JP2001162448A - Device and method for electric discharge machining - Google Patents

Abstract

PROBLEM TO BE SOLVED: To assure a high machining accuracy with a simple procedure without being affected by the various types of factors varying a discharge gap such as discharge area and machining fluid. SOLUTION: The position of a discharge electrode discharged in the same electrical conditions as the final electrical conditions where a specified reference surface is used in an actual machining is measured during or before machining, a predetermined amount of machining is added to a measured value and an actual discharge machining is performed using an added result as a new machining end position.

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 and apparatus which can eliminate a dimensional error factor generated in electric discharge machining, particularly, a dimensional error of a discharge gap.

[0002]

2. Description of the Related Art Electric discharge machining is a method of machining a workpiece by using a discharge electrode and a workpiece (work) in a machining fluid as two electrodes and directly generating a discharge between the discharge electrode and the workpiece. It is used for processing in a wide range of fields.

In the conventional electric discharge machining, before the electric discharge machining, an electrode is brought into contact with a reference surface of a workpiece to measure the position of the electrode. EDM is performed by moving the electrodes,
At the time of electric discharge machining, a position obtained by subtracting a gap length of electric discharge machining (hereinafter referred to as an electric discharge gap) from the set machining amount is set as a machining end position, and the electrode is fed to this machining end position.

Accordingly, in this conventional electric discharge machining,
Unless the discharge gap value of the electric discharge machining, which increases or decreases depending on various machining conditions, is specified accurately, the machining cannot be performed with high accuracy.

Other factors affecting the machining accuracy include thermal displacement and electrode wear. Among them, the discharge gap greatly affects the accuracy.

As a method of correcting these error factors,
A technique disclosed in Japanese Patent Publication No. 2559789 has been proposed.

In this prior art, a minute discharge is generated for a predetermined time at a reference plane position set at a predetermined position under a gap detection condition at which a gap with an electrode becomes a specific value before starting machining. After the reference surface is set in the machining depth direction, the electrode is moved to the machining position to perform a predetermined electric discharge machining. In this electric discharge machining, the electrode feed amount is
The value obtained by subtracting the set value of the discharge gap from the machining depth from the reference plane is set as the target value.

Further, in this prior art, a characteristic of the gap that converges to a specific value under the gap detection condition is utilized to eliminate a machining gap error during machining, a machining error due to electrode wear and thermal deformation during machining. After detecting and further processing,
The electrode position is detected by performing discharge using the gap detection condition at the bottom position of the processing hole, a processing depth error is measured based on the detection result, and a total processing error is calculated from the detected various errors. If an error is large and correction processing is necessary, correction processing based on the detected error is performed.

[0009]

However, the micro-discharge treatment prior to the start of machining, which is performed in the above-described prior art, is merely a means of setting a reference plane. The discharge gap value that increases or decreases variously according to the conditions is set to a specific value, and the set discharge gap value is subtracted from the machining depth from the reference plane to obtain the electrode feed amount.

In this conventional technique, in addition to the error due to the discharge gap, a machining error due to electrode wear and thermal deformation is taken into account, and an error from the target value is determined based on the complicated and complicated procedure described above. Is to be detected. Further, in the above-described conventional technique, when an error from a target value is large, it is necessary to perform correction processing, and the operation is extremely inefficient.

Incidentally, one of the factors for increasing or decreasing the discharge gap is the area of the discharge surface of the discharge electrode. FIG. 11 shows the relationship between the machining area (discharge area) and the discharge gap. As is clear from FIG. 11, the discharge gap increases as the machining area increases.

As described above, the discharge gap changes in accordance with the machining area. However, in the above-described prior art, the setting of the discharge gap value is not performed in consideration of the machining area value. Otherwise, satisfactory processing accuracy cannot be obtained. Although it is preferable to set the discharge gap value finely for each processing area in order to perform the processing with high accuracy, the amount of the discharge gap becomes very large, and it is also a difficult operation to judge and select an appropriate value. Furthermore, since the discharge gap changes depending on the change and deterioration of the kinematic viscosity due to the use time of the working fluid and the material of the workpiece, it must be taken into account.

Further, in powder discharge in which machining is performed by mixing a metal powder into a working fluid, one of the other factors for increasing or decreasing the discharge gap is the amount of the powder to be mixed into the working fluid.

FIG. 12 shows the relationship between the powder mixing concentration and the discharge gap. As is clear from FIG. 12, the discharge gap is almost proportional to the powder mixing concentration.

As described above, although the discharge gap changes depending on the concentration of the powder mixed therein, the above-described prior art does not set the discharge gap value in consideration of this, so that the above-described error detection processing and correction processing are performed. What not to do is
Satisfactory processing accuracy cannot be obtained. In addition, since the powder mixing concentration of the processing fluid changes depending on the processing time,
In order to cope with this, it is necessary to periodically exchange the working fluid for a new one or to change the set value of the discharge gap according to time.

As described above, the discharge gap, which greatly affects the machining accuracy, varies depending on various machining conditions such as the machining area and the state of the machining fluid. Therefore, it is impossible to match the result after machining with a preset discharge gap value. A high processing accuracy could not be obtained unless the troublesome and complicated error detection processing and correction processing as in the above-described conventional technique were performed.

The present invention has been made in view of such circumstances, and is not affected by various factors that change the discharge gap, such as the discharge area and the state of the machining fluid, and can be corrected in a simple procedure. It is an object of the present invention to provide an electric discharge machining method and apparatus capable of ensuring machining accuracy with high accuracy without performing electric discharge machining.

[0018]

According to the present invention, a discharge is generated between the discharge electrode and the workpiece while a machining fluid is supplied between the discharge electrode and the workpiece. In an electric discharge machining method for electric discharge machining of a workpiece,
Before or during machining, a first step of performing a discharge at a predetermined reference plane portion under the same electrical conditions as those used at the time of final machining, and measuring a coordinate position at which the discharge has occurred, and A second step of adding a required machining amount to the coordinate position; a result of addition of the second step as a machining end position; and, at the time of final machining, the same electrical conditions as those used in the first step are used. And a third step of performing an electric discharge machining.

That is, during or before machining in the machining process, the position of the discharge electrode which is discharged for a predetermined time under the same electric conditions as the final electric conditions used for actual machining on a predetermined reference plane is measured. To the machining amount given in advance, and the result of the addition is set as a new machining end position to execute the actual electric discharge machining.

In the present invention, the reference surface is discharged for a predetermined period of time (several seconds) under the same electrical finishing conditions as the actual machining conditions, using the electrodes used for the machining portion surface to be subjected to electric discharge machining. Utilizing that the same discharge gap as the machined part is obtained, therefore, even if the actual discharge gap is unknown or changed, the electrode is extended from the discharge position on the reference surface to the machining end position with the required machining amount added. By performing the electric discharge machining by feeding, high machining accuracy can be maintained.

The measurement and processing of the present invention are performed under the same electrical conditions, in the same working fluid and with the same electrode.
In addition, since the processing is performed with the same processing area, the processing state during measurement and processing becomes the same, and no error occurs due to these changes. Also, if the discharge measurement of the reference surface is performed during the machining, the electric discharge machining time becomes short afterwards,
The influence of errors due to electrode consumption and thermal displacement is small and can be ignored.

Further, it is possible to maintain high processing accuracy without performing correction processing after processing as in the prior art.

In one embodiment of the present invention, a discharge is generated between the discharge electrode and the workpiece in a state in which a machining fluid is supplied between the discharge electrode and the workpiece, so that the workpiece is generated. Before or during machining, an electric discharge machine is used to perform electric discharge at the same electric conditions as those used at the time of final machining at a predetermined reference plane part, and the coordinate position where the electric discharge occurs is measured. Measurement control means, a memory means for storing a required machining amount corresponding to each of a plurality of discharge electrodes used for machining, and a machining amount of the discharge electrode stored in the memory means at the obtained coordinate position. An arithmetic means for adding, and an electric discharge machining system for performing the electric discharge machining using the same electrical conditions as those used for measurement by the measurement control means at the time of final machining, wherein the result of the addition is a machining end position. So that comprises a means.

According to the present invention, the machining amounts of a plurality of discharge electrodes used for machining are stored, the measurement control means for performing the above-described discharge measurement, the adding means for computing the machining end position, and the computed machining end position. Since the electric discharge machining control means for performing the actual electric discharge machining is provided, the electric discharge machining can be automatically and continuously performed in addition to the effects described above.

[0025]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 shows the configuration of an electric discharge machine to which the present invention is applied and a control system thereof.

In FIG. 1, the processing table 4 is provided with an X-direction driving device 5 and a Y-direction driving device 7, whereby the processing table 4 can be moved in the X and Y directions orthogonal to each other on a horizontal plane. it can. Further, the processing table 4 is provided with an X-direction position detection device 6 and a Y-direction position detection device 8 for detecting the movement position.

A workpiece 3 is arranged on the processing table 4. A machining tank 18 is provided so as to surround the work 3, and the machining tank 18 is filled with a machining fluid 17 mixed with metal powder for electric discharge machining. As the working fluid 17, water, oil, or the like may be used in addition to the above.

At the lower end of the machining head 1 of the electric discharge machine,
The discharge electrode 2 is detachably mounted. The processing head 1 is equipped with a Z-direction driving device 9 for moving the processing head 1 in a vertical (height) direction with respect to the processing table 4 and a Z-direction detecting device 10 for detecting the moving position. In this case, although not shown, the electrode 2 can be automatically replaced with another electrode using an automatic hand.

The automatic control device 11 for controlling the machining table 4 and the electric discharge machine includes a numerical control device 12
(Hereinafter, referred to as an NC device), a power supply control device 13, a discharge circuit 14, a discharge detection means 15, and the like, and are used in combination with a controller 16.

When a discharge is generated between the electrode 2 and the work 3, the discharge detecting means 15 detects this and outputs a detection signal to the NC unit 12.

From the NC device 12, X-direction driving devices 5,
A command for driving the Y-direction driving device 7 and the Z-direction driving device 9 is output. Also, the NC device 12 has the X
The position information of the processing table 4 and the processing head 1 at each time are input from the direction position detecting device 6, the Y direction position detecting device 8, and the Z direction position detecting device 10, and the position information is stored in the memories M1, M2, M3. Is written to a predetermined storage area.

The NC unit 12 is provided with a controller 16
Is written in one of the memories M1, M2 and M3, and the stored information and necessary programs (processing operation, feed amount, Processing direction, electrical conditions, etc.)
/ Y / Z driving devices 5, 7, 9
The power supply control unit 13 applies a required discharge voltage to the discharge electrode 2 via the power supply control unit 13 and the discharge circuit 14.
And, it operates to output a voltage command to the discharge circuit 14.

The operation procedure and details of the electric discharge machining will be described below with reference to the flow chart shown in FIG. 2, the process chart shown in FIG. 3, and FIG.

Step 100 in FIG. 2: First, for the workpiece 3 on the processing table 4, the processing section 3A of the workpiece 3
Is input to the NC device 12. The target depth data H includes, for example, a predetermined reference position Q (XO, Y0, Z) set on the workpiece 3.
0) to the target depth position Pa (X1, Y1, Z1) in the X, Y, and Z directions.
Y, ΔZ), and the data H is input to the NC device 12. This aiming depth data H is stored in the memory area M1 of the NC device 12.

A predetermined reference position Q on the work 3
A predetermined position about 1 mm above (XO, Y0, Z0) is set to a start point (measurement reference position) P2 (X2, Y
2, Z2), and teach (teaching) the position P2 to the machine. In the teaching, it is preferable that the electrode 2 is actually moved to the position before the machining to teach the coordinate position P2 to the machine. This is usually work 3
This is because it is unknown where is set on the processing table 4 and it is necessary to teach after the work is actually set.

The input setting for the target depth data H and the measurement reference position P2 is executed for all the machining parts 3A to be continuously subjected to electric discharge machining this time. When the electrodes are replaced, the above H, P2
Enter and set all required information such as

Step 110 in FIG. 2: The powder processing liquid 17 is filled in the processing tank 18 to start automatic processing.

Step 120 in FIG. 2: As shown in FIG. 3A, the processing table 4 is moved in the X and Y directions,
By driving the direction driving device 9, the lower surface of the electrode 2 is positioned at the teaching position P2.

Step 130 in FIG. 2: As shown on the left side of FIG. 3A or FIG. 4, when the lower surface of the electrode 2 is located at the teaching position P 2, a control signal is sent from the power supply controller 13 to the discharge circuit 14. Then, the discharge voltage is applied between the electrode 2 and the work 3, and the Z-direction driving device 9 is driven at a low speed to lower the electrode 2 at a very low speed.

Here, at the time of the above-mentioned electric discharge, the electric discharge is performed under the same electric conditions as those of the final finishing stage in the actual processing performed thereafter. That is, at the time of the discharge, a discharge current set for the final finishing stage is employed, and the discharge is performed with this discharge current.

As the discharge gap A between the electrode 2 and the workpiece 3 narrows due to the downward movement of the electrode 2, dielectric breakdown occurs in the machining fluid 17 in the discharge gap A, and a discharge occurs. The occurrence of this discharge is determined by the discharge detecting means 1
5 and the detection signal is output by the discharge detecting means 15
Are input to the NC device 12 from the.

When the discharge detection signal is input, the NC device 12 measures a predetermined time Ta (for example, 3 seconds) from the input time, and when the predetermined time Ta elapses, the NC device 12 descends. To stop. And the NC device 12
Measures the stop position P3 (X3, Y3, Z3) and stores it in the memory area M2. This position P3 becomes a new reference position for the subsequent electric discharge machining.

Next, the NC unit 12 stores the new reference position data P3 stored in the memory area M2 in step 1
00, the target depth data H (Δ
X, ΔY, ΔZ) are added, and the result of the addition is stored in the memory area M3 as processing end position data P4 (X4, Y4, Z4) in actual processing.

In the Z direction, the new reference position data P3
The addition calculation Z4 = Z3 + ΔZ is performed according to the following calculation formula for adding the processing step data ΔZ to the Z coordinate Z3 of FIG.

FIG. 2 step 140: FIG.
As shown in (c), the electrode 2 is moved to the machining start position above the machining end position data P4 (X4, Y4, Z4) stored in the memory area M3, and the actual electric discharge machining is started. The Z direction position of the processing start position is located at a predetermined position above the work processing position in accordance with a processing program given in advance.

Step 150 in FIG. 2: In the case of electric discharge machining, in order to increase machining efficiency, a rough machining, a semi-finishing machining, and a final finishing machining are performed, such as a discharge voltage, a machining surface roughness, an electrode feed amount, and a swing radius. The processing is performed while changing the processing conditions stepwise (see FIG. 3D). For example, as the machining proceeds to rough machining, intermediate finishing, and final finishing, the electrode feed amount increases and the machining current decreases.

Steps 160 and 170 in FIG. 2: When the processing conditions are changed in this way, the processing conditions finally become those at the time of the final finishing stage. Then, at the time of the final finishing stage, the discharge current is reduced to the same value as the discharge current used at the time of the measurement in the previous step 130.

In the final finishing stage, electric discharge machining is performed with the final finishing discharge current which is the same value as the discharge current value used in the measurement in the previous step 130. When the lower end of the electrode 2 reaches the processing end position data P4 (X4, Y4, Z4) stored in the memory area M3, as shown in the right side of FIG. 3 (e) and FIG. Processing ends.

After processing is completed, an instruction is issued by the controller 16 to move to the next processing section and perform the same processing, or to perform electrode replacement and perform processing in another processing section in the same manner. become.

As described above, in this embodiment, processing and measurement are performed under the same electrical conditions, the same processing shape, the same processing area, the same processing liquid, and the same processing liquid state. Is the same as the discharge gap A ′ during machining. And this same discharge gap A
= A ′, the machining end position Z
4, the electric discharge machining can be easily performed with high dimensional accuracy without performing various types of error measurement unlike the related art.

Further, movement by these NC programs,
Since the machining command is performed using information input in advance and information automatically collected, electric discharge machining can be automatically performed with high dimensional accuracy.

FIGS. 5 and 6 show another embodiment of the present invention.

In this embodiment, instead of performing the discharge measurement before machining as in the previous embodiment, the discharge measurement is performed during machining at a stage before performing the electric discharge machining under the final conditions.

That is, at first, as in the above, the NC unit 1
With respect to No. 2, input settings are made for the target depth data H and the measurement reference position P2 (step 100). At this time, the target depth data H is several μm to 1 μm smaller than the normal target value.
It is set to be 0 μm shallower.

Next, electric discharge machining is started without performing electric discharge measurement (step 110, FIG. 6A).

In the electric discharge machining, in the same manner as described above, the machining is performed by changing the machining conditions such as the discharge voltage, the machining surface roughness, the electrode feed amount, and the swing radius stepwise to rough machining and semi-finishing machining. Go. Then, the machining is performed up to the condition before the final stage, and the electric discharge machining is temporarily suspended here.

Then, the electrode 2 is moved to the measurement reference position P2 (step 125, FIG. 6 (b)).
Discharge measurement is performed under the same electrical conditions as final processing and final finishing, and the electrode position P3 at a point in time when a predetermined time has elapsed since the start of discharge is measured.

Next, as described above, the measurement data P3
, And a new machining end position P4 is calculated (step 130, FIG. 6).
(C)).

Next, the apparatus moves to the machining section again, restarts electric discharge machining, and executes the remaining electric discharge machining (step 14).
5, FIG. 6 (d)).

In the final finishing stage, the previous step 13
0 is the same value as the discharge current used during measurement.
Electric discharge machining is performed with the electric discharge current at the time of the final finishing. Processing ends when the lower end of the electrode 2 reaches the processing end position data P4 (step 160, FIG. 6).
(E)).

In this embodiment, since the reference is measured during the machining, the electric discharge machining time after the measurement becomes short, and the influence of the error due to the amount of electrode consumption and thermal displacement is reduced, and is ignored. become able to.

In each of the above embodiments, the reference surface of the workpiece 3 is discharged for several seconds at the time of discharge measurement. At this time, the discharge current is the current of the weak electric condition of the final processing. Therefore, the progress of processing is extremely small.

FIG. 7 shows that the work material is copper alloy steel and the electrode is 1
The surface roughness of the final condition was Rmax3.
The discharge gap was determined seven times when the electric discharge machining was performed on the same surface for 3 seconds under the condition that the powder concentration of the working fluid was 20 μm or less at μm or less. As can be seen from the data in FIG. 7, even if the discharge measurement is repeatedly performed several tens of times on the same surface, the variation in the discharge gap can be suppressed to 1 μm or less, so that high-precision machining can be performed.

FIG. 8 shows an embodiment of the present invention in which an electrode having a special shape is used.

In this case, the bottom surface of the electrode 2 is slanted, and a hole having a slanted bottom surface is subjected to electric discharge machining using this electrode.

In this case, as shown in FIG. 9, the electrode 2 is provided with a temporary reference surface 2b having the same area as the discharge surface 2a above the discharge surface 2a. Is used to measure the discharge of the reference surface of the work 2. still,
Providing the notch (recess) 20 so as to be adjacent to the temporary reference surface 2b is a guide when only the temporary reference surface 2b is opposed to the surface of the work 2.

In FIG. 8, the length L from the temporary reference plane 2b to the electrode tip is measured in advance. This length L is
If it is shorter than the processing step ΔZ, it will interfere with the processed part.
Must be set longer.

As shown on the left side of FIG. 8, discharge measurement is performed using the temporary reference plane 2b in the same manner as described above, and the electrode position Z3 at the time when a predetermined time has elapsed since the start of the discharge is measured. .

Then, with reference to the measurement position Z3, a machining end position Z4 at the time of electric discharge machining is obtained by the following equation.

Z4 = Z3− (L−ΔZ) Then, in the same manner as described above, the electric discharge machining is performed by setting the Z4 position to the machining end position, so that the electric discharge gap A during the measurement and the electric discharge gap A during the machining are performed. A 'can be made the same as above.

In this case, the value (L-ΔZ) may be calculated in advance and input as the machining amount in the drawing when setting the initial input to the NC device.

In the case of an electrode having such a special shape, the provisional reference surface 2 having the same area as the discharge surface 2a of the discharge electrode is also used.
By creating b above the discharge surface 2a of the discharge electrode, highly accurate electric discharge machining can be performed.

The above description has been made with respect to the machining in the Z direction. However, even when the electrode is moved in the lateral direction (side direction) to form a hole extending in the lateral direction, the same discharge measurement as described above is carried out. Accurate electric discharge machining can be performed.

FIG. 10 shows that the side surface of the electrode 2 is
A step is provided at the boundary between the electrode 2 having the discharge effective portion 2c and the grip 30 attached to the machining head 1. In this case, the discharge effective portion 2
The area of the side surface of the machining hole formed by moving c is equal to the area of the discharge effective portion 2c.

Then, the same discharge measurement as described above is performed using the discharge effective portion 2c in the lateral direction with respect to the side surface reference 3a of the workpiece to determine the machining end position in the lateral direction. Thereafter, the electrode 2 is moved to the actual processing position, and furthermore, at this processing position, the electrode is moved laterally to the determined processing end position to form a hole extending in the horizontal direction. In this way, it is possible to cope with a lateral error.

In the above embodiment, the present invention is applied to the sinking electric discharge machining.
Is replaced by a wire electrode as shown in FIG. 13, so that the present invention can be applied to wire cut electric discharge machining.

In the above embodiment, the reference surface is set on the surface of the workpiece. However, a dummy reference other than the workpiece is placed, and the reference surface is set there to perform the discharge measurement. It may be.

[0079]

As described above, according to the present invention, the reference position of the workpiece is directly discharged under the electric conditions at the final stage of actual machining, the position including the discharge gap is measured, and the measured position is used as a reference. Since the actual electric discharge machining is executed by newly obtaining the machining end position, high machining accuracy can be maintained even if the actual electric discharge gap is unknown or changed due to various factors.

The measurement and the processing of the present invention are performed under the same electric conditions, in the same working fluid and with the same electrode.
In addition, since the processing is performed with the same processing area, the processing state during measurement and processing becomes the same, and no error occurs due to these changes. Also, if the discharge measurement of the reference surface is performed during the machining, the electric discharge machining time becomes short afterwards,
The influence of errors due to electrode consumption and thermal displacement is small and can be ignored. Further, the processing accuracy can be maintained at high accuracy without performing correction processing after the processing as in the related art.

Further, according to the present invention, the machining control means for storing the machining depth amounts of a plurality of discharge electrodes used for machining, the above-described electric discharge measurement, the adding means for computing the machining end position, and the computed arithmetic means. Since the electric discharge machining control means for performing the actual electric discharge machining using the machining end position is provided, in addition to the above-described effects, the electric discharge machining can be automatically and continuously performed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of an electric discharge machine to which the present invention is applied.

FIG. 2 is a flowchart showing a processing operation procedure according to the embodiment of the present invention.

FIG. 3 is a process chart showing a processing operation procedure according to the embodiment of the present invention.

FIG. 4 is a diagram illustrating the principle of the embodiment of the present invention.

FIG. 5 is a flowchart showing a processing operation procedure according to another embodiment of the present invention.

FIG. 6 is a process chart showing a processing operation procedure according to another embodiment of the present invention.

FIG. 7 is a graph showing the relationship between the number of machining repetitions and the discharge gap.

FIG. 8 is a principle diagram illustrating another embodiment of the present invention.

FIG. 9 is a diagram showing electrodes used in the embodiment of FIG.

FIG. 10 is a diagram illustrating another embodiment of the present invention.

FIG. 11 is a graph showing a relationship between a machining area and a discharge gap.

FIG. 12 is a graph showing a relationship between a powder mixing concentration and a discharge gap.

FIG. 13 is a diagram showing an embodiment when the present invention is applied to wire cut electric discharge machining.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 processing head 2 discharge electrode 3 workpiece (work) 3A processing unit 4 processing table 5 X-direction drive device 6 X-direction position detection device 7 Y-direction drive device 8 Y-direction position detection device 9 Z-direction drive device 10 Z-direction position Detecting device 11 Automatic control device 12 NC device 13 Power supply control device 14 Discharge circuit 15 Discharge detection means 16 Controller 17 Working fluid 18 Working tank 20 Notch

Claims (9)

[Claims] 1. An electric discharge machine for electric discharge machining of a workpiece by generating a discharge between the discharge electrode and the workpiece while a machining fluid is supplied between the discharge electrode and the workpiece. In the method, before or during machining, a first step of performing a discharge at a predetermined reference plane portion under the same electrical conditions as those used at the time of final machining, and measuring a coordinate position at which the discharge has occurred; A second step of adding a required machining amount to the obtained coordinate position; and a result of the addition in the second step as a machining end position, and the same electric conditions as those used in the first step at the time of final machining. A third step of performing electric discharge machining using conditions; and an electric discharge machining method characterized by comprising: 2. The electric discharge machining method according to claim 1, wherein in the first step, electric discharge is performed using a discharge surface of the discharge electrode. 3. The discharge electrode, wherein a flat surface having the same area as a discharge surface facing the workpiece to perform electrical discharge machining on the workpiece is provided above the discharge surface, In the first step, the discharge at the time of the measurement is performed using the flat surface of the discharge electrode. In the third step, the distance between the discharge surface and the flat surface is subtracted from the addition result. 2. The electric discharge machining method according to claim 1, wherein the electric discharge machining is performed with the result of the subtraction as a machining end position. 4. In the first step, the position of the measurement start point of the reference plane part is set by teaching the coordinate position of the measurement start point for the measurement performed on the reference plane part. The electric discharge machining method according to claim 1, wherein 5. The electric discharge machining performed in the third step is performed by using the same electrode as that used in the electric discharge in the first step.
2. The electric discharge machining method according to item 1. 6. The electric discharge machining method according to claim 1, wherein the discharge electrode is a wire electrode wire used in wire electric discharge machining. 7. An electric discharge machining apparatus for performing electric discharge machining of the workpiece by generating a discharge between the discharge electrode and the workpiece while a machining fluid is supplied between the discharge electrode and the workpiece. A measuring control means for causing electric discharge to be performed under the same electric conditions as those used at the time of final machining at a predetermined reference surface portion before or during machining, and measuring a coordinate position at which the electric discharge has occurred; A memory means for storing a required machining amount for each of a plurality of discharge electrodes used for calculating, a computing means for adding the machining amount of the discharge electrode stored in the memory means to the obtained coordinate position, An electric discharge machining control unit that performs an electric discharge machining using the same electric condition as the electric condition used at the time of the measurement by the measurement control unit at the time of final machining, with the addition result being a machining end position. Discharge machining apparatus characterized by the. 8. The electric discharge machining apparatus according to claim 7, wherein said measurement control means performs a discharge at the time of said measurement using a discharge surface of said discharge electrode. 9. A flat surface having an area equal to an area of a discharge surface opposed to the workpiece for electrical discharge machining of the workpiece is provided above the discharge surface of the discharge electrode; Causes the electric discharge at the time of the measurement to be performed using the flat surface of the discharge electrode, and the electric discharge machining control means subtracts the distance between the electric discharge surface and the flat surface from the addition result, and finishes the subtraction result. The electric discharge machining apparatus according to claim 7, wherein electric discharge machining is performed at the position.