Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2003-04-28
2004-09-14
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C700S162000, C700S182000
Reexamination Certificate
active
06791053
ABSTRACT:
TECHNICAL FIELD
The present invention relates to improvements in a CAD/CAM device used for an electric discharge machine that conducts electric discharge machining on a workpiece by supplying electric power for machining to between an electrode and the workpiece.
BACKGROUND ART
FIG. 4
is an arrangement view of an electric discharge machine. In the view, reference numeral
1
is a mechanical body of the electric discharge machine, reference numeral
2
is a control section of the electric discharge machine, reference numeral
3
is a motor of Z-axis, reference numeral
4
is a head, reference numeral
5
is a clamp device, reference numeral
6
is a surface plate, reference numeral
7
is a machining tank, reference numeral
8
is an insulating machining solution stored in the machining tank
7
, reference numeral
9
is a motor for driving the machining tank, reference numeral
10
is a manual switch for elevating the machining tank, reference numeral
11
is an automatic electrode replacing device, reference numeral
12
is a machining electric power supply means, reference numeral
13
is a memory for storing an NC program, reference numeral
14
is an NC program analysis section, reference numeral
15
is a shaft drive section, reference numeral
16
is a machining tank drive section, reference mark E is an electrode, reference mark W is a workpiece, and reference mark H
L
is a level of a surface of the machining solution.
The shaft drive section
15
, the motor
3
of Z-axis and motors of X-axis and Y-axis, which are not shown in the view, correspond to a positioning means. The machining tank drive section
16
and the machining tank drive motor
9
correspond to a machining tank drive means for changing level H
L
of the surface of the machining solution with respect to workpiece W when the machining tank
7
is driven and made to ascend and descend.
Electrode E can be attached to and detached from the clamp device
5
of the head
4
by the automatic electrode replacing device
11
. Electrode E is attached to the clamp device
5
of the head
4
, and workpiece W is put and fixed onto the surface plate
6
arranged in the machining tank
7
. Under the above condition, electrode E and workpiece W are relatively positioned by the positioning means, and then electric discharge is generated in the machining solution
8
while voltage is being impressed upon between electrode E and workpiece W by the machining electric power supply means
12
. When electric discharge is generated between electrode E and workpiece W, workpiece W is melted and removed, so that electric discharge machining can be carried out.
An NC program for giving a command of operation of the electric discharge machine is stored in the memory
13
. This NC program is analyzed by the NC program analysis section
14
. This NC program analysis section
14
outputs moving commands to the shaft drive section
15
and the machining tank drive section
16
.
An ascending and descending motion of the machining tank
7
is carried out by the machining tank drive motor
9
that is driven by the machining tank drive section
16
. When the machining tank
7
is made to ascend and descend by the machining tank drive motor
9
, level H
L
of the surface of the machining solution is changed with respect to the position of workpiece W. For example, as disclosed in JP-A-5-261620, level H
L
of the surface of the machining solution is set at a position higher than the level of workpiece W by a distance not less than 50 mm, for example, level H
L
of the surface of the machining solution is set at a position higher than the level of workpiece W by a safe distance of about 100 mm. The reason why level H
L
of the surface of the machining solution is set at the position described above will be explained as follows. When level H
L
of the surface of the machining solution is too low with respect to the level of workpiece W, electric discharge is conducted in air. Accordingly, there is a possibility of the occurrence of fire. When level H
L
of the surface of the machining solution is too high with respect to the level of workpiece W, it is difficult for an operator to observe a state of electric discharge. Further, the clamp device
5
is soaked in the machining solution
8
, which could cause a mechanical breakdown.
When machining solution surface level H
L
is set at a level which is obtained when a safe distance is added to the level of workpiece W (This level is referred to as “safe level” H
LS
hereinafter.), it is necessary for an operator to adjust the level of the machining tank
7
by the manual switch
10
for ascending and descending the machining tank or alternatively it is necessary for an operator to give a command of the safe level or safe distance by an NC program. Each time the level of workpiece W is changed, safe level H
LS
must be adjusted, and further the operator must always conduct the adjustment.
FIG. 5
is a system arrangement view of the conventional CAD/CAM device
17
. In the view, reference numeral
18
is an electrode drawing data, reference numeral
19
is a workpiece drawing data, reference numeral
20
is a path deciding section, reference numeral
21
is an NC program, reference numeral
22
is a path checking means, and reference numeral
23
is a display means such as a CRT.
In the conventional CAD/CAM device
17
, the electrode drawing data
18
and the workpiece drawing data
19
are read in, and the path deciding section
20
decides a path of the machining motion according to the data which have been read in and the NC program
21
is created. The thus created NC program
21
is stored in the memory
13
arranged in the control section
2
of the electric discharge machine shown in FIG.
4
. The path check means
22
confirms a path between electrode E and workpiece W.
As the method of checking the NC program
21
, there are provided two methods. One is a method of graphic check conducted on a display of the display means
23
, and the other is a method of dry-run check conducted by a dry running. The method of graphic check is conducted as follows. In the graphic check, the machine is not actually operated but the NC program
21
is operated on the display means
23
or the display of the electric discharge machine so as to conduct checking on each shaft. The path is graphically displayed on the display means
23
or the display of the electric discharge machine, so that operation of each shaft can be checked by the coordinate values shown on the display. In the method of dry-run check, operation of each shaft is checked while the machine is being operated. Dry running in which the workpiece is not actually machined is conducted while the machining solution
8
is not being provided, so that operation of each shaft can be checked at high speed.
Setting of level H
L
of the machining solution at safe level H
LS
depends upon the operator as described above. Therefore, it is impossible for the conventional methods of graphic check and dry-run check to check a positional relation between electrode E and level H
LS
of the surface of the machining solution. Accordingly, even if graphic check and dry-run check are conducted, the following problems may be encountered. When electrode E to be used is too short, the clamp device
5
is soaked in the machining solution
8
in the process of electric discharge machining. Alternatively, when machining is conducted at a deep position in the machining solution, the clamp device
5
is soaked in the machining solution
8
.
When it is found that electrode E cannot be used as described above because the clamp device
5
has been soaked in the machining solution
8
after the actual machining process, electrode E must be manufactured again, which causes a decrease in the productivity and an increase in the manufacturing cost.
Especially in the case where a profile of workpiece W is complicated or a plurality of workpieces W, the level of which are different from each other, are present, and further in the case where machining is conducted while a pluralit
Kagiya Naoaki
Sugiyama Kazuhisa
Evans Geoffrey S.
Mitsubishi Denki & Kabushiki Kaisha
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