the discharge energy and the microhardness. ......................61
Figure 22. The effect of the TN-coating on the microhardness. .......................................62
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Figure 23. The effect of electrode rotational speed on the microhardness ........................63
Figure 24. The main effects plot for the microhardness. ...................................................64
Figure 25. The interaction effects plot for the microhardness. ..........................................65
Figure 26. The crater size measurements using a SEM image. .........................................67
Figure 27. The scatter plot - the discharge energy and the crater size. .............................71
Figure 28. The effect of the TN-coating on the crater size ...............................................72
Figure 29. The effect of electrode rotational speed on the crater size ...............................73
Figure 30. The main effects plot for the crater size. ..........................................................74
Figure 31. The interaction effects plot for the crater size.. ................................................75
Figure 32. The concentration levels of the surface elements ............................................80
Figure 33. The effect of the TN-coating on element characterization. .............................81
Figure 34. The effect of electrode rotational speed on element characterization. .............83
Figure 35. The main effects of voltage and capacitance on the elements. ........................88
Figure 36. SEM images - the discharge energy from 0.05 µJ to 4.05 µJ. .........................90
Figure 37. SEM images – the discharge energy from 6.27 µJ to 29.48 µJ. ......................91
Figure 38. The optimization plot for the first set of response variables. ...........................93
Figure 39. The optimization plot for the second set of response variables. ......................94
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LIST OF TABLES
Table 1. Relationship between MRR and the micro-EDM process parameters. ...............16
Table 2. The chemical composition and mechanical properties of Ti-6Al-4V. .................29
Table 3. Independent variables and their levels. ................................................................31
Table 4. Machining time using an uncoated WC electrode. ..............................................39
Table 5. Machining time using the TN-coated WC electrode. ..........................................40
Table 6. Levels of the discharge energy and machining time. ...........................................41
Table 7. The ANOVA table for machining time based on the full factorial design. .........47
Table 8. Tool wear (Δl) using an uncoated WC electrode. ................................................49
Table 9. Tool wear (Δl) using the TN-coated WC electrode. ............................................50
Table 10. Levels of the discharge energy and tool wear. ...................................................51
Table 11. The ANOVA table for tool wear (Δl) based on the full factorial design. ..........57
Table 12. The surface microhardness using an uncoated WC electrode. ..........................58
Table 13. The surface microhardness using the TN-coated WC electrode. .......................59
Table 14. Levels of the discharge energy and the microhardness. ....................................60
Table 15. The ANOVA table for the microhardness based on the full factorial design. ...66
Table 16. The crater size using an uncoated WC electrode. ..............................................68
Table 17. The crater size using the TN-coated WC electrode. ..........................................69
Table 18. Levels of the discharge energy and the crater size. ...........................................70
Table 19. The ANOVA table for crater size based on the full factorial design. ................76
Table 20. Element characterization using an uncoated WC electrode...............................77
Table 21. Element characterization using the TN-coated WC electrode. ..........................78
Table 22. Levels of the discharge energy and element characterization. ..........................79
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