Wire electrical discharge machine

Details Wire electrical discharge machine Wire electrical discharge machine

2000-05-10

2001-09-25

Evans, Geoffrey S. (Department: 1725)

Electric heating

Metal heating

Cutting or disintegrating

Reexamination Certificate

active

06294749

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in a wire electrical discharge machine for supplying electricity to a wire electrode traveling in an upper or lower wire guide section.
2. Description of the Related Art
A conventional wire electrical discharge machine will be described with reference to
FIGS. 6 and 7
. In
FIGS. 6 and 7
, the wire electrical discharge machine is comprised of a bed
1
serving as a base; a table
5
for fixing a workpiece
3
which is processed by a wire electrode
2
; a processing tank
7
in which a working fluid is stored; an X-axis driving section
13
for moving the table
5
in an X-axis direction by moving an X-axis table
9
by driving an X-axis motor
8
; a Y-axis driving section
17
for moving the table
5
in a Y-axis direction by causing a column
19
to move along a longitudinal direction of a lower arm
20
fixed to the base
1
, by driving a Y-axis motor
15
; a Z-axis driving section
21
for moving the table
5
in a Z-axis direction and fixed to the column
19
; a lower wire guide
25
fixed to the lower arm
20
via an insulating plate on a vertical surface of a distal end of the lower arm
20
; an upper wire guide
30
fixed to a distal end portion of the Z-axis driving section
21
so as to guide the wire electrode
2
; an electric supply section
60
incorporated in the upper wire guide
30
so as to supply electricity to the wire electrode
2
; and a feeding/collecting section for feeding and collecting the wire electrode
2
.
The upper wire guide
30
allows the working fluid to flow to the workpiece
3
while guiding the wire electrode
2
, and is arranged such that an upper end portion of a guide body portion
33
having a collar is engaged with and fixed to a guide attaching plate
31
which has a channel for supplying the working fluid to the workpiece
3
and a guide hole for passing the wire electrode
2
therethrough. A hollow cylindrical portion for guiding the wire electrode
2
is provided in the guide body portion
33
. In this cylindrical portion, a cooling hole
33
x
for allowing the working fluid for cooling the wire electrode to flow in its interior is provided, and as a central hole of a rectifying plate
35
having a plurality of holes
35
a
for the working fluid to flow therethrough is engaged with and fixed to an outer peripheral surface of the cylindrical portion, a pool
36
is formed between a channel outlet of the guide attaching plate
31
and the holes
35
a
of the rectifying plate
35
.
A lower auxiliary guide
38
for guiding the wire electrode
2
is fixed in the interior of a lower portion of the guide body portion
33
, and an upper auxiliary guide
39
is also fixed in the interior of an auxiliary plate
37
fixed to an upper portion of the guide attaching plate
31
. It should be noted that the guide attaching plate
31
and the auxiliary plate
39
are fixed to an upper block
41
.
A jet nozzle
40
for guiding the wire electrode
2
into a guide hole in the lower wire guide
25
by means of the fluid has its outer peripheral surface fixed to an inner peripheral surface of the rectifying plate
35
, and has a collar whose top surface is fixed to a holding portion
35
b
of the rectifying plate
35
via a spring
45
, the jet nozzle
40
and the like being covered with a working fluid nozzle
47
. The arrangement provided is such that the tip of the jet nozzle
40
returns to avoid contact with the workpiece
3
as the spring
45
is compressed by the pressure of the fluid to lower the tip of the jet nozzle
40
and stop the supply of the working fluid. It should be noted that a pipe
50
for the jet nozzle
40
and a pipe
55
for the working fluid nozzle
47
are connected to inlet ports of the guide attaching plate
31
. In addition, since the basic configuration of the lower wire guide is identical to that of the upper wire guide, a description thereof will be omitted.
The electric supply section
60
is comprised of an electric supply die
62
for supplying electricity to the wire electrode
2
, a die holding plate
64
for fixing this electric supply die
62
and pressing it toward the wire electrode
2
side, and a drawer plate
66
capable of inserting or withdrawing the electric supply die
62
, the electric supply die
62
being electrically connected to an unillustrated power source.
The wire electrode feeding/collecting section is arranged such that the wire electrode
2
passes through a pipe
89
and is accommodated in a collecting box
90
by means of rollers
83
,
85
, and
87
for changing the direction of the wire electrode
2
wound around a wire bobbin
80
.
Referring to
FIGS. 6 and 7
, a description will be given of the operation of the wire electrical discharge machine having the above-described construction. First, when the working fluid is supplied to the pipe
50
, the jet nozzle
40
moves downward under the pressure of the working fluid while pressing the spring
45
, and a jet stream jets out from a jetting hole
40
a
of the jet nozzle
40
, which in turn causes the wire electrode
2
to pass through the interior of this jet stream and guides the wire electrode
2
to the lower wire guide
25
, connecting the wire electrode
2
thereto.
During processing, the working fluid from the pipe
50
is stopped, which in turn causes the jet nozzle
40
to return upward by means of the spring
45
, and the working fluid from the pipe
55
passes through the channel inside the guide attaching plate
31
, the curving and the like of the fluid due to the occurrence of turbulence being alleviated by means of the pool
36
. The working fluid then passes through the holes
35
a
in the rectifying plate
35
for stabilizing the direction in which the working fluid jets out from a jetting hole
47
a
of the working fluid nozzle
47
, and the working fluid jets out from the jetting hole
47
a.
Meanwhile, the wire electrode
2
is energized by the unillustrated power source through the electric supply die
62
. At the same time, since a large current flows across the contacting portions of the electric supply die
62
and the wire electrode
2
, and intense heat is produced therein, the working fluid is supplied from the cooling hole
33
x
to a wire passage
31
a
by being raised upward by means of the back pressure inside the working fluid nozzle
47
, and passes the contacting portions, thereby absorbing Joule heat produced in the contacting portions. Accordingly, processing is continued while maintaining the contacting portions at a substantially fixed temperature. It should be noted that the electric supply die in the lower guide is also cooled by similar action.
Electrical discharge between the workpiece
3
and the wire electrode
2
is continued, and while the table
5
is being moved along the X-, Y-, and Z-axes by moving the X-axis driving section
17
, the Y-axis driving section
19
, and the Z-axis driving section
21
, the high-speed working fluid from the working fluid nozzle
47
is supplied to a gap between the workpiece
3
and the working fluid nozzle
47
(hereafter referred to as the gap between the electrodes), thereby discharging and removing the processing sludge produced in the gap between the electrodes. While electrical discharge is continued in a state in which a proper gap is maintained between the electrodes and the resistance value is maintained to a fixed value, processing is continued.
However, with the electrical discharge machine having the above-described construction, as the wire electrode
2
travels while vibrating at its portion of contact with the electric supply die
62
, noncontacting portions are produced and very small arc discharge occurs at the noncontacting portions. Accordingly, the surface of the electric supply die
62
becomes roughened, and the wire electrode
2
which is softer than the electric supply die
62
becomes eroded, thereby producing wire dust. Moreover, also in the electric supply die of the lower wire guide, the surface of the electric supply die which passe

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