Wire electric discharge machine

Details Wire electric discharge machine Wire electric discharge machine

2003-03-20

2004-11-09

Evans, Geoffrey S. (Department: 1725)

Electric heating

Metal heating

Cutting or disintegrating

Reexamination Certificate

active

06815630

ABSTRACT:

TECHNICAL FIELD
The present invention relates to improvements in a wire electric discharge machine to conduct machining on a workpiece by electric discharge energy when electric power for machining is supplied between a wire electrode and the workpiece.
BACKGROUND ART
FIG. 5
is an arrangement view showing a conventional wire electric discharge machine. In the drawing, reference numeral
1
is a wire electrode, reference numeral
1
a
is a used wire electrode, reference numeral
2
is a supply bobbin, reference numeral
3
is a tension brake, reference numeral
4
is a column, reference numeral
5
is an upper guide, reference numeral
6
is a workpiece, reference numeral
7
is a lower guide, reference numeral
8
is a lower roller, reference numeral
9
is a lower arm, reference numeral
10
is a saddle, reference numeral
11
is a wire recovery section fixed to the saddle
10
, reference numeral
12
is a capstan roller, reference numeral
13
is a pinch roller, reference numeral
14
is a feed motor for driving the capstan roller
12
, reference numeral
15
is a hollow wire guide, reference numeral
16
is a wire cutter, reference numeral
16
a
is a cutting blade of the wire cutter
16
, reference numeral
17
is a wire recovery box, reference mark A is a traveling direction of the wire electrode
1
, the traveling direction of which is changed by the lower roller
8
, reference mark B is a straight line connecting the rotational center of the capstan roller
12
with that of the pinch roller
13
, and reference mark C is a point at which the pinch roller
13
is pressed against the capstan roller
12
.
The pinch roller
13
comes into pressure contact with the capstan roller
12
at point C when a restoring force generated by a spring not shown acts on the pinch roller
13
. The wire guide
15
is used to guide the wire electrode
1
, which has passed through a wire electrode holding section provided between the capstan roller
12
and the pinch roller
13
, to the wire cutter
16
(after starting wire electric discharge machining, a used wire electrode
1
a
is guided to the wire cutter).
Next, operation will be explained below. Tension of the wire electrode
1
is controlled by the tension brake
3
arranged on the upstream side of traveling of the wire electrode with respect to the workpiece
6
. The wire electrode
1
is held by the capstan roller
12
and the pinch roller
13
which are arranged on the downstream side of traveling of the wire electrode with respect to the workpiece
6
(after starting wire electric discharge machining, a used wire electrode
1
a
is held by the capstan roller and the pinch roller). While the wire electrode
1
is being held between the capstan roller
12
and the pinch roller
13
, the wire electrode
1
is made to travel being pulled by the driving torque generated by the feed motor
14
. As described above, while the wire electrode
1
is traveling, electric power for machining is supplied between the workpiece
6
and the wire electrode
1
, and wire electric discharge machining is conducted on the workpiece
6
.
The used wire electrode
1
a
, which has been consumed in the process of wire electric discharge machining, passes through the lower guide
7
, lower roller
8
, lower arm
9
, saddle
10
and wire recovery section
11
and is cut by the wire cutter
16
and then accommodated in the wire recovery box
17
. Alternatively, in some cases, the used wire electrode
1
a
is dropped into the wire recovery box
17
and recovered as it is without being cut by the wire cutter
16
.
Recently, due to the increases in the sizes of the supply bobbin
2
and the wire recovery box
17
, the wire electrode having larger diameter can be used. In this case, the used wire electrode
1
a
is cut with the wire cutter
16
, for example, the used wire electrode
1
a
is cut with the wire cutter disclosed in Japanese Unexamined Patent Publication No. 9-267221 and recovered.
As shown in
FIG. 5
, in the case where the capstan roller
12
and the pinch roller
13
are arranged symmetrically to each other with respect to the used wire electrode
1
a
, that is, in the case where straight line B connecting the rotational center of the capstan roller
12
with that of the pinch roller
13
is perpendicular to wire electrode traveling direction A which has been changed by the lower roller
8
after the completion of the electric discharge, the wire electrode supply is suitably automatized when the wire electrode is connected. However, the following problems may be encountered. Since the used wire electrode
1
a
, which has been consumed after the completion of electric discharge machining, is held and pulled only by pressing point C at which the pinch roller
13
is pressed against the capstan roller
12
, a heavy load is given to the holding section to hold the used wire electrode
1
a
by the pinch roller
12
and the capstan roller
12
because tension given to the wire electrode
1
changes in the process of electric discharge machining of the workpiece
6
. Accordingly, the wire electrode
1
a
tends to break.
FIG. 6
is a schematic illustration to explain an arrangement of the capstan roller
12
and the pinch roller
13
by which the problem of breaking of a wire electrode can be solved. In the drawing, reference mark D indicates a direction changing point at which the wire electrode traveling direction is changed from wire electrode traveling direction A. Like reference characters are used to indicate like parts in
FIGS. 5 and 6
.
The arrangement shown in FIG.
6
(
a
) is disclosed, for example, in Japanese Unexamined Patent Publication No. 59-232730, and the arrangement shown in FIG.
6
(
b
) is disclosed, for example, in Japanese Unexamined Patent Publication No. 1-92029. The arrangement shown in FIG.
6
(
c
) is a well known arrangement commonly applied to an actual product. In any arrangement, straight line B connecting the rotational center of the capstan roller
12
with that of the pinch roller
13
is not perpendicular to traveling direction A of the wire electrode
1
, the direction of which is changed by the lower roller
8
. In the above arrangement, the wire electrode
1
is pulled by an outer diameter portion (portion of the capstan roller
12
round which the wire electrode
1
is wound) of the capstan roller
12
between pressing point C, at which the pinch roller
13
is pressed against the capstan roller
12
, and direction changing position D at which the wire electrode traveling direction is changed from wire electrode traveling direction A. Therefore, it is difficult for the wire electrode
1
to break in this arrangement compared with the arrangement shown in
FIG. 5
in which the wire electrode is pulled only by pressing point C at which the pinch roller
13
is pressed against the capstan roller
12
.
However, the arrangements shown in FIGS.
6
(
a
) and
6
(
b
) have the following problems. When the wire electrodes
1
are connected with each other, it is difficult for the wire electrode
1
, the direction of which is changed by the lower roller
8
, to be automatically fed between the capstan roller
12
and the pinch roller
13
. Accordingly, it is difficult to automatize the feed of the wire electrode
1
. The arrangement shown in FIG.
6
(
c
) is suitable for automatization of the feed of the wire electrode
1
in the case of connecting the wire electrode
1
with each other, however, in the arrangement shown in FIG.
6
(
c
), the traveling direction of the wire electrode
1
is changed obliquely downward from wire electrode traveling direction A. Therefore, in the case of connecting the wire electrodes
1
with each other, since the wire electrode
1
is conveyed to the wire recovery section
11
in a machining solution, the machining solution enters the wire cutter
16
from a gap between the capstan roller
12
and the pinch roller
13
, which causes a problem in which rust is generated on the cutting blade
16
a.
FIG. 7
is a view showing an example in which the wire cutter
16
is not used in the arrangement

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