JP6433344B2 - High frequency vibration assisted plasma discharge grinding apparatus and method - Google Patents

Description

  The present invention relates to a high-frequency vibration assisted grinding apparatus that propagates high-frequency vibrations to a grinding wheel to grind a workpiece, and in particular, processing of difficult-to-cut materials by plasma discharge by suitably combining high-frequency vibrations, plasma discharge, and grinding. High-frequency vibration assisted plasma discharge grinding that enables free cutting of the surface to enable grinding at low processing pressures, and that allows the machining fluid to flow through the small-diameter pipe electrode to enable suitable plasma discharge and grinding. The present invention relates to an apparatus and a method thereof.

2. Description of the Related Art Conventionally, there has been an electrolytic grinding apparatus for applying an electric voltage between a grinding wheel and a surface of a workpiece via an electrolytic solution to electrolytically grind the surface of the workpiece (see Patent Document 1).
This electrolytic grinding apparatus applies electrolytic voltage between the grinding wheel and the workpiece via an electrolytic solution to perform electrolytic grinding. The grinding <abrasive kinetic energy> and electrolysis <electrical energy to the workpiece> This is a processing technology that combines two elements.

JP-A-3-251317

However, the above-mentioned conventional electrolytic grinding apparatus has a sufficiently large hole diameter of the workpiece, and has a large depth relative to the intended inner diameter of the present invention, that is, a machining hole having a high aspect ratio or a small diameter work piece. It could not be applied to a technique for grinding and electric discharge machining of the inner peripheral surface of a processing hole of an object with high accuracy and high efficiency.
Further, in conventional machining such as grinding, as shown in FIG. 8, when machining the inner peripheral surface of a workpiece W made of a difficult-to-cut material such as a titanium alloy, particularly a thin workpiece W, Since the processing pressure of the grindstone 51 is high, the thin processing surface is deformed, and high-precision processing is difficult. At this time, as a means for injecting the machining fluid 52 from the machining fluid supply means into the blind hole (blind hole) of the small-diameter workpiece W, even if the machining fluid is poured from the outside of the hole, it does not enter the inside of the hole through a slight gap. For this reason, the machining fluid 52 is injected from the tip of the grindstone 51 using a liquid-passing (coolance through type) grindstone 51 having a through hole 53. In this case, the machining liquid 52 delivered from the tip of the liquid-passing type grindstone 51 reaches the bottom Wb of the blind hole but hardly reaches the inner wall surface Wa that is the machining surface.

In addition, in the case of a thin pipe-shaped grinding wheel that sends the machining fluid to the machining surface, or a thin pipe electrode used for electric discharge machining, when supplying the machining fluid to the tip machining point through the pipe, As the inner diameter of the pipe becomes smaller, high pressure is required to deliver the machining fluid due to the viscosity of the machining fluid and bubbles in the pipe, and sometimes a high-pressure pump exceeding 1 MPa (about 10 atmospheres) is required. There was a case. The use of such a high-pressure pump is not only high in cost of the apparatus, but also easily breaks down when high pressure is applied, resulting in a great problem in reliability and life of the apparatus.
Furthermore, when machining the inner peripheral surface of a machining hole with a high aspect ratio or a small-diameter workpiece using plasma discharge, the discharge will disappear if the machining point of the discharge electrode and the workpiece are short-circuited. When the short circuit is electrically detected, the machining point of the electrode is retracted from the workpiece to avoid the short circuit, while the machining point of the electrode is excessively retracted from the workpiece or is subjected to electrical discharge machining. If the workpiece surface retreats, the gap between the discharge electrode machining point and the workpiece will be too wide and the discharge will stop, so the discharge interval should be set so that the discharge electrode machining point is close to the workpiece. Servo control was performed to maintain.
Electric discharge machining using servo control that keeps the discharge interval while repeating this short-circuiting / cutting takes time because of the intermittent machining, and the electrode is not good in machining efficiency, but the electrode is finely moved forward and backward. High-precision electrical discharge machining could not be expected due to the multiple movements of feeding forward as machining progressed repeatedly.

  The present invention has been made in view of the circumstances described above, and the object thereof is to prevent deformation of a thin processed surface when processing the inner peripheral surface of a thin workpiece of difficult-to-cut material. Enables low grinding wheel processing pressure and sends the processing fluid to the pipe electrode without the need for a high-pressure pump when processing while sending the processing fluid to the processing point at the tip of the small-diameter liquid-type pipe electrode. In addition, a high-frequency vibration-assisted plasma discharge grinding apparatus and method capable of performing high-precision machining by suitably maintaining the machining point at the tip of the pipe electrode and the discharge interval of the workpiece without using servo control Is to provide.

As a result of diligent research in view of the above problems, the present inventor has excellent surface roughness accuracy and is suitable for shape processing even for thin, small-diameter inner peripheral surfaces of difficult-to-cut materials that have been difficult to grind until now. The inventors have devised a plasma discharge grinding apparatus and method using high frequency vibration so as to enable smooth grinding.
That is, the high-frequency vibration-assisted plasma discharge grinding apparatus of the present invention includes an electric discharge machining electrode having a center hole through which a machining fluid is passed inside a grinding wheel in which non-conductive abrasive grains are bonded and solidified by a conductive binder, and the electric discharge machining. A spindle for rotationally driving the electrode, a vibration means for high-frequency vibration of the spindle in the axial direction, a high-frequency pulse power source for high-frequency vibration for driving the vibration means, and a machining liquid is supplied through the center hole of the electric discharge machining electrode A machining fluid supply means; and a high-frequency pulse power supply for plasma discharge that applies a high-frequency pulse current for generating a plasma discharge between the electric discharge machining electrode and the workpiece, the electric discharge machining electrode on the surface of the workpiece Along the axial direction, the machining liquid is passed through the center hole of the electric discharge machining electrode by causing high-frequency vibration having an oscillation frequency of 20 kHz or more and an amplitude of several μm to several tens of μm. And the distance between the workpiece and the rotating electric discharge machining electrode is 10 μm or less of the protruding height of the abrasive grains, and the electrodes are electrically short-circuited in a state where the workpiece and the abrasive grains of the electric discharge machining electrode are in contact with each other. It is characterized in that the plasma discharge is sustained.
With such a configuration, when processing is performed while sending the processing liquid to the processing point at the tip of a small-diameter liquid-type pipe electrode, the processing liquid is sent to the pipe electrode without the need for a high-pressure pump. In addition, the machining point at the tip of the pipe electrode and the discharge interval of the workpiece can be suitably maintained without using servo control, so that high-precision machining can be performed, and high-precision machining can be performed efficiently. In addition, since grinding can be performed locally even on difficult-to-cut materials such as titanium alloys, shape accuracy after processing can be improved.

Further, the frequency of the high frequency pulse power source for plasma discharge is higher than the frequency of the high frequency pulse power source for high frequency vibration.
As a result, the plasma discharge is maintained with high accuracy while maintaining the machining point at the tip of the pipe electrode and the discharge interval of the workpiece without short-circuiting between the electrodes in a state where the workpiece and the abrasive grains of the EDM electrode are in contact with each other. Can be processed.

Further, the electric discharge machining electrode is characterized by forming a radial slit penetrating from the central hole of the electric discharge machining electrode toward the outer periphery in a longitudinal section perpendicular to the central axis.
Thereby, the machining fluid is directly supplied from the slit toward the machining surface of the workpiece, and the machining efficiency is excellent.

  The high-frequency vibration-assisted plasma discharge grinding method of the present invention includes a pipe-shaped electric discharge machining electrode for passing a machining liquid into a grinding wheel obtained by bonding and solidifying non-conductive abrasive grains with a conductive binder, and the electric discharge machining. A spindle for rotationally driving the electrode, a vibrating means for high-frequency vibration of the spindle in the axial direction, a high-frequency pulse power source for high-frequency vibration for driving the vibrating means, and a plasma discharge between the electric discharge machining electrode and the workpiece In a high frequency vibration assisted plasma discharge grinding apparatus comprising a high frequency pulse power source for plasma discharge for applying a high frequency pulse current for generating a vibration frequency of the electric discharge machining electrode in the axial direction along the workpiece surface is 20 kHz or more In addition, the high frequency vibration having an amplitude of several μm to several tens of μm allows the machining liquid to pass through the center hole of the electric discharge machining electrode and rotates with the workpiece. Maintaining plasma discharge without electrically shorting between the electrodes in a state where the workpiece and the abrasive grains of the electrical discharge machining electrode are in contact with the gap between the electromachining electrodes and the protruding height of the abrasive grains of 10 μm or less, The plasma etches the workpiece to generate a softened layer on the local processed surface, and the softened layer is ground by the abrasive grains of the electric discharge machining electrode.

It is explanatory drawing which shows the high frequency vibration assistance plasma discharge grinding apparatus of this invention. It is explanatory drawing which shows the state in which the electric discharge machining electrode in the high frequency vibration assistance plasma discharge grinding apparatus of this invention processes a workpiece. It is explanatory drawing which shows the electrical discharge machining electrode of the high frequency vibration assistance plasma discharge grinding apparatus of this invention. It is explanatory drawing which shows the state which supplies a processing liquid to the pipe electrode in the plasma discharge grinding apparatus for high frequency vibration of this invention, FIG. 4 (A) is a state which does not apply a high frequency vibration, FIG.4 (B) adds a high frequency vibration. It represents the state. It is explanatory drawing which shows the state in which the electric discharge machining electrode in the plasma discharge grinding apparatus for high frequency vibration of this invention carries out plasma discharge, FIG. 5 (A) is the state which does not apply a high frequency vibration, FIG. 5 (B) added the high frequency vibration. Represents a state. It is explanatory drawing which shows the process between the workpiece and the electrical discharge machining electrode in the high frequency vibration assisted plasma electrical discharge grinding apparatus of this invention, and shows the comparison by the presence or absence of the application of a high frequency vibration and an electrical discharge machining voltage. It is explanatory drawing which shows the comparison between the process between the workpiece and the electrical discharge machining electrode, and the conventional machining method in the high frequency vibration assisted plasma electrical discharge grinding apparatus of the present invention. It is explanatory drawing which shows the state in which the grindstone in the conventional high frequency vibration assistance plasma discharge grinding apparatus processes a workpiece.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for implementing a high-frequency vibration-assisted plasma discharge grinding apparatus according to the present invention will be described in detail with reference to the accompanying drawings. 1 to 7 are diagrams illustrating embodiments of the present invention. In these drawings, the same reference numerals denote the same components, and the basic configuration and operation are the same. To do.
<Configuration>
As shown in FIG. 1, a high-frequency vibration-assisted plasma discharge grinding apparatus 1 according to the present invention includes an electric discharge machining electrode 2 that is a grinding wheel provided with abrasive grains, a spindle 3 that rotationally drives the electrode, and an axial direction of the spindle 3. A high-frequency pulse power source 4 for high-frequency vibration for driving appropriate vibration means for applying high-frequency vibration to the electrode, and a high-frequency pulse power source 5 for plasma discharge for generating plasma discharge between the electric discharge machining electrode 2 and the workpiece, And a machining fluid supply means 7 for providing a machining fluid 6 for grinding and plasma discharge on the machining surface.
The spindle 3 is provided with a fine hole at the axial center together with the electric discharge machining electrode 2 and supplies it to the machining area through the machining liquid 6 from an appropriate machining liquid supply means 7. By making the electric discharge machining electrode 2 have a liquid-passing structure, even the inner peripheral surface of the workpiece W having a small diameter and a blind hole (blind hole) can be ground while suitably supplying the machining fluid. Then, by operating the high-frequency pulse power supply 4 for high-frequency vibration, the spindle 3 reciprocates (oscillates) in the Z-axis direction with high-frequency vibration in the axial direction, that is, the Z-axis direction in FIG. Meanwhile, the inner peripheral surface of the workpiece W is ground. Then, the workpiece (table) is fed forward as the machining progresses.
The Y table 8 on which the workpiece W is placed and fixed is movable in the Y axis direction, and the X table 9 on which the Y table 8 is placed is movable in the X axis direction. And the control means (not shown) for controlling the grinding process by the high frequency vibration assistance plasma discharge grinding apparatus 1 including the X table 9, the Y table 8 and each pulse power source is separately provided.

FIG. 2 is a machining example different from that in FIG. 1, and schematically shows a state where the electric discharge machining electrode 2 is grinding the inner peripheral surface Wa of the chucked workpiece W. The electric discharge machining electrode 2 is formed by bonding and solidifying non-conductive abrasive grains such as diamond abrasive grains with a conductive binder. In a state where the abrasive grains protruding from the surface of the electric discharge machining electrode 2 grind the workpiece W, the protruding height of the abrasive grains from the conductive binder is the distance between the electric discharge machining electrode 2 and the workpiece W. In the case of the present embodiment, in order to perform high-precision grinding, it is preferable that the protrusion height of the abrasive grains is less than 20 μm, preferably less than 10 μm.
In the figure, reference numeral 6 denotes a machining fluid supplied from the machining fluid supply means 7 through the spindle 3 and the pores of the electric discharge machining electrode 2. Reference numeral 10 denotes a machining area in which the electric discharge machining electrode 2 is machining the inner peripheral surface of the workpiece W, and a plasma discharge described later is generated at this location.

The high-frequency pulse power supply 4 for high-frequency vibration drives the excitation means to drive the spindle 3 provided with the electric discharge machining electrode 2 in the axial direction at a frequency of 20 kHz or more, preferably 40 kHz or more, and an amplitude of several μm to several tens. High-frequency vibration at μm.
The plasma discharge high-frequency pulse power supply 5 sets the protrusion height of the abrasive grains between the grinding wheel 2 (more precisely, the conductive binder) and the workpiece W as a preset plasma discharge voltage. And a high frequency pulse current having a pulse width of 1 microsecond or less (submicrosecond) level is applied.

FIG. 3 shows the spindle 3 and the electric discharge machining electrode 2 which is a grinding wheel attached to the spindle 3. The male screw 2 a protruding from the electric discharge machining electrode 2 can be screwed into the female screw 3 a provided at the tip of the spindle 3 to be detachable. The structure is integrated in a stable state.
The electric discharge machining electrode 2 is formed with a radial cross-shaped slit 11 penetrating from the fine hole 2b passing through the electric discharge machining electrode 2 toward the outer periphery in a longitudinal section perpendicular to the central axis, and a machining liquid supply means 7 is discharged from the slit 11 of the electric discharge machining electrode 2 through the pore 3b of the spindle 3 and supplied to the inner peripheral surface Wa of the workpiece W.
The fine hole 2b of the central axis of the electric discharge machining electrode 2 is not a through hole but a blind hole, and the machining liquid 6 from the machining liquid supply means 7 passes through the entire inner peripheral surface of the workpiece W which is the machining surface from the slit 11. Supplied around the lap.

FIG. 4 is a photograph showing a state in which the machining fluid supplied from the machining fluid supply means 7 at the pressure of a normal pump that is not a high-pressure pump is discharged from the tip of a pipe electrode having pores. ) Represents a state in which the machining fluid adheres to the tip of the pipe electrode as water droplets and falls intermittently without being vibrated at a high frequency (the ring-shaped light reflected on the water droplets in the photograph is used for shooting). FIG. 4 (B) shows that the pipe electrode is 20 kHz or more in the axial direction and the amplitude is several μm to several tens of μm, so that the machining fluid is continuous from the tip of the pipe electrode. It shows a state of erupting.
In this test condition, a small-diameter pipe electrode is made of copper having an outer diameter of 0.38 mm, an inner diameter of 0.19 mm, and a length of 10 mm, and the processing liquid to be supplied is water.
As can be seen from the comparison of this test, when the machining fluid is supplied from the machining fluid supply means at a normal pressure other than the high pressure pump through the pores of the pipe electrode, if the pipe inner diameter is small, the viscosity of the machining fluid and the inside of the pipe While the machining fluid is not sent out due to the influence of bubbles, the pipe electrode is vibrated at a high frequency with an oscillation frequency of 20 kHz or more and an amplitude of several μm to several tens of μm in the axial direction. An action of lowering and an action of changing large bubbles into small-diameter microbubbles are generated, whereby the machining liquid is delivered.

FIG. 5 shows a state in which a discharge voltage is applied between the plasma discharge electrode and the workpiece and the plasma discharge electrode and the workpiece are brought into contact with each other. FIG. 5A shows a short circuit between the plasma discharge electrode and the workpiece. 5B is the same as FIG. 5A by vibrating the plasma discharge electrode in the axial direction at 20 kHz or higher and with an amplitude of several μm to several tens of μm. This represents a state in which plasma discharge continues to occur even under conditions.
In FIG. 5B, reference numeral 12 denotes plasma discharge generated between the plasma discharge electrode and the workpiece.

<Method of free-cutting difficult-to-cut materials>
The high frequency vibration assisted plasma discharge grinding method of the present invention having such a configuration will be described in detail below.
FIG. 6 (A) shows the state of the machining area in which the high-frequency pulse power source 4 for high-frequency vibration and the high-frequency pulse power source 5 for plasma discharge are off before plasma discharge machining. The abrasive grains 13 are joined and protruded. A machining liquid 6 mainly composed of water is supplied between the conductive binder, that is, the electric discharge machining electrode 14 and the workpiece W, that is, between the protruding heights of the abrasive grains 13.

Next, FIG. 6 (B) shows a state where the high frequency pulse power supply 4 for high frequency vibration is operated from the state of FIG. 6 (A) and the electric discharge machining electrode 14 is vibrating at a high frequency of 20 kHz or more in the horizontal direction of the figure. ing.
In this state, the machining fluid 6 supplied from the machining fluid supply means 7 can be used for the spindle 3 and the electrical discharge machining electrode 2 by vibrating the electrical discharge machining electrode 14 at a high frequency even when a normal pressure pump is used. The machining fluid 6 is supplied between the electric discharge machining electrode 14 and the workpiece W through the pores, and this machining fluid 6 is electrolyzed and has a diameter of several hundreds even when pure water having low conductivity is used. Bubbles of about μm are generated. And since the gas phase is more likely to generate sparks due to electric discharge than the liquid phase, the processed surface tends to be non-uniform.
The bubbles are broken by high-frequency vibration between narrow electrodes and changed to microbubbles 15 which are uniform microbubbles having a diameter of several μm or less. The liquid phase and the air (gas phase) of the microbubbles 15 are uniformly and densely mixed to form a liquid phase / gas phase mixed state.
In addition, the microbubbles 15 generate active oxygen such as OH radicals having a high oxidizing power by the energy at the time of crushing, and thus are effective for free machining of the processed surface.

  Then, in addition to the state shown in FIG. 6B in which the electric discharge machining electrode 14 vibrates at a high frequency, the plasma discharge high-frequency pulse power source 5 is operated, so that a uniform liquid phase is obtained as shown in FIG. 6C. An environment in which uniform plasma 16 is continuously generated without spark discharge is formed at a place where the electric discharge machining electrode 14 and the workpiece W are in contact between the extremely small electrodes filled with the gas phase.

When a voltage is applied between the electrodes by the plasma discharge high-frequency pulse power supply 5, bubbles of non-uniform size are generated between the electrodes due to the electrolysis of water, which is also broken by the high-frequency vibration between the narrow electrodes. To microbubbles 15.
The voltage applied by the plasma discharge high-frequency pulse power supply 5 between the electric discharge machining electrode 14 and the workpiece W is not short-circuited between the electric discharge machining electrode 14 and the workpiece W, and spark discharge and arc discharge are performed. Set the high frequency pulse so that it does not. Then, the machining fluid 6 between the electric discharge machining electrode 14 and the workpiece W is atomized by high-frequency vibration, and microbubbles 15 are generated by cavitation, and this electrode is in a mixed liquid phase / gas phase mixed state. By applying a high frequency pulse voltage with the electric discharge machining electrode 14 side as the negative electrode and the workpiece W side as the positive electrode, the uniform electric plasma 16 shown in FIGS. 2 and 5 is brought into contact with the electric discharge machining electrode 14 and the workpiece W. Generate locally at the place where you want to. By virtue of high-frequency vibration between narrow electrodes of less than 10 μm, which is the protruding height of the abrasive grains, there is no longer a situation where the electrodes are short-circuited and the discharge disappears, and plasma discharge between the electrodes can be sustained. It is.
As described above, according to the present embodiment, the electrodes do not short-circuit and the discharge does not disappear, so as in the conventional servo control, while maintaining the discharge interval by repeating the short-circuit and cutting, the processing can be performed. Machining is completed simply by moving forward at a constant speed without performing forward feed control as it progresses.

This plasma 16 ionizes the water of the machining fluid 6 located there, thereby further generating active oxygen such as OH radicals having a high oxidizing power, and the active oxygen is a work piece with which the electric discharge machining electrode 14 contacts. The softened layer 17 is generated by softening the surface of W by locally etching. Then, the softened layer 17 can be suitably ground by the electric discharge machining electrode 14 at a low machining pressure without accompanying tool deformation.
Since the generation site of the plasma 16 and the generation site of the microbubble 15 due to cavitation are local, and the active oxygen such as OH radicals has a short life, the generated softened layer 17 is formed of the workpiece W. Since it does not extend over the inner peripheral surface Wa and is limited only to the contact portion of the electric discharge machining electrode 14, it does not etch other than the machining surface as in the electrolytic machining.
And although the process waste 18 which generate | occur | produces when the softening layer 17 is ground and removed by the electric discharge machining electrode 14 is finely scattered between electrodes, these are discharged | emitted out of a process area by high frequency vibration. Also, the surface of the electrode is always cleaned and kept activated.

FIG. 7 is a view of a thin workpiece made of a difficult-to-cut material such as a titanium alloy, and FIG. 7 (A) machining, FIG. 7 (B) electrolytic machining, and FIG. 7 (C) electric discharge machining. FIG. 7D shows a difference from the processing by the high frequency vibration assisted plasma discharge grinding apparatus of the present invention.
In the machining shown in FIG. 7A, when the grinding wheel grinds the inner peripheral surface of the workpiece whose pilot hole is eccentric, the workpiece is deformed because the grinding wheel processing pressure is high. There was a risk that the eccentricity of the peripheral surface could not be removed and the eccentricity could be increased.
In the electrolytic processing of FIG. 7B, the inner peripheral surface is processed following the eccentric prepared hole due to the electrolytic action acting over the entire inner peripheral surface. The eccentricity of could not be removed.
In the electric discharge machining shown in FIG. 7C, even if only the electric discharge machining is performed on a rough hole having a large surface roughness before finishing, the surface roughness does not become small (smooth) but highly accurate. The inner peripheral surface could not be processed.
On the other hand, in FIG. 7D, the workpiece is not deformed by reducing the grindstone processing pressure of the electric discharge machining electrode with the aid of the high frequency vibration and the plasma discharge, and the plasma discharge is applied to the inside of the workpiece. Since the peripheral surface is locally generated and processed by free-cutting, it represents that it can be processed into a highly accurate inner peripheral surface that is concentric with the outer periphery and has a small surface roughness without following the eccentric prepared hole. .

  The present invention performs local grinding between an electric discharge machining electrode and a workpiece with the aid of high-frequency vibration and plasma discharge, and removes material, eliminates chips, and clogs the grindstone. In addition to the physical effect of prevention, the plasma discharge is sustained by ultrasonic vibration, and the effect of enabling the supply of the machining fluid that passes through the pores of the electric discharge machining electrode by ultrasonic vibration is achieved at low pressure.

  The high frequency vibration-assisted plasma discharge grinding apparatus and method of the present invention can be used in the processing industry for grinding various materials such as metals precisely and efficiently.

DESCRIPTION OF SYMBOLS 1 ... High frequency vibration assistance plasma discharge grinding apparatus 2 ... Electrical discharge machining electrode 2b ... Fine hole 3 ... Spindle 3b ... Fine hole 4 ... High frequency pulse power source for high frequency vibration 5 ... High frequency pulse power source for plasma discharge 6 ... Working fluid 7 ... Working fluid supply Means 8 ... Y table 9 ... X table 10 ... working area 11 ... slit 12 ... plasma discharge 13 ... abrasive grain 14 ... electric discharge machining electrode 15 ... micro bubble 16 ... plasma 17 ... softening layer 18 ... work scrap W ... workpiece

Claims (4)

An electric discharge machining electrode having a central hole through which a machining liquid is passed inside a grinding wheel obtained by bonding and solidifying non-conductive abrasive grains with a conductive binder;
A spindle for rotationally driving the electric discharge machining electrode;
Vibration means for high-frequency vibration of the spindle in the axial direction;
A high-frequency pulse power supply for high-frequency vibration for driving the excitation means;
Machining fluid supply means for supplying machining fluid through the center hole of the electric discharge machining electrode;
A high-frequency pulse power source for plasma discharge that applies a high-frequency pulse current for generating a plasma discharge between the electric discharge machining electrode and the workpiece,
The electric discharge machining electrode is vibrated in the axial direction along the surface of the workpiece with a high frequency vibration having an oscillation frequency of 20 kHz or more and an amplitude of several μm to several tens of μm. The distance between the workpiece and the rotating electric discharge machining electrode is set to 10 μm or less of the protrusion height of the abrasive grains, and plasma discharge is performed without causing an electrical short circuit between the workpiece and the abrasive grains in contact with the abrasive grains of the electric discharge machining electrode. A high-frequency vibration-assisted plasma discharge grinding apparatus characterized by being sustained.   2. The high frequency vibration assisted plasma discharge grinding apparatus according to claim 1, wherein the frequency of the high frequency pulse power source for plasma discharge is higher than the frequency of the high frequency pulse power source for high frequency vibration.   The high frequency vibration-assisted plasma discharge according to claim 1 or 2, wherein the electric discharge machining electrode has a longitudinal section perpendicular to the central axis and a radial slit penetrating from the central hole of the electric discharge machining electrode toward the outer periphery. Grinding equipment. A pipe-shaped electric discharge machining electrode for passing a machining liquid into a grinding wheel obtained by bonding and solidifying non-conductive abrasive grains with a conductive binder;
A spindle for rotationally driving the electric discharge machining electrode;
Vibration means for high-frequency vibration of the spindle in the axial direction;
A high-frequency pulse power supply for high-frequency vibration for driving the excitation means;
In a high frequency vibration assisted plasma discharge grinding apparatus comprising: a high frequency pulse power source for plasma discharge that applies a high frequency pulse current for generating a plasma discharge between the electric discharge machining electrode and a workpiece;
The electric discharge machining electrode is vibrated in the axial direction along the surface of the workpiece with a high frequency vibration having an oscillation frequency of 20 kHz or more and an amplitude of several μm to several tens of μm. The distance between the workpiece and the rotating electric discharge machining electrode is set to 10 μm or less of the protrusion height of the abrasive grains, and plasma discharge is performed without causing an electrical short circuit between the workpiece and the abrasive grains in contact with the abrasive grains of the electric discharge machining electrode. The plasma is assisted by high frequency vibration, wherein the plasma etches the workpiece to form a softened layer on the local machining surface, and the softened layer is ground by the abrasive grains of the electric discharge machining electrode. Electric discharge grinding method.