JPH068058A - Electric discharge machine - Google Patents

Abstract

PURPOSE:To provide an electric discharge machine capable of adjusting electric discharge gap length with high response speed and accuracy and capable of moving the tool electrode side to enable the adjustment of electric discharge gap length in the direction parallel to the moving direction of a workpiece, with its electric discharge gap adjusting mechanism having two freedom or more in mechanical motion. CONSTITUTION:An electric discharge machine is provided with drive mechanism for moving a tool electrode 5 or a workpiece, or both of them, and this drive mechanism is formed of the combination of long distance motion mechanism with large movable distance and micro distance motion mechanism with smaller movable distance and higher response speed than the long distance motion mechanism. The long distance motion mechanism and micro distance motion mechanism have the freedom of motion in the overlapped state, and the freedom- of-motion of the micro distance motion mechanism is to be two or more. The actuator of the micro distance motion mechanism may be an electrostrictive element or a magnetostrictive element at times.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention applies a voltage between a tool electrode and a workpiece, which are opposed to each other in a liquid with a minute gap therebetween, to generate an electric discharge, thereby removing the material of the workpiece. The present invention relates to an electric discharge machine that removes and processes.

[0002]

2. Description of the Related Art In electrical discharge machining, long-distance motion with a large movable distance to realize a relative positional relationship (machining space area) between a tool electrode and a work piece, and between the tool electrode and the work piece are performed. In order to maintain the discharge gap length d appropriately, both a small distance movement with a movable distance smaller than a long distance movement is required.

These are ultimately achieved by mechanically moving the tool electrode, the work piece, or both. However, conventionally, the drive mechanism of the tool electrode or the work piece or both in the electric discharge machine has a degree of freedom in mechanical movement of the tool electrode and the work piece (movement by three axes of X, Y and Z). They only had the same number of degrees of freedom. Alternatively, even if there are more degrees of freedom than the mechanical movement of the tool electrode and the work piece, among the driving machines that realize these degrees of freedom, the driving machine that realizes the overlapping movement degrees of freedom. In this combination, the precision of control such as response speed of each mechanism is about the same, and the movable distance of each mechanism is too large as compared with the distance required for the minute distance movement required for adjusting the discharge gap length. That is, the conventional electric discharge machine does not distinguish between the mechanism for long-distance motion and the mechanism for minute-distance motion, and both motions are performed by the same mechanism.

Therefore, in particular, the precision and response speed of the minute distance movement for controlling the discharge gap length are not sufficient, and the efficiency of the electric discharge machining is reduced due to abnormal discharge or defective discharge of machining waste, and the machining The precision and finish were not good enough.

Further, in the electric discharge machine, there are a case where the tool electrode is moved and a case where the work piece is moved in order to adjust the electric discharge gap length. However, there is a difference between the mass of the tool electrode and the work piece. While machining is performed on one workpiece at the same time, there are two types of machining: one in which the tool electrode is moved to adjust the discharge gap length and the other in which the workpiece is moved to adjust the discharge gap length. , The control accuracy varies depending on the direction,
There was a problem that there were differences in processing accuracy and surface finish.

On the other hand, as described above, the driving mechanism for the tool electrode, the work piece, or both has more freedom than the mechanical movement of the tool electrode, the work piece, or both, and moreover, the discharge gap. The response speed of the mechanism corresponding to the length adjustment is higher than that of the mechanism corresponding to other degrees of freedom, and the moving distance of this mechanism is set to be as small as the distance required for the minute distance movement. (Japanese Patent Application No. 3-121773)
issue).

However, such a mechanism for adjusting the discharge gap length has one degree of freedom, and even if the mechanism has a high response speed for adjusting the discharge gap length, this high response speed depends on the shape to be processed. Can not use the mechanism with
As a result, the efficiency of electric discharge machining decreased due to abnormal discharge and defective discharge of machining waste, and the machining accuracy and finish were not sufficient.

FIG. 5 is a conventional example thereof. In a die-sinking electric discharge machine 1, a transmission mechanism 4 including a servo motor 2 and a ball screw 3 causes a tool electrode 5 to move for a long distance and a piezoelectric element 6 as an actuator. By the discharge gap adjusting mechanism 7,
The discharge gap length d between the tool electrode 5 and the workpiece 8 is adjusted.
However, in this case, the discharge gap length on the side surface of the tool electrode 5 (the discharge gap length in the direction parallel to the moving direction of the workpiece)
Adjustment of the table 9 for moving the work piece 8
It is difficult to adjust the discharge gap as fast and minute as the discharge gap adjusting mechanism 7 using the piezoelectric element 6 as an actuator.

[0009]

SUMMARY OF THE INVENTION The present invention provides an electric discharge machine capable of adjusting the electric discharge gap length with high response speed and accuracy.
An electric discharge machine that can move the tool electrode side to adjust the length of the discharge gap in a direction parallel to the direction of movement of the workpiece, and the discharge gap adjustment mechanism has two or more degrees of freedom in movement. The challenge is to provide machines.

[0010]

The present invention relates to an electric discharge machine. A drive mechanism for moving the tool electrode, the work piece, or both is provided. The drive mechanism is composed of a combination of a long distance movement mechanism having a large movable distance and a minute distance movement mechanism having a smaller movable distance and a faster response speed. The long-distance motion mechanism and the minute-distance motion mechanism have overlapping degrees of freedom of motion. The small distance movement mechanism has two or more degrees of freedom of movement.

The actuator of the minute distance movement mechanism may be a piezoelectric element. The actuator of the small distance movement mechanism may be a magnetostrictive element. The fine distance movement mechanism may be entirely incorporated in the drive mechanism of the tool electrode.

[0012]

The long-distance movement mechanism realizes a relative positional relationship between the tool electrode and the work piece by a large movable distance. The small distance movement mechanism appropriately maintains the discharge gap length between the tool electrode and the work piece due to the small movable distance. Piezoelectric element,
The magnetostrictive element realizes a high response speed with respect to a small distance movement. The configuration in which the minute distance movement mechanism has two or more degrees of freedom allows adjustment of the discharge gap length in a direction parallel to the movement of the workpiece with high response speed and accuracy. The structure in which the minute distance movement mechanism is incorporated on the tool electrode side allows the discharge gap length to be adjusted with high response speed and accuracy.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a die-sinking electric discharge machine 1 as a first embodiment, and like the conventional example, a transmission mechanism 4 including a servomotor 2 and a ball screw 3, a discharge gap adjusting mechanism 7, a tool electrode. 5 and table 9. The workpiece 8 is placed on the table 9 and is movable on the plane in a controlled XY direction. The transmission mechanism 4, the discharge gap adjusting mechanism 7 and the tool electrode 5 are arranged such that the basic movement axis coincides with the vertical Z axis, and the tool electrode 5 is the discharge gap adjusting mechanism 7
Is fixed to the lower surface of the guide frame 10 and the lower end faces the workpiece 8.

Reference numeral S1 is a position detecting sensor for detecting the position of the tool electrode 5, and reference numeral S2 is a gap length detecting sensor for detecting the discharge gap length d. This gap length detection sensor S
In the case of No. 2, several pieces are installed at necessary places in the X, Y, Z directions. X,
The gap length detection in the Y direction is detection of the discharge gap length in a direction parallel to the moving direction of the workpiece 8. The electric discharge machine 1 includes a numerical control device similar to the conventional one, and operates under the control thereof.

The discharge gap adjusting mechanism 7 (FIG. 2) is provided with a piezoelectric element 6 (x, x, y) corresponding to the guide frame 10 in the X, Y, Z directions.
y, z), the upper surface is attached to the lower portion of the transmission mechanism 4 to be the fixed side, and the lower surface is attached with the tool electrode 5 to be the movable side. The guide frame 10 is provided with an integral parallel leaf spring structure, and is provided with a Z portion having a spring wall 11 vertically displaced from above and an X portion having a spring wall 12 displaced forward and backward and a spring wall displaced laterally. A piezoelectric element 6z (electrostrictive element) as an actuator, which is configured by the Y portion including 13, is provided between the spring walls 11 that are arranged to face each other, similarly, the piezoelectric element 6x is provided between the spring walls 12, and the piezoelectric element 6y. Are arranged between the spring walls 13, and both ends are fixed to the walls. These piezoelectric elements 6 are under the control of the numerical controller.

Therefore, each piezoelectric element 6 (x, y, z)
When a voltage is applied to them and they function as actuators due to the deformation due to the piezo effect, the tool electrode 5 is moved in the X, Y, Z directions and their combined directions. That is, the tool electrode 5 has three degrees of freedom of movement by the discharge interval adjusting mechanism 7. However, the piezoelectric element 6
Due to the characteristics of, its movable distance is very small and it moves at high speed.

As described above, in the electric discharge machine 1, the transmission mechanism 4, the electric discharge gap adjusting mechanism 7 and the table 9 are provided.
Controls the distance of the gap between the tool electrode 5 and the workpiece 8,
A drive mechanism for moving the tool electrode 5, the workpiece 8 or both of them is maintained in order to maintain them.

Of the drive mechanism, the transmission mechanism 4 and the table 9 roughly and at a large movable distance form a relative positional relationship (machining space area) between the tool electrode 5 and the workpiece 8. Since it is realized, it constitutes a long-distance motion mechanism. This mechanism is mechanical in terms of movement, X,
It has three degrees of freedom in the Y and Z directions.

On the other hand, the discharge gap adjusting mechanism 7 described above is used.
Is a minute distance motion mechanism having a movable distance smaller than that of the long distance motion mechanism and a response speed faster than this because the actuator is the piezoelectric element 6. This minute distance movement mechanism has two or more degrees of freedom of movement as described above,
Moreover, it has a degree of freedom overlapping with the long-distance motion mechanism.

In the electric discharge machining, as in the conventional case, the tool electrode 5 and the work piece 8 are opposed to each other in the liquid with a minute gap therebetween, and a voltage is applied between the tool electrode 5 and the work piece 8 to discharge. It is done by generating. First, the relative position of the workpiece 8 and the tool electrode 5 on the vertical plane and the plane is determined by the long-distance movement mechanism, and then the tool electrode 5 according to the progress of the machining is referred to while referring to the signal from the position detection sensor S1. And the workpiece 8 are fed.

During this time, the signal of the gap length detecting sensor S2 is monitored, and when a signal deviating from the set appropriate discharge gap length d is detected, the numerical control device sends the signal to the discharge gap length d. Judge the position of the sensor S2,
Pulse distribution is applied to the long-distance motion mechanism, and
The piezoelectric element 6 (x,
These are driven by applying an operating voltage to one or more of y, z).

Then, since the response speed of the piezoelectric element 6 is higher, the piezoelectric element 6 to which the voltage is applied first functions as an actuator, and the discharge gap at which the deviation signal is output is set as an appropriate discharge gap d. , Eliminate the abnormality. As a result, the concentrated discharge, the short circuit or the discharge stop is prevented in advance, and the high speed movement of the tool electrode 5 causes the machining waste generated in the discharge gap to be washed away to remove the machining waste in the discharge gap.

During this time, the servo motor 2 of the transmission mechanism 4 and the servo motor for sending the table 9 are driven to correct the discharge gap between the tool electrode 5 and the workpiece 8 and restore the proper discharge gap length d. The piezoelectric element 6 is deformed in the plus direction and the minus direction by an amount corresponding to the applied voltage centering on the deformed position by the bias voltage, and the operating voltage is applied in a pulsed manner. The pulse length is determined according to the response speed of the long-distance moving mechanism, and the driving of the minute-distance moving mechanism and the long-distance moving mechanism is completed at the same time. In this way, the adjustment of the discharge gap length d is performed with high response speed and high accuracy.

Further, in the first embodiment, since all the minute distance moving mechanisms as the discharge gap adjusting mechanism 7 are incorporated in the drive mechanism of the tool electrode 5, the mass driven by the minute distance moving mechanism is small. Therefore, the accuracy is further improved as compared with the case where the workpiece 8 side having a larger mass than the tool electrode 5 side is usually driven by the minute distance movement mechanism. Moreover, this accuracy does not vary depending on the direction (X, Y, Z, or a composite direction thereof) of adjusting the discharge gap length.

FIG. 3 shows a discharge gap adjusting mechanism 7 according to the second embodiment. Compared to the discharge gap adjusting mechanism 7 according to the first embodiment described above, a guide frame 10 having a parallel spring structure is provided with three parts at the Z portion.
The piezoelectric elements 6z (1,2,3) are arranged in a triangle, and
The difference is that two piezoelectric elements 6x (1,2) are arranged in the X section.

According to this embodiment, the discharge gap adjusting mechanism 7
Of the piezoelectric element 6z (1,2,3) causes the tool electrode 5 to rotate in the roll and the pitch direction, and the piezoelectric element 6x (1,2) has a different displacement amount. It can be given to rotate in the yaw direction. As a result, the position of the tool electrode 5 as well as the attitude of this electrode can be controlled in detail, and in the electrical discharge machining of the workpiece 8 of all shapes, the electrical discharge machining between the tool electrode 5 and the workpiece 8 is performed. The gap length d can be maintained at an appropriate value.

FIG. 7 shows a discharge gap adjusting mechanism 7 in the third embodiment, which uses a magnetostrictive element 14 (x, y, z) as an actuator as compared with the first and second embodiments. Reference numeral 15 (x, y, z) is a coil for driving these. There is no particular difference in function from the case of the first embodiment.

The above is an embodiment, and the present invention is not limited to the illustrated specific configuration. The piezoelectric element 6 may be another electric strain element, and various arrangements in the guide frame 10 are possible. It is not necessary to integrate all the mechanisms for ensuring two or more degrees of freedom, unlike the discharge gap adjusting mechanism 7 of the embodiment. A single degree of freedom may be obtained by combining the deformations of a plurality of piezoelectric elements. The discharge gap adjusting mechanism 7 is
It may be used only for a cleaning operation in which the high response speed is used to promote the flow of the working fluid between the discharge gaps and to discharge the working chips in the gaps.

[0029]

EFFECTS OF THE INVENTION Regardless of the machining shape, removal of machining scraps and maintenance of stable discharge by mechanical control of the discharge gap length d in electrical discharge machining are improved, electrical discharge machining is made more stable, and high machining efficiency and good machining are achieved. It is possible to obtain various finishing characteristics.

Of the movements of the tool electrode and the workpiece during electric discharge machining, the discharge gap adjusting operation, which requires a particularly fine and high-speed operation, is mainly responsible for the mechanism for performing this minute movement (minute distance movement mechanism). By doing so, compared with the case where the discharge gap control operation is also performed by the mechanism that performs long-distance movement (long-distance movement mechanism), the discharge gap is adjusted at high speed and accurately.

By incorporating a fine and high-speed moving mechanism into the driving mechanism of the tool electrode, which generally has a smaller mass than the work piece, the discharge gap in the direction parallel to the movement direction of the work piece is adjusted. The movement is also carried out by the drive mechanism towards the tool electrode with the smaller mass. As a result, the discharge gap can be adjusted faster and more accurately than in the case where a mechanism for performing a minute movement is incorporated in a drive mechanism for a workpiece having a large mass.

In addition, when the discharge gap length is adjusted only by a mechanism that performs long-distance movement, the tool electrode is moved to adjust the discharge gap length and the workpiece to move the discharge gap length. In the direction of adjustment, there is a difference in the control accuracy of the discharge gap length, which causes a difference in processing accuracy and surface finish.
This is solved by performing the discharge gap control movement in both directions by a minute distance movement mechanism that drives the tool electrode.

If a mechanism for performing high-speed fine movement in a plurality of directions, for example, 3 directions, is incorporated, effective discharge is achieved by the high-speed minute movement in these 3 directions and the combined movement thereof in adjusting the discharge gap in any direction. The gap is adjusted.
Furthermore, by incorporating a mechanism that performs fine movement at high speed in 6 degrees of freedom, it becomes possible to finely adjust all the relative positions and orientations of the tool electrode and the work piece at high speed.
Optimal motion can be realized by adjusting the discharge gap.

[Brief description of drawings]

FIG. 1 is a front view schematically showing a mechanism (first embodiment).

FIG. 2 is a front view of a main part (first embodiment).

FIG. 3 is a front view of a main part (second embodiment).

FIG. 4 is a front view of a main part (third embodiment).

FIG. 5 is a front view schematically showing the mechanism (conventional example).

[Explanation of symbols]

1 Electric Discharge Machine 2 Servo Motor 3 Ball Screw 4 Transmission Mechanism 5 Tool Electrode 6 Piezoelectric Element 7 Discharge Gap Adjustment Mechanism 8 Workpiece 9 Table 10 Guide Frame

Claims (4)

[Claims] 1. An electric discharge for removing a material of a workpiece to perform machining by applying a voltage between a tool electrode and a workpiece which are opposed to each other with a minute gap in a liquid to generate an electric discharge. It is a processing machine and has a drive mechanism for moving the tool electrode and / or the workpiece in order to control and maintain the distance between the tool electrode and the workpiece, and this drive mechanism has a large movable distance. A combination of a long-distance motion mechanism and a degree of freedom of motion that overlaps with it, and a combination of a minute distance motion mechanism having a smaller movable distance and a faster response speed than this An electric discharge machine characterized by having two or more. 2. The electric discharge machine according to claim 1, wherein the minute distance movement mechanism uses a piezoelectric element as an actuator. 3. The electric discharge machine according to claim 1, wherein the minute distance movement mechanism uses a magnetostrictive element as an actuator. 4. The small distance movement mechanism is entirely incorporated in the tool electrode driving mechanism.
The electric discharge machine according to claim 3.