JP5247670B2 - EDM machine - Google Patents

Description

  The present invention relates to an electric discharge machining apparatus for removing a workpiece by applying a voltage between an electrode and a workpiece and generating an electric discharge between the electrodes. The present invention relates to a device for detecting that an object has been penetrated.

  In a conventional electric discharge machining apparatus, a penetration detection plate is installed in the vicinity of the lower end of the workpiece so as not to make electrical contact with the workpiece, and a voltage is applied between the penetration detection plate via a resistor with the electrode as a reference. When the potential of the penetration detection plate is high to the applied voltage, non-penetration, and when the electrode and penetration detection plate are in contact, the penetration detection plate potential is close to the electrode potential. (For example, Patent Document 1 and Patent Document 2).

JP-A-11-123616 JP2002-292522

  In the conventional electric discharge machining apparatus, it is necessary to apply a detection voltage between the electrode and the penetration detection plate and measure the potential with reference to the electrode. On the other hand, in order to perform electric discharge machining, it is necessary to apply an electric discharge machining voltage between the electrode and the workpiece, so that the potential of the reference electrode varies. For this reason, when detecting the electrical contact between the electrode and the penetration detection plate, it must be detected in a situation where the reference potential fluctuates. Further, since the penetration detection power source cannot be grounded, it is easily affected by noise.

  Therefore, an object of the present invention is to provide an electric discharge machining apparatus capable of accurately determining penetration without erroneous detection.

In order to achieve the above object, an electric discharge machining apparatus according to the present invention comprises:
A machining electrode, a penetration detection plate provided opposite to the machining electrode, and a machining power source for applying a voltage between a workpiece and the machining electrode, the penetration electrode between the machining electrode and the penetration detection plate In an electric discharge machine that forms a through-hole in a workpiece that is arranged so as not to contact the detection plate,
A through detection plate potential comparator which has a first input terminal and a second input terminal to which the through detection plate is connected, and compares the potential of the first input terminal with the potential of the second input terminal;
A reference power source for applying a voltage to the second input terminal with respect to the workpiece;
And a penetration detection power supply that applies a voltage having the same polarity as the reference power supply and an absolute value larger than that of the reference power supply to the penetration detection plate through a resistor with respect to the workpiece.

The electrical discharge machining apparatus according to the present invention configured as described above applies a voltage based on a workpiece whose potential does not vary and determines the potential of the penetration detection plate. can do.
In addition, according to the present invention, it is possible to accurately detect that the machining electrode has advanced by the distance between the workpiece to be set and the penetration detection plate after penetrating the workpiece.

It is the schematic which shows the electric discharge machining apparatus of Embodiment 1 which concerns on this invention. It is the schematic which shows the electric discharge machining apparatus of Embodiment 2 which concerns on this invention. It is the schematic which shows the electric discharge machining apparatus of Embodiment 3 which concerns on this invention. It is the schematic which shows the electric discharge machining apparatus of Embodiment 4 which concerns on this invention. It is the schematic which shows the electric discharge machining apparatus of Embodiment 5 which concerns on this invention. It is the schematic which shows the electric discharge machining apparatus of Embodiment 6 which concerns on this invention.

Embodiment 1 FIG.
FIG. 1 is a schematic diagram showing the electric discharge machining apparatus according to the first embodiment of the present invention. The electric discharge machining apparatus according to the first embodiment includes a machining processing unit and a first penetration detection circuit unit.
1 to 6 attached to the present specification, the processing electrode 1 and the workpiece 3 are drawn apart from each other, but this is for the convenience of drawing and is electrically separated. It does not indicate that.

In the first embodiment, the processing unit is provided facing the workpiece 3, and the machining electrode 1 that forms a through-hole in the workpiece 3 by repeating discharge with the workpiece 3. The electrode holder 2 that holds the machining electrode 1 and the machining power source 5 that applies a machining pulse between the machining electrode 1 and the workpiece 3 are configured. In the first embodiment, for example, the machining electrode 1 has a cylindrical shape of φ0.1 mm, and the electrode holder 2 moves downward while rotating in the horizontal direction.
Here, the rotation or movement speed control of the electrode holder 2 is performed by a drive device, but the drive device is not shown.

The first penetration detection circuit unit includes a penetration detection plate 4, a penetration detection power source 6, a penetration detection resistor 7, a reference power source 8, and a penetration detection comparator 9. Further, the workpiece 3 and the workpiece of the processing unit are processed. The electrode 1 is comprised.
The penetration detection plate 4 is provided on the opposite side of the processing electrode 1 and the electrode holder 2 so as to face the workpiece 3 and not to be in electrical contact with the workpiece 3.
One end of the penetration detection power supply 6 is grounded, and one end of the penetration detection resistor 7 is connected to the other end.
Further, one end of the penetration detection power supply 6 that is grounded is configured to be electrically connected to the workpiece 3.
The penetration detection power supply 6 connected as described above applies a voltage to the penetration detection plate 4 via the penetration detection resistor 7 with the workpiece 3 as a reference.

The other end of the penetration detection resistor 7 is connected to the penetration detection plate 4 and to the first input terminal of the penetration detection comparator 9.
The second input terminal of the penetration detection comparator 9 is connected to the other end of the penetration detection reference power supply 8 whose one end is grounded. The penetration detection reference power supply 8 generates a comparison potential (penetration detection reference potential) using the grounded workpiece 3 as a reference. The penetration detection comparator 9 connected as described above is connected to the potential of the penetration detection plate 4 and the penetration. Compare with detection reference potential.

  Here, the voltage of the penetration detection power source 6 and the resistance value of the penetration detection resistor 7 are the potential of the first input terminal of the penetration detection comparator 9 when the machining electrode 1 is electrically separated from the penetration detection plate 4. The absolute value is higher than the absolute value of the penetration detection reference potential (the potential of the second input terminal of the penetration detection comparator 9) generated by the penetration detection reference power supply 8, and the machining electrode 1 is conducted to the workpiece 3 The absolute value of the potential of the first input terminal of the penetration detection comparator 9 when contacting the penetration detection plate 4 is lower than the absolute value of the penetration detection reference potential (the potential of the second input terminal of the penetration detection comparator 9). Is set to be

When the resistance value of the workpiece 3 and the machining electrode 1 is sufficiently smaller than the resistance value of the penetration detection resistor 7, the penetration detection plate 4 is grounded via the machining electrode 1 and the workpiece 3. The measurement current flowing through the penetration detection plate 4, the machining electrode 1, and the workpiece 3 is substantially zero, and is determined by the voltage of the penetration detection power supply 6 and the resistance value of the penetration detection resistor 7.
Further, the measurement current is set in consideration of safety at the time of machining work. In the first embodiment, for example, the voltage of the penetration detection power supply 6 is 10 V, the penetration detection resistor 7 is 10 k ohms, and the penetration detection reference power supply Set the voltage of 8 to 5V.

In the electric discharge machining apparatus according to the first embodiment of the present invention configured as described above, the machining electrode 1 is moved downward by the electrode holder 2 that rotates in the horizontal direction, for example, a workpiece 3 having a thickness of 10 mm. Through.
In the first embodiment, penetration detection is performed as follows during the penetration processing.

  In the first embodiment, the voltage between the workpiece 3 and the penetration detection plate 4 is applied by the penetration detection power source 6 while the machining pulse applied between the machining electrode 1 and the workpiece 3 is stopped from the machining power source 5. Apply. Considering the time required for the rise of the voltage at the first input terminal of the penetration detection comparator 9 after applying this voltage, for example, the potential of the penetration detection plate 4 and the potential of the penetration detection reference power supply 8 are set after 3 μs. The penetration detection comparator 9 makes a comparison.

At this time, when the machining electrode 1 and the penetration detection plate 4 are not in contact with each other, a current flows through a circuit including the penetration detection power supply 6, the penetration detection resistor 7, the penetration detection plate 4, the machining electrode 1, and the workpiece 3. Therefore, the absolute value of the potential of the penetration detection plate 4 is substantially equal to the voltage value (10 V) of the penetration detection power supply 6 and is larger than the absolute value of the potential of the penetration detection reference power supply 8.
In this case, it is determined that the through machining has not been completed.

When the workpiece 3 and the machining electrode 1 are in contact with each other and the machining electrode 1 and the penetration detection plate 4 are in contact, the absolute value of the potential of the penetration detection plate 4 is generated by the penetration detection reference power source 8. Smaller than the absolute value of the applied potential. For example, when the resistance value of the workpiece 3 and the processing electrode 1 is sufficiently smaller than the resistance value of the penetration detection resistor 7, the potential of the penetration detection plate 4 is substantially equal to the ground potential.
In this case, it is determined that the penetration process has been completed.

According to the electric discharge machining apparatus of the first embodiment configured as described above, the voltage of the penetration detection plate 4 is compared with the voltage of the reference power supply 8 with reference to the workpiece 3 that is grounded and does not vary in potential. It is possible to accurately detect that the machining electrode 1 has penetrated the workpiece 3 and contacted the penetration detection plate 4.
Further, according to the electric discharge machining apparatus of the first embodiment, it is possible to detect that the machining electrode 1 has penetrated the workpiece 3 and contacted the penetration detection plate 4 with the simple configuration shown in FIG.

  For example, when a workpiece having a thickness of 10 mm is penetrated with a cylindrical electrode having a diameter of φ0.1 mm with a gap of about several μm between the machining electrode and the workpiece, machining scraps and electrodes between the machining electrode and the workpiece Due to the rotation of the electrode due to the horizontal rotation of the electrode, electrical contact between the machining electrode and the workpiece for a short time frequently occurs. The electrical discharge machining apparatus according to the first embodiment can detect that the machining electrode 1 penetrates the workpiece 3 and contacts the penetration detection plate 4 at the moment when the machining electrode and the workpiece are in electrical contact.

In the above description of the first embodiment, the case where the cylindrical electrode 1 is processed while being rotated in the horizontal direction has been described as an example. However, the present invention is not limited to this, and the prism or complex shape is not limited thereto. This electrode can be used for the penetration processing, or the electrode can be lowered and processed without being rotated. In such a case, the same effect can be obtained.
The voltage applied to the penetration detection plate 4 may be a positive voltage or a negative voltage. Furthermore, the penetration detection plate 4 is not limited to a plate shape, and may be a block shape, a rod shape, or a spherical shape.

Embodiment 2. FIG.
FIG. 2 is a schematic diagram showing an electric discharge machining apparatus according to Embodiment 2 of the present invention. The electric discharge machining apparatus according to the second embodiment is the same as the electric discharge machining apparatus according to the first embodiment except that the electric discharge machining apparatus further includes a second penetration detection circuit unit configured by the electrode reference power supply 12 and the machining electrode potential comparator 13. The configuration is the same as that of the electric discharge machining apparatus of the first embodiment.

Specifically, the first input terminal of the machining electrode potential comparator 13 is connected to the machining electrode 1, and the other input terminal of the electrode reference power supply 12 whose one end is grounded is connected to the second input terminal of the machining electrode potential comparator 13. Is connected. The machining electrode potential comparator 13 compares the potential of the machining electrode 1 with the potential generated by the electrode reference power source 12.
That is, in the second embodiment, the electrode reference power source 12 generates a comparison potential with the workpiece 3 as a reference.
Here, the voltage of the electrode reference power supply 12 is set so as to have the same polarity as the penetration detection power supply and an absolute value smaller than that of the penetration detection power supply with reference to the grounded workpiece 3. It is set to the same voltage as the reference power supply 8, for example, 5V.

  In the electric discharge machining apparatus according to the second embodiment configured as described above, the workpiece is detected by the penetration detection power source 6 while the machining pulse applied between the machining electrode 1 and the workpiece 3 is stopped from the machining power source 5. A voltage is applied between the object 3 and the penetration detection plate 4. Considering the time required for the voltage rising at each first input terminal of the penetration detection comparator 9 and the machining electrode potential comparator 13 after applying this voltage, for example, the penetration detection comparator 9 obtained after 3 μsec. And based on the comparison result in the machining electrode potential comparator 13, it is determined whether or not it has penetrated.

  At the time of this penetration detection operation, in the electric discharge machining apparatus of the second embodiment, the comparator 9 and the presence of contact between the penetration detection plate 4 and the machining electrode 1 and the presence or absence of contact of the machining electrode 1 with the workpiece 3 are determined. The potential of the comparison input terminal of the comparator 13 is as shown in the following table with respect to the reference potential.

  As described above, in the electric discharge machining apparatus according to the second embodiment of the present invention, when the absolute value of the potential of the first input terminal of the penetration detection comparator 9 is smaller than the absolute value of the reference potential, or the machining electrode potential comparator When the absolute value of the potential of the 13th first input terminal is larger than the absolute value of the reference potential, it is determined that the first input terminal has penetrated.

  Therefore, according to the electric discharge machining apparatus according to the second embodiment of the present invention, the contact between the machining electrode 1 and the penetration detection plate 4 can be instantaneously detected without being affected by the state of the machining electrode 1 and the workpiece 3. / Non-penetration can be determined.

Embodiment 3 FIG.
FIG. 3 is a schematic diagram showing an electric discharge machining apparatus according to Embodiment 3 of the present invention. In the electric discharge machining apparatus according to the third embodiment, the electric discharge machining apparatus according to the second embodiment is further provided between the machining electrode 1 and the workpiece 3 during machining preparation in which the machining pulse from the machining power supply 5 is stopped. The configuration is the same as that of the electric discharge machining apparatus according to the second embodiment except that a contact detection power supply 10 that applies a voltage via the contact detection resistor 11 is provided.
The contact detection power supply 10 is set to a voltage value having the same polarity as the reference power supply 12 and having an absolute value larger than that of the reference power supply 12 with respect to the workpiece, and applies the voltage to the machining electrode 1 via the contact detection resistor 11. To do.
Specifically, the contact detection resistor 11 is set to 10 kΩ, for example, and the voltage of the contact detection power supply is set to 10 V, for example.

  In the electric discharge machining apparatus according to the third embodiment configured as described above, when the machining pulse from the machining power supply 5 is stopped, a voltage is applied between the machining electrode 1 and the workpiece 3 by the contact detection power supply 10. Applied, the contact state between the machining electrode 1 and the workpiece 3 is determined. Specifically, if the machining electrode 1 and the workpiece 3 are not in contact with each other, the absolute value of the potential of the machining electrode 1 becomes larger than the absolute value of the potential of the electrode reference power source 12, and the machining electrode 1 and the workpiece 3 are processed. Since the absolute value of the potential of the machining electrode 1 is small, the machining electrode 1 and the workpiece 3 are processed when the absolute value of the input potential of the machining electrode potential comparator 13 is higher than the absolute value of the reference potential. If the input potential of the machining electrode potential comparator 13 is lower than the reference potential, it is determined that the machining electrode 1 and the workpiece 3 are in contact with each other.

  Further, while the machining pulse from the machining power supply 5 is paused, the contact detection power supply 10 is turned off, and a voltage is applied to the penetration detection plate 4 by the penetration detection power supply 6 to input the potential of the penetration detection comparator 9. Through / non-penetration is determined based on the level of the reference potential. Specifically, when the absolute value of the potential of the first input terminal of the penetration detection comparator 9 is smaller than the absolute value of the reference potential, or the absolute value of the potential of the first input terminal of the machining electrode potential comparator 13 is the reference potential. If it is larger than the absolute value of, it is determined that it has penetrated.

  In the electric discharge machining apparatus according to Embodiment 3 described above, a contact detection circuit that detects contact between the machining electrode 1 and the workpiece 3 during machining preparation, and penetration detection that detects that the machining electrode has penetrated the workpiece by machining. A part of the circuit can be made common to reduce the circuit scale, and through detection can be performed with high speed and high accuracy.

Embodiment 4 FIG.
FIG. 4 is a schematic diagram showing an electric discharge machining apparatus according to Embodiment 4 of the present invention. The electric discharge machining apparatus according to the fourth embodiment is the same as the electric discharge machining apparatus according to the first embodiment. 10 is configured in the same manner as the electric discharge machining apparatus according to the first embodiment except that the apparatus 10 is provided.
The contact detection power supply 10 connected as described above applies a voltage having a polarity different from that of the penetration detection power supply 6 to the machining electrode 1 through the contact detection resistor 11 with respect to the workpiece.
Specifically, the contact detection resistor 11 is set to 10 kΩ, for example, and the voltage of the contact detection power supply 10 is set to −10 V, for example.

  In the electric discharge machining apparatus according to the fourth embodiment, the penetration detection plate 4 and the machining electrode 1 are applied by simultaneously applying voltages having different polarities to the penetration detection plate 4 and the machining electrode 1 by the penetration detection power source 6 and the contact detection power source 10. Even if it is in contact but not in contact with the workpiece 3, the potential of the penetration detection plate 4 is 0V. The contact between the electrode and the penetration detection plate can be detected instantaneously without being affected by the state of the workpiece.

Embodiment 5 FIG.
FIG. 5 is a schematic diagram showing an electric discharge machining apparatus according to the fifth embodiment of the present invention. The electric discharge machining apparatus according to the fifth embodiment is the same as the electric discharge machining apparatus according to the first embodiment. The electrode ground resistance 15 and the electrode ground resistance connection switch 14 are connected in series between the machining electrode 1 and the workpiece 3. The configuration is the same as that of the electric discharge machining apparatus according to the first embodiment except that
The electrode grounding resistor 15 connected between the machining electrode 1 and the workpiece 3 is set lower than the resistance value of the penetration detection resistor 7 connected between the penetration detection plate 4 and the penetration detection power source 6. 1 kΩ is set.

  In the configuration as described above, a voltage is applied between the penetration detection plate 4 and the workpiece 3 by the penetration detection power source 6 and at the same time the electrode installation resistance connection switch 14 is connected to connect the machining electrode 1 and the workpiece 3 to the electrode. Connect with grounding resistor 15. Thus, by connecting the machining electrode 1 to the workpiece 3 with a resistance smaller than the penetration detection resistor 7, the penetration detection plate 4 and the machining electrode 1 are in contact, but the workpiece 3 is in contact. Even if not, since the potential of the penetration detection plate 4 is equal to or lower than the voltage of the reference power supply 8 (1 V when the electrode ground resistance 15 is 1 kΩ), the potential of the penetration detection plate 4 is simply compared by the penetration detection comparator 9. The contact between the electrode and the penetration detection plate can be detected instantaneously without being affected by the state of the electrode and the workpiece.

Embodiment 6 FIG.
FIG. 6 is a schematic diagram showing an electric discharge machining apparatus according to Embodiment 6 of the present invention. The electric discharge machining apparatus according to the sixth embodiment is the same as the electric discharge machining apparatus according to the third embodiment except that the electric discharge machining apparatus according to the third embodiment further includes a pulse transformer 16 at the output of the penetration detection power supply 6. It is configured.

  The electric discharge machining apparatus according to the sixth embodiment configured as described above has the same function and effect as those of the electric discharge machining apparatus according to the third embodiment. Further, the penetration detection electrode is based on the workpiece 3 by the pulse transformer 16. Since the potential of 4 can be 0 V on average, corrosion of the workpiece 3 can be prevented.

  In the sixth embodiment, a pulse transformer is used. Instead, a high-pass filter that cuts off a low frequency region, or an AC power source having both a positive power source and a negative power source and a switch may be used. Even if configured as described above, the same effects as those of the sixth embodiment can be obtained.

  DESCRIPTION OF SYMBOLS 1 Processing electrode, 2 Electrode holder 2, 3 Workpiece, 4 Through detection board, 5 Processing power supply, 6 Through detection power supply, 7 Through detection resistance, 8 Through detection reference power supply, 9 Through detection comparator, 10 Contact detection power supply, 11 Contact detection resistance, 12 electrode reference power supply, 13 machining electrode potential comparator, 14 electrode installation resistance, 15 electrode ground resistance, 16 pulse transformer.

Claims (6)

A machining electrode, a penetration detection plate provided opposite to the machining electrode, and a machining power source for applying a voltage between a workpiece and the machining electrode, the penetration electrode between the machining electrode and the penetration detection plate In an electric discharge machine that forms a through-hole in a workpiece that is arranged so as not to contact the detection plate,
A through detection plate potential comparator which has a first input terminal and a second input terminal to which the through detection plate is connected, and compares the potential of the first input terminal with the potential of the second input terminal;
A reference power source for applying a voltage to the second input terminal with respect to the workpiece;
An electrical discharge machining, further comprising a penetration detection power supply that applies a voltage having the same polarity as the reference power supply and a larger absolute value than the reference power supply to the penetration detection plate through a resistor with respect to the workpiece. apparatus. A machining electrode potential comparator provided with a machining electrode potential input terminal and a reference input terminal connected to the machining electrode;
Using a workpiece as a reference, a reference power supply that applies a voltage having the same polarity as the penetration detection power supply and a smaller absolute value than the penetration detection power supply to the reference input terminal,
The electric discharge machining apparatus according to claim 1, further comprising:   The electric discharge machining apparatus according to claim 2, further comprising a contact detection power supply that applies a voltage having the same polarity as the reference power supply and an absolute value larger than that of the reference power supply to the machining electrode with respect to the workpiece. .   The electric discharge machining apparatus according to claim 1, further comprising a contact detection power supply that applies a voltage having a polarity different from that of the penetration detection power supply to the machining electrode through a resistor with respect to the workpiece.   The electric discharge machining apparatus according to claim 1, wherein a resistance lower than a resistance value of the resistance connected between a penetration detection plate and a penetration detection power source is connected between the machining electrode and the workpiece.   The electrical discharge machining apparatus according to claim 1, wherein the voltage applied to the penetration detection plate is an alternating current.

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