Electricity: motive power systems – Positional servo systems – Program- or pattern-controlled systems
Reexamination Certificate
2002-05-20
2004-09-07
Hsieh, Shih-Yung (Department: 2837)
Electricity: motive power systems
Positional servo systems
Program- or pattern-controlled systems
C318S579000, C219S069170, C219S069110
Reexamination Certificate
active
06788019
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of and an apparatus for electric discharge machining in which a voltage is applied between a tool electrode and a workpiece so as to generate an electric discharge and execute machining (“working”). More particularly, this invention relates to a method of and an apparatus for electric discharge machining which can achieve a high speed response in X-axis, Y-axis and Z-axis directions for driving an electrode, and improve machining accuracy.
BACKGROUND ART
In electric discharge machining, a tool electrode and a workpiece are arranged in a machining fluid, a voltage is applied therebetween and an electric discharge is generated so as to erode the workpiece. In an electric discharge machining apparatus, in order to machine a desired shape while maintaining a stable machining state, a driving apparatus which adjusts positions of the tool electrode or the workpiece is provided.
FIG. 17
is a schematic view which shows an outline structure of a conventional electric discharge machining apparatus which is described, for example, in pages 63-64 of “Discharge Machining Technique—From Basics to Future Development” issued by Nikkan Kogyo Shinbun, Ltd (1997).
In
FIG. 17
, reference numeral
101
denotes a tool electrode, reference numeral
102
denotes a workpiece, reference numeral
103
denotes a machining fluid, reference numeral
104
denotes a machining tank, reference numeral
1201
denotes an electrode mounting section which mounts the tool electrode
101
, reference numeral
501
denotes a head section which supports the electrode mounting section
1201
, reference numeral
502
denotes a head drive section which drives the tool electrode
101
, the electrode mounting section
1201
and the head section
501
, reference numeral
503
denotes a column section, reference numeral
504
denotes a column driving section which drives the tool electrode
101
, the electrode mounting section
1201
, the head section
501
, the head driving section
502
and the column section
503
, reference numeral
505
denotes a saddle section, reference numeral
506
denotes a saddle driving section which drives the tool electrode
101
, the electrode mounting section
1201
, the head section
501
, the head driving section
502
, the column section
503
, the column driving section
504
and the saddle section
505
, and reference numeral
507
denotes a bed section. The head driving section
502
, the column driving section
504
and the saddle driving section
506
are, for example, constituted by an AC motor and a ball screw, and respectively constitute a driving section which positions the electrode in Z direction, a driving section which positions in Y direction and a driving section which positions in X direction. Further, reference numeral
119
denotes a machining power supply which supplies a machining energy to the tool electrode
101
and the workpiece
102
, reference numeral
120
denotes a machining state detecting apparatus which detects a machining state, reference numeral
1202
denotes a servo amplifier which supplies a drive current to each of the electrode mounting section
1201
, the head driving section
502
, the column driving section
504
and the saddle driving section
506
so as to execute positioning, and reference numeral
1203
denotes a control apparatus giving a command value to the servo amplifier
1202
and the machining power supply
119
. Further, reference numeral
122
denotes an electric discharge machining process progressed between the tool electrode
101
and the workpiece
102
.
FIG. 18
shows a gap control system which controls machining state in the electric discharge machining apparatus shown in FIG.
17
. In
FIG. 18
, reference numeral
301
denotes an electric discharge machining process section, reference numeral
302
denotes a machining state detecting section, reference numeral
303
denotes a reference value setting section, reference numeral
304
denotes a machining pass setting section, reference numeral
1301
denotes a machining control section, reference numeral
1302
denotes a XYZ driving control section, reference numeral
1303
denotes a current amplifier section, reference numeral
1304
denotes a XYZ driving section, and reference numeral
1305
denotes a XYZ driving apparatus constituted by the XYZ driving control section
1302
, the current amplifier section
1303
and the XYZ driving section
1304
. The electric discharge machining process section
301
corresponds to the electric discharge machining process
122
, the machining state detecting section
302
corresponds to the machining state detecting apparatus
120
, the XYZ driving control section
1302
and the current amplifier section
1303
correspond to the servo amplifier
1202
, and the XYZ driving section
1304
corresponds to the head driving section
502
, the column driving section
504
and the saddle driving section
506
, respectively. Further, the reference value setting section
303
, the machining pass setting section
304
and the machining control section
1301
are constructed in the control apparatus
1203
. Further, y indicates a state variable of the electric discharge machining process, ym indicates a detected value detected by the machining state detecting section
302
, r indicates a reference value set by the reference value setting section
303
, e indicates a deviation determined from the reference value r and the detected value ym, Rp indicates a machining pass vector set by the machining pass setting section
304
, Up indicates a position command value to the XYZ driving control section
1302
, Uc indicates a current command value to the current amplifier section
1303
, Ic indicates a current amount supplied to the XYZ driving section
1304
, St indicates a position detected value obtained from the XYZ driving section
1304
, and Mp indicates an electrode position operating amount operated by the XYZ driving section
1304
. The position command value Up to the XYZ driving control section
1302
is determined by the machining control section
1301
on the basis of the deviation e and the machining pass vector Rp. Since the machining pass vector Rp is given by a Cartesian coordinate system (XYZ), the position command value Up is in the same Cartesian coordinate system (XYZ). Further, the position detected value St is the detected value in the X direction, the Y direction and the Z direction. Accordingly, in the XYZ driving control section
1302
, the position command value Up and the position detected value St are compared, and the current command value Uc to the current amplifier section
1303
is determined. The current command value Uc is given to each of three current amplifiers for the head driving section
502
, the column driving section
504
and the saddle driving section
506
. That is, in the conventional gap control system shown in
FIG. 18
, it is made such as to detect, for example, an average gap voltage by the machining state detecting section
302
, and move the tool electrode by the XYZ driving apparatus
1305
so that the detected value coincides with a predetermined reference value, thereby achieving a stable machining state.
However, the machining state irregularly changes, and in order to maintain a stable machining state, a high speed response of the XYZ driving apparatus becomes important. When a stable machining state can not be maintained, a short-circuit state, a continuous arc state or the like is frequently generated, and an effective electric discharging state contributing to the machining is reduced, so that the machining speed is reduced. Further, since the short-circuit state, the continuous arc state or the like is frequently generated, a crack or a pit is formed on the machined surface, or an abnormal wear of a tool electrode is locally generated, so that a reduction of machining surface quality or a deterioration of machining accuracy is caused. When a high speed response of the XYZ driving apparatus can not be expected, since it is intended to maintain
Imai Yoshihito
Miyake Hidetaka
Nakagawa Takayuki
Hsieh Shih-Yung
Leydig , Voit & Mayer, Ltd.
Martin Edgardo San
Mitsubishi Denki & Kabushiki Kaisha
LandOfFree
Electric discharge machining device and 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 Electric discharge machining device and electric discharge..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Electric discharge machining device and electric discharge... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3197526