Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
1999-08-09
2001-08-21
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069130
Reexamination Certificate
active
06278076
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a wire cut electric discharge machine which moves one of either a wire electrode or a workpiece with respect to the other in an X-Y plane. In particular, the present invention relates to a wire cut electric discharge machine capable of forming a taper cut surface in a workpiece by tilting a traveling wire electrode with respect to the X-Y plane.
BACKGROUND
In wire cut electric discharge machines, either the wire electrode or the workpiece is moved relative to the other within a horizontal plane (“the X-Y plane”) determined by two perpendicular axes as the wire electrode travels between a pair of wire guides perpendicular to the X-Y plane. In many cases, the work piece is affixed to a work stand, and the work stand is attached to a table mounted on a bed movable within the X-Y plane.
Also known, as illustrated in
FIG. 5
, are wire cut electric discharge machines in which the table does not move, and each of the arms to which the wire guides are attached is supported by a part capable of moving within the X-Y plane. The wire cut electric discharge machine comprises a bed
1
, a non-moving table
2
mounted on top of the bed
1
, and a movable column
21
. A work stand
7
is affixed to the table
2
, and a workpiece W is attached to the work stand
7
. A machining tank sidewall
8
which surrounds the workpiece W is also affixed the table
2
.
A column
21
is mounted on the bed
1
so as to be movable in the X direction, and a ram
22
is mounted on top of the column
21
so as to be movable along the Y axis, which is perpendicular to the X axis. A head
9
is provided on the portion of ram
22
which protrudes toward the machining tank side, such that it can move in the Z axis which is perpendicular to the X-Y plane.
A wire supply device comprising a device to impart tension to a wire electrode E and multiple pulleys is provided on the machining head
9
. A taper cut unit
23
, formed of sliders
231
and
232
, is provided on the bottom edge of the machining head
9
. The slider
231
is movable in the U axis direction which is parallel to the X axis, and the slider
232
is movable in the V axis direction which is parallel to the Y axis. An automatic wire threader
13
—the “AWT”—which automatically pushes the wire electrode E through a hole in the workpiece W, is attached to the taper cut unit
23
. In the illustrated example, upper arm
11
is also attached on one edge to the taper cut unit
23
, and an upper wire guide device
14
is attached to the other end of the upper arm
11
. An approximately L-shaped lower arm
15
is affixed at one end to the bottom of the ram
22
, and extends downward in the column
21
through a hole in the ceiling of the column
21
. The lower arm
15
next penetrates the sidewall
8
of the horizontally extending machining tank, and a lower wire guide device
16
is attached to the other end of the lower arm
15
.
During machining, the wire electrode E normally moves in the X-Y plane relative to the workpiece W, and travels between the pair of wire guide devices
14
and
16
perpendicular to the X-Y plane. For example, when fabricating a die with a tapered surface, machining is usually done by tilting the wire electrode E which travels between the pair of wire guide devices
14
and
16
by some angle away from the Z axis. With “taper cuts” of this type, the upper wire guide device
14
moves in the U-V plane which is determined by the orthogonal U and V axes, by means of the taper cut unit
23
. The size of the taper cut unit
23
is limited by the machine's rigidity, such that the maximum movement of the upper wire guide device
14
is normally about 70 mm in both the U and V axes.
In recent years there has been a need for wire cut electric discharge machines having a large degree of movement in the U and V axes in order to form a sloped surface with a substantial angle on a workpiece of some thickness. A wire cut electric discharge machine with such features but without a loss of machine rigidity is illustrated in FIG.
6
. The same reference numerals (as used in
FIG. 5
) are used to designate the same elements as in the wire cut electric discharge machine of
FIG. 6
, so an explanation thereof is omitted. A mechanical cover
100
, which blocks electromagnetic radiation above a certain frequency in accordance with the law, covers the wire cut machine.
The mechanical cover
100
, which blocks electromagnetic radiation above a certain frequency is accordance with EMC (electromagnetic compatibility) regulations, covers the wire cut electric discharge machine. A moving body
3
is mounted on a bed
1
so as to be movable along the X axis, and a moving body
4
is mounted on a column
21
so as to be moveable along the Y axis which is perpendicular to the X axis. The lower arm
15
is supported at one end by a moving body
4
. A moving body
5
is mounted on the moving body
4
so as to be movable along the U axis which is parallel to the X axis, and a moving body
6
is mounted on the moving body
5
so as to be movable along the V axis which is parallel to the Y axis. A panel
10
is provided on the portion of the moving body
6
which protrudes toward the machining tank side, so as to be movable along the Z axis which is perpendicular to the X-Y plane. A wire supply device comprising a wire bobbin
12
around which is wound the wire electrode E, a device for imparting tension the wire electrode E, and multiple pulleys, is provided on the panel
10
. Furthermore, the automatic wire threader
13
and the upper arm
11
are attached to the panel
10
. A numerical control device
30
comprising a computer controls movement in the X axis, the Y axis, the U axis, the V axis, and the Z axis directions.
As is clear from the diagrams, the wire cut electric discharge machine in
FIG. 6
provides a maximum movement for the moving body
5
and the moving body
6
which is greater than that of sliders
231
and
232
in FIG.
5
. In recent wire cut electric discharge machines, a greater maximum movement is sought with respect to the U and V axes, as is a smaller installation footprint. Therefore when the panel
10
and the machining tank side wall
8
are designed for minimum size, there is a danger that these parts may be physically struck by other mechanical components. It is necessary, for example, to prevent the head
9
from striking other mechanical components such as the machining tank side wall
8
or the mechanical cover
100
, or excessive overhang of the head
9
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a wire cut electric discharge machine which assures a greater maximum movement with respect to the U and V axes, wile at the same time reliably preventing physical striking by movable mechanical components of other mechanical components.
Other objects of the present invention will be described below, and will be apparent to practitioners of the art.
In order to accomplish the above and other objects, a wire cut electric discharge machine according to the present invention has a first wire guide movable relative to a workpiece in a first axial direction, and a second wire guide movable relative to a workpiece in a second axial direction which is parallel to the first axial direction, for machining the workpiece by generating an electrical discharge between a wire electrode traveling between the first and second wire guide and, the workpiece. where the sum of the degree of movement in the first axial direction and the degree of movement in the second axial direction is limited.
In order to accomplish the above and other objects, a wire cut electric discharge machine according to the present invention has a first wire guide movable relative to a workpiece in a first axial direction, and a second wire guide movable relative to a workpiece in a second axial direction which is parallel to the first axial direction, for machining the workpiece by generating an electrical discharge between a wire electrode traveling between the first and second wire guide
Devinsky Paul
Evans Geoffrey S.
McDermott & Will & Emery
Sodick Co. Ltd.
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