Wire electrical discharge machine

Details Wire electrical discharge machine Wire electrical discharge machine

2000-01-05

2001-09-25

Evans, Geoffrey S. (Department: 1725)

Electric heating

Metal heating

Cutting or disintegrating

C219S069140

Reexamination Certificate

active

06294748

ABSTRACT:

TECHNICAL FIELD
The present invention relates to improvements on a wire electrical discharge machine so as to allow a water-column generating nozzle for guiding a wire electrode by means of a fluid to be realized by a simple mechanism having a small fluid loss.
BACKGROUND ART
A conventional wire electrical discharge machine will be described with reference to
FIGS. 8 and 9
. In
FIGS. 8 and 9
, 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 a 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
through. A hollow cylindrical portion for guiding the wire electrode
2
is provided in the guide body portion
33
. 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 this 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
and a die holding plate
64
for fixing this electric supply die
62
, the electric supply die
62
being electrically connected to an unillustrated power source.
The 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. 8 and 9
, 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
, and while electrical discharge between the workpiece
3
and the wire electrode
2
is continued and 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, since the jet nozzle
40
undergoes the extending and retracting operation separately and independently of the working fluid nozzle
47
, the extending/retracting mechanism is complex, and since the jet nozzle
40
is lowered by the fluid against the reaction force of the spring
45
, there has been a problem in that the fluid loss is large.
Further, after the working fluid passes through the channel in the guide attaching plate
31
from the pipe
55
, and temporarily stays in the pool
36
with its pressure thereby increased, the working fluid passes through the holes
35
a
in the rectifying plate
35
and undergoes conversion to velocity energy, then stays in a space portion formed by the rectifying plate
35
and the inner surface of the working fluid nozzle
47
and is converted to pressure energy. The high-speed fluid is then jetted out from the jetting hole
47
a
in the working fluid nozzle
47
to the gap between the electrodes as the velocity energy.
Namely, since the form of energy of the working fluid undergoes four conversions in terms of both the velocity and pressure, the retained energy of the working fluid is gradually lost at the inlet of the guide attaching plate
31
, causing a decline in the velocity energy when the working fluid jets out from the jetting hole
47
a
of the working fluid nozzle
47
. Accordingly, there has been a problem in that, particularly when the gap between the electrodes has become wide apart, the pressure of the working fluid drops, and the disturbance in the je

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