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Properties of Micro-Holes for Nozzle by Micro-EDM
G. Cusanelli, M. Minello, F. Torchia, W. Ammann, P.-E. Grize
Posalux S.A., rue F. Oppliger 18, 2500 Bienne 6, Switzerland
15th International Symposium on Electromachining (ISEM XV)
學生：陳信誠
學號：m9710246
班級：碩機械一甲
太陽能材料與模組製造實驗室
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大綱
 摘要
 前言
 實驗
 結果與討論
 結論
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摘要
 The micro Electrical Discharge Machining
(EDM) technique is used for machining hard
conductive materials and achieves holes from
0.05 to 1.8 mm in diameter. The holes are
machined with a high repeatability, without burrs
and material alteration. The technology currently
in production in the automotive industry is used
to drill diesel and gasoline nozzles coming from
the direct injection technology.
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前言
 The introduction of die-sinking in the 90s to process small
mechanical parts and micro pharmacy applications allowed
for a superior level of precision. Roughness in the region of
0.1 Ra and spark gaps of about 5 μm could be obtained.
 EDM drilling remains the method of choice for diameters
above 50 μm. The geometry of the holes is very important
to the injection nozzle market.
 Tapered holes allow for better spray efficiency , reduction
of cavitation phenomena and self-cleaning of the nozzle
holes.
 The goal of this article is to show how to control the conical
shape and characteristics of the holes.
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實驗
1. Nozzles made of hardened steel (HRC 57-63), Cr-Ni
are drilled using micro-EDM technologies on
Posalux’s FP1 (One spindle machine for flexible batch
production) and Posalux’s HP4 (Four spindles
machine for mass production).
2. The electrode is hardened steel (WC/Co, 6% Co). The
measurements of the diameter, shape and position of
the hole are measured using a Werth Video Check IP
machine.
3. The variation and control of the flow is performed by
a Sonplas machine with up to 138 bar (2000 psi),
depending on customer requirements.
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儀器介紹
The rotation of the electrode,
which is maintained by shifting
collets and passes through the
guiding collets, is done in
order to optimize quality and
drilling speed.
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機器規格
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CONTROL OF TAPERED HOLE
The “double clamping” (DC) unit is used
to drill holes with control on the geometry.
The DC unit is composed of shifting
collets, a tilting head, guiding collets and
adjustable rings.
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These two processes occur with a rotation
between 500-1000 rev/min of the electrode
during machining. Rotation of the
electrode allows for better flushing of the
eroded material and better control of the
hole geometry.
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結果與討論
Tapered holes can be obtained naturally with EDM drilling
parameters by varying the electrode diameters. With the
consistent run-out and with the energy level adapted to the
electrode chosen, the following observations can be made:
•With small electrode diameters (< 100 mm), the hole obtained
has a natural positive cone.
•For an electrode with a diameter of 100 mm, a cylindrical hole
is obtained.
•With large electrode diameters (> 100 mm), the cone obtained
is negative.
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It is mechanically possible to control
the hole geometry with the adjustable
rings by changing the taper set-up
value. A slope is given to the
electrode through mechanical
adjustment. The rotation of the
electrode allows a round hole with
the desired taper.
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The cut of various
machined holes can be
seen, with the goal of
obtaining various conical
geometries, thus changing
the taper set-up of the
adjustable rings.
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 Small diameter
This is primarily due to the increase in the
supplied energy that could be applied to a larger
electrode.
 Thickness of the white layer
Therefore, the white layer remaining after the
micro-EDM process is dependent exclusively on
the energy level.
 Roughness
This implies that the roughness depends
essentially on the energy used for erosion.
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 Shape measurements
The results show an average of variation of ± 2 μm
at the hole entrance and of ± 4 μm at the hole exit.
But these shape measurements can not be
performed in process due to its duration.
 Flow measurements
The high reproducibility of the holes drilled on
Posalux machine performs a flow variation in ± 3
% of a nominal value.
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結論
 At the moment, due to the technological control of
the EDM process, it is possible to fully answer the
high pressure direct injection needs of the
automotive industry.
However, current work indicates that there is
considerable potential with regards to higher
geometrical hole control and reductions in erosion
time. The production of tapered holes for diesel
nozzles is currently under control and the market of
gasoline direct injection is beginning to
developwith very similar needs.
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Thanks for your attention!
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