JP2549045B2 - Wire electric discharge machining method and device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire electric discharge machining method and apparatus, and more particularly to a wire electric discharge machining method and apparatus with improved machining accuracy when finishing machining an out-corner portion.

[0002]

2. Description of the Related Art A wire electric discharge machining apparatus for electric discharge machining a workpiece by supplying a pulse voltage between both electrodes via a machining liquid between a wire electrode and a workpiece (workpiece) electrode to generate an electric discharge is complicated. Since it can perform electrical discharge machining of various shapes, it is used in a wide range of machining fields such as mold manufacturing. Such electric discharge machining utilizes electric discharge between the wire electrode and the work, and the movement trajectory of the wire electrode for machining the work is offset in consideration of the diameter dimension of the wire electrode.
Therefore, for example, as the offset locus indicating the wire transfer locus when processing the out-corner portion of the work, as shown in FIG. 6A, a locus offset by D corresponding to the radius of the wire electrode is set. To be done. The discharge between the wire electrode and the work occurs in the direction perpendicular to the work and the center of the wire electrode, and machining is also performed at the contact point with the perpendicular, but due to the offset D, the corner a of the work is compared with other parts. As a result, discharge is performed for a long time, the corner portion is over-processed, and the processing accuracy deteriorates. For example, FIG.
In (A), the machining of the corner a is only required to be performed in the portion b of the offset locus, but the wire electrode moves along the offset locus from b to c, and the discharge pulse is supplied during that time. Therefore, the discharge continues. As a result, as shown in FIG. 6B, sagging occurs at the corners, the edge shape deteriorates, and the processing accuracy deteriorates.

By the way, Japanese Patent Publication No. 2-11371 discloses an electric discharge machining method for improving the deterioration of machining accuracy due to the offset locus of the wire electrode. The publication discloses a method of performing highly accurate machining of a curved portion such as an arc on both the in-corner and the out-corner, and it is determined whether the machining is the in-corner or the out-corner, and the wire electrode and The relative movement speed of the work is reduced during in-corner machining and increased during out-corner machining to improve the machining accuracy of the corners.

[0004]

As described above, in the conventional wire electric discharge machining method, machining accuracy is deteriorated because a long-time electric discharge is generated only in a part of the work due to the offset trajectory of the wire electrode. There is a problem. On the other hand, the technique disclosed in Japanese Patent Publication No. 2-11371 is applied to the processing of the out-corner portion, and the moving speed of the wire electrode at the corner portion is increased with respect to the moving speed of the wire electrode before reaching the corner portion. A method of shortening the discharge time can be considered. However, it is impossible to reduce the discharge time to zero, and although the sag is slightly improved, it is not in a satisfactory state.

Therefore, an object of the present invention is to provide a wire electric discharge machining method and apparatus in which the electric discharge machining accuracy at the out corner of the work corner is remarkably improved.

[0006]

In order to solve the above-mentioned problems, in the wire electric discharge machining method according to the present invention, a discharge pulse is supplied between a wire electrode and a work so that a straight line or a curved line in the machining shape of the work intersects. In a wire electric discharge machining method for electric discharge machining of an out-corner of an intersection point formed by the following method, an offset trajectory separated by a predetermined distance from a work shape to be machined, which represents a moving path of the wire electrode, and two methods set up at the intersection point. The positions of the first intersection and the second intersection with the line vector are obtained, and the supply of the discharge pulse is interrupted when the wire electrode is located on the offset locus sandwiched between the vicinity of the first intersection and the vicinity of the second intersection. The supply of the discharge pulse is restarted when the wire electrode passes near the second intersection.

Further, the wire electric discharge machine according to the present invention supplies an electric discharge pulse between the wire electrode and the work, and discharges an out corner of an intersection formed by intersecting a straight line or a curve in the machining shape of the work. In the wire electric discharge machine, the first of the offset locus, which represents the moving path of the wire electrode, and which is separated from the work shape to be machined by a predetermined distance, and the two normal vectors standing at the intersection point.
Intersection position calculating means for obtaining the positions of the intersection and the second intersection,
When the wire electrode is located on the offset locus sandwiched between the vicinity of the first intersection and the vicinity of the second intersection obtained by the intersection position calculation means, the supply of the discharge pulse is interrupted, and the wire electrode causes the second intersection point. Discharge pulse control means for restarting the supply of the discharge pulse after passing through the vicinity.

[0008]

According to the present invention, when electric discharge machining is performed at an out-corner portion, which is an intersection of two straight lines or curves of a work shape to be machined, a wire is placed in an offset locus region sandwiched by two normal vectors from the intersection. By interrupting the supply of the discharge pulse during the time when the electrode is positioned, it is possible to suppress the occurrence of sagging at the corner and improve the machining accuracy. Then, when the wire electrode passes through the offset locus region, the supply of the discharge pulse is restarted.

[0009]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 is a flowchart showing a processing procedure of an embodiment of a wire electric discharge machining method and apparatus according to the present invention. FIG. 2 is a block diagram showing the configuration of a wire electric discharge machining method and device according to the present invention.

In FIG. 2, a work 1 is a wire electrode 2
Is arranged so as to be movable in the X and Y directions, and a discharge pulse having a predetermined frequency is applied from the machining power supply unit 3 between the power supplies 2A and 2B of the wire electrode 2 and the work 1. The voltage between contacts from the detection control unit 4 is supplied to the CPU 56 via the I / O control unit 52 of the NC unit 5. Data such as an NC program is stored in the data storage unit 51 of the NC unit 5, and the operation control unit 55 has, for example, a keyboard, and various commands are sent to each unit. The program storage unit 57 stores a system program indicating the processing procedure of the CPU 56. The communication control unit 58 communicates with the outside. The motor control unit 53 based on a command from the CPU 56
Is driven and X, through the operation of the motor drive unit 54,
The movement of the work 1 is controlled by driving the Y-axis motor 6. Further, the CPU 56 reads the NC program stored in the data storage unit 51, analyzes the NC program to create an offset program, and outputs the offset program. Of the offset loci shown in FIG. 6A, the block process of the locus from b to c is an additional block process set specially, and the discharge pulse transmission is interrupted to stop the discharge.

Referring to FIG. 3, when performing electrical discharge machining of a workpiece including a horizontal first surface and a vertical second surface sandwiching a right-angled corner portion a, the offset locus is:
In addition to the normal processing blocks N1 and N2, additional blocks T1 and T2 for stopping the supply of the discharge pulse to the wire electrode are included. The additional blocks T1 and T2 have a corner a
To the first surface and the second surface, the two normal vectors (ab) and (ac) intersect at the horizontal and vertical offset loci at intersection points b and c, that is, the interval between normal vectors. Is defined by the additional block T between b and d in FIG.
1, a block between d and c is defined as an additional block T2. The b is the first intersection and the c is the second intersection, and the intersection position calculating means for calculating the positions of these two intersections is included in the CPU 56. The additional block does not necessarily have to pass the point d, and can take an arbitrary path from the point b to the point c. The path may be a straight line or a curved line, and if it is a straight line, high speed machining is possible.

The interval in which the discharge pulse is interrupted is NC
It is created as an additional block program when creating the offset block. For example, when an NC program as shown in FIG. 4A is read, the CPU 56 creates an offset program as shown in FIG. When creating this offset program, the flag P0 is added to the program of the additional block, and the processing of the additional block when executing the offset program is performed.

The operation processing procedure of this embodiment will be described with reference to FIG. 1. First, an NC program is read from the data storage unit 51 (step S1), and an offset program is created based on the read NC program (step S1). S2). When there is an additional block when creating this offset program, the flag "P0"
Is added. Next, the created offset program is executed to determine whether the processing block is a normal block (step S3). Here, if it is determined that the block is a normal block, a discharge pulse is generated (ON) in order to perform a normal discharge machining process (step S4), and then the step S
Return to processing of 1. On the other hand, in step S3, when the flag "P0" is detected and it is determined that the block is not the normal block but the additional block, the discharge pulse is stopped from being sent to the wire electrode in order to interrupt the discharge operation (step S3). S5), and the process returns to step S1 again. The CPU 56 includes a discharge pulse control unit that turns on and off the discharge pulse in steps S4 and S5. Due to the above processing, deterioration of the machining accuracy of the straight out corner portion,
The occurrence of sagging is prevented. Then, after the wire electrode has passed through the additional block portion, the supply of the discharge pulse is restarted to allow the subsequent processing to proceed.

In the above embodiment, the additional blocks are
As shown in FIG. 3, two normal vectors (ab), (a
Although it is defined by the point b and the point d sandwiched in c), it can be started slightly before the point b or can be extended slightly behind the point d.

In the embodiment described above, the work shape to be machined is given by the NC program, and the offset locus offset by the predetermined distance is obtained by the CPU 56.
The additional blocks T1 and T2 are defined by obtaining the first intersection point b and the second intersection point c between the two normal vectors at the intersection point a and the offset locus. On the other hand, the NC program may specify the center path of the wire electrode, that is, the offset locus, instead of specifying the work shape to be machined. At this time, the program finds the positions of the intersection points b and c in advance, and when the NC program is created,
A command to interrupt the discharge pulse may be issued between c.

Further, FIG. 5 shows a case where the machining shape to be machined is an out-corner of an intersection a of a straight line and a curved line. In this case as well, the intersection point b of the two normals (ab) and (ac) set up from the intersection point a and the offset locus,
When the wire electrode is located in the area sandwiched by c, the supply of the discharge pulse is stopped. Although not shown, the same method and apparatus may be used to process the out-corner of the intersection formed by intersecting the curves.

[0017]

As described above, the wire electrical discharge machining method and apparatus according to the present invention, when performing electrical discharge machining at the out-corner portion of the corner of the workpiece, the offset locus defined by the normal vector from the intersection point. Since the supply of the discharge pulse is interrupted in the area, the corner portion is not processed excessively, the occurrence of sagging in the corner portion can be suppressed, and the processing accuracy is significantly improved. Then, as in the prior art, in the method of increasing the moving speed of the wire electrode in the offset locus region while supplying the discharge pulse, it is impossible to make the moving time zero,
While the sag still remains, in the present invention, the electric discharge phenomenon is completely eliminated in the offset locus region, so the sagging problem is solved.

[Brief description of drawings]

FIG. 1 is a flowchart showing an operation processing procedure of an embodiment of a wire electric discharge machining method and apparatus according to the present invention.

FIG. 2 is a block diagram showing the configuration of a wire electric discharge machining method and apparatus according to the present invention.

FIG. 3 is a diagram for explaining processing blocks in the embodiment of the present invention.

FIG. 4 is a diagram showing an NC program and an offset program including an additional block created based on the NC program according to an embodiment of the present invention.

FIG. 5 is a diagram for explaining processing blocks in another embodiment of the present invention.

FIG. 6 is a diagram for explaining an electric discharge machining process of a conventional wire electric discharge machining method and apparatus.

[Explanation of symbols]

1 Work 2 Wire Electrodes 2A, 2B Power Supply 3 Machining Power Supply 4 Detection Control 5 NC NC 6 X / Y-axis Motor

Claims (2)

(57) [Claims] 1. A workpiece is rough-machined by supplying a discharge pulse between the wire electrode and the workpiece and including an out-corner of an intersection formed by intersecting straight lines or curves in the machining shape of the workpiece. In a wire electric discharge machining method for performing precision machining by finishing machining after machining, an offset trajectory separated by a predetermined distance from a workpiece shape to be machined, which represents a moving path of the wire electrode, and two methods set at the intersections. The positions of the first intersection and the second intersection with the line vector are obtained, the wire electrode moves on the offset locus, and the wire electrode is placed on the offset locus sandwiched between the vicinity of the first intersection and the vicinity of the second intersection. Is positioned, the supply of the discharge pulse is interrupted, and the wire electrode moves to the second electrode.
A wire electric discharge machining method characterized in that supply of an electric discharge pulse is restarted when the vicinity of the intersection is reached. 2. A workpiece is rough-machined by supplying an electric discharge pulse between the wire electrode and the workpiece, and including an out-corner of an intersection formed by intersecting straight lines or curves in the machining shape of the workpiece. In a wire electric discharge machining apparatus for performing precision machining by finishing machining after machining, an offset trajectory separated from a work shape to be machined that represents a moving path of the wire electrode by a predetermined distance and two methods set at the intersections. Intersection position calculating means for obtaining the positions of the first intersection and the second intersection with the line vector, and the wire electrode moves along the offset locus, and the vicinity of the first intersection and the second intersection obtained by the intersection position calculating means When the wire electrode is located on the offset locus sandwiched by the vicinity, the supply of the discharge pulse is interrupted, and when the wire electrode reaches the vicinity of the second intersection, the discharge is released. Wire electrical discharge machining apparatus characterized by comprising a discharge pulse control means for restarting the supply of the pulses, the.