JPH068052A - Electric discharge machining method - Google Patents

Abstract

PURPOSE:To prevent the generation of concentrated electric discharge and release the concentrated electric discharge efficiently at the time of being generated. CONSTITUTION:Split machining tool electrodes 2, 2' are driven by servo motors 3, 3' through transmission mechanism 4, 4'. Voltage is applied between the machining tool electrodes 2, 2' and a workpiece 1 by an electric discharge machining power unit 5, and currents flowing to the split machining tool electrodes 2, 2' are detected by current sensors 7, 7'. An electrode motion control device 6 performs the driving control of the servo motors 3, 3' on the basis of the average gap voltage Vg so as to move the split machining tool electrodes 2, 2'. The concentration of eletric discharge (whether electric discharge is concentrated on either the electrode 2 or 2') is detected by signals from the current sensors 7, 7', and in the case of detecting concentrated electric discharge, the electrode motion control device 6 moves the electrode, to which concentrated electric discharge is generated, away from the workpiece, and brings the other electrode close to the workpiece. Gaps between the electrodes 2, 2' and the workpiece are also made large and small alternately and periodically.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method,
In particular, it relates to an electric discharge machining method using a die-sinking electric discharge machine.

[0002]

2. Description of the Related Art A die-sinking electric discharge machine is such that a machining tool electrode and a workpiece are made to face each other with a minute gap in a machining tank filled with an insulating machining fluid. A voltage is applied between the two to generate an electric discharge to partially remove the workpiece, and the electric discharge position is sequentially changed to process the workpiece. Therefore, it is not preferable that the discharge positions are concentrated at a fixed position. However, due to the non-uniformity of the discharge gap contamination state (processing waste concentration), residual ion concentration, etc.,
Occurrence of electric discharge may be locally concentrated between the machining tool electrode and the workpiece. In such a case, conventionally, the machining tool electrode or the workpiece is moved to increase the distance between the machining tool electrode and the workpiece, thereby increasing the resistance between them and preventing the occurrence of discharge. The frequency of discharge occurrence at the concentrated discharge position is reduced.

[0003]

As described above, when a concentrated discharge is generated, conventionally, the machining tool electrode is moved relatively to the work piece to uniformly increase the gap between the work tool electrode and the work piece electrode, and the concentration is increased. It is intended to prevent discharge, but in this method,
Since the gap between the machining tool electrode and the workpiece is increased regardless of the location (position) where the concentrated discharge is generated, the gap is similarly increased not at the location where the concentrated discharge is generated but at other positions as well. Will be done. Therefore, at the position where the concentration of processing dust and residual ions is high due to the concentrated discharge (near the position where the concentrated discharge occurs), it becomes easier for the discharge to continue to occur than at other positions. Was not easy, and it was not a satisfactory method of releasing concentrated discharge.

Further, if it is attempted to reduce the frequency of discharge at a place where the generation of discharge is concentrated, there is a problem that the overall discharge frequency is reduced and the machining efficiency is deteriorated. Therefore, an object of the present invention is to provide an electric discharge machining method in which a concentrated discharge is unlikely to occur, and further to provide an electric discharge machining method capable of easily eliminating the concentrated discharge when the concentrated discharge occurs. is there.

[0005]

SUMMARY OF THE INVENTION According to the present invention, either one or both of the machining tool electrode and the workpiece are periodically arranged so that the distance between the machining tool electrode and the facing surface of the workpiece becomes uneven. It is possible to prevent the occurrence of concentrated discharge by adopting a method of forcibly moving the discharge generation position by moving the discharge position to the center. Also,
When a concentrated discharge is detected, one or both of the machining tool electrode and the work piece are moved periodically so that the distance between the machining tool electrode and the facing surface of the work piece is non-uniform. By forcibly moving the position, the concentrated discharge is released. Further, the position where the electric discharge is generated is detected, and the distance between the machining tool electrode at the position where the electric discharge is concentrated and the work piece is made relatively large with respect to other positions. Either one or both are moved to forcibly move the discharge generation position to cancel the concentrated discharge.

As a method of making the distance between the machining tool electrode and the facing surface of the workpiece uneven, at least one of the machining tool electrode and the workpiece is divided into a plurality of pieces, and the machining tool electrode and the workpiece are opposed to each other. The distance between the surfaces is moved so as to be nonuniform in the above-mentioned division unit, or at least one of the machining tool electrode and the workpiece is changed in the facing surface posture with respect to the other, so that the machining tool electrode and the workpiece are A method of making the distance between the facing surfaces of the workpiece non-uniform, and further, one of the machining tool electrode or the workpiece is divided into a plurality of parts, and the machining tool is formed by partial displacement of the one and change of the facing surface attitude of the other. The above problems have been solved by adopting a method of making the distance between the electrode and the facing surface of the workpiece nonuniform.

[0007]

By moving the divided machining tool electrode or the work piece in units of division, or by changing the facing surface posture of the machining tool electrode or the work piece, the work tool electrode and the work piece are The machining tool electrode is periodically moved relative to the workpiece so that the distance between the facing surfaces becomes non-uniform. As a result, discharge is likely to occur at the facing distance between the machining tool electrode and the workpiece, that is, at a position where the gap is small, and discharge is relatively unlikely to occur at a position where the gap is large. However, it is possible to suppress the occurrence of concentrated discharge and uniformly generate discharge between the machining tool electrode and the facing surface of the workpiece. Further, only when a concentrated discharge is detected, the machining tool electrode and the workpiece are relatively periodically moved so that the distance between the machining tool electrode and the facing surface of the workpiece becomes uneven. The discharge generation position is forcibly moved to cancel the concentrated discharge. Furthermore, the position where the electric discharge is generated is detected, and the machining tool electrode and the work piece are moved relative to each other so that the distance between the work tool electrode at the position where the electric discharge is concentrated and the work piece is relatively large compared to other positions. The discharge by increasing the resistance at the position where the concentrated discharge is generated, suppressing the discharge generation, promoting the discharge generation at other positions, and forcibly moving the discharge generation position to cancel the concentrated discharge. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of the essential parts of an electric discharge machine for carrying out the first embodiment of the present invention.

In FIG. 1, 1 is a workpiece, 2 and 2'are divided machining tool electrodes, and this embodiment shows an example in which the machining tool electrode is divided into two. The machining tool electrodes 2 and 2'are driven by servomotors 3 and 3'via transmission mechanisms 4 and 4'which convert the rotational movement of the ball screw / nut into a linear movement. Further, each machining tool electrode 2, 2 ′ has a conductor wire 10 branched from a conductor wire 9 connected to the electric power source device 5 for electric discharge machining,
10 ′ is further connected, and the workpiece 1 and the electric discharge machining power source device 5 are connected to each other by a conductive wire 11. The electric discharge machining power source device 5 connects between the machining tool electrodes 2, 2 ′ and the workpiece 1. A voltage is applied. The electric discharge machining power supply device 5 is the same as a conventionally known electric discharge machining power supply device.

Further, current sensors 7, 7'for detecting the currents i1, i2 flowing in the conducting wires 10, 10 ', that is, the discharge currents flowing in the machining tool electrodes 2, 2', respectively, are provided. The currents detected by 7'are smoothed by smoothing circuits 8 and 8 ', respectively, and input to the electrode movement control device 6. Further, the electrode motion control device 6 detects the voltage of the lead wire 9 and smoothes it by the smoothing circuit 12 to detect the average gap voltage Vg between the machining tool electrodes 2, 2'and the workpiece 1. ing. The electrode motion control device 6 includes a processor, ROM, RA
It is composed of a memory such as M, an input / output circuit, an A / D converter, a servo circuit for driving and controlling the servomotors 3 and 3 ′, a servo amplifier, and the like, and is equivalent to the conventionally known electrode movement control device 6.

Although the processing tank and the like are not shown in FIG. 1, the workpiece 1 is attached by attaching it to an insulating processing liquid stored in the processing tank, and the processing tool electrodes 2 and 2'are attached. When electric discharge machining is started by facing the work piece 1 with a minute gap, the electric discharge machining power source device 5 causes the machining tool electrodes 2, 2 ′ and the work piece 1 through the conductors 9, 11. A voltage is intermittently applied between the machining tool electrodes 2 and 2'and the workpiece 1
Electric discharge is generated between them to perform electric discharge machining. On the other hand, in the electrode movement control device 6, the average gap voltage Vg detected from the conductor 9 via the smoothing circuit 12, and the conductors 10 and 10.
The signals I1 and I2 obtained by detecting the current flowing through the ′ by the current sensors 7 and 7 ′ and smoothing the detection signals by the smoothing circuits 8 and 8 ′ are input, and the A / D converter in the electrode movement control device 6 is input. Converts these input signals into digital signals, and the processor of the electrode motion control device 6 carries out the processing shown in FIG. 2 based on the converted signals to drive the machining tool electrodes 2, 2 '. Control 3,3 '.

The machining tool electrodes 2 and 2 are attached to the electrode motion control device 6.
Setting voltage Vs (servo voltage) that determines the machining feed rate
When the electric discharge machining start command is input after setting the amount A for displacing and moving the divided machining tool electrodes 2, 2 ', the electric discharge machining power supply device 5 causes the machining tool electrodes 2, 2' And a voltage is intermittently applied between the workpiece 1 and
Electric discharge is generated and electric discharge machining is started. Further, the processor of the electrode movement control device 6 executes the processing shown in FIG. 2 every predetermined period, and first, the average gap voltage Vg that is input is input.
Is read, and a value obtained by subtracting the set target voltage Vs from the average gap voltage Vg is used to calculate the machining tool electrodes 2 and 2 from the voltage difference.
The movement amount is calculated by multiplying the movement amount of ‘(the movement amount of the servo motors 3, 3 ′) by the feedback gain Kg for conversion,
This movement amount is used as the command position Z of the current machining tool electrodes 2 and 2 '.
Is added to a register for storing a new movement command position Z (step S1). In this embodiment, it is assumed that the machining tool electrodes 2, 2'move in the Z-axis direction, and the machining tool electrodes 2, 2'move in the direction of the workpiece 1 (lower side in FIG. 1). The Z axis is in the positive direction. That is, the command position Z of the new machining tool electrodes 2 and 2'is calculated by performing the following formula 1.

New position (Z) = current command position (Z) + (Vg−Vs) Kg (1) Next, it is determined whether or not concentrated discharge has occurred (step S
2) If no concentrated discharge has occurred (the processing for determining whether or not the concentrated discharge still occurs will be described later), the machining tool electrode command position Z calculated in step S1 is divided into each machining tool electrode. Movement command position Z for 2, 2 '
1, Z2 (step S3), and drive control of the servomotors 3, 3'to move to the position (step S3).
7). When the servomotors 3 and 3'are driven, the machining tool electrodes 2 and 2'will move to the instructed positions Z1 and Z2 via the transmission mechanisms 4 and 4 '. Hereinafter, unless the concentrated discharge is detected, the processor of the electrode movement control device 6 carries out the processing of the steps S1, S2, S3 and S7 every predetermined period. The control by this process is the same as the control of the conventional machining tool electrode. When the gap between the machining tool electrodes 2 and 2'and the workpiece 1 is large, and as a result, the average gap voltage Vg is high,
(Vg-Vs) Kg calculated by the above formula 1 also has a large value, the machining tool electrodes 2 and 2'also move greatly, and the gap (gap) is reduced. If the gap is reduced, discharge easily occurs. Therefore, the average gap voltage decreases, and the movement amount of the machining tool electrodes 2 and 2 ′ also decreases. After all, the moving speed of the machining tool electrodes 2 and 2'is determined by the set target voltage Vs, and the gap voltage Vg is controlled so as to match the target voltage Vs. This point is no different from the conventional one, and the divided machining tool electrodes 2, 2 '
Since the same commanded position is commanded, the divided machining tool electrodes 2 and 2'move integrally, and this point is no different from the conventional case.

However, when the concentrated discharge is detected in step S2, in the present embodiment, the divided machining tool electrodes 2, 2'are moved so as to cancel the concentrated discharge. Therefore, first, the concentrated discharge detection process will be described. The current sensor 7 detects a current i1 flowing through one of the divided machining tool electrodes 2 and the current sensor 7 ′ detects a current i2 flowing through the other machining tool electrode 2 ′. The signals after smoothing the detection signals from 7 ′ by smoothing circuits 8 and 8 ′ are I1 and I2.
2, the signals I1 and I2 are
It represents the high frequency of each discharge on the side of the machining tool electrode 2 '. That is, when the electric discharge occurs only in the machining tool electrode 2, only the current i1 is generated, and the current i2 hardly flows. Therefore, the signal I1 obtained by smoothing the detected current values has a large value, but the signal I2 has a small value. On the contrary, when the electric discharge occurs only on the machining tool electrode 2'side, the signal I2 has a large value, but the signal I1 has a small value. Therefore, the rate of occurrence of electric discharge on the side of the machining tool electrode 2 is obtained from the signals I1 and I2, and when this rate is not within the set range, it is determined that concentrated electric discharge has occurred. That is, the concentrated discharge is determined by the following two equations.

LL <I1 / (I1 + I2) <LH (2) When the value of I1 / (I1 + I2) is less than or equal to the set lower limit value LL, it means that the signal I1 is small and I2 is large, and on the machining tool electrode 2 side. Means that there is little discharge and the discharge is concentrated on the side of the machining tool electrode 2 '. Also, I1 / (I
When the value of (1 + I2) is equal to or more than the set upper limit value LH, it means that, on the contrary, the electric discharge is small on the side of the machining tool electrode 2 ′ and the electric discharge is concentrated on the side of the machining tool electrode 2. And I
When the value of 1 / (I1 + I2) is between the lower limit value LL and the upper limit value LH, it is determined that the discharge is dispersed and the concentrated discharge is not generated.

Thus, when it is determined in step S2 that the discharge is not concentrated, the above-described step S3 is performed.
The same electrode motion control as in the conventional S7 is performed. However, when it is determined that the discharge is concentrated, the process proceeds to step S4, the signals I1 and I2 are compared, and when I1 is large, that is, the current i1 flowing through the machining tool electrode 2 is large, and the machining tool electrode is large. When it is determined that the electric discharge is concentrated on the 2 side, the command position Z1 to the machining tool electrode 2 is a value obtained by subtracting the set amount A from the position Z calculated in step S1 (Z
-A), and the command position Z2 to the other machining tool electrode 2 '
Is (Z + A), and the machining tool electrode 2 and the machining tool electrode 2
The movement command position to ′ ′ is changed (step S5), and the servomotors 3 and 3 ′ are drive-controlled so as to move to this position (step S7). As a result, the machining tool electrode 2 on the side where the electric discharge is concentrated becomes far from the workpiece 1 and its gap becomes large. However, the other machining tool electrode 2'approaches the workpiece 1 and its gap becomes smaller. Therefore, the discharge is less likely to occur on the side of the machining tool electrode 2 and is more likely to occur on the side of the machining tool electrode 2 ', and the concentration of the discharge is forcibly released.

On the other hand, when it is determined in step S4 that the signal I2 is large (the discharge is concentrated on the machining tool electrode 2'side), conversely, the command position Z1 to the machining tool electrode 2 is set to (Z + A). , The command position Z2 to the other machining tool electrode 2'is (ZA) (step S6), and the command position Z
1, servomotors 3 and 3'are driven to move the machining tool electrode 2 and machining tool electrode 2 '(step S
7). As a result, the machining tool electrode side where the electric discharge is concentrated is moved away from the work piece 1 and the other machining tool electrode is brought closer to the work piece side, so that the gap on the side where the electric discharge is concentrated becomes large. Is less likely to occur, and the other machining tool electrode has a smaller gap and discharge is more likely to occur, thereby forcibly canceling the concentration of discharge.

FIG. 3 is a block diagram of a main part of an electric discharge machine for carrying out the second embodiment of the present invention. The electric discharge machine and the electric discharge machine shown in FIG. 1 are such that the machining tool electrode 2 is not divided. , And the driving method of the machining tool electrode 2 is different. In this embodiment, the machining tool electrode 2 is rotatably connected to the output shaft of a transmission mechanism 4 that converts the rotational movement of the servomotor 3 into a linear movement at a substantially central position P1 of the machining tool electrode 2. Another servo motor 3'is attached to this output shaft, and the servo motor 3'is
The output shaft of the transmission mechanism 4'for converting the rotational movement of the above into a linear movement rotatably connects the end P2 of the machining tool electrode 2. Further, at both ends of the machining tool electrode 2, the electric discharge machining power supply device 5 has a conductor wire 10 branched from a conductor wire 9 for voltage application,
10 'is connected to the workpiece 1 and the electric power source device 5 for electric discharge machining.
A voltage is applied between the working tool electrode 2 and the work piece 1 by the conductive wire 11 connected therebetween. Further, current sensors 7 and 7'for detecting the currents i1 and i2 flowing through the conductors 10 and 10 'are provided, and the detection signals of these current sensors 7 and 7'are smoothed by the smoothing circuits 8 and 8'. I1 and I2 are input to the electrode motion control device 6, and the gap voltage between the machining tool electrode 2 and the workpiece 1 is detected from the potential of the conductor 9 and smoothed by the smoothing circuit 12 to obtain the average gap voltage Vg. Obtain, electrode movement control device 6
The point that the voltage Vg is input to is the same as in the first embodiment shown in FIG.

In the second embodiment, the machining tool electrode 2 is swung about the position P1 so that the gap of the machining tool electrode with respect to the work piece 1 is periodically nonuniform. Thus, the concentration of the discharge is prevented, and the concentration of the discharge cancels the concentrated discharge by shortening the swing cycle.

Next, the operation of this embodiment will be described with reference to the electrode motion control device 6
The process performed by the processor of FIG. 4 every predetermined period Tc will be described with reference to the flowchart shown in FIG. The target voltage Vs that determines the moving speed of the machining tool electrode 2, the swing amplitude B, and the swing cycle Tp are set in advance, and electric discharge machining is started.

When the electric discharge is started, the electric power source device 5 for electric discharge machining intermittently applies a voltage between the machining tool electrode 2 and the workpiece 1 to start the electric discharge machining as in the conventional case. on the other hand,
The current i flowing through the conductors 10 and 10 'with the current sensors 7 and 7'
Signals I1 and I2 obtained by detecting 1 and i2 and being smoothed by the smoothing circuits 8 and 8'are input to the electrode movement control device 6,
/ D converted. Further, the average gap voltage Vg output from the smoothing circuit 12 is also input to the electrode movement control device 6 and A
/ D converted. Therefore, the processor of the electrode movement control device 6 reads the input average gap voltage Vg and subtracts the set target voltage Vs from the average gap voltage Vg to obtain a value obtained by subtracting the set target voltage Vs from the voltage difference. ´
The moving amount is calculated by multiplying it by the feedback gain Kg for conversion, and this moving amount is added to the register that stores the current commanded position Z of the machining tool electrode 2 to obtain a new moved commanded position Z. That is, the movement command position Z is obtained by performing the calculation of the above formula 1 (step Q1). Next, it is determined whether or not discharge is concentrated (step Q2).
Whether or not this concentrated discharge has occurred is determined in the above-mentioned 2
It is judged by the formula.

The position where the electric discharge is generated is close to the position P3 where the conductor wire 10 is connected to the machining tool electrode 2, and the conductor wire 10 '
When it is distant from the position P4 where is connected, the resistance due to the machining tool electrode 2 between the position P3 and the discharge position is smaller than the resistance between the position P4 and the discharge position. Therefore, the current i1 flowing through the conducting wire 10 becomes larger than the current i2 flowing through the conducting wire 10 '. Similarly, when discharge occurs at a position closer to position P4 than position P3, current i2 becomes larger than current i1. Therefore, a signal I obtained by detecting the currents i1 and i2 by the current sensors 7 and 7'and smoothing the detection signals by the smoothing circuits 8 and 8 '.
1 and I2, when a concentrated discharge is generated and the discharge occurrence point becomes a fixed position, one of the signals I1 and I2 becomes large and the other signal becomes small. It can be determined whether or not.

In this way, it is determined whether or not there is a concentrated discharge, and when it is determined that no concentrated discharge has occurred, the value of the timer is compared with the value of the set swing period Tp (step Q3).
The timer is set to "0" by initialization when the power is turned on.

If the value of the timer does not exceed the value of the set oscillation period Tp, the timer is incremented (step Q4) and the servo motor is moved to the position of the position Z obtained in step Q1 stored in the register. 3 and drive the servomotor 3'to the moving position of the servomotor 3'stored in the register W (step Q
9). The swing amplitude B is set in the register W by initialization. As a result, the machining tool electrode 2
Is driven by the servomotors 3 and 3 ', so that the position P2 is tilted closer to the workpiece 1 than the position P1.

Hereinafter, unless concentrated discharge is detected, the processing of steps Q1, Q2, Q3, Q4 and Q9 is executed every processing cycle Tc, and when the value of the timer becomes equal to or greater than the value Tp of the set oscillation cycle in step Q3. , The timer is reset to "0" (step Q5), and it is judged whether the value of the register W is positive (step Q6).
Is set to a negative value (-B), and if negative, a positive value (+ B) of the swing amplitude B is set (steps Q7 and Q8), and the servomotors 3 and 3'are calculated in step Q1. The moved position Z and the position B or -B stored in the register W are moved. In this way, the machining tool electrode 2 swings around the position P1 (the connecting point of the output shaft of the transmission mechanism driven by the servomotor 3) with the swing period Tp and the amplitude B, and the electric discharge machining proceeds. It will be.

On the other hand, if it is determined in step Q2 that there is a concentrated discharge, the process proceeds to step Q6, and if the amplitude value stored in the register W is negative, it is a positive value + B, and if it is positive, a negative value −.
Store B in register W (steps Q6, Q7, Q
8) Then, the servomotor 3'is moved to the position of the value stored in the register W (step Q9). As a result, the machining tool electrode 2 oscillates in this processing cycle Tc, and the concentrated discharge is thereby eliminated.

In the above-mentioned embodiment, the concentrated discharge is detected by the judgment of the above-mentioned formula 2, but especially the second discharge is detected.
In this embodiment, when the concentrated discharge occurs at the midpoint between the positions P3 and P4, the current i flowing through the conductors 10 and 10 '
Since 1 and i2 are almost equal to each other, the phenomenon that the concentrated discharge cannot be detected by the above formula 2 occurs. Therefore, as a method of detecting the concentrated discharge more accurately, the conductive wire 10,
The signals from the current sensors 7 and 7 ′ that detect the currents i1 and i2 flowing in 10 ′ are input to the peak hold circuit during a period in which a voltage is applied to the machining tool electrode 2 and the workpiece 1 (so-called ON section), The peak current is obtained (hereinafter, this peak hold signal is set to I1p with respect to the current i1 and the current i2
To I2p), and I1p / I2p by the division circuit
Then, the I1p / I2p is differentiated, the differential signal is further full-wave rectified and smoothed, and the full-wave rectified and smoothed signal is compared with a reference value by a comparator to detect concentrated discharge. Good. That is, if no concentrated discharge occurs, the signal I1p / I2p from the division circuit always changes. However, if a concentrated discharge occurs, the signal I1p / I2p
The change in the size of is small. Therefore, when this signal is differentiated, the signal obtained by differentiating it will fluctuate greatly in positive and negative when no concentrated discharge occurs, but when concentrated discharge occurs, this differentiated signal is small. Become. Therefore, the signal obtained by full-wave rectifying and smoothing this differentiated signal becomes equal to or lower than the reference value when the concentrated discharge occurs, and exceeds the reference value when the concentrated discharge does not occur. Whether or not it can be detected.

In the first embodiment, the divided machining tool electrodes 2 and 2'are provided with two independent servo motors 3 and 3 '.
However, the machining tool electrodes 2, 2 divided by the driving device as shown in the second embodiment shown in FIG.
′ May be driven. That is, one split machining electrode 2
Is driven by the servomotor 3 via the transmission mechanism 4, and the other split machining tool electrode 2'is driven by the servomotor 3'attached to the output shaft of the transmission mechanism via the transmission mechanism 4 '. Good. In this case, in the process by the electrode movement control device 6, in FIG. 2, the command Z2 issued in step S3 as a command to the servomotor 3'is "0".
And the command in step S5 is Z2 = 2A
In step S6, the difference is that Z2 = -2A.

Also in the embodiment shown in FIG. 3, the machining tool electrode 2 may be swung by two independent servo motors as shown in FIG. In this case, the electrode movement control device 6
The only difference is that steps Q7 and Q8 in the flowchart shown in FIG. 4 change to W = Z−B and W = Z + B, respectively.

Further, in the above-mentioned first embodiment, an example in which the machining tool electrode is divided into two has been shown, but it may be divided into a larger number. Further, the workpiece may be divided instead of dividing the machining tool electrode, and the divided workpiece may be controlled to move instead of the divided machining tool electrode. Also,
The first and second embodiments may be put together to divide one of the machining tool electrode and the workpiece and swing the other to change the posture.

[0031]

According to the present invention, the machining tool electrode is moved relative to the workpiece so that the gap between the machining tool electrode and the facing surface of the workpiece becomes non-uniform. Since the point where the gap becomes small varies, it is possible to prevent the occurrence of concentrated discharge. Further, only when the concentrated discharge occurs, the discharge position can be forcibly moved and the concentrated discharge can be eliminated by making the gap between the machining tool electrode and the facing surface of the workpiece uneven. In particular, the concentrated discharge can be canceled by detecting the concentrated discharge position and increasing the gap at the concentrated discharge position.

[Brief description of drawings]

FIG. 1 is a block diagram of a main part of an electric discharge machine that implements a first embodiment of the present invention.

FIG. 2 is a flowchart of processing executed by a processor of the electrode movement control device according to the first embodiment.

FIG. 3 is a block diagram of a main part of an electric discharge machine for carrying out a second embodiment of the present invention.

FIG. 4 is a flowchart of processing executed by a processor of the electrode movement control device according to the second embodiment.

[Explanation of symbols]

 1 Workpiece 2,2 'Machining tool electrode 3,3' Servo motor 4,4 'Transmission mechanism 5 Electric discharge power supply device 6 Electrode motion control device 7,7' Current sensor 8,8 ', 12 Smoothing circuit

Claims (6)

[Claims] 1. A machining tool electrode and a workpiece are opposed to each other with a minute gap filled with an insulating machining liquid, and a voltage is applied between the two to cause an electric discharge to remove the workpiece. In the electrical discharge machining method described above, one or both of the machining tool electrode and the work piece are periodically moved to set the electric discharge generation position so that the distance between the machining tool electrode and the facing surface of the work piece becomes uneven. An electric discharge machining method characterized in that it is forcibly moved. 2. A machining tool electrode and a workpiece are opposed to each other with a minute gap filled with an insulating machining liquid, and a voltage is applied between the two to generate an electric discharge to remove the workpiece. In the electric discharge machining method, when concentrated discharge is detected,
To periodically move either or both of the machining tool electrode and the workpiece so that the distance between the machining tool electrode and the facing surface of the workpiece becomes non-uniform, and the discharge generation position is forcibly moved. An electric discharge machining method characterized by: 3. A machining tool electrode and a workpiece are opposed to each other with a minute gap filled with an insulating machining liquid, and a voltage is applied between them to generate an electric discharge to remove the workpiece. In this electric discharge machining method, the position where the electric discharge is generated is detected and the distance between the machining tool electrode at the position where the electric discharge is concentrated and the workpiece is relatively large with respect to other positions. An electric discharge machining method characterized in that either or both of the workpieces are moved to forcibly move the electric discharge generation position. 4. At least one of the machining tool electrode and the work piece is divided into a plurality of pieces, and the distance between the machining tool electrode and the facing surface of the work piece is moved so as to be nonuniform in each division unit. The electric discharge machining method according to claim 2 or 3. 5. The distance between the machining tool electrode and the facing surface of the workpiece is made non-uniform by changing the facing surface attitude of at least one of the machining tool electrode and the workpiece. The electric discharge machining method according to claim 1, claim 2, or claim 3. 6. One of the machining tool electrode and the work piece is divided into a plurality of parts, and the distance between the machining tool electrode and the opposite surface of the work piece is unbalanced due to partial displacement of the one and change of the facing surface attitude of the other. The electric discharge machining method according to claim 1, wherein the electric discharge machining method is uniform.