Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2002-06-04
2004-03-30
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069170
Reexamination Certificate
active
06713705
ABSTRACT:
This application is a 371 of PCT/JP00/0660, filed Oct. 5, 2000.
1. Technical Field
The present invention relates to improvements in a wire electric discharge machining method and a wire electric discharge machine in which electric power is supplied between a wire electrode and a workpiece so that a workpiece is machined by electric discharge energy generated between the wire electrode and the workpiece.
2. Background Art
Electric discharge machining has acquired a steadfast position as a technique for machining metallic dies and others. Therefore, electric discharge machining has been widely used for machining metallic dies in the automobile industry, electric appliance industry and semiconductor industry.
FIGS. 8A
to
8
E are schematic illustrations for explaining a mechanism of electric discharge machining. In the drawing, reference numeral
1
is an electrode, reference numeral
2
is a workpiece, reference numeral
3
is an arc column, reference numeral
4
is a machining solution and reference numeral
5
represents chips created in the process of electric discharge machining. While the following processes (a) to (e), which correspond to
FIGS. 8A
to
8
E, are being repeatedly conducted, removal machining is conducted on the workpiece
2
by electric discharge. Each process proceeds as follows.
(a) Formation of the arc column
3
by the generation of electric discharge
(b) Local melt of the workpiece and vaporization of the machining solution
4
by the thermal energy of electric discharge
(c) Generation of vaporizing explosive power by the machining solution
4
(d) Dispersion of the melted portion (chips
5
)
(e) Cooling, coagulation and restoration of insulation between the electrodes executed by the machining solution
The present invention relates to wire electric discharge machining used for gouging, cutting and so forth. Concerning the technique of wire electric discharge machining, there is a strong demand for higher accuracy. For example, when metallic dies used in the field of manufacturing semiconductors, the dimensional accuracy of which is high, are machined, it is necessary to conduct machining with high accuracy of 1 to 2 &mgr;m.
FIGS. 9A
to
9
C are schematic illustrations showing an example of the wire electric discharge machining process. In the drawing, reference numeral
1
a
is a wire electrode, reference numeral
2
is a workpiece, reference numeral
4
a
is water which is a machining solution, and reference numeral
6
is an initial hole.
FIG. 9A
shows a first cut process which is a rough machining process,
FIG. 9B
shows a second cut process which is an intermediate finishing process to be conducted after the rough machining process, and
FIG. 9C
shows a third cut process which is a final finishing process.
An example of the first cut process shown in
FIG. 9A
shows a gouging process in which the wire electrode
1
a
is threaded into the initial hole
6
and the workpiece
2
is gouged by electric discharge. In the case of the first cut process described above, since the surface roughness and the accuracy are finished in the later process, it is unnecessary to machine the workpiece with high accuracy, and it is important to increase a rate of machining so as to enhance the productivity. In order to enhance the rate of wire electric discharge machining, water
4
a
is jetted out between the electrodes so that chips can be effectively ejected from between the electrodes. In order to spray water
4
a
between the electrodes uniformly and prevent the breaking of the wire electrode
1
a
, a method is adopted in which water
4
a
is stored up in a machining tank and the workpiece
2
is dipped in the water
4
a
. As described above, a means for supplying a machining solution between the electrodes is used.
In the conventional wire electric discharge machining method described above, the second cut process (shown in FIG.
9
B), which is conducted after the first cut process (shown in FIG.
9
A), and the third cut process (shown in FIG.
9
C), are conducted in the water
4
a
which is a machining solution.
FIG. 10
is a view showing an example of the waveforms of voltage and current between the electrodes. In the view, V is a voltage between the electrodes, and I is a current between the electrodes, and t is time. A state at time T
1
in
FIG. 10
shows that voltage is impressed between the wire electrode
1
a
and the workpiece
2
. When voltage is impressed between the electrodes, an attraction force acts between the positive and the negative polarity. By this electrostatic force, the wire electrode
1
a
, the rigidity of which is low, is drawn onto the workpiece
2
side, which could be a cause of vibration of the wire electrode
1
a
. Due to the vibration, it becomes difficult to conduct electric discharge machining with high accuracy.
A state at time T
2
in
FIG. 10
shows that vaporizing explosive power is generated in the machining solution by electric discharge energy (for example, shown in FIG.
8
C). The wire electrode
1
a
is given a strong force by the vaporizing explosive power created in the machining solution in a direction opposite to the workpiece
2
, and vibration is generated. Due to the vibration, irregularities are caused on the profile of the workpiece
2
, which impairs the dimensional accuracy.
In the industry of semiconductors in which wire electric discharge machining is utilized, the following cases are increased. For example, in the case of machining metallic dies of IC lead frames, very high accuracy and very smooth surface roughness are required when a workpiece is machined, the dimensional accuracy of which is 1 &mgr;m, and the surface roughness of which is not more than 1 &mgr;m Rmax. In the case where high accuracy and smooth surface roughness are required as described above, remarkable problems are caused by the aforementioned vibration of the wire electrode.
DISCLOSURE OF THE INVENTION
The present invention has been accomplished to solve the above problems. It is an object of the present invention to provide a wire electric discharge machining method and a wire electric discharge machine suitable for conducting electric discharge machining with high accuracy and reliability.
The present invention provides a wire electric discharge machining method in which electric discharge is generated between a wire electrode and a workpiece so as to machine the workpiece by electric discharge, comprising the steps of: machining the workpiece while at least two types of machining in three types of machining including machining in a machining solution, machining in mist and machining in gas are being combined with each other; and removing at least one of the liquid of the machining solution adhering to the workpiece and the liquid of the machining solution having a possibility that the liquid drips onto a machining face of the workpiece at least at one of the point of time before the start of machining except for the machining conducted in the machining solution and the point of time after the operation of an automatic wire connecting device for conducting an automatic wire connection while the wire electrode is being held by a water column.
The present invention provides a wire electric discharge machine in which electric discharge is generated between a wire electrode and a workpiece so as to machine the workpiece by electric discharge, comprising: at least one of the machining solution supply means for supplying a machining solution between the electrodes and the mist supply means for supplying mist between the electrodes; pressurized gas jetting means for removing at least one of the liquid of the machining solution adhering to the workpiece and the liquid of the machining solution having a possibility that the liquid drips onto a machining face of the workpiece at least at one of the point of time before the start of machining except for the machining conducted in the machining solution and the point of time after the operation of an automatic wire connecting device for conducting an automatic wire connection while the wi
Goto Akihiro
Satou Seiji
Evans Geoffrey S.
Mitsubishi Denki & Kabushiki Kaisha
Sughrue & Mion, PLLC
LandOfFree
Wire electric discharge machining method and wire electric... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wire electric discharge machining method and wire electric..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wire electric discharge machining method and wire electric... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3204274