Electric heating – Metal heating – Cutting or disintegrating
Reexamination Certificate
2001-09-25
2003-08-19
Evans, Geoffrey S. (Department: 1725)
Electric heating
Metal heating
Cutting or disintegrating
C219S069170
Reexamination Certificate
active
06608275
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a technology for machining an object by generating an electric discharge between the object and an electrode. More particularly, this invention relates to a technology for controlling a jump operation in which distance between the object and the electrode is temporarily increased at each of predetermined times or depending on the machining state.
BACKGROUND ART
Conventionally, an electric discharge machining device performs a jump operation. This jump operation is an operation in which distance between the object and the electrode (“interelectrode distance”) is temporarily increased at each of predetermined times or depending on the machining state. Machining waste deposited between the electrode and the object can be removed efficiently because of this jump operation. Moreover, speed or precision of electric discharge machining can be improved.
FIG. 14
is a block diagram showing the configuration of a conventional electric discharge machining device. Moreover, FIGS.
15
(
a
)-
15
(
d
) are time charts for explaining a jump operation performed by the conventional electric discharge machining device. FIG.
15
(
a
) is a time chart showing a change in interelectrode distance in the jump operation, FIG.
15
(
b
) is a time chart showing a change in speed in the jump operation, FIG.
15
(
c
) is a time chart showing a change in acceleration in the jump operation, and FIG.
15
(
d
) is a graph showing a result of Fourier transform of the time chart in FIG.
15
(
a
).
Referring to
FIG. 14
, the interelectrode voltage detection unit
7
detects a voltage between the electrode
11
and the object
12
(“interelectrode voltage”). The interelectrode servo control unit
3
controls the position of the main shaft
13
according to the detected interelectrode voltage. Moreover, the interelectrode servo control unit
3
performs electric discharge machining of the object
12
by using an electric discharge phenomenon. The jump control unit
102
controls temporarily increasing the interelectrode distance at each of predetermined times or depending on the machining state. Whether machining by the interelectrode servo control unit
3
is to be performed or a jump operation by the jump control unit
102
is to be performed can be selected with the switching unit SW
10
. When the jump control unit
102
performs a jump operation, the jump control unit
102
notifies the interelectrode servo control unit
3
the jump operation is to be performed, and switches the switching unit SW
10
from the interelectrode servo control unit
3
to the jump control unit
102
.
The jump operation will be described below with reference to FIGS.
15
(
a
)-
15
(
d
). The jump control unit
102
starts the jump operation at a point of time at which a predetermined time has elapsed or a point of time t
1
at which a predetermined machining state is set. In the jump operation, the electrode
11
is raised at a speed V
1
until the interelectrode distance changes from a distance l
1
to a distance l
2
. At a point of time t
2
at which the interelectrode distance is distance l
2
, the electrode
11
is switched from an up state to a down state to move the electrode
11
downward at a speed −V
1
. At a point of time at which the interelectrode distance is a distance l
3
, the speed −V
1
of the of the electrode
11
is changed into the speed −V
2
, and the electrode
11
is reduced in speed, and the interelectrode distance returns to the distance l
1
. At the point of time t
3
, the speed −V
1
is reduced to the speed −V
2
because the electrode
11
may collide with the object to be machined
12
by inertia of the electrode
11
when the electrode
11
is moved downward at the speed −V
1
.
In this conventional electric discharge machining device, since the speed is sharply changed at the points of time t
1
, t
2
, and t
3
, the response of a mechanical control system is delayed, or a target is overshot. In addition, since the locus of the interelectrode distance is a locus containing a high-frequency component, a resonance of the mechanical system is excited, and vibration remains after the jump operation is completed. In this case, since the electric discharge machining is performed by applying a voltage across the electrodes in a state in which the interelectrode distance between the electrode
11
and the object to be machined
12
is kept at several &mgr;m to tens of &mgr;m, a problem that machining precision or speed is considerably decreased by slight residual vibration is posed.
Moreover, conventionally, a deceleration distance (l
3
−l
1
) may be increased to prevent machining precision from being degraded by the influence of residual vibration or the overshooting of the shaft. However, in this case, it takes long time to perform the jump operation, and a problem that the entire machining time is extended is posed.
More specifically, a jump operation performed by the conventional electric discharge machining device has a problem in machining precision or machining speed is considerably decreased depending on a setting of residual vibration or deceleration distance because speed or acceleration is sharply changed.
In fact, with respect to the object
12
to be machined and the electrode
11
, an optimum set frequency and the allowable maximum component value of the frequency in the jump operation change, depending on the mass of the electric discharge machining device, a machining condition, aging of the electric discharge machining device, and the like. In this case, when these two elements are adjusted, the machining time is shortened, and the machining precision can be increased. It is hard for an operator of the electric discharge machining device to adjust the set frequency and the allowable maximum component value optimally.
DISCLOSURE OF THE INVENTION
This invention has been made to solve the above problems, and has as its object to obtain an electric discharge machining device and an electric discharge machining method which can shorten machining time and which can improve a machining precision.
In order to solve the this problem, the electric discharge machining device according to this invention comprises an interelectrode servo control unit which controls an interelectrode distance which is a distance between an electrode and an object to be machined while applying a predetermined voltage across the electrode and the object; and a jump control unit which controls a jump operation in which the interelectrode distance is temporarily increased at every predetermined time or depending on a machining state. The jump control unit includes a command locus generation unit which generates a smooth command locus having a frequency component in a predetermined frequency range which is not higher than a predetermined frequency or lower than the predetermined frequency. The jump control unit controls the jump operation by using a smooth command locus generated by the command locus generation unit. For example, since the command locus generation unit is designed to generate a command locus by using a sine wave having a low-frequency component which is lower than a resonance frequency of a mechanical system, vibration of the mechanical system does not remain upon completion of the jump operation, and precise machining can be performed.
The electric discharge machining device according to another invention comprises an interelectrode servo control unit which controls an interelectrode distance which is a distance between an electrode and an object while applying a predetermined voltage across the electrode and the object; and a jump control unit which controls a jump operation in which the interelectrode distance is temporarily increased at every predetermined time or depending on a machining state. The jump control unit includes a command locus generation unit which generates a smooth command locus having a frequency component in a predetermined frequency range except for a frequency range of a first frequency which is lowe
Imai Yoshihito
Nakagawa Takayuki
Evans Geoffrey S.
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Jump control method and apparatus for electric does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Jump control method and apparatus for electric, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Jump control method and apparatus for electric will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3085133