Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2000-11-17
2002-08-13
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069120, C219S069170
Reexamination Certificate
active
06433295
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to improvements in a method of electric discharge machining and device thereof for conducting electric discharge machining on a workpiece by supplying electric power between an electrode and the workpiece.
FIG. 7
is a view showing an overall arrangement of a wire electric discharge machine which is an example of the conventional electric discharge device. In the drawing, reference numeral
2
is a workpiece, reference numeral
3
is a lower nozzle for spraying work fluid during working, reference numeral
4
is an NC device, reference numeral
5
is an upper nozzle for spraying work fluid during working, reference numeral
6
is a wire electrode for working, reference numeral
7
is a tapering device, in which U-axis drive unit and V-axis drive unit are housed, for moving the upper nozzle
5
with respect to the lower nozzle
3
in the case of tapering, reference numeral
8
is a surface plate table on which the workpiece
2
is set, reference numeral
9
is a power source for supplying electric power for working to the workpiece
2
and the wire electrode
6
, reference numeral
21
is a wire bobbin round which the wire electrode
6
is wound, reference numeral
22
is a pulley for changing a direction of the wire electrode
6
, reference numeral
23
is a tensioner for giving a constant intensity of tension to the wire electrode
6
, reference numeral
24
is a wire recovery roller for feeding the wire electrode
6
, reference numeral
27
is an X-axis servo motor for moving the surface plate table
8
in the direction of X-axis, reference numeral
28
is a Y-axis servo motor for moving the surface plate table
8
in the direction of Y-axis, reference numeral
29
is a servo motor of Z-axis for moving the tapering device
7
and the upper nozzle
5
in the direction of Z-axis, reference numeral
30
is a servo motor of U-axis for moving the tapering device
7
in the direction of U-axis, and reference numeral
31
is a servo motor of V-axis for moving the tapering device
7
in the direction of V-axis. In this case, electric power supply to the workpiece
2
and the wire electrode
6
is omitted here.
FIGS. 8
a
and
8
b
are arrangement views of a surface plate table of a conventional wire electric discharge machine for obtaining smoother surface roughness on a work surface. In the drawing, reference numeral
1
is an insulating member, reference numeral
2
is a workpiece, reference numeral
3
is a lower nozzle for spraying work fluid in the process of working, reference numeral
5
is an upper nozzle for spraying work fluid in the process of working, reference numeral
10
is a feeder cable, reference numeral
11
is a finish feeder cable, reference numeral
12
is a contactor for opening and closing the feeder cable
10
and the finish feeder cable
11
, reference numeral
13
is an auxiliary contactor for opening and closing electric power supply from the feeder cable
10
to the workpiece
2
, and reference numeral
14
is a work tank for storing work fluid so that the workpiece
2
, lower nozzle
3
and upper nozzle
5
can be dipped in the work fluid.
In FIGS
8
a
and
8
b,
electric power supply to the wire electrode is not shown, for clarity.
Next, a method of electric power supply will be explained below. For example, when working is conducted under the condition that the surface roughness of a work surface is more than 3 &mgr;mRmax, both the feeder cable
10
and the finish feeder cable
11
are used for working, and when working is conducted under the condition that the surface roughness of a work surface is not more than 3 &mgr;mRmax, which is smoother than the above surface roughness, only the finish feeder cable
11
is used for working so that an intensity of electric discharge energy can be reduced to conduct working with high accuracy. The above is an example in which material of the workpiece
2
is SKD
11
, thickness of the workpiece is 20 mm, material of the wire electrode
6
is brass and diameter of the wire electrode
6
is 0.2 mm. In the case where material of the workpiece
2
is changed or thickness of the workpiece
2
is changed, and in the case where material of the wire electrode
6
is changed or diameter of the wire electrode
6
is changed, surface roughness of the work face, by which an intensity of electric power to be supplied is changed, is changed. In the above example, surface roughness 3 &mgr;mRmax is changed.
A case in which surface roughness of the work face, by which an intensity of electric power to be supplied is changed, is 3 &mgr;mRmax will be explained as follows.
In the structure shown in FIG.
8
(
a
), the insulating member
1
is arranged in an upper portion of the surface plate table
8
, and the workpiece
2
is set in an upper portion of the insulating member
1
. The frequency of working determined by the required surface roughness of a product is inputted into the working program, and the energy setting of the working electric power source
9
with respect to the frequency of working is also inputted into the working program, and then the program is carried out.
In the case of working in which surface roughness of the work face is not more than 3 &mgr;mRmax, electric power supply from the feeder cable
10
is stopped by the contactor
12
, and electric power is supplied only by the finish feeder cable
11
. When the auxiliary contactor
13
is opened at the same time, the workpiece
2
is insulated except for the supply of electric power by the finish feeder cable
11
. Therefore, no electric current is supplied to the workpiece
2
except for the electric current supplied by the finish feeder cable
11
. Therefore, it becomes possible to conduct working of smoother surface roughness.
However, the structure shown in FIG.
8
(
a
) has the following disadvantages. The insulating member
1
is arranged in an upper portion of the surface plane table
8
. Therefore, it is necessary to attach the insulating member
1
onto the surface plane table
8
at a site where working is actually conducted. Further, it is also necessary to fix the workpiece
2
to the insulating member
1
. For the above reasons, compared with a case in which the workpiece
2
is directly attached onto the surface plane table
8
, it takes much longer time for preparation. As a result, the manufacturing cost of the parts manufactured by electric discharge might be increased.
In the structure shown in FIG.
8
(
b
), the workpiece
2
is directly arranged in an upper portion of the surface plane table
8
. According to the structure shown in FIG.
8
(
b
), the frequency of working determined by the required surface roughness of a product is inputted into the working program, and the energy setting of the working electric power source
9
with respect to the frequency of working is also inputted into the working program, and then the program is carried out. In the case of working in which surface roughness of the work face is not more than 3 &mgr;mRmax, electric power supply from the feeder cable
10
is stopped by the contactor
12
, so that electric power is supplied only by the finish feeder cable
11
. Therefore, no electric current is supplied to the workpiece
2
except for the electric current supplied by the finish feeder cable
11
. Therefore, it becomes possible to conduct working of smoother surface roughness.
However, the structure shown in FIG.
8
(
b
) has the following disadvantages. In the structure shown in FIG.
8
(
b
), the insulating member
1
is attached to a lower portion of the surface plate table
8
. However, when the working tank
14
and the surface plane table
8
are arranged close to each other and an area in which the working tank
14
and the surface plane table
8
are opposed to each other is large, the working tank
14
and the surface plane table
8
compose a type of condenser. Therefore, when AC voltage is impressed between the working tank
14
and the surface plane table
8
, an electric current flows between them although they are electrically insulate
LandOfFree
Surface roughness dependent methods of electric discharge... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Surface roughness dependent methods of electric discharge..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Surface roughness dependent methods of electric discharge... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2887293