This paper aims to investigate the effect of μ-EDM process parameters on Material Removal Rate (MRR), Hole Taper and Diameter over cut on Inconel-718 material using rotating electrode

1. Electrical Discharge Drilling of micro-hole on
Inconel 718 using Rotary Tubular Electrode
International Conference on Materials,
Manufacturing and Modelling(2019)
By
V.S.SRISAILESH
JIBIN OOMMEN
DR. MOHAN R.

2. Introduction
• Applications in the field of automobiles, aeronautics, medical
and electronics manufacturing deal with miniaturized devices
and features.
• Micro machining technologies met the increasing stringent
design requirement and tight tolerances of the products.
• Micro Electro Discharge Machining Drilling (μ-EDM-drilling),
provides comparative advantages owing to its capability of
machining difficult-to-cut materials and high aspect ratio holes.
• Inconel 718 is a Nickel based Heat Resistant Super Alloy from
Ni used in hot section parts of gas turbines, injection nozzles,
turbine blades [1].
• The superior properties of the alloy makes it suitable material
for every challenging applications.
2

3. 16-05-2020 3
Objective
This paper aims to investigate the effect of μ-EDM process
parameters on Material Removal Rate(MRR), Hole Taper and
Diameter over cut on Inconel-718 material using rotating
electrode
Scope
The scope of this project is limited to sample of thickness 10mm
with the hole drilled of diameter 0.5mm with the tubular brass
electrode.

4. 4
Identification of machine type
and availability
Selection of Work material
and availability
Identification process
parameter for micro drilling
Prediction of MRR, DOC and
Taper using Scanning Electron
Microscope
Results and Discussion
Report Preparation
Sample Preparation
Conduct Experiments
- With tool rotation
Literature review
Methodology

5. • Work Material : INCONEL – 718
• Electrode drill : Brass (0.5mm)
• Di – electric fluid : De – mineralized water
• Dimension of Work piece
 Diameter : 45 mm
 Thickness : 10 mm
Experimental setup

6. Parameter Value
Voltage (V) 15
Polarity Positive (+ve) work
piece
Spark Gap (µm) 50
Feed rate (mm/min) 4
Thickness of material (mm) 10
Diameter of the electrode (mm) 0.5
Spindle Speed (mm) 135
Process parameters - Fixed

7. Exp. No Peak current(A) Pulse-on Time(µs) Pulse-off
Time(µs)
1 3 6 3
2 3 7 4
3 3 9 6
4 4 6 4
5 4 7 6
6 4 9 3
7 5 6 6
8 5 7 3
9 5 9 4
Process parameters - Variable

8. Fig. Minimum hole diameter
and maximum hole diameter
of Top hole (100X)
Fig. Minimum hole diameter
and maximum hole diameter
of Bottom hole (100X)
SEM Results

9. Results
Experimental results of various combinations of parameters

10. RESULT
• From the main effects plot for MRR shown in figure indicates that
existence of optimal values of process parameters for maximum
material removal which is at level 2 in all three parameters.
• The percentage of contributions of current, Ton and Toff are 53.33%,
26.86% and 18.76% respectively.
• The overall diameter over cut is observed to be within 20% of the
tool diameter.

11. From the figure 5, hole taper is decreases with increase in current as
well as Ton values and Toff showed increase taper at higher levels
with contribution of 36.34%, 46.88% and 16.77% respectively.
RESULT

12. The diameter over cut is much influenced by current and Ton
compared to Toff which is show in figure .
RESULT

13. Results
Summary of Taguchi L9 orthogonal array analysis of experimental results
Factors
MRR Taper Diameter Overcut
Current Ton Toff Current Ton Toff Current Ton Toff
Current 5.426 6.686 6.116 0.3303 0.2457 0.2987 92.62 87.55
102.2
7
Ton 7.746 7.134 6.976 0.3030 0.3360 0.2813 113.73 109.63 93.42
Toff 6.615 5.967 6.695 0.2603 0.3120 0.3137 92.14 101.32
102.8
1
Delta 2.319 1.168 0.816 0.0700 0.0903 0.0323 21.59 22.08 9.39
Rank 1 2 3 2 1 3 2 1 3
% of
contribution
53.33 26.86 18.76 36.34 46.88 16.77 40.69 41.62 17.69

14. • In this paper, holes of 0.5 mm diameter were drilled on Inconel 718
using spark EDM process using brass tubular electrode. The chosen
process parameter and its order of importance were analyzed.
• The experimental results showed that each process parameters
influences at different levels on Material removal rate, hole taper and
diameter over cut.
• Further, concludes that peak current shows dominant effect on
material removal rate and Ton on hole taper. The overall diameter
over cut is observed to be within 20% of the tool diameter.
CONCLUSION

15. References
1. Misal ND, Sadaiah M. Investigation on Surface Roughness of Inconel 718 in
Photochemical Machining. Advances in Materials Science and Engineering. 2017;2017.
2. Dabade UA, Karidkar SS. Analysis of response variables in WEDM of Inconel 718 using
Taguchi technique. Procedia CIRP. 2016;41:886-91.
3. Kuppan P, Rajadurai A, Narayanan S. Influence of EDM process parameters in deep hole
drilling of Inconel 718. The International Journal of Advanced Manufacturing
Technology. 2008 ;38 (1-2):74-84.
4. Manikandan N, Kumanan S, Sathiyanarayanan C. Multiple performance optimization of
electrochemical drilling of Inconel 625 using Taguchi based Grey Relational Analysis.
Engineering Science and Technology, an International Journal. 2017;20(2):662-71.
5. Masuzawa T. State of the art of micromachining. CIRP Annals-Manufacturing Technology.
2000 Jan 1;49(2):473-88.
6. Imran M, Mativenga PT, Kannan S, Novovic D. An experimental investigation of deep-
hole microdrilling capability for a nickel-based superalloy . Proceedings of the Institution
of Mechanical Engineers, Part B: Journal of Engineering Manufacture. 2008;
222(12):1589-96.
7. Rahman AA, Mamat A, Wagiman A. Effect of machining parameters on hole quality of
micro drilling for brass. Modern applied science. 2009 ;3(5):221.
8. Sundaram MM, Pavalarajan GB, Rajurkar KP. A study on process parameters of ultrasonic
assisted micro EDM based on Taguchi method. Journal of Materials Engineering and
Performance. 2008; 17(2):210-5.

16. Thanks

17. Machine Specifications:
EDM Drill – Speed II (make – Sparkonix India Pvt. Ltd
Technical specifications Values
Electrode Diameter 0.3mm – 3mm
Current 35A
Input Power supply 3 Phase, 415 V, 50 Hz with
Neutral and Earth
Maximum speed 50mm/min
Power 5kVA
Dielectric Fluid De – mineralized water (Soft
water)
Best Surface Finish µRa 1.25 – 1.75

18. Properties of Inconel – 718
• Chemical properties:
• Density : 8.19 g/cm3
• Thermal coefficient : 11.4 W/m.K
18

19. Formulae used
DOC = Dtop - Dbottom