JPH06126542A - Method and apparatus for electric discharge machining - Google Patents

Abstract

PURPOSE:To provide automatically a swing pattern similar to an electrode shape and enable high accuracy electric discharge machining even if the electrode has a complicated shape by monitoring average interpole voltage between the electrode and a workpiece to correct successively the swing pattern for providing the fixed average interpole voltage. CONSTITUTION:After the start of a process, first a swing commanding table preparing section 11 searches a program of the swing from NC working programs to divide the turning-round passage of the searched swing pattern into (n) sections and prepare the (n) sections of swing commanding tables. Next, a servo speed generating section 13 and swing speed generating section 14 obtain the output pulses to be sent motors 6x, 6y and 6z and send the pulses to a pulse composing section 15. An interpole voltage detecting section 3 detects interpole voltage to obtain average interpole voltage in the swing commanding table unit. The swing commanding table is corrected by the use of a correction amount to calculate the shift vector of a new swing pattern and the obtained swing commanding table is transmitted to a memory 12A of a control section 12 and written therein.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric discharge machining method and apparatus, and more particularly to an electric discharge machining method and apparatus for automatically correcting an optimum swing locus corresponding to an electrode shape.

[0002]

2. Description of the Related Art During die-sinking electrical discharge machining, a machining electrode is oscillated with respect to a workpiece to be machined so that a concave portion having a predetermined shape is formed by electric discharge or the inner surface of a hole is subjected to electrical discharge machining in a predetermined shape. In so-called rocking type electric discharge machining, by using an electrode having a desired machining shape, machining having a shape similar to the electrode shape can be performed. The details of such a swing type electric discharge machining method are disclosed in Japanese Patent Publication No. 55-16773.
As the orbital path (rocking pattern) of rocking motion,
A simple pattern such as a square pattern or a circular pattern is used.

Further, a method of previously storing the electrode shape as numerical data corresponding to the processed shape and determining the swing pattern (trajectory) on the basis of the stored numerical data becomes the applicant of the present application. No. 3-79233.

[0004]

As described above, in the conventional swing type electric discharge machining, the electrode shape corresponding to the machined shape is expressed in advance as numerical data, and the swing pattern is determined based on this numerical data. , So as to obtain a processed shape similar to the electrode shape. However, in such an electric discharge machining method, since the swing pattern has to be determined by calculation based on the electrode shape data, the user has to register the electrode shape data for each electrode shape. However, the registration of the shape data requires complicated work.

Therefore, it is an object of the present invention to provide an electric discharge machining method and apparatus capable of automatically generating an optimum swing pattern even with a complicated electrode shape and obtaining a highly accurate machined shape. It is in.

[0006]

In order to solve the above-mentioned problems, an electric discharge machining method according to the present invention is an electric discharge machining method in which an electrode is oscillated with respect to a work along a predetermined oscillating pattern. , The circular path of the swing pattern is divided into a plurality of regions defined by a command table for commanding the movement of the electrodes, and the inter-electrode voltage between the electrode and the work is detected for each of the divided regions to oscillate. The command data in the command table is modified so that the average inter-electrode voltage in the plurality of regions becomes substantially equal for each revolution, and the fluctuation pattern is sequentially modified to be similar to the electrodes. To process.

Further, the electric discharge machining apparatus according to the present invention is an electric discharge machining apparatus which performs electric discharge machining while oscillating an electrode with respect to a work along a predetermined oscillating pattern. First means for dividing into regions and creating a swing command table for commanding the movement of the electrode for each divided region; and second means for storing the swing command table.
Means, a third means for detecting an inter-electrode voltage between the electrode and the work, a fourth means for obtaining a voltage difference between the inter-electrode voltage and a predetermined reference voltage value, and the voltage difference. Then, the electrode is swung in accordance with a fifth means for correcting the swing command table and storing it in the second means, and a swing pattern determined by the swing command table output from the second means. And a sixth means for operating.

[0008]

According to the present invention, when the swing pattern of the electrode is determined, the gap obtained from the voltage between the electrode and the work is monitored, and the swing pattern is successively corrected so that the gap becomes constant. Thus, even if the electrode shape is complicated, a swing pattern similar to the electrode shape is automatically obtained from a simple initial swing pattern of a square or a circle.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a configuration diagram showing a basic device for realizing the electric discharge machining method according to the present invention. Electrode 1
A voltage is applied from a machining power source 8 between the workpiece 2 and the workpiece 2 for electric discharge machining, and the gap voltage between the electrode 1 and the workpiece 2 is detected and detected by the gap voltage detection unit 3. Information on the gap between the poles corresponding to the voltage between the poles is obtained. The oscillating pattern creating unit 4 creates an oscillating pattern that makes the average inter-electrode voltage constant over the oscillating circuit of the electrode based on the gap information from the inter-electrode voltage detecting unit 3 by a method described later. The drive unit 5 drives the feed shaft drive motor 6 to move the electrodes according to the swing pattern created by the swing pattern creation unit 4.

According to the present invention, the successive swing pattern is corrected so that all the mean inter-electrode voltages in the swing circuit are constant based on the gap information obtained from the voltage between the electrodes and the workpiece during the swing circuit. Then, even with a complicated electrode shape, a swing pattern similar to the electrode shape is finally created to perform high-precision processing. Thus, for example, in FIG.
When a pentagonal electrode as shown in (A) is used, even if the first swing pattern is a square pattern as shown in (B), a pattern in which the gap LG is constant as described above. If it is created while sequentially correcting (see (C) in the same figure), the swing pattern gradually approaches the electrode shape, and finally, a pentagonal swing pattern (D) similar to the electrode shape (A). Is obtained.

Next, a description will be given of the process of sequentially correcting and creating the swing pattern so that the gap becomes constant. At the start of processing, for example, a square oscillation pattern is used, hexagons as shown in FIG. 3 are used as electrodes, and the oscillation radius (half the oscillation width of the square oscillation) is 100 μm. Each swing command table (when the swing pattern path is divided into n) is represented by R1, R2, R3 in FIG.
Corresponding to each area of ..., each swing table # 1, # 2, #
3, ..., # 6, ..., #n are represented as shown in FIG. 4 in the case of the incremental display. That is, in the swing command tables # 1 to # 3, the incremental in the x-axis direction is zero, the incremental in the y-axis direction is designated by 20 μm, and the feed speed is designated by 50 mm / min.

When the swing command table # 3 is completed,
The voltage difference V obtained by subtracting a predetermined reference value from the average inter-electrode voltage (corresponding to the gap interval) obtained in the process of the table # 3 is detected. This voltage difference V indicates how much the current electrode position deviates from the reference gap corresponding to the reference value. In order to keep the gap constant, the increment vector ( Vector in the direction connecting the centers) is corrected. An example of the relationship between the voltage difference and the correction amount is shown in FIG.

If the voltage difference obtained by the processing of the swing command table # 3 is -6V, the correction amount is -2 from FIG.
μm is obtained. Therefore, V in FIG. 5 may be obtained as the corrected movement vector. That is, the swing command table # 3 corresponds to the vector V1, and in this case, −
2 μm correction amount (2 μm long vector V toward the center
2) is required, and the combined vector V, which is a combination of the vectors V1 and V2, becomes the corrected command of the swing command table # 3. In FIG. 5, the starting point coordinates of the vector V1 are (0,
0) is 100 μm away from the center in the x direction and the end point coordinates are (0, 20), so the angle θ 2 = tan-1 100/20 = 7
8.6 degrees is obtained, and in the end, the incremental x-direction and the incremental y-direction of the movement vector V are -1.9 μm and 19.6 μm, respectively, so the corrected swing command table is as shown in FIG. . After that, the processing of other swing command tables is sequentially continued.

The change in the swing pattern before and after the correction is shown in FIG. After the above correction is applied to the swing pattern in which only the y direction is incremented as shown in (A), the table # is displayed as shown in (B).
At 3, it shifts to the left and gradually approaches the shape of the electrode. That is, as shown in FIG. 9 showing the change of the swing pattern shape, the initial pattern at the start of swing is a square as shown in (A). (FIG. 7B), and finally, a hexagonal swing pattern similar to the electrode shape is created as shown in FIG.

FIG. 10 shows a concrete example of the configuration of an apparatus for realizing the electric discharge machining method according to the present invention. The movement command creating unit 11 receives the machining program data, creates an electrode swing command table, and supplies the table to the control unit 12. The control unit 12 stores the supplied swing command table in the memory 12A and stores the swing command table corrected as described above in the memory 12A. The servo speed generator 13 and the swing speed generator 14 respectively generate a pulse designating a servo speed and a swing speed obtained by a known method based on the swing command table read from the memory 12A. The pulse synthesizing unit 15 synthesizes the pulses from the servo velocity generating unit 13 and the swing velocity generating unit 14 to generate x, y and z.
Corresponding pulses are output to the axial feed motors 6x, 6y and 6z. The feed screws 7x, 7y and 7z are driven by these motors 6x, 6y and 6z to control the movement of the electrode 1.

A voltage for electric discharge machining is applied from the machining power source 8 to the electrode 1 and the work 2, and the machining gap voltage between the electrode 1 and the work 2 is detected by the machining gap voltage detector 3. Here, the detected inter-electrode voltage is sent to the control unit 12, and the above-described swing command table correction process for making the gap constant is performed.

FIG. 11 is a flow chart showing the procedure of correcting the swing command table in the swing command table creating section 11 and the control section 12 in FIG. After the processing is started, the swing command table creating unit 11 first searches the NC machining program for a swing-related program, divides the orbit path of the searched swing pattern (trajectory) into n, and swings n swing command tables. After creating (step S1), processing is started (step S2). Next, the swing command table is transferred to and stored in the memory 12A of the control unit 12 (step S3). Based on these swing command table data (swing movement distance, speed, etc.), the servo speed generating section 13 and the swing speed generating section 14 operate on the motors 6x, 6y and 6 respectively.
An output pulse to be sent to z is obtained and sent to the pulse synthesizing unit 15 (step S4). The inter-electrode voltage detector 3 detects the inter-electrode voltage (step S5), and obtains the average inter-electrode voltage in units of the swing command table (step S6). After that, it is determined whether or not the processing of the swing command table is completed (step S7). If not completed, the processing returns to step S4, and if completed, the reference voltage is obtained in step S6. Subtract the average inter-electrode voltage (step S
8) Then, the correction amount is read from the obtained voltage difference using a table as shown in FIG. 6 (step S9). Then, the swing command table is corrected using the correction amount, and the movement vector of the new swing pattern (trajectory) is calculated (step S1).
0), the obtained swing command table is transferred to the memory 12A of the control unit 12 and written (step S11). Subsequently, it is determined whether or not all the processing is completed (step S12). If not completed, the processing returns to step S3, and if completed, the processing is terminated.

In the above-described embodiment, the electrode movement may not reach the target position or may exceed the target position due to the modification of the swing command table using the correction amount. This can be solved by performing a correction when performing the subsequent table correction processing.

[0019]

As described above, the electrical discharge machining method and apparatus according to the present invention monitors the average inter-electrode voltage between the electrode and the work when determining the swing pattern of the electrode, Since the swing pattern is corrected so that the value becomes constant, it is not necessary to calculate the swing pattern based on the electrode shape data in advance even if the electrode shape is complicated, and the electrode is automatically An oscillating pattern similar to the shape can be obtained, which enables extremely high usability and high-precision electrical discharge machining.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of a basic configuration for realizing an electric discharge machining method according to the present invention.

FIG. 2 is a diagram showing how the swing pattern is updated in sequence according to the present invention.

FIG. 3 is a diagram showing sections of each swing command table obtained by dividing a swing locus corresponding to a hexagonal electrode shape into n in the embodiment of the present invention.

FIG. 4 is a diagram showing an example of a swing command table in FIG.

FIG. 5 is a diagram for explaining an example of updating the swing command table for making the gap constant in the embodiment of the present invention.

FIG. 6 is a diagram showing a relationship between a voltage difference between electrodes and a correction amount in the embodiment of the present invention.

FIG. 7 is a diagram showing an example of an updated swing command table in the embodiment of the present invention.

FIG. 8 is a diagram showing changes in the movement locus of the electrode based on the swing command table by updating in FIG.

FIG. 9 is a diagram showing changes in a swing pattern in the example of the present invention.

FIG. 10 is a specific configuration diagram for realizing the electric discharge machining method according to the present invention.

11 is a flowchart mainly showing an operation processing procedure in a control unit of FIG.

[Explanation of symbols]

 1 Electrode 2 Work 3 Inter-electrode voltage detection unit 4 Pattern creation unit 5 Motor drive unit 6, 6X, 6Y, 6Z Motor 7, 7X, 7Y, 7Z Feed screw 8 Machining power supply 11 Swing command table creation unit 12 Control unit 12A memory 13 Servo speed generator 14 Oscillation speed generator 15 Pulse combiner

Claims (2)

[Claims] 1. An electric discharge machining method in which an electrode is oscillated relative to a workpiece while oscillating along a predetermined oscillating pattern, wherein a circular path of the oscillating pattern is a command table for instructing movement of the electrode. Divide into multiple defined areas,
The inter-electrode voltage between the electrode and the work is detected for each divided region, and the command data in the command table is corrected so that the average inter-electrode voltage in the plurality of regions becomes substantially equal for each swing revolution. A spark erosion machining method, characterized in that oscillating machining is performed while sequentially modifying the oscillating pattern so as to be similar to the electrode. 2. An electric discharge machining apparatus for performing electric discharge machining on a workpiece while swinging an electrode along a predetermined swing pattern, wherein a circular path of the swing pattern is divided into a plurality of regions,
First means for creating a swing command table for commanding the movement of the electrode for each divided area, second means for storing the swing command table, and detection of the inter-electrode voltage between the electrode and the work. And a fourth means for obtaining a voltage difference between the inter-electrode voltage and a predetermined reference voltage value, and the swing command table is corrected in accordance with the voltage difference, and the second means is provided. Means for storing in the means, and sixth means for swinging the electrode according to a swing pattern determined by the swing command table output from the second means. And electrical discharge machine.