JP2000354914A - Electric discharge machine - Google Patents

Abstract

(57) Abstract: Provided is an electric discharge machine capable of performing machining of a shape different from the tip end surface of a tool electrode in a short time and obtaining a good machining surface. A workpiece 7 is moved to an X-direction moving stage 21.
And the Y-direction moving stage section 22 is moved to arbitrary positions in the X direction and the Y direction orthogonal to each other on the same plane. A discharge for machining is generated between the tool electrode 4 moved in the machining direction orthogonal to the X and Y directions and the workpiece 7. The movement position of the workpiece 7 in the X direction and the Y direction is calculated by an operation based on the detected position data of the tool electrode 4 with respect to the workpiece 7 and the processing data, and the workpiece 7 is Movement control is continuously performed to arbitrary movement positions in the X and Y directions based on the processing shape in accordance with the movement position.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to electric discharge machining mainly used for micromachining of micro holes and micro slits by utilizing electric discharge generated in a micro discharge gap between a tool electrode and a workpiece. It is about the machine.

[0002]

2. Description of the Related Art Conventionally, a micro-discharge machining technique has been mainly used as a method for forming a fine hole, such as a method for forming a hole in a nozzle of an ink jet printer. An ultra-fine electric discharge machine has been developed. Such an electric discharge machine has an overall configuration as shown in the schematic configuration diagram of FIG. That is,
This type of electric discharge machine includes a machining head unit 1 attached with a tool electrode 4 and moving up and down, a positioning mechanism unit 2 for controlling movement of a workpiece 7 and positioning the workpiece 7 with respect to the tool electrode 4. , And a control box section 3 having an NC control section as a basic configuration.

The machining head 1 has a tool electrode 4 attached to a lower end of a mandrel 8 in a vertical arrangement.
A ball screw (not shown) in which the tool electrode 4 is driven to rotate with high accuracy by a DC motor or the like (not shown) and driven by a motor 9 as a vertical drive source.
, And is processed with high precision in the processing direction vertically below. The reason for rotating the tool electrode 4 is that
This is to ensure the discharge of processing waste and the roundness.

A positioning mechanism 2 is provided with a machining tank 11 filled with an electric discharge machining liquid 10 made of an insulating liquid such as pure water.
And a sample table 12 installed inside the processing tank 11,
The processing tank 11 mounted and fixed on the upper surface is moved in arbitrary directions of the X direction and the Y direction orthogonal to each other in the horizontal plane.
The XY stage 13 includes a Y stage 13 and a stage driving mechanism 14 that controls the movement of the XY stage 13.
The workpiece 7 is placed and fixed on the sample table 12 in the electric discharge machining fluid 10 and is positioned with respect to the tool electrode 4 by the XY stage 13 whose movement is controlled by the stage driving mechanism 14.

[0005] Although the inside of the control box section 3 is not shown, a central processing unit and a tool box 4 between the tool electrode 4 and the workpiece 7 through a capacitor switch under the control of the central processing unit. The control unit controls the stage drive mechanism unit 14 under the control of a discharge circuit for applying a pulse voltage to the central processing unit, and controls the rotation of the motor 9 with high precision to precisely feed the machining head unit 1. It is configured to include a drive control unit and the like.

In this electric discharge machine, when a voltage is applied from the electric discharge circuit between the tool electrode 4 and the workpiece 7 with the electric discharge machining liquid 10 interposed therebetween, the tool head 4 is lowered by lowering the machining head 4. Is used to process a fine hole by using an electric discharge generated when a predetermined minute gap is brought close to the workpiece 7. This machining progresses while repeating the melting of the workpiece 7 and the removal of electric discharge machining chips by the heat generated by the intermittent electric discharge between the tool electrode 4 and the workpiece 7, and the machining by the discharge traces. Drilling or the like is performed on the material 7.

This electric discharge machine has various major features as follows. That is, micro-discharge machining can be performed by minimizing the discharge energy and miniaturizing the tool electrode 4, and the workpiece 7 of any material can be machined as long as it has conductivity. Even the workpiece 7 having a high hardness can be easily processed. In addition, it is possible to process a workpiece having a high specific resistance, such as silicon ferrite, which has a problem such as cracking in ordinary electric discharge machining. It can be processed without giving a processing force, and can be processed with high accuracy on a curved surface, an inclined surface, a thin plate, or the like, which is difficult with drilling or the like. Furthermore, if the hole system is 50 μm or more, it is possible to machine a hole 10 times deeper than it, so it is also suitable for machining of dies used for plastic working such as punching of micro mechanical parts. It has various great features such as being able to.

[0008]

In the above-mentioned electric discharge machine,
The tip of the tool electrode 4 is machined into a state in which the tip of the tool electrode 4 is projected onto the workpiece 7, and as the machining progresses, a hole or the like in which the tip of the tool electrode 4 is projected is machined. Therefore, when processing into a shape different from the tip end surface of the tool electrode 4, the position of the workpiece 7 with respect to the tool electrode 4 is processed by controlling the movement of the XY stage 13 by driving the stage drive mechanism 14. Positioning is sequentially performed so as to correspond to the shape, and electric discharge machining is repeated for each positioning.

For example, when machining a tapered (tapered) hole having a gradually decreasing cross-sectional area downward, first, a hole penetrating with a cross-sectional area equal to the tip surface of the tool electrode 4 is formed. A process is performed on the processed hole so as to increase the diameter of the hole so that the diameter of the hole in the upper portion becomes maximum. When performing the machining to enlarge the diameter of the machined hole, the machining by the tool electrode 4 is performed while positioning the workpiece 7 so that the tool electrode 4 faces the hole edge of the machined hole and performing electric discharge machining. The relative position of the workpiece 7 with respect to the tool electrode 4 is changed so that the position is sequentially displaced inward of the processed hole from the start of processing. The process of increasing the diameter of the machined hole is repeated while sequentially changing the relative position of the workpiece 7 with respect to the tool electrode 4, and is continued until the position of the tool electrode 4 goes around the machined hole.

However, in the conventional electric discharge machine, when machining a large shape different from the tip surface of the tool electrode 4 as described above, the relative position of the workpiece 7 with respect to the tool electrode 4 corresponds to the machining shape. Since the electric discharge machining at each of the positioning points is repeated while sequentially changing the position, there is a disadvantage that the machining time is long, and the electric discharge machining is performed every time the relative position of the workpiece 7 to the tool electrode 4 is sequentially changed. To start,
For example, there is a problem that an accurate roundness cannot be obtained, a stepped machining mark is formed on a machined surface, and a machined surface roughness is deteriorated due to excessive discharge caused by generation of machining chips and burrs.

In view of the above, the present invention has been made in view of the above-mentioned conventional problems, and can perform machining of a shape different from the tip end surface of a tool electrode in a short time and obtain a good machined surface. It is an object of the present invention to provide an electric discharge machine capable of performing such operations.

[0012]

In order to achieve the above object, an electric discharge machine according to the present invention comprises a sample table for holding a workpiece in an electric discharge machining fluid and a sample table which is orthogonal to each other on the same plane. An X-direction moving stage portion and a Y-direction moving stage portion for moving to an arbitrary position in the X direction and the Y direction, and the work material provided movably in a processing direction orthogonal to both the X direction and the Y direction. A tool electrode that generates a machining discharge between the workpiece and the workpiece by proximity to the workpiece, a position detector that detects a position of the tool electrode with respect to the workpiece, and detection position data from the position detector. An arithmetic circuit for calculating the respective movement positions of the workpiece in the X direction and the Y direction by performing an operation based on the data and the processing data; And a drive control unit for controlling the movement of the stage unit and the Y-direction moving stage unit, respectively, wherein the workpiece is moved to an arbitrary position in the X direction and the Y direction based on the processing shape in accordance with the moving position of the tool electrode. It is configured to control movement continuously.

In this electric discharge machine, when performing electric discharge machining of a large shape different from the end face shape of the tool electrode, the work material is calculated based on the position of the tool electrode moving in the machining direction and the machining data. The movement of the workpiece is controlled by a continuous movement trajectory in synchronization with the movement of the tool electrode toward the movement position in the X direction and the Y direction. In addition to being carried out in a short time, no step-like discharge marks are generated on the machining surface, and since the machining is continuous, it is possible to efficiently remove machining chips and generate no burrs. Generation can be reliably prevented and a good machined surface can be obtained.

In the above invention, there is provided a discharge detecting section for detecting the occurrence of a discharge between the tool electrode and the workpiece and outputting a discharge detection signal, wherein the position detecting section detects when the discharge detection signal is inputted. It is preferable that the operation of detecting the position of the tool electrode with respect to the workpiece is started from the step of outputting the detected position data, and that the arithmetic circuit starts the arithmetic operation from the time of inputting the detected position data.

[0015] Thus, the tool electrode can be quickly moved to the proximity position where discharge occurs between the workpiece and the workpiece, so that the machining time can be further reduced. In addition, the position of the tool electrode is detected with reference to the time when the discharge occurs, and the movement position of the workpiece is calculated based on the detected position of the tool electrode. Based on this, it is possible to accurately calculate and control the workpiece, and to process the workpiece to a shape corresponding to the processing data with high accuracy, and to improve the roughness of the processed surface.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an electric discharge machine according to an embodiment of the present invention. In FIG. 1, the same or equivalent components as those in FIG. 3 are denoted by the same reference numerals. In this electric discharge machine, a machining head section 17 rotatably supporting a tool electrode 4 is guided by a guide mechanism section 19 by a ball screw (not shown) rotated by driving a motor 18 as a vertical movement drive source. The tool electrode 4 is moved up and down to process and feed the tool electrode 4 with high precision in a vertically downward machining direction.

On the other hand, the workpiece 7 mounted and held on the sample table 12 in the electric discharge machining fluid 10 is moved by the XY stage 20 in the same plane (in this case, a horizontal plane) in the X and Y directions orthogonal to each other. The tool electrode 4 is moved in any direction.
Is positioned with respect to. The XY stage 20 is a sample stage 1
An X-direction moving stage section 21 for moving 2 in the X direction;
Y for moving the X-direction moving stage 21 in the Y direction
And a direction moving stage section 22. X
The direction moving stage unit 21 is moved in the X direction on the upper surface of the Y direction moving stage unit 22 by an X direction driving mechanism unit 23 composed of a piezo actuator (not shown) which is a high-precision vibrating element. Is controlled. The Y-direction moving stage section 22 is controlled to move in the Y-direction by a Y-direction driving mechanism section 24 also composed of a piezo actuator constituted by using a piezo element, so that the X-direction moving stage section 21 is integrally formed in the Y-direction. Move control.

A motor 18 serving as a drive source for vertically moving the tool electrode 4
The rotation of the motor 18 is controlled via a motor drive circuit 25, and a rotation detector 27 including an encoder or the like detects the rotation of the motor 18 and outputs a rotation detection signal. On the other hand, the discharge circuit 28 generates an intermittent discharge by applying a predetermined pulse-like discharge voltage between the tool electrode 4 and the workpiece 7, and the discharge circuit 28 is covered by a large number of discharge traces generated by the generated discharge. Processing such as drilling is performed on the processing material 7. The discharge detection unit 29 detects the occurrence of discharge between the tool electrode 4 and the workpiece 7 based on a change in the voltage value of the discharge circuit 28, and outputs a discharge detection signal. The position detection unit 30 starts the rotation of the motor 18 and detects the rotation of the motor 18 from the time when the discharge detection signal is input from the discharge detection unit 29. Is calculated, and the calculated detected position data is output as an electric signal such as a voltage. On the other hand, the motor drive circuit 25
Switches from the time when the discharge detection signal is input to the rotation for controlling the rotation of the motor at a predetermined speed.

The arithmetic circuit 31 calculates the moving position of the workpiece 7 in the X and Y directions corresponding to the detected position data input from the position detecting section 30 based on the processing data of a preset processing shape. , And outputs the calculated X-direction movement position data and Y-direction movement position data. The signal generator 32 generates signals of the X-direction movement amount and the Y-direction movement amount respectively corresponding to the X-direction and Y-direction movement position data of the calculation result input from the calculation circuit 31, and the X-direction drive control unit 33 and Y-direction drive control unit 34
Are output individually.

Each of the X-direction drive control unit 33 and the Y-direction drive control unit 34 has a built-in amplitude modulation circuit.
X-direction drive mechanism 23 and Y in accordance with the direction movement amount signal
By controlling the driving of each piezo element of the direction drive mechanism 24, the position of the workpiece 7 is controlled to move relative to the position of the tool electrode 4 in synchronization with the processing data. Although not shown in FIG. 1 because of its well-known configuration, the electric discharge machine includes an XY table for controlling the positioning of the XY stage 20 at arbitrary positions in the X and Y directions orthogonal to each other. ing.

Next, the operation of the electric discharge machine will be described.
This will be described with reference to FIG. In this embodiment, an example will be described in which a tapered hole having a tapered shape as viewed from the surface of a workpiece 7 is machined using a rod-shaped tool electrode 4 having a circular cross section, that is, a thin columnar tool. . When the workpiece 7 is set on the sample stage 12, the XY stage 20 is controlled to move in response to a command from a controller (not shown), so that the portion of the workpiece 7 where the tapered hole is to be processed is the tool electrode 4. It is positioned just below.

Subsequently, the motor drive circuit 25 starts the motor 18 in response to a command from the controller,
The tool electrode 4 starts the descending operation and moves close to the workpiece 7. At this time, a predetermined discharge voltage is applied from the discharge circuit 28 between the tool electrode 4 and the workpiece 7. Thus, at time t _{0 in} FIG. 2A when the distance between the tool electrode 4 and the workpiece 7 is reduced to a predetermined value, the insulation of the electric discharge machining fluid 10 is broken and an arc discharge that starts a spark discharge. Occurs. Here, since a pulse current is supplied from the discharge circuit 28, the arc discharge is extinguished in a short time, but the generated heat causes melting or evaporation of the discharge generating portion, thereby forming a crater. The arc discharge is sequentially generated from a position close to the facing surface, and a crater is generated over the entire area of the workpiece 7 corresponding to the shape of the end face of the tool electrode 4.
Processing proceeds so that the gap between both poles becomes uniform.

The discharge detector 29 detects the occurrence of the arc discharge based on a change in the voltage of the discharge circuit 28, and outputs a discharge detection signal to the position detector 30 and the motor drive circuit 25, respectively. The motor drive circuit 25 starts the rotation control of the motor 18 so as to advance the tool electrode 4 toward the workpiece 7 at the set speed from the time when the discharge detection signal is input. As a result, the position of the tool electrode 4 is controlled so as to always maintain a small gap with which the electric discharge can be continued with respect to the processing surface of the workpiece 7, and the tool electrode 4 is directed toward the hole in the workpiece 7 as the machining progresses. It descends at the required speed.

On the other hand, the position detecting section 30
From the time when the discharge detection signal is input from the
The relative position of the tool electrode 4 with respect to the workpiece 7 is calculated by performing an operation based on the rotation detection signal input from the controller 7, and the calculated detection position data is output to the arithmetic circuit 31 as an electric signal such as a voltage. I do. The arithmetic circuit 31 calculates the moving position of the workpiece 7 in the X direction and the Y direction based on the detected position data of the tool electrode 4 and the processing data input from the rotation detecting unit 27, respectively, and calculates the X position of the calculation result. The movement position data in the direction and the movement position data in the Y direction are output to the signal generator 32, respectively. The signal generator 32 generates an X-direction movement amount signal and a Y-direction movement amount signal respectively corresponding to the input movement position data in the X-direction and the Y-direction, respectively. It is output individually to the control unit 34.

As shown in FIGS. 2B and 2C, the X-direction drive control unit 33 and the Y-direction drive control unit 34 respond to the input X-direction movement amount signal and Y-direction movement amount signal, respectively. The piezo elements of the X-direction moving stage unit 21 and the Y-direction moving stage unit 22 are respectively subjected to vibration control. Here, as is clear from the comparison between FIGS. 2B and 2C, the piezo elements of the X-direction moving stage 21 and the Y-direction moving stage 22 have a phase of 90 ° with each other.
Driving is performed so as to have a sine wave driving waveform in which the amplitude shifts and the amplitude gradually decreases.

Therefore, the workpiece 7 is circularly moved by the driving of the piezo elements of the X-direction moving stage 21 and the Y-direction moving stage 22, and the tool electrode 4 is moved.
Continuously moves to a circular motion in which the diameter of the moving trajectory that makes a circular motion sequentially decreases in synchronization with the progress of the hole in the drilling direction. As a result, in the workpiece 7, a tapered hole is formed in a short time by continuous processing by the tool electrode 4, and a step-like discharge mark is not generated on the processing surface. As a result, it is possible to efficiently remove the processing waste, generate no burrs, prevent the occurrence of excessive discharge, and obtain a good processed surface.

When the machining of the tapered hole is completed at t _{1 in} FIG. 2, the discharge is stopped, and the discharge detection unit 29 stops outputting the discharge detection signal, so that the motor drive circuit 25 stops the rotation of the motor 18 and , The detected position data is no longer output from the position
The driving of the moving stage units 21 and 22 in the directions is also stopped.

[0028]

As described above, according to the electric discharge machine of the present invention, when performing electric discharge machining of a large shape different from the end surface shape of the tool electrode, the workpiece is oriented in the machining direction of the tool electrode. Since the movement is controlled along a continuous movement trajectory in synchronization with the movement of the tool electrode toward the movement position in the X direction and the Y direction calculated based on the movement position and the processing data, In addition, the machining of a predetermined shape is performed in a short time by continuous electric discharge machining with the tool electrode, and no stepped discharge marks are generated on the machining surface. In addition, no burrs are generated, and the occurrence of excessive discharge is reliably prevented, so that a good machined surface can be obtained.

[Brief description of the drawings]

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

2A is a view showing the movement of a tool electrode of the electric discharge machine, and FIGS. 2B and 2C show the movement state of a moving stage in the X and Y directions corresponding to the position of the tool electrode. FIG.

FIG. 3 is a schematic configuration diagram of a conventional electric discharge machine.

[Explanation of symbols]

 Reference Signs List 4 Tool electrode 7 Workpiece 10 Electric discharge machining liquid 12 Sample table 21 X-direction moving stage unit 22 Y-direction moving stage unit 29 Discharge detection unit 30 Position detection unit 31 Arithmetic circuits 33, 34 Drive control unit

Claims (2)

[Claims] 1. A sample stage for holding a workpiece in an electric discharge machining fluid, an X-direction moving stage unit for moving the sample stage to arbitrary positions in an X direction and a Y direction orthogonal to each other on the same plane, and a Y stage. A direction moving stage portion, a tool movably provided in a processing direction orthogonal to both the X direction and the Y direction, and generating a discharge for processing between the workpiece and the workpiece by proximity to the workpiece. An electrode; a position detection unit that detects a position of the tool electrode with respect to the workpiece; and an X-direction and a Y-direction of the workpiece by performing an operation based on detected position data and processing data from the position detection unit.
An operation circuit that calculates each movement position in the direction; and a drive control unit that controls movement of the X-direction movement stage unit and the Y-direction movement stage unit based on the movement position data of the operation result of the operation circuit, An electric discharge machine characterized by being configured to continuously control the movement of a workpiece to an arbitrary position in an X direction and a Y direction based on a machining shape corresponding to a moving position of the tool electrode. 2. A discharge detecting section for detecting the occurrence of discharge between a tool electrode and a workpiece and outputting a discharge detection signal, wherein a position detection section detects the discharge from the time when the discharge detection signal is inputted. 2. The apparatus according to claim 1, wherein the operation of detecting the position of the tool electrode with respect to the workpiece is started to output detected position data, and the arithmetic circuit is configured to start the arithmetic operation from the time of input of the detected position data. 3. Electric discharge machine.