WO2002055250A1

WO2002055250A1 - Wire electric discharge machining method and device

Info

Publication number: WO2002055250A1
Application number: PCT/JP2001/000215
Authority: WO
Inventors: Hiroatsu Kobayashi; Akihiro Goto; Takuji Magara
Original assignee: Mitsubishi Denki Kabushiki Kaisha
Priority date: 2001-01-16
Filing date: 2001-01-16
Publication date: 2002-07-18

Abstract

A wire electric discharge machining device for machining a workpiece (2) in gas and/or mist by feeding electric discharge energy between the poles for a wire electrode (1a) and the workpiece (2) by a machining power feeding means (18) and relatively moving the wire electrode (1a) and the workpiece (2) by a positioning means, wherein the device comprises a high frequency vibration imparting means (10, 17) for setting the wire electrode (1a) and the workpiece (2) in relative high frequency vibration, and a control means (19) for controlling such high frequency vibration. It is possible to attain high accuracy and improved productivity in wire electric discharge machining.

Description

Description Wire electric discharge machining method and device

The present invention relates to an improvement in a wire electric discharge machining method and apparatus for supplying machining power between a wire electrode and a workpiece and processing the workpiece by a discharger. Background art

EDM has established a solid position as a machining technology for dies and the like, and has been used extensively in the dies and machining fields of the automobile industry, home appliance industry, semiconductor industry, and so on.

Fig. 4 is an explanatory view of the mechanism of electric discharge machining. In the figure, 1 is an electrode, 2 is a workpiece, 3 is an arc column, 4 is a machining fluid, and 5 is machining waste generated by electric discharge machining. . While the following cycles (a) to (e) (corresponding to (a) to (e) in FIG. 4) are repeated, removal processing of the workpiece 2 by electric discharge proceeds. That is, (a) formation of the arc column 3 due to the generation of electric discharge, (b) local melting and vaporization of the working fluid 4 due to the heat energy of the discharge, (c) generation of a vaporizing explosive force of the working fluid 4, (d) melting (E) Scattering of the processing waste (5), (e) Cooling, solidification, and insulation recovery between the electrodes due to the working fluid.

TECHNICAL FIELD The present invention relates to wire electric discharge machining used for boring, cutting and the like among electric discharge machining. The demand for high-precision wire electric discharge machining is increasing in particular.For example, machining of high-precision dies used in the semiconductor industry, etc., requires a high machining accuracy of about 1 to 2 m. It is becoming. FIG. 5 is an explanatory view showing an example of a machining process of wire electric discharge machining, in which 1 a is a wire electrode, 2 is a workpiece, 4 a is water as a machining fluid, and 6 is an initial hole. Fig. 5 (a) shows the first cut, which is rough machining, Fig. 5 (b) shows the second cut, which is medium finishing after roughing, and Fig. 5 (c) shows final cutting. A third cut is shown.

FIG. 5 (a) shows an example of the first cut processing in which the wire electrode la is passed through the initial hole 6 and the workpiece 2 is penetrated. In the case of such a fast cut, the surface roughness and precision are finished in the subsequent processing, so not so severe surface roughness and precision are required, and it is important to increase the processing speed especially to improve productivity It is. In wire electric discharge machining, in order to increase the machining speed, water 4a is blown out between the gaps in order to efficiently discharge machining waste from the gaps. In addition, in order to eliminate uneven distribution of water 4a between the poles and prevent disconnection of the wire electrode 1a, a method of immersing the workpiece 2 by storing the water 4a in a processing tank (not shown) is used. It is required. Thus, the working fluid supply means for supplying the working fluid between the poles is used. .

In the conventional wire electric discharge machining as described above, machining such as the second cut (FIG. 5 (b)) and the third cut (FIG. 5 (c)) after the first cut (FIG. 5 (a)) is also performed. It is performed in water 4a, which is a processing fluid.

When a voltage is applied between the wire electrode 1 a and the pole of the workpiece 2, the positive and negative polarities are attracted to each other. It will be pulled to the 2 side. This causes the vibration of the wire electrode 1a, and there is a problem that such high amplitude and uncertain transient vibration make high-precision machining difficult. Also, in a state where the explosive power of the machining fluid is generated by the discharge energy (for example, (c) in FIG. 4), the wire electrode 1 a is in the opposite direction to the workpiece 2 due to the vaporized explosive power of the machining fluid. A large force acts on, causing vibration. Due to such vibration, irregularities are generated in the shape of the workpiece 2, leading to a problem that accuracy is deteriorated.

In the semiconductor industry, which is a field of application of wire electric discharge machining, for example, in the processing of dies for IC lead frames, it is necessary to process workpieces with a shape accuracy of 111 and a surface roughness of 1 mR max or less. Applications that require extremely high precision and extremely smooth surface roughness are increasing.In such applications, in particular, the problems caused by the vibration of the wire electrode as described above are prominent. .

As a measure to solve such problems of wire submerged wire electric discharge machining, a technology related to submerged wire electric discharge machining, which performs wire electric discharge machining in the air without intervening machining fluid between the electrodes, has been disclosed. (Tokyo University of Agriculture and Technology, Adachi et al., "High Accuracy of Second Cut by Air Discharge Machining", Mold Technology, Vol. 14, No. 7, 1999, pp. 154, Nikkan Kogyo Shimbun) . This technology discloses that the straightness of the cut surface of the workpiece can be improved by wire electric discharge machining in the atmosphere, and this technology has great significance in terms of high accuracy. On the other hand, there were problems in processing stability and processing speed, such as a short circuit between the wire electrode and the workpiece being easily generated, and practical application was difficult. Disclosure of the invention

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a wire electric discharge machining method and apparatus capable of realizing high precision of wire electric discharge machining and improvement of machining productivity. Aim. A wire electric discharge machining method according to the present invention is a wire electric discharge machining method for machining a workpiece by generating an electric discharge between a wire electrode and a workpiece, and performing rough machining in a machining fluid. A first step, and a second step of performing finishing processing in the air or in a mist. In the second step, the processing is performed while relatively vibrating the wire electrode and the workpiece with high frequency. You do it.

Further, a wire electric discharge machining method according to the present invention is a wire electric discharge machining method for machining the workpiece by generating an electric discharge between a wire electrode and the workpiece, wherein the rough machining is performed in a machining fluid. A first step of performing finishing, a second step of performing finishing in a mist, and a third step of performing finishing in the air, wherein the second and third steps include: The processing is performed while relatively oscillating the wire electrode and the workpiece with high frequency.

Further, the wire electric discharge machining method according to the present invention performs the heating while controlling the relative high frequency vibration between the wire electrode and the workpiece so as not to be a standing wave.

In a wire electric discharge machining apparatus according to the present invention, electric discharge energy is supplied between a wire electrode and a workpiece by a machining power supply means, and the wire electrode and the workpiece are relatively moved by a positioning means. A wire electric discharge machine for machining the workpiece in the air or in a mist, comprising: a high frequency vibration applying means for relatively high frequency vibration of the wire electrode and the workpiece; and And control means for controlling. Further, in the wire electric discharge machining apparatus according to the present invention, the high-frequency vibration applying means includes a high-frequency vibrator having at least two degrees of freedom in a direction orthogonal and parallel to the traveling direction of the wire electrode. The high-frequency vibrator is controlled so that the relative high-frequency vibration between the wire electrode and the workpiece does not become a standing wave. Further, in the wire electric discharge machine according to the present invention, the high-frequency vibrator is a direct drive actuator such as a piezoelectric element, a magnetostrictive element, an ultrasonic motor, or a linear motor.

Since the wire electric discharge machining method and apparatus according to the present invention are configured as described above, in the finishing machining, machining is performed without intervening machining fluid between the electrodes, and the shape accuracy and surface roughness of the workpiece are reduced. Can be improved.

In addition, machining dust, gas, etc. generated between the poles can be efficiently removed, and the action of suppressing electric discharge concentration and short circuit can be achieved, so that air wire electric discharge machining is stabilized and the machining speed is improved. Therefore, processing productivity can be improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an explanatory diagram showing an example of a wire electric discharge machining method according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a configuration of the wire electric discharge machine according to the embodiment of the present invention.

FIG. 3 is a diagram illustrating a configuration example and a function of a high-frequency vibration applying unit according to the embodiment of the present invention.

FIG. 4 is an explanatory view of a mechanism of electric discharge machining.

FIG. 5 is an explanatory diagram showing an example of a machining process of wire electric discharge machining. BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is an explanatory diagram showing an example of a wire electric discharge machining method according to an embodiment of the present invention. In the figure, la wire electrode, 2 is a workpiece, 4a is water as a machining fluid, and 6 is Initial hole 7 is a gas such as air. Fig. 1 (a) shows the first cut, which is rough machining, and Fig. 1 (b) shows the second cut, which is finishing machining after rough machining. . First The names of the power cut and the second cut are for convenience only, and the wire electric discharge machining does not necessarily end in two times. In the case of processing that requires high accuracy for the workpiece, the processing may be performed seven or eight times.

Next, an outline of the processing method will be described. The first cut shown in FIG. 1 (a) is a process in which the wire electrode 1a is passed through the initial hole 6 and the workpiece 2 is penetrated. In the first cut, since the surface roughness and precision are finished in the subsequent processing, not so strict surface roughness and precision are required, and it is important to increase the processing speed especially to improve productivity. Processing is performed with water 4a, which is a processing liquid, interposed between the poles as in FIG. In ordinary wire electric discharge machining, machining is performed in the machining fluid even after the first cut, but there are problems such as uncertain transient vibration of the wire electrode as shown in the background art. Not suitable. The present invention improves the shape accuracy and surface roughness of a workpiece by performing processing without intervening machining fluid between the poles in finishing.

In the second cut, which is the finishing process shown in Fig. 1 (b), in order to suppress the vibration of the wire electrode 1a and improve the processing accuracy, the processing is performed in the gas 7 instead of the processing fluid 4a. Is what you do. By such aerial wire electrical discharge machining, uncertain transient vibration of the wire electrode 1a can be suppressed as described below.

That is, the electrostatic force acting on the wire electrode 1a and the workpiece 2 when a voltage is applied between the poles is proportional to the dielectric constant between the poles. When the intervening substance is gas 7, the electrostatic force is several tenths (for example, the dielectric constant is the smallest in vacuum, and the About 80 times in vacuum). Further, since the vaporizing explosive force due to the discharge is generated by the liquid interposed between the poles, when only the gas 7 exists between the poles, the wire electrode 1a is hardly affected by the vaporizing explosive force. I do not receive it. Therefore, uncertain transient vibration of the wire electrode 1a can be suppressed.

As described above, aerial wire electric discharge machining is effective for high-precision machining, but there is a problem that the machining speed is slower than that of submerged wire electric discharge machining as shown in the background art. The main reasons for this are that the amount of workpiece removal is reduced due to the elimination of the vaporizing explosive force generated by discharge, as in submerged electric discharge machining. This is because it adheres to the surface of the workpiece and makes the processing unstable.

FIG. 2 is an explanatory diagram showing a configuration of a wire electric discharge machine according to an embodiment of the present invention, and shows an example of a configuration capable of realizing aerial wire electric discharge machining as shown in FIG. 1 (b). It is a thing. In FIG. 2, la is a wire electrode, 2 is a workpiece, 7 is a gas such as air, oxygen, nitrogen, or an inert gas, 8 is a wire pobin, 9a and 9b are wire electrodes 1a and a workpiece. A gas supply means for supplying gas 7 between the poles of the workpiece 2, 10 is a high frequency vibration applying machine, 11 is a capstan roller, 12 is a pinch roller, and 13 is a horizontal surface of the workpiece 2. An X table for driving in the direction (X direction), 14 is a Y table for driving the workpiece 2 in the horizontal direction (Y direction), and 15 is a motor (not shown) for driving the X table 13. X-axis servo amplifier for driving and controlling the evening, 16 is a Y-axis servo amplifier for driving and controlling a motor (not shown) that drives the Y table 14, and 17 is a servo amplifier for driving and controlling the high frequency vibration applying actuator 10. Reference numeral 18 denotes processing power supply means, and reference numeral 19 denotes control means.

Here, the high frequency vibration imparting function 10 and the support amplifier 17 constitute high frequency vibration imparting means. FIG. 3 is an explanatory view of a configuration example and a function of the high-frequency vibration applying means. In the figure, 10a is a tip engaging member, 10Ob and 10c are piezoelectric elements, magnetostrictive elements, Sound wave motor or linear It is a high-frequency vibrator made of a motor or the like. FIG. 3 (b) schematically shows a high-frequency vibration waveform applied to the wire electrode 1a by the high-frequency vibration applying means.

The gas supply means 9a and 9b can be realized by, for example, forming a nozzle around the wire electrode la and supplying a pressurized gas. By supplying the pressurized gas between the electrodes, it is possible to prevent the machining chips removed by the discharge from adhering to the wire electrode and the surface of the workpiece. The air discharge machining can be performed in the air without using such gas supply means 9a and 9b.

Next, the operation will be described. The wire electrode 1a is pinched and pulled by the capstan opening 11 and the pinch roller 12 so that the wire electrode 1a runs, the wire electrode 1a and the workpiece 2 are opposed to each other, and the gas supply means 9a and While supplying gas 7 between the electrode between the wire electrode 1a and the workpiece 2 by 9b, machining power, which is discharge energy, is supplied by the machining power supply means 18 between the poles, and the positioning means X Finish the work 2 by relatively moving the wire electrode 1 a and the work 2 using the table 13 and the Y table 14. The control means 19 controls the relative positioning control of the wire electrode la and the workpiece 2 and the control of the electric machining conditions by the positioning means. Further, the high-frequency vibrators 10b and 10c constituting the high-frequency vibration applying function 10 are driven by the control means 19 through the support amplifier 17 and are driven through the tip engaging member 10a. High frequency vibration is applied to the wire electrode 1a. That is, the wire electrode la is excited by the high-frequency vibrator 10c together with the vibration component (for example, the X direction in the figure) perpendicular to the wire electrode 1a excited by the high-frequency vibrator 10c. A vibration component parallel to a (for example, Z direction in the figure) is also added. The vibration applied to the wire electrode 1 in this manner is not a standing wave, but as shown in FIG. The control means 19 is controlled so that multiple vibrations such that the positions of antinodes and nodes of the vibration mode of the input electrode 1a constantly change are obtained. Therefore, unlike in the case of the standing wave vibration, the processed surface of the workpiece does not have a striped pattern.

In addition, by performing aerial wire discharge machining while applying such high-frequency vibration to the wire electrode 1a, machining dust, gas, and the like generated between the electrodes can be efficiently removed, thereby suppressing discharge concentration and short circuit. Since it has an effect, the aerial wire discharge processing is stable and the processing speed is improved. Therefore, there is an effect that processing productivity can be improved.

In addition, since the high-frequency oscillators 10b and 10c, which are the actuators that directly drive the tip engaging member 10a, are used as the high-frequency vibration applying actuator 10, the response is high, and the wire electrode la Even when the material, diameter, wire tension, and the like change, the vibration amplitude, frequency, and the like can be controlled with high accuracy and stability. In particular, in the electric discharge machining, the gap between the electrodes is smaller than that in the electric discharge machining, and it is difficult to control the amplitude of the wire electrode. Therefore, the direct drive type high frequency vibration applying actuator 10 as described above is used. It is necessary to perform high-precision control.

In the above description, the case where the two-degree-of-freedom actuator consisting of the high-frequency oscillators 10b and 10c is used as the high-frequency oscillator constituting the high-frequency vibration applying actuator 10 has been described. For example, an actuator having three or more degrees of freedom to excite the vibration of the wire electrode in the X direction, the Y direction, and the Z direction may be used.

Further, in the above description, the case where the high frequency vibration is applied to the wire electrode 1a by the high frequency vibration applying means has been described. However, it is sufficient that the wire electrode 1a and the workpiece 2 are relatively high frequency vibrated. Alternatively, high frequency vibration may be applied to the workpiece 2 instead of the wire electrode 1a. In the above description, the case where the roughing is performed in the working fluid and the finishing is performed in the air has been described. However, the same effect can be obtained when the finishing is performed in the mist. Industrial applicability

As described above, the wire electric discharge machining method and apparatus according to the present invention are particularly suitable for being used for high precision electric discharge machining.

Claims

The scope of the claims

1. In a wire electric discharge machining method of machining a workpiece by generating an electric discharge between a wire electrode and a workpiece,

A first step of performing rough machining in a machining fluid,

A second step of performing finishing processing in the air or in a mist, wherein the second step performs the processing while relatively vibrating the wire electrode and the workpiece with high frequency. Wire electric discharge machining method.

2. A wire electric discharge machining method for machining the workpiece by generating an electric discharge between the wire electrode and the workpiece.

A first step of performing rough machining in a machining fluid,

A second step of finishing in the mist,

Equipped with a third step of finishing in the air,

In the second and third steps, a wire electric discharge machining method is characterized in that machining is performed while the wire electrode and the workpiece are vibrated relative to each other at a high frequency. ,

3. The wire electric discharge machining method according to claim 1, wherein the machining is performed while controlling the relative high frequency vibration between the wire electrode and the workpiece so as not to be a standing wave.

4. Discharge energy is supplied between the wire electrode and the workpiece by the processing power supply means, and the wire electrode and the workpiece are moved relative to each other by the positioning means. In wire electric discharge machines that process workpieces, High-frequency vibration applying means for relatively high-frequency vibration of the wire electrode and the workpiece;

Control means for controlling the high-frequency vibration applying means. ,

5. In Claim 4, the high-frequency vibration applying means has a high-frequency vibrator having two or more degrees of freedom in directions perpendicular and parallel to the wire electrode traveling direction, and the control means controls the wire electrode and the workpiece. A wire electric discharge machine characterized by controlling the high-frequency vibrator so that the relative high-frequency vibration does not become a standing wave.

6. The wire electric discharge machine according to claim 5, wherein the high-frequency vibrator is a directly driven actuator such as a piezoelectric element, a magnetostrictive element, an ultrasonic motor, or a linear motor.