1. Indian Institute of Technology
Ropar[India]
Manufacturing with Metallic Materials MEL202
ELECTRO JET DRILLING
By
Manish Anand

2. CONTENTS
 Introduction
 Working
 Experimental Results and Discussions
 MRR
 Radial Overcut
 Hole Taper
 Desirable Conditions of hole
 Advantages and Disadvantages
 Conclusions
 References

3. Introduction
 Demands of small size machines have directed our
attention to nontraditional techniques
 EJD is Non-traditional method
 Micro level hole drilling
 Use in = cooling holes in jet turbine blades,
printed circuit board, inkjet printer head, surgical
implants,

4. Working
a negatively charged stream of acid electrolyte is impinged on the workpiece to form
a hole.
The acid electrolyte (10–25% concentration) is passed under pressure (0.3–1.0 MPa)
through a finely drawn glass tube nozzle.
The electrolyte jet acts as a cathode when a platinum wire, inserted into the glass
tube well above the fine capillary is connected to the negative terminal of a DC
power supply. The workpiece acts as an anode.
When a suitable electric potential is applied across the two electrodes, the material
removal takes place through electrolytic dissolution as the electrolyte stream strikes
the workpiece.
The metal ions thus removed are carried away with the flow of the electrolyte. A
much longer and thinner electrolyte flow path requires much higher voltage (150–750
V) so as to effect sufficient current flow.

6. Lack of Knowledge
 Available literature mainly deals with qualitative
description
 Relation between influencing parameters and effects are
not completely known.
 Experiments
 Central composite Design[CCD]
 Response Surface Method[RSM]
INPUT OUTPUT
Applied Voltage, Electrolyte Overcut, Taper, material
concentration, Feed Rate Removal

7.  Material Removal Rate(MRR) MRR=(W1-W2)/time
W1,W2 are initial and final weight of work piece.
 Radial Overcut The difference between the size of the electrode and the size
of the cavity created during machining.
Overcut =[d(entry)-d(glass capillary)]/2
d(entry),d(glass capillary are diameter of entry to work piece and capillary
 Hole Taper An angled, gradually narrowing feature on a part.
Tapper(Ø)=Tan-1[(dentry-dexit)/2t]
dentry-dexit=difference between diameters of jet interring to piece and exiting
piece.
t= thickness of work piece.

8. Experimental results and discussion
 Using CCD and RSD techniques experiment and data
collection was performance.
 Graphs were plotted and discussions were noted.

9. Experiment setup

10. MRR
• Applied Voltage
– As voltage increases-current increases-MRR
increases(Faraday’s Law)
– Increases rapidly above 350 V
• Electrolyte Conc.
– Increase in electrolytes conc. –increases MRR
–because it increases conductivity –more
amount of current flow
• Feed rate
– Increase in FR-reduces inter electrode gap-
leads to smaller ohmic resistance-inc
electrolyzing current
Main Effect of Input parameters on MRR
3D surface of MRR model

11. Radial Overcut
• Decides the quality of EJD holes
• Applied Voltage
– Increases in applied voltage- greater overcut
• Electrolyte Conc.
– Increase in electrolytic conc.-greater overcut
• Feed Rate
– Higher feed rate-less radial overcut-because
less interaction time
• Current
– Inc. in current-increases overcut
Main Effect of parameter over radial overcut
3D surfaces of radial overcut

12. Hole Taper
• Hole taper –depends on diff. between hole
entrance diameter and hole exit diameter.
• Increasing applied voltage and electrolyte
concentration- results in greater hole taper -
reasons for this is that the electro jet remains
in contact with the entry side of the
workpiece for a maximum period of time
resulting in a larger hole entrance diameter
than the hole exit diameter
Main effect of input parameters on hole taper
3D surface of hole taper model

13. Desirable Condition for hole making
• Low overcut and reduced hole taper
– In favoured condition
• V=325 DC Volts
• 17.5 % electrolyte conc.
• Feed rate 0.5 mm/min

14. Advantages and Disadvantages
• Advantages
– Micro-level holes can be made.
– Applied on hard and brittle material
– Material are removed easily
– Less costly than traditional drilling
• Disadvantages
– Set up should not vibrate otherwise hole will get large
or deform.
– More maintenance

15. Conclusions
• Applied voltage, electrolyte concentration, feed rate and interaction between the
applied voltage and electrolyte concentration are the significant parameters in all
the three models.
• The increase in feed rate not only enhances the material removal but it also
enables to control the radial overcut as well as hole taper. Since the fine glass
nozzle, used to direct the electrolyte jet on the workpiece in the EJD process,
moves inside the workpiece therefore a judicious selection of feed rate is very
important for the success of the process in view of the fragile nature of the glass.
The selected feed rates should be compatible with the dissolution efficiency of the
work material at the applied potential level.
• Within the overall range of test conditions employed, the optimum results, that is
maximum MRR with least radial overcut and small hole taper were achieved in the
following ranges of the parameters.
– Voltage: 190−325 V
– Electrolyte concentration: 13-17.5%
– Feed rate: 0.2–0.5 mm/min.
• Higher applied voltage, though it results in greater MRR, tends to produce holes of
poor quality in terms of large radial overcut and hole taper.

16. References
• Iit roorkee sites
• Ahmed MS, Duffield A (1990) The drilling of
small deep holes by acid ECM. Proc Advanced
Machining Technology III Conference, Chicago,
IL, 4–6 Sept 1990, MR90-243, pp1–13
• Design-Expert Version 6.0.8, Stat-Ease Inc.,
Minneapolis
• Montgomery DC, Peck EA (1992) Introduction
to linear regression analysis. Wiley, New York