Transcript 下載/瀏覽Download

MICRO-EDM DRILLING OF TAPERED
HOLES FOR INDUSTRIAL APPLICATIONS
C. Diver, J. Atkinson, H.J. Helml, L. Li
ADVISOR：PROF. HSU, YI - CHU
ADVISEE：TSENG, WEI - CHUN
Institute of Mechanical – Engineering – Department
Date：2009 / 05 / 19
1
OUTLINE
Introduction
 Experimental procedures
 Reverse tapered hole drilling technique
development
 Results and discussion
 Conclusion

2
INTRODUCTION

EDM has traditionally been used for producing complex moulds
for injection moulding or forming. It has also been widely used
for cutting profiles out of metal plates by means of wire EDM.


Diesel fuel injection nozzles.
Turbine blades.
3
INTRODUCTION
4
EXPERIMENTAL PROCEDURES
5
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
6
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
7
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
De-ionised - ∼4×104 Ω-cm
Dielectric
Oils - 2×10−14 Ω-cm
removal
rates
surface
aspect
ratios
energy
transfer
DI-Water
faster
poorer
lower
more
Oil
slower
better
higher
less
8
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT

Feed and rotate the electrode at the angle required to achieve the
desired hole taper.
9
RESULTS AND DISCUSSIONS
k-factor hole, which is a method of characterising a
reverse tapered hole.
where 10 is equivalent to a 1mm hole length, D1 the
diameter at electrode exit, D2 the diameter at electrode
entry, and 10 is a function of hole length.
The k-factor raise from 1.5 to 6.5, made it by redesigned
method.
10
RESULTS AND DISCUSSIONS
Impression of a hole from
existing equipment
Impression of a tapered
hole using the improved
drilling technique.
11
RESULTS AND DISCUSSIONS
Diameter measurements of a sample of 100 holes showed a
diameter variation of up to 8 μ m. The diameter at electrode
entry was between 106 and 114 μ m.
12
RESULTS AND DISCUSSIONS
Ra ~ 0.3 μm.
This shows that the technique maintains the surface finish
quality achievable with standard micro-EDM.
13
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
roundness values of 2–3 μm. The hole diameter is 130 μm
14
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
The final assessment of the concept was to test it on four
separate EDM heads and to produce 1500 holes per head, 6
holes per plate and 250 plates. Thirty of the 250 plates were
measured.
15
REVERSE TAPERED HOLE DRILLING TECHNIQUE
DEVELOPMENT
16
RESULTS AND DISCUSSIONS
17
RESULTS AND DISCUSSIONS
This technique has been successfully tested in an industrial
environment.

Improvement in the hole quality and reverse tapered
holes.

Easily adapted to fit an existing system and the results have
shown that the solution is stable and repeatable.

18
CONCLUSIONS
High quality reverse tapered holes can be produced.
 The hole diameter variation within 3 μm.
 Cycle times similar to standard EDM.
 The k-factor values up to k = 6.5 have been produced.
 Ra = 0.3 μm.
 The solution can be applied to existing equipment
without the need for a major retrofit.
 One main application area is for diesel fuel
injection nozzles to improve emissions from diesel
engines without the need for higher injection
pressures or smaller diameter holes.

19
Thanks for your attention !
20