JP2002292522A - Electric discharge apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electric discharge apparatus A in which variations of thrust-out length of a welding rod after having pierced a workpiece is prevented. SOLUTION: The electric discharge machine A is equipped with a discharge power source 21, and a target 3 which is disposed in an insulated state to abut on an electrode rod 101 within a hole 100 of a workpiece 10 at a predetermined penetration place, and an electrode rod.target contact detection circuit 6 which detects contact of the electrode rod 4 and the target 3, and a workpiece.target contact detection circuit 7 which detects contact of the workpiece 10 and the target 3. While a communicating hole 23 which passes from an outer wall of the workpiece 10 to the hole 100 of the workpiece 10 is formed by an electric discharging, non-contact state of the workpiece 10 and the target 3 is monitored by the workpiece.target contact detection circuit 7, and also a control unit terminates the electric discharging when a contact of the electrode rod 4 and the target 3 is detected by the electrode rod.target contact detection circuit 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an electric discharge machine.

[0002]

2. Description of the Related Art Conventionally, there has been known an electric discharge machining apparatus for machining a work by applying a high voltage between an electrode rod and a work to discharge the work. When a hole is formed in a workpiece by this electric discharge machine, penetration of the hole (penetration of an electrode rod) is determined by the feed amount of the NC axis of the electric discharge machine.

At that time, since the electrode rod is consumed during processing,
The feed amount of the NC shaft is determined in advance in consideration of the consumption amount of the electrode rod.

[0004]

However, since the amount of wear varies depending on the processing state, the amount of wear is not constant. As a result, the amount of protrusion of the electrode rod varies, and the following problems (a) and (b) occur. appear.

[0005] (a) In the electric discharge machining for machining a fine hole, the electrode rod vibrates in the radial direction due to a small diameter and low rigidity, and a run-out occurs. Therefore, when the amount of protrusion from the guide holding the electrode changes, the amount of deflection of the electrode tip changes. Since the machining hole diameter of the electric discharge machining is determined by the outermost diameter of the trajectory of the electrode rod in the radial direction, if the amount of deflection changes, the accuracy of the hole diameter varies.

(B) When a workpiece having an opposing surface, such as a blind hole like an injection nozzle shown in FIG. 7, is subjected to fine hole processing, a discharge mark is formed on the opposing surface of the processed portion due to a variation in the protruding length of the electrode rod. May be attached.

There is a technique (Japanese Patent Laid-Open No. Hei 9-239625) for detecting penetration of an electrode rod based on a change in discharge current so as not to be affected by variations in electrode wear. However, in this technique, the feed of the electrode rod is not directly detected. For this reason, the accuracy of the protrusion length cannot be set to ± 0.03 mm or less. Further, when the holes are deep, the short-circuit current generated by sludge during processing increases, and the accuracy is further deteriorated.

[0008] An object of the present invention is to provide an electric discharge machining apparatus capable of preventing variation in the protruding length of an electrode rod after penetrating a work.

[0009]

[MEANS FOR SOLVING THE PROBLEMS] [Embodiment 1] An electric discharge machining apparatus is an electric discharge machining apparatus which is provided between an electrode rod to which vibration or rotation around an axis is applied by an actuator and an electrode rod and a conductive work. A discharge power supply for applying a voltage between the electrodes, a conductive target insulated from the workpiece so as to face a portion of the workpiece that is expected to penetrate the recess or hole in the workpiece communicating with the outside, and an electrode rod and the target. An electrode rod / target contact detecting means for detecting the contact between the electrode rod and the target by conduction with the electrode, and a machining control means for controlling the operation of the actuator and the discharge power supply and controlling the electric discharge machining.

During the formation of the communication hole from the outer wall of the work to the recess or the hole of the work by the electric discharge machining, when the tip of the electrode rod comes out of the recess or the hole of the work and reaches the place where the electrode rod is to be penetrated, The electrode rod and the target are electrically connected, the electrode rod / target contact detecting means detects the contact between the electrode rod and the target, and the machining control means ends the electric discharge machining.

Thus, the electric discharge machining apparatus can prevent a variation in the protruding length of the electrode rod after penetrating the work. For this reason, variation in the diameter of the communication hole can be reduced. Further, it is possible to prevent the formation of discharge traces on the opposing surface after the electrode rod penetrates. In addition, although it is easily affected by processing waste, the manufacturing cost is low.

According to a second aspect of the present invention, the electric discharge machining apparatus applies a voltage for electric discharge machining between an electrode rod to which vibration or rotation around an axis is given by an actuator, and an electrode rod and a conductive work. And a target arranged so as to face a recessed part of the workpiece communicating with the outside or a place where the electrode rod is to be penetrated in the hole, and a load generated by the electrode rod pressing the target, the electrode rod and the target Electrode / target contact detection means for detecting the contact of the electric field, and machining control means for controlling the operation of the actuator and the discharge power supply and controlling the electric discharge machining.

During the formation of a communication hole from the outer wall of the work to the recess or hole of the work due to electric discharge machining, when the tip of the electrode rod comes out of the recess or hole of the work and reaches a position where the electrode rod is to be penetrated, Since the electrode rod presses the target, the electrode rod / target contact detection means detects the contact between the electrode rod and the target, and the machining control means ends the electric discharge machining.

Thus, the electric discharge machining apparatus can prevent a variation in the protruding length of the electrode rod after penetrating the workpiece. For this reason, variation in the diameter of the communication hole can be reduced. Further, it is possible to prevent the formation of discharge traces on the opposing surface after the electrode rod penetrates. Although the manufacturing cost is slightly higher, it is hardly affected by processing waste.

According to a third aspect of the present invention, the electric discharge machining apparatus applies an electric discharge machining voltage between the electrode rod to which vibration and rotation around an axis are applied by an actuator, and the electrode rod and the conductive work. And a conductive target insulated from the workpiece so as to face a recessed part of the workpiece communicating with the outside or a place where the electrode rod is to be penetrated in the hole, and the continuity between the electrode rod and the target. An electrode rod / target contact detecting means for detecting contact between the rod and the target, a work / target contact detecting means for detecting contact between the work and the target by conducting the work and the target, and an operation of the actuator and the discharge power supply. And machining control means for controlling electric discharge machining.

The workpiece / target contact detecting means detects that the workpiece and the target are not in contact with each other during the formation of the communication hole from the outer wall of the workpiece to the recess or the hole of the workpiece by electric discharge machining. Means monitor. During the formation of a communication hole from the outer wall of the workpiece to the recess or hole of the workpiece by electric discharge machining, if the tip of the electrode rod comes out of the recess or hole of the workpiece and reaches the expected location for electrode rod penetration, The electrical connection between the targets is established, the electrode rod / target contact detecting means detects the contact between the electrode rod and the target, and the machining control means ends the electric discharge machining.

Thus, the electric discharge machining apparatus can prevent a variation in the protruding length of the electrode rod after penetrating the workpiece. For this reason, variation in the diameter of the communication hole can be reduced. Further, it is possible to prevent the formation of discharge traces on the opposing surface after the electrode rod penetrates.

Further, since the contact between the work and the target can be avoided by the work / target contact detecting means, it is possible to prevent a problem that the target is erroneously subjected to electric discharge machining. In addition, although it is easily affected by processing waste, the manufacturing cost is low.

[Claim 4] (During normal machining) During the electric discharge machining, the first resistor, the second resistor, the first photocoupler, the third resistor, the second photocoupler, and the fourth , The current flows through the first resistor and the second photocoupler.

(Electrode Bar Contact with Target) When the communication hole is completed and the electrode bar comes into contact with the target, the second photocoupler has the same potential as the electrode bar. Current flowing through the first photocoupler, the third resistor, the second photocoupler, and the fourth resistor is not passed through the second photocoupler and the fourth resistor, and , A second resistor, a first photocoupler, a third resistor, a second diode, a target, and an electrode rod. Therefore, no current flows through the second photocoupler, and the second photocoupler changes to a non-conductive state.

(Explanation of First and Second Zener Diodes) In actual machining, the voltage of the discharge power supply greatly changes (about several tens V to 300 V) depending on the machining state.
Since the current flowing through the first and second photocouplers changes greatly, if no countermeasure is taken, the first and second photocouplers will be damaged by overcurrent.

As a countermeasure, the cathode of the first Zener diode is connected to the first connection point, and the anode is connected to the second connection point.
Connected to the connection point. The cathode of the second Zener diode is connected to the third connection point, and the anode is connected to the other end of the fourth resistor. Thus, even if the voltage of the discharge power supply changes, the voltage between the first connection point and the second connection point is maintained at the breakdown voltage of the first Zener diode, and the voltage between the third connection point and the fourth resistor is maintained. The voltage between the other ends is held at the breakdown voltage of the second Zener diode.

Further, the second Zener diode is
Since the target and the electrode rod are connected in parallel, the voltage between the target and the electrode rod is always about several volts (breakdown voltage). Therefore, the discharge between the target and the electrode rod is very small and the target does not wear out. .

It should be noted that when the target comes into contact with the work due to the generation of machining debris or the displacement of the target, the action of the second Zener diode becomes invalid,
A high voltage is applied between the electrode and the target, causing the target to be EDM.

To prevent this, a work / target contact detecting means is provided. While the discharge power supply is operating, the first
Are turned on. When the target comes into contact with the workpiece, no current flows to the first photocoupler while the discharge power supply is operating, and the first photocoupler changes to a non-conductive state. By using this to activate an alarm or the like, it is possible to notify the worker that the target is in contact with the work.

[Claim 5] In order to reduce the influence of processing chips, one or more of the following are performed. In the case where the electrode bar and the target are electrically connected via the processing waste, the conductive state of the second photocoupler is short (several tens of microseconds).
When the electrode rod directly contacts the target (for example, ec to several tens of msec), the conduction state of the second photocoupler is maintained for a long time (at least 0.1 sec). For this reason,
The output of the second photocoupler is processed by a low-pass filter so that only the output waveform in which the electrode rod directly contacts the target passes.

When the electrode rod and the target are conducted through the processing waste, the conduction state of the second photocoupler is unstable. Therefore, the electrode rod based on the conduction and non-conduction of the second photocoupler. Increase the judgment value for target contact detection. The processing waste is removed by injecting the processing waste removal fluid to the target.

[0028]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an electric discharge machining apparatus A according to a first embodiment of the present invention (as set forth in claims 1, 3, 4, and 5) will be described.
This will be described with reference to FIGS. As shown in the figure, the electric discharge machining apparatus A includes a machining apparatus main body 1 and a control unit 2.

The processing apparatus body 1 includes a target 3, an electrode rod feed head 11, an NC shaft 12, an electrode rod 4, and an electrode guide 1.
3, a work receiver 14, a working fluid nozzle 15, a sludge removing nozzle 16, a target insulating guide 17, an electrode tip dressing device 18, a working fluid supply device 19, and the like. The conductive target 3 is insulated from the work 10 by the target insulating guide 17 so that the tip faces a portion 101 to penetrate the electrode rod in the hole 100 of the work 10 which communicates with the outside.

The electrode rod feed head 11 is mounted on an NC shaft 12. The electrode rod 4 is attached to the electrode rod feed head 11 so as to face the work 10 attached to the work receiver 14.

The electrode rod feed head 11 contains a piezoelectric element (not shown), and the electrode rod 4 (made of tungsten) is fed toward the work 10 by contraction of the piezoelectric element. The machining fluid supply device 19 is provided at a lower portion of the machining device main body 1 and includes a pump, a filter, a tank, and the like, and ejects machining fluid from the machining fluid nozzle 15 to the workpiece 10 during electric discharge machining.

The control unit 2 includes a discharge power source 21, a contact current detection circuit 5, an NC axis control device 22, and the like. The contact current detection circuit 5 includes an electrode rod / target contact detection circuit 6 for detecting contact between the electrode rod 4 and the target 3, and a work / target contact detection circuit 7 for detecting contact between the work 10 and the target 3. Have been.

The work / target contact detection circuit 7 includes a resistor 71 (first resistor) having one end 711 connected to the positive pole 211 of the discharge power source 21 and a connection point 73 (first resistor) having one end 721 connected to the other end 712 of the resistor 71. Resistor 7 connected at 1 connection point)
2 (second resistor), a photocoupler 74 (first photocoupler) having an anode 741 connected to the other end 722 of the resistor 72, and a photocoupler 74 having one end 761 at a connection point 75 (second connection point). (First photocoupler) cathode 74
2 and a cathode 77 (third resistor).
1 is connected to a connection point 73 and an anode 772 is connected to a connection point 75 (a first zener diode), operational amplifiers 781 and 782, a work / target contact reference voltage variable VR783, and a cathode 79.
1 is connected to a connection point 75, and an anode 792 is electrically connected to the target 3 by a diode 79 (first diode).
And the like.

The electrode rod / target contact detection circuit 6 has a resistor 76 (third resistor) having one end 761 connected to the connection point 75 and the other end 762 connected to the anode 611 of the photocoupler 61 (second photocoupler). ), A photocoupler 61 (second photocoupler) having the anode 611 connected to the other end 762 of the resistor 76 at the connection point 62 (third connection point), and one end 631 connected to the cathode 612 of the photocoupler 61. A resistor 63 (fourth resistor) having the other end 632 connected to the minus pole 212 of the discharge power source 21, a cathode 641 is connected to the connection point 62 (third connection point), and an anode 642 is connected to the resistance 63 (fourth resistance). The Zener diode 64 (second Zener diode) connected to the other end 632 of the resistor), the cathode 651 is connected to the target 3, and the anode 652 is connected to the connection point 62. Diode 65 (second diode), a low-pass filter 66, an operational amplifier 671,
672 and electrode rod / target contact reference voltage variable VR6
73.

The electrode / target contact detection circuit 6 operates as follows. (Normal machining) During electric discharge machining, resistance 71, 72, 7
6, 63 and the photocouplers 74, 61 flow, so that the photocouplers 74, 61 become conductive. As a result, in the operational amplifier 671, the positive side is 0
Since the reference voltage (less than 5 V) is applied to the V and-sides, the output becomes 0 V. Therefore, the operational amplifier 672 at the last stage is 0
V (L) is output.

(Electrode Bar 4 Contacting Target 3) When the communication hole 23 is completed and the electrode bar 4 comes into contact with the target 3, the input side of the photocoupler 61 has the same potential as the electrode bar 4. The current flowing through the photocouplers 72, 76, 63 and the photocouplers 74, 61 flows through the diode 65, the target 3, and the electrode rod 4 in this order without passing through the photocoupler 61 and the resistor 63. Therefore, no current flows through the photocoupler 61, so that the photocoupler 61 is turned off.

In the operational amplifier 671, the reference voltage (less than 5 V) of the negative input is compared with the comparison voltage (+) of the positive input.
5V), the output changes to + 5V (H).
Therefore, the output of the operational amplifier 672 at the final stage is 0 V
(L) to + 5V (H).

In actual machining, since the voltage of the discharge power supply 21 is changed between several tens of V and 300 V in accordance with the machining state, the current flowing through the photocouplers 74 and 61 greatly changes. If not, the photocouplers 74 and 61 will be damaged by overcurrent.

As a measure against this, a Zener diode 77
Of the anode 77 is connected to the connection point 73,
2 is connected to a connection point 75. The cathode 641 of the Zener diode 64 is connected to the connection point 62, and the anode 642 is connected to the other end 632 of the resistor 63. Thus, even if the voltage of the discharge power supply 21 changes, the connection point 7
3- Between the connection point 75 is held at the breakdown voltage of the Zener diode 77, and between the connection point 62 and the other end 632 of the resistor 63 is held at the breakdown voltage of the Zener diode 64.

Further, since the Zener diode 64 is connected in parallel between the target 3 and the electrode rod 4,
Since the voltage between the target 3 and the electrode rod 4 is always about several volts (breakdown voltage), the discharge between the target 3 and the electrode rod 4 is very small and the target 3 is not consumed.

The low-pass filter 66 has a function of preventing a current waveform relating to machining dust remaining between the electrode rod 4 and the target 3 ((a) → (b) in FIG. 3). The contact current generated when the electrode rod 4 comes into contact with the target 3 lasts for at least 0.1 sec or more, but the waveform of the contact current generated when the electrode rod 4 comes into contact with the processing waste is several tens μsec to several tens μsec. Since the pulse is a short pulse of msec (confirmed in an experiment), it can be blocked by a low-pass filter 66 (cutoff frequency: 100 Hz according to the waveform of the contact current generated by the processing chips).

For a longer pulse that cannot be completely removed by the low-pass filter 66, the electrode rod / target contact reference voltage 660 is set higher by the electrode rod / target contact reference voltage variable VR673 (see FIG. 3). Identify. In addition, as shown in FIG.
, A configuration may be added in which the processing fluid is sprayed toward the target 3 to prevent erroneous detection due to current related to the processing waste.

It should be noted that due to the generation of machining waste and the displacement of the target 3, the target 3 is
, A high voltage is applied between the electrode rod 4 and the target 3, and the target 3 is subjected to electric discharge machining.

To prevent this, a work / target contact detection circuit 7 is provided. While the discharge power supply 21 is operating, the photocoupler 74 is conductive, and the output 784 of the last stage is 0V. When the target 3 comes into contact with the workpiece 10, the output 784 of the final stage is output while the discharge power supply 31 is operating.
Becomes 5V (H). Using this output, an alarm is activated to notify the operator that the target 3 is in contact with the workpiece 10.

Next, an evaluation test of the electric discharge machining apparatus A of this embodiment will be described. Electric discharge machine A shown in FIGS. 1 and 2
In, a workpiece 10 (steel material) having a thickness of 1.2 mm was subjected to electric discharge machining using the electrode rod 4 having a diameter of 0.14 mm.

As shown in FIG. 4, in the electric discharge machining by the electric discharge machine A, the variation of the hole diameter was reduced to ± 7 μ in the evaluation of ± 3σ. In addition, there were no discharge marks (see FIG. 7) due to discharge to the opposing surface after penetrating the hole or the electrode rod.
This is considered to be because the protruding length of the electrode rod 4 is kept constant.

On the other hand, in the electric discharge machining apparatus disclosed in Japanese Patent Application Laid-Open No. 9-239625, the variation in the hole diameter was ± 12 μ in ± 3σ evaluation. In addition, discharge marks (see FIG. 6) caused by discharge to the opposing surface after the holes have not penetrated or the electrode rods have penetrated several tens%
Occurred.

Next, a second embodiment of the present invention (an embodiment of the present invention) will be described with reference to FIG. As shown in FIG. 5, the electric discharge machining apparatus B includes an electrode rod 4, a support 31 supporting the target 3, a strain gauge 32 for detecting a minute load generated when the electrode rod 4 presses the target 3, An electrode rod / target contact detection circuit 33 is provided. The target 3 is connected to the work 1 by the support 31 and communicates with the outside.
It is arranged so that the front end faces the electrode rod penetrating scheduled portion 101 in the hole 100.

Then, during the formation of the communication hole 23 leading from the outer wall of the work 10 to the hole 100 of the work 10 by electric discharge machining, the tip of the electrode rod 4 comes out into the hole 100 of the work 10 and the electrode rod 101 Is reached, the electrode rod 4 presses the target 3 and the strain gauge 32 sends out an output. The electrode rod / target contact detection circuit 33 detects the contact between the electrode rod 4 and the target 3, and the control unit 2 discharges. Finish the processing.

As a result, the electric discharge machining apparatus B is
Of the protruding length after penetrating the workpiece can be prevented. For this reason, variation in the hole diameter of the communication hole 23 can be reduced. Further, it is possible to prevent the formation of discharge traces (see FIG. 6) on the opposing surface after penetrating the electrode rod. In addition, since the strain gauge 32 is used, the manufacturing cost is slightly increased, but there is an advantage that the strain gauge 32 is hardly affected by processing chips.

The present invention includes the following embodiments in addition to the above embodiments. a. In the technology described in Japanese Patent Application Laid-Open No. 9-239625,
Regarding the removal of the taper, after the electrode has penetrated, for a certain time,
A configuration is adopted in which the electrode is stopped to maintain the processing voltage (or increase by several tens of volts).

When this technique is applied to the electric discharge machining apparatus A as it is, when the electrode rod 4 is in contact with the target 3, a part of the discharge current flows through the target 3, so that the taper removing efficiency is reduced.

To solve this problem, if the electrode rod 4 is pulled back by 0.01 mm or more immediately after the electrode rod 4 comes into contact with the target 3, the taper removal efficiency does not decrease. JP 9
The technique described in JP-A-239625 can detect the moment when the electrode rod 4 penetrates the work 10. Therefore, by using the technique of the present invention in combination with the technique described in JP-A-9-239625, erroneous detection due to noise can be prevented, and the reliability of detection can be improved.

B. In the above embodiment, the vibration and rotation are given by electric power, but the vibration and rotation may be given by air pressure.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an electric discharge machine according to a first embodiment of the present invention.

FIG. 2 is an electric circuit diagram of the electric discharge machine.

FIG. 3 is an explanatory diagram showing an effect of a low-pass filter of the electric discharge machine.

FIG. 4 is a graph showing variations in hole diameters when electric discharge machining is performed using the electric discharge machine (with a target) and the conventional electric discharge machine (without a target).

FIG. 5 is a configuration diagram of an electric discharge machine according to a second embodiment of the present invention.

FIG. 6 is an explanatory view showing the formation of discharge traces on the opposing surface after penetrating the electrode rod.

FIG. 7 is an explanatory diagram of discharge marks on a facing surface of a machined part when a workpiece having a facing surface is subjected to pore machining.

[Explanation of symbols]

A, B Electric discharge machine 2 Control unit (machining control means) 3 Target 4 Electrode rod 6 Electrode rod / target contact detection circuit (electrode rod / target contact detection means) 7 Work / target contact detection circuit (work / target contact detection means) ) 10 Workpiece 21 Discharge power supply 23 Communication hole 32 Strain gauge (electrode rod / target contact detection circuit) 33 Electrode rod / target contact detection circuit (electrode rod / target contact detection circuit) 61 Photocoupler (second photocoupler) 62 Connection Point (third connection point) 63 Resistance (fourth resistance) 64 Zener diode (second zener diode) 65 Diode (second diode) 66 Low-pass filter 71 Resistance (first resistance) 72 Resistance (second) 73) Connection point (first connection point) 74 Photocoupler (first photo (Pla) 75 Connection point (second connection point) 76 Resistance (third resistance) 77 Zener diode (first zener diode) 79 Diode (first diode) 100 hole 101 expected electrode rod penetration point 211 plus pole ( (Positive pole side) 611 anode (anode side) 612 cathode (cathode side) 641 cathode 642 anode 651 cathode 652 anode 711 one end 712 other end 721 one end 722 other end 741 anode (anode side) 742 cathode (cathode side) 771 cathode 772 anode anode 791 cathode 792 anode

Continuing from the front page (72) Inventor Hiromitsu Morita 1-1-1, Showa-cho, Kariya-shi, Aichi Pref. ) Inventor Kensaku Kato 1-1-1, Showa-cho, Kariya-shi, Aichi F-term in DENSO Corporation (reference) 3C059 AA01 AB01 CC04 CH01 CH03 HA14

Claims (5)

[Claims] 1. An electrode rod to which vibration or rotation around an axis is applied by an actuator, a discharge power supply for applying a voltage for electric discharge machining between the electrode rod and a conductive work, and communication with the outside. A conductive target insulated from the work so as to face a place where the electrode rod is to be penetrated in a recess or a hole of the work, and the electrode rod and the target are electrically connected to each other by conduction between the electrode rod and the target. An electrode rod / target contact detecting means for detecting contact with a target, and an operation of the actuator and the discharge power supply;
Machining control means for controlling electric discharge machining, wherein, during formation of a communication hole leading from the outer wall of the work to a recess or hole of the work by electric discharge machining, the electrode rod / target contact detection means is connected to the electrode rod. The electric discharge machining apparatus according to claim 1, wherein when the contact with the target is detected, the machining control means ends the electric discharge machining. 2. An electrode rod to which vibration or rotation about an axis is applied by an actuator, a discharge power supply for applying a voltage for electric discharge machining between the electrode rod and a conductive work, and communication with the outside. A target arranged to face the electrode rod through-hole in the recess or hole of the work, and a load generated by pushing the target by the electrode rod, whereby the electrode rod and the target are brought into contact with each other. An electrode rod / target contact detecting means for detecting, and an operation of the actuator and the discharge power supply,
Machining control means for controlling electric discharge machining, wherein, during formation of a communication hole leading from the outer wall of the work to a recess or hole of the work by electric discharge machining, the electrode rod / target contact detection means is connected to the electrode rod. An electric discharge machining apparatus, wherein upon detection of contact with the target, the machining control means ends electric discharge machining. 3. An electrode rod to which vibration or rotation around an axis is applied by an actuator, a discharge power supply for applying a voltage for electric discharge machining between the electrode rod and a conductive work, and communication with the outside. A conductive target insulated from the work so as to face a place where the electrode rod is to be penetrated in a recess or a hole of the work, and the electrode rod and the target are electrically connected to each other by conduction between the electrode rod and the target. An electrode rod / target contact detection means for detecting contact with a target; a work / target contact detection means for detecting contact between the work and the target by conducting the work and the target; the actuator and the discharge Controls the operation of the power supply,
Machining control means for controlling electric discharge machining, wherein during the formation of the communication hole from the outer wall of the work to the recess or hole of the work by electric discharge machining, the work and the target are in a non-contact state. The electric discharge machining, wherein the work / target contact detection means monitors, and the machining control means terminates the electric discharge machining when the electrode rod / target contact detection means detects the contact between the electrode rod and the target. apparatus. 4. The discharge power supply applies a negative voltage to the electrode rod and a positive voltage to the work, and the work / target contact detection means and the electrode rod / target contact detection means are connected to a positive pole of the discharge power supply. A first resistor connected to one end of the first resistor, a second resistor connected to one end of the first resistor at a first connection point, and an anode connected to the other end of the second resistor. A first photocoupler, a third resistor having one end connected to the cathode side of the first photocoupler at a second connection point, and a third resistor having an anode side at a third connection point. A second photocoupler connected to one end; a fourth resistor having one end connected to the cathode side of the second photocoupler and the other end connected to the negative pole side of the discharge power supply; Connect the anode to the second connection point A first zener diode connected to a third connection point; a second zener diode having a cathode connected to the third connection point and an anode connected to the other end of the fourth resistor; and a cathode connected to the second connection point. A diode connected to the target and an anode connected to the target; a cathode connected to the target and an anode connected to the third
4. An electric discharge machining apparatus according to claim 3, wherein said second electric discharge machining apparatus comprises a second diode connected to said connection point. 5. A process for processing the output of the second photocoupler with a low-pass filter, increasing a determination value of electrode rod / target contact detection based on conduction / non-conduction of the second photocoupler, and The electric discharge machining apparatus according to claim 4, wherein one or more of the steps of injecting the machining debris removing fluid are performed.