JPH11221719A - Wire cut electric discharge machining method and its device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the accuracy in work shape in consideration of a complex wire electrode by moving the electrode along the first and second auxiliary paths expanding outward from the neighborhood of an intersection with a perpendicular drawn from a vertex and the correction offset path of a third auxiliary path, in the working of an acute angled out-corner. SOLUTION: The intersections of the perpendiculars drawn from a vertex CP of a corner to an offset path PO, and the offset path PO are respectively the change points O3 and O6 . Then a first auxiliary path of a specific length is determined in such manner that it is inclined at about 10 deg. on the change point O3 as a starting point in the direction of the vertex O1 of the offset path PO to be separated outward from the offset path PO. Similarly a second auxiliary path inclined at about 10 deg. on the change point O6 is determined. Further a line segment connecting the end points O4 , O5 of the first and second auxiliary paths is determined as a third auxiliary path. The discharge machining of a work is performed while relatively moving the wire electrode and the work along the correction offset path.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire cut electric discharge machining method and a wire cut electric discharge machine for performing electric discharge machining of a machining shape including an acute out corner in a predetermined NC program trajectory.

[0002]

2. Description of the Related Art Generally, in a wire electric discharge machine, a wire electrode is supported by a pair of wire guides with a predetermined clearance, and is stretched in a state where a predetermined tension is applied to a workpiece in a substantially vertical direction. While being bridged, it runs in one direction and is updated. The wire electrode is disposed facing the workpiece with a predetermined gap, and the wire electrode is applied along a predetermined path to the workpiece while intermittently applying a voltage for processing to the gap. The workpiece is processed into a desired shape by relative movement.

Normally, a pulse-shaped machining current having a predetermined current value is supplied to a discharge gap formed between both electrodes, with the wire electrode being a negative electrode and the workpiece being a positive electrode.
At this time, electrical machining conditions that affect the electric discharge machining energy such as the ON time and OFF time of the voltage pulse applied to the gap between the wire electrode and the workpiece, the average machining current value, and the servo reference voltage value are required. Initial settings are made according to the processing surface roughness, processing shape accuracy, processing time, and the like. Further, depending on the type of the wire cut electric discharge machine, a plurality of electric discharge machines having different electric characteristics are properly used.

When a workpiece is subjected to electrical discharge machining from a state where no electrical discharge machining has been performed, at least the diameter of the wire electrode and the distance of the discharge gap along the relative movement path of the wire electrode on the workpiece. The portion of the workpiece facing the wire electrode including is a portion that is entirely removed by electric discharge. In machining with such a large amount of machining removal, the discharge energy is increased to increase the machining removal amount per discharge,
It is desirable to shorten the processing time. Therefore, a relatively high peak current value or a pulsed processing current having a long time width is intermittently supplied so that a larger average processing current value can be obtained.

[0005] By the way, when machining with relatively large discharge energy, detailed explanation is omitted, but it is known that the machining surface roughness and machining accuracy of the machined product are not so good as expected for various reasons. Have been. For this reason, in many cases, a previously cut workpiece is used as a workpiece, and the workpiece is again subjected to electrical discharge machining with a relatively small discharge energy so as to smooth the processed surface. Hereinafter, this type of processing is referred to as end face finishing, and the first processing described above will be described as a rough processing.

[0006] End face finishing is often divided into a plurality of machining steps according to the required machining surface roughness and machining shape accuracy, and the same machining step is performed several times while gradually reducing the discharge energy. Repeated. Therefore, in the wire cut electric discharge machining, the rough machining process is called a first cut, and the end face finishing machining process is further called a second cut and a third cut in the machining order. Therefore, the electrical processing conditions are not always set to the same value throughout the entire processing, but are initialized stepwise according to the required processing surface roughness, processing shape accuracy, processing time, and the like.

Usually, when cutting or contouring a workpiece by relatively moving a tool along a predetermined path,
The tool is relatively moved along an offset path shifted out of the NC program trajectory in consideration of the tool diameter, instead of the NC program (machining program) trajectory representing the desired machining shape. In particular, in wire-cut electric discharge machining, as described above, since there is a discharge gap estimated between the wire electrode and the workpiece by generally electric machining conditions,
The wire electrode is relatively moved on the offset path corrected by a predetermined correction amount (offset value) in consideration of the diameter of the wire electrode and the discharge gap.

[0008] At this time, in the type of processing for cutting out a necessary part from the workpiece, an offset path is set outside the line of the processing shape. Further, in a type of processing in which an unnecessary part is removed from a workpiece to obtain a necessary part, an offset path is set inside a line of the processing shape. Therefore, when machining a corner portion, N
Even if the C program trajectory is the same, the machining method differs in some points depending on whether the direction offset with respect to the corner is outside (out corner) or inside (in corner).

In a wire electric discharge machine equipped with an NC (numerical control) device, an offset direction and an offset value are set together with elements of a desired machining shape including coordinate values and relative movement directions in an NC program created in advance. ing. In addition, parameter values such as initial processing conditions are also N
It is substantially set using the C code. When a workpiece is machined by a plurality of machining steps, the estimated discharge gap becomes smaller as some electrical machining conditions are set smaller step by step, so the offset value is also machined. It is set to a small value step by step for each process.

[0010] EDM is used exclusively as an EDM medium for controlling the insulating state of the discharge gap. The working fluid can also be used as a coolant for cooling the wire electrode, and suppresses a rise in the temperature of the wire electrode and the gap due to heat generated by electric discharge or supplied current. In addition, the machining fluid is supplied as a jet to quickly remove machining dust remaining in gaps such as metal powder melted and scattered by electric discharge and impurities generated by decomposition of substances contained in the machining fluid. It also has the effect of purifying the gap.

On the other hand, the jet of the machining fluid exerts an irregular and difficult-to-measure force on the wire electrode, and often becomes one of the sources of vibration of the wire electrode. In addition, since the wire electrode has a complicated movement at the point where the discharge occurs due to the influence of the discharge reaction force and the electrostatic force, the vibration of the machining fluid may be increased. Therefore, the wire electrode constantly vibrates in a complicated manner, and the relative position in the horizontal direction of the portion of the wire electrode supported by the wire guide and the portion of the wire electrode where the discharge occurs is always different.

[0012] Due to the influence of such vibration of the wire electrode, a "sharp" corner may occur at an out-corner having an acute angle smaller than 90 degrees, and a desired sharp edge may not be obtained on a processed product. In particular, when the corner angle is smaller than 10 degrees or less, the shape of the corner may be distorted. Hereinafter, the above point will be described more specifically with reference to FIGS. FIG. 5 shows an example of a certain form of processing, and FIG. 6 is an enlarged view of a part of the out-corner having an acute angle.

As shown in FIG. 5, for example, a processed product W
When performing a process of cutting D from the workpiece WP, there may be an out-corner portion having an acute angle indicated by a symbol SP. The machining surface of the machining shape shown in FIG. 5 has a tapered surface in part, but the NC program trajectory representing the desired machining shape is the trajectory indicated by reference numeral PN in FIG. .

In the case of the first cut, the workpiece W
Since the workpiece WP is machined while the wire electrode EL is sandwiched in the machining groove formed in P, the discharge reaction force G and the force F of the machining fluid jet act in a direction orthogonal to the direction in which machining proceeds. The vibration of the wire electrode EL in that direction is suppressed. However, since the already processed portion of the workpiece WP is in an open state, the discharge reaction force G and the force F of the machining liquid jet act as shown in FIG. In the direction, the wire electrode EL is vibrated. For this reason, the wire electrode EL relatively moves in a state where the processed portion is apparently delayed from the portion positioned by the pair of wire guides of the wire electrode EL.

When the relative movement direction of the wire electrode EL is changed at the vertex O ₁ of the corner of the offset path PO at the acute corner, the discharge reaction force G and the force V acting in the direction of machining are changed. The force F of the working fluid jet acts substantially as shown in FIG. 6B. At this time, the maximum amplitude L of the vibration of the wire electrode EL extends to the direction of the corner vertex CP in the NC program locus PN. Therefore, as shown in FIG.
The corner edge of the portion cut out as the processed product WD is not sharply formed due to "corner dripping".

When the wire electrode EL passes through the vertex O ₁ ,
Wire electrode EL in the direction orthogonal to the direction of processing
Is gradually suppressed, and the amplitude of the vibration gradually decreases. Then, by the time the relative position of the wire electrode EL reaches the point O ₂ shown in FIG. 6B, EL to the wire electrode becomes state sandwiched again processed groove, vibration of the direction of the wire electrode EL is converged You.

No matter how many times the end face finishing is performed in a plurality of processing steps, errors in the processed shape due to corner droop gradually increase without being corrected in relation to the processed shape accuracy. Then, in the processing step at the final stage of the end face finishing processing, depending on the required processing shape accuracy, the corner droop is no longer negligible and eventually results in a desired shape not being obtained.

In general, the relative movement between the wire electrode and the workpiece is temporarily stopped for a preset time at a corner portion of the offset path, and the application of a voltage pulse for processing is paused. After reducing the overall deflection of the wire electrode between the pair of wire guides, relative movement of the wire electrode and the workpiece again at a predetermined speed,
A processing method in which application of the voltage pulse is restarted is employed.

When a particularly high form accuracy is to be obtained, as a special processing method, there is a method in which the approach path of the offset path PO to the corner is modified so as to spread outward, and processing is performed along the corrected offset path. is there. According to this method, the bending of the wire electrode on the side surface of the workpiece W
It is less likely to directly affect the side surface of D, and the distortion of the out corner is reduced.

[0020]

However, in the machining method in which the electric discharge machining and the relative movement feed are temporarily stopped, when the electric discharge machining and the relative movement feed are resumed, the same effect is produced. . In addition, even with a processing method for correcting the approach path to the corner so as to spread outward, a similar effect occurs when the corner portion is turned back to escape from the corner. In any of the above-described methods, the influence of the vibration of the wire electrode, particularly the influence of the vibration due to the force of the machining liquid jet, is hardly taken into account. It cannot be sufficiently removed and is not a sufficient method for suppressing corner dripping.

Further, it is not easy for an operator to preset the time for stopping the relative movement of the wire electrode and the correction amount for correcting the offset path to spread outward in the NC program or the like.

An object of the present invention is to provide a wire cut electric discharge machining method which can improve a machining shape of a machining shape including an acute angled out corner by improving the machining method for machining a machining shape including an acute angled out corner. Is the main purpose.
Another object of the present invention is to provide a wire electric discharge machine which realizes the wire electric discharge method. Other advantages of the technology of the present invention will be described together with specific embodiments.

[0023]

In view of the above, specifically,
The wire-cut electric discharge machining method according to the present invention is arranged so that the intersection points O ₃ and O ₆ of the acute angle of the NC program trajectory PN on the offset path PO with the perpendicular drawn from the vertex CP of the out corner SP or near the intersection point , The first auxiliary path, the second auxiliary path, and the vertex C that extend outside the NC program locus PN and do not intersect with each other.
The wire electrode and the wire electrode are located along an offset path that is located outside an arc centered at P and whose radius is an offset value, and that is modified by a third auxiliary path that connects the first auxiliary path and the second auxiliary path. The workpiece is relatively moved.

Preferably, the first auxiliary path and the second auxiliary path have the same length. Also, at least one of the auxiliary routes is a straight line. Furthermore, the first
The angle formed by the second correction path and the second correction path with the offset path PO is set to 10 ° or more.

Further, the wire-cut electric discharge machining method according to the present invention includes a step of setting an offset path PO, a step of searching for an out-angle corner SP having an acute angle included in the NC program trajectory PN, and a step of offsetting when a corner SP exists. The vertex CP of the corner on the offset path PO on the path PO
Calculating the intersection points O ₃ and O ₆ with the perpendicular drawn down from
The first auxiliary path and the second auxiliary path each having a length obtained by multiplying an offset value located outside the offset path PO at a predetermined angle θ set at a predetermined angle θ and connected to the intersections O ₃ and O ₆ by a predetermined predetermined magnification k. Setting an auxiliary path, setting a third auxiliary path connecting the first auxiliary path and the second auxiliary path, and setting the offset path PO by the first to third auxiliary paths. And a step of moving the wire electrode and the workpiece based on the corrected offset path.

The wire-cut electric discharge machine according to the present invention includes a means 911 for calculating an offset path PO obtained by shifting the NC program trajectory PN representing a desired machining shape by a predetermined offset value, and an out corner SP having an acute angle to the NC program trajectory PN. Means 912 for judging whether or not it is included, at intersections O ₃ and O ₆ of the offset path PO on the offset path PO with a perpendicular drawn down from the vertex CP of the corner or near the intersection when there is a corner SP The first auxiliary path and the second auxiliary path which extend outside the NC program trajectory PN at a predetermined angle θ from the point and do not intersect with each other are located outside a circular arc having a center at the vertex CP of the corner and an offset value as a radius. Means 913 for calculating a first auxiliary path and a third auxiliary path connected to the second auxiliary path, An arithmetic unit including means 913 for correcting the set path PO with the first to third auxiliary paths, and means 913 for calculating and outputting a relative movement command value based on the corrected offset path. 91
Is provided.

[0027]

1 and 2 show an example of a wire-cut electric discharge machine which can carry out the wire-cut electric discharge machining method of the present invention. In FIG.
1 shows a schematic configuration of an entire wire cut electric discharge machine and a machining fluid supply device. FIG. 2 shows a main configuration of the machining power supply unit.

The wire-cut electric discharge machine mainly comprises a main body of the wire-cut electric discharge machine, and a machining power supply unit including an NC device and a machining power supply provided in parallel with the machine. An airframe structure 1 serving as a base of the machine is a bed 11
And a column 12 erected on the rear upper surface.

The workpiece moving mechanism 2 is composed of a cross table that can be moved by a servo motor mounted on the bed 11. The cross table is provided with an X-table 2X movable in the X-axis direction driven by the servomotor 21X and a Y-table 2Y movable in the Y-axis direction driven by the servomotor 21Y. It can move in two axial directions. The workpiece WP is placed on the X-axis table 2X.
A work tank 23 is placed so as to surround a work stand 22 to which the work stand 22 is attached, and a workpiece WP installed on the work stand 22.

The wire guide mechanism 3 includes an upper guide unit 31 attached to the tip of the upper arm 3U and a lower arm 3
L includes a lower guide unit 32 attached to the tip of L. The wire electrode EL is stretched between a pair of wire guides of the upper wire guide GU in the upper guide unit 31 and the lower wire guide GL in the lower guide unit 32, and is guided for positioning. The lower arm 3L is provided with the processing tank 2
4 is fixed to the column 12 through the rear wall of the rear.

The wire feeding mechanism 4 is provided on the entire panel of the column 12, and supplies a bobbin 41 serving as a wire electrode supply section, a tension roller 42 for applying tension to the wire electrode EL, and a wire electrode. Feeding roller 43 for feeding
And an automatic connection unit 44. The automatic connection unit 44 allows a wire electrode EL to be automatically stretched to a wire collection mechanism (not shown) via a lower wire guide GL by passing through a through hole provided in advance in the workpiece WP. .

The wire electrode collecting mechanism (not shown) includes a wire transport device for turning the wire electrode EL passing through the lower arm GL and sending the wire electrode EL, a winding roller for winding the wire electrode EL, and a wire roller for winding the wire electrode EL. Includes buckets to retrieve.

The taper unit 5 includes a servo motor 51U
, A U table 5U moved in a U axis direction parallel to the X axis direction, and a V table 5V moved in a V axis direction parallel to the Y axis direction by a servomotor 51V. Since the upper arm 3U is hung down from the U table 5U and the automatic connection unit 44 is attached to the front end thereof, the upper guide unit 31 can be freely moved with respect to the lower guide unit 32. Therefore, by moving the taper unit 5, the wire electrode EL can be inclined with respect to the vertical direction.

The working fluid output from the working fluid supply device 6 including the pump 61, the filter 62, and the pure water device 63 is supplied from the nozzles 31N and 32N provided in the upper guide unit 31 and the lower guide unit 32, respectively. It is supplied as a jet substantially coaxially in the direction in which the wire electrode EL is stretched. Further, the processing liquid remaining in the processing tank 24 is returned to the processing liquid storage tank 65 through the drain pipe 64.

The machining head 7 is moved up and down by a servomotor 71 in a Z-axis direction perpendicular to the X-axis and the Y-axis. As the processing head 7 moves, the upper wire guide GU and the automatic connection unit 44 simultaneously move up and down via the taper unit 5 attached below the processing head 7.

The machining power supply unit 8 includes an NC unit 9 and a machining power supply circuit 81 in a housing installed adjacent to the machine.
And other electrical circuits. A display device 82 such as a CRT or an LED is mounted on a front panel of the housing, and an input device 83 including a switch and a keyboard and a reading device 84 are installed near the display device 82.

The arithmetic unit 91 of the NC unit 9 includes a storage unit in which a predetermined processing program is stored, and according to the processing program, the parameter data input from the input device 83 or the NC data input from the reading device 84.
Decrypt the program. In addition, necessary calculations are performed in accordance with the processing program to control each device. The storage device 92 temporarily stores necessary data in a predetermined storage area. At this time, a gap detection signal obtained by the detection circuit 85 and a feedback signal of a position detection device (not shown) are input to the arithmetic device 91 as appropriate.

For example, a command signal relating to a machining voltage pulse applied to the gap between the wire electrode EL and the workpiece WP is output to the machining control circuit 86, and a gate signal is transmitted from the gate circuit to generate the machining power supply circuit 81. On / off of at least one switching element is controlled. Also, the values of the variable DC power supply and the variable current limiting resistor (not shown) are adjusted. The pulsed machining current output here is supplied to the discharge gap via the coaxial cable CB.

Although not shown, the wire supply mechanism 4,
The wire collecting mechanism or the working fluid supply device 6 can be controlled in the same manner, and the pressure of the working fluid jet, the traveling speed of the wire electrode, the tension of the wire electrode, and the like can be managed collectively.

In particular, FIG. 2 shows a functionally divided operation device 91 capable of performing various operations in accordance with a predetermined processing program. In the main operation unit 911, an NC program in which information on desired processing is programmed is decoded. Then, the NC related to the relative movement obtained by decoding
By performing interpolation based on the data, the NC program locus PN
And an offset path data obtained by shifting the NC program locus PN in a predetermined direction by a predetermined correction amount are calculated. At this time, the NC program trajectory and the offset path are converted into display data via the main processing unit 911, and the display device 83
Can be displayed.

A corner discriminating unit 912 for searching for an acute out corner determines whether or not the NC program trajectory, that is, the desired machining shape includes the acute out corner, based on the NC data obtained by the main arithmetic unit 911. Find out. In the case where an out-corner having an acute angle exists, the offset path correcting unit 913 sets a block of the NC program trajectory represented by two program blocks forming the out-corner and a block of two offset paths corresponding to the out-corner. From the above, first to third auxiliary routes to be described later are obtained. Then, an offset path corrected by these auxiliary paths is set.

The amount of movement of each axis is obtained from the corrected offset path data, and the relative movement command value for each axis is output to the command signal generator 93. The relative movement trajectory based on the corrected offset path can also be displayed on the display device 82 via the main calculation unit 911,
These data can be stored in the storage device 92.

From the command signal generator 93, the relative movement command value based on the corrected offset path output from the offset path correction section 913 is converted into a motor control pulse and distributed to the motor driver 87 for each axis. . Servo motors 21X, 2
1Y, 51U, 51V, 71 are controlled synchronously, and tables 2X, 2Y, 5U, 5
V, and at least one of the processing heads 7 is driven,
The wire electrode EL moves relatively along the corrected offset path. At this time, in a predetermined axial direction (generally, in the X-axis and Y-axis directions), a servo signal from a servo device (not shown) is interrupted by the movement command signal, and the wire electrode EL is servo-moved.

Next, an example of electrical discharge machining of an acute out-corner by the machining method of the present invention will be described with reference to FIG. 3A and 3B are the same as the NC program trajectory shown in FIG.

First, an NC program is decoded, and an offset path PO serving as a basis of a first cut corresponding to each shape element is determined based on data of the NC program locus PN obtained by decoding and data of an offset direction and an offset value. Set. At this time, since the NC program trajectory PN is programmed for each shape element (program block), the set offset path PO
Also corresponds to each program block.

By scanning the data of the NC program locus PN including the coordinate data, the shape data, and the moving direction data, the existence of the acute out corner SP having a corner angle smaller than 90 degrees as shown in FIG. 5 is checked. . When the out corner SP is present, the intersection between the two perpendiculars lowered from the vertex CP of the corner, which is the connection point of the two NC program trajectory blocks forming the corner, to the offset path PO and the offset path PO are determined. And O ₃ where the desired machining shape is not impaired.
And O ₆ .

Next, in the direction of the vertex O ₁ of the corner of the offset path PO, starting from the change point O ₃ , the offset path P
A straight line having a predetermined length inclined by a predetermined angle θ so as to be further outward with respect to the NC program locus PN than O is set as a first auxiliary route. Similarly, in the direction of the vertex O ₁ , the predetermined angle θ is set so as to be further away from the change point O _{6 with} respect to the NC program trajectory PN than the offset path PO.
A line segment having the same length as the inclined first auxiliary path is set as the second auxiliary path.

Then, as shown in FIG. 3B, a line segment connecting the end points O ₄ and O _{5 of} the first and second auxiliary paths determined earlier is set as a third auxiliary path. In order not to erode the vertex CP of the corner, the third auxiliary path is provided at least in a region outside the arc with the radius at an offset value centered on the vertex CP of the corner as shown by hatching in FIG. 3A. Need to be located.

When setting the auxiliary route, the predetermined angle θ and the length of the first and second auxiliary routes must be determined. This is because the degree of spread of these auxiliary paths to the outside is particularly closely related to the amplitude of the vibration of the wire electrode, and when the predetermined angle θ is small,
This is because the side surface of the processed shape is deformed excessively.
Further, their lengths are particularly closely related to the position of the third auxiliary path described above. Specifically, if the predetermined angle of the first and second auxiliary paths is small, the third When the wire electrode relatively moves along the auxiliary path of
This is because the tip of P is removed.

As a result of various experiments, the length is calculated by multiplying the offset value by the predetermined magnification k. When the predetermined angle θ is 10 ° and the predetermined magnification k is 1.2,
It has been found that even if these values are fixed values, there is almost no problem in actual machining regardless of the size of the corner angle. It is considered that this is because various parameters, processing conditions, and offset values in the normal first cut are also within a predetermined settable range. Within this normal range, if the predetermined angle θ is larger than approximately 10 °, there is almost no problem in machining accuracy, and the predetermined magnification depends on the size of the predetermined angle θ. It should be noted that if the predetermined angle θ is increased more than necessary, the predetermined magnification k increases accordingly, the distance that must be subjected to electric discharge machining is increased, and the machining time is unnecessarily lengthened.

As described above, it is difficult to set a correction value when processing an acute out-corner with high accuracy by the processing method for setting the auxiliary route. However, in the present invention, it is difficult to set the correction value. This has the advantage that hard correction value setting is almost unnecessary.

It has been found that a large distance between a pair of wire guides affects the theoretical amplitude of the vibration of the wire electrode. Therefore, in the case where the range of the plate thickness of the workpiece which can be processed by the wire-cut electric discharge machine is wide (large specifications), it is not necessary to be delicate, but every predetermined range of the plate thickness (for example, every 10 mm). Preferably, a predetermined angle θ and a predetermined magnification k corresponding to the plate thickness are determined in advance. At this time, a known setting value setting system that has been used when setting the initial value of the processing condition can be adopted, and the relationship between the parameter such as the plate thickness and the predetermined angle θ and the predetermined magnification k is stored in the storage device. And the selection and setting based on a specific input value, the burden on the operator does not increase.

The amplitude of the vibration of the wire electrode is calculated using a known calculation method for calculating the amplitude of the vibration of the wire electrode. Angle θ according to various machining conditions
Setting the predetermined magnification k to a detailed value is not so difficult in today's days when arithmetic devices have been developed. However, the vibration of the wire electrode EL is still being studied by many researchers, and it is not always possible to obtain a favorable effect in actual processing from theoretical values. Therefore, a predetermined angle θ and a predetermined magnification k are calculated by calculation.
Even if is obtained, it is preferable to set it after performing a processing experiment, and it may be difficult to set the predetermined angle θ and the predetermined magnification k instead.

The workpiece is subjected to electrical discharge machining while the wire electrode and the workpiece are relatively moved along the corrected offset path obtained by correcting the offset path PO by the first to third auxiliary paths set as described above. I do. As a basic method of interpolating a linear shape or an arc shape from the NC data on the relative movement programmed in the NC program and outputting a movement command value to each axis moving device, a conventionally known method is adopted.

After the second cut, it is preferable to perform processing along a path similar to the first cut, so as not to impair the processed shape, unless it is unavoidable for some reason. Therefore, after the second cut, the auxiliary path is similarly set using the offset value set for each processing step, and electric discharge machining is performed along the corrected offset path.

In the first auxiliary path set in this way, the wire electrode spreads out of the processed product,
The error that the amplitude of the vibration of the wire electrode expands at the top of the corner is corrected within the range where there is no problem with the actual machining shape accuracy.
It prevents corner edges from being formed sharply. Further, in the second auxiliary path, when the wire electrode turns around the vertex of the corner and escapes from the corner, the corner edge is prevented from being distorted and deformed. And the third
In the auxiliary path, the corner apex is prevented from being removed, and the first and second auxiliary paths are connected at almost the shortest distance, so that the processing efficiency is not unnecessarily reduced.

The change point O on the offset path PO described above.
₃ , O ₆ is shifted from corner vertex CP to corner offset path PO
The reason for setting the intersection of the perpendicular line and the offset path PO is that there is no problem in the machining shape accuracy and the calculation from the NC data is easy, and unless it is too far from the change points O ₃ and O ₆ , Another point on the offset path PO can be set as a change point.

The third correction is located outside an arc centered on the vertex CP of the corner and having a radius of the offset value and intersects with two blocks of the offset path PO corresponding to the NC program trajectory PN forming the corner. After setting the path first, it is also possible to set the first and second correction paths that spread outside the offset path PO at a predetermined angle θ.

FIG. 4 is a diagram showing a second embodiment obtained by modifying the embodiment shown in FIG. 3B. In FIG. 4, items having the same meaning are denoted by the same reference numerals as in FIG. 3B. In this embodiment, first to third auxiliary paths having a gentle arc shape that is relatively close to a straight line are set.
Even if such an auxiliary route is set, an effect almost the same as that of the first embodiment described above can be expected.

[0060]

According to the wire electric discharge machining method and apparatus of the present invention, since the offset path of the wire electrode is set in consideration of the complicated wire electrode caused by various factors, the machining shape of the acute angle out corner is set. The accuracy is improved. In addition, since the processing time is not greatly sacrificed in order to obtain the processing shape accuracy, there is an effect that the processing shape accuracy can be efficiently obtained.

Further, it is not necessary for the operator to set difficult parameters, and the machining shape accuracy at the out-corner at an acute angle can be easily obtained, and the working time can be shortened.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing the entirety of a wire-cut electric discharge machine which implements a wire-cut electric discharge machining method of the present invention.

FIG. 2 is a configuration diagram of a main part of a wire electric discharge machine according to the present invention.

FIG. 3 is an example of machining of an acute-angled out-corner portion according to an embodiment of the wire-cut electric discharge machining method of the present invention,
(A) is a plan view showing a setting area of an auxiliary route, and (B) is a plan view showing a state after a wire electrode has passed through a corner.

FIG. 4 is a diagram showing an example of machining an acute out-corner portion according to another embodiment of the wire electric discharge machining method of the present invention.

FIG. 5 is a perspective view of a workpiece showing a mode of processing including an out-angle of an acute angle.

FIGS. 6A and 6B are examples of machining of an acute-angled outer corner portion by a conventional wire-cut electric discharge machining method, wherein FIG. 6A shows a state before the wire electrode passes through the corner, and FIG. 6B shows a state after the wire electrode passes through the corner. FIG.

[Explanation of symbols]

1, machine body structure 2, workpiece moving mechanism 3, wire guide mechanism 4, wire supply mechanism 5, taper unit 6, machining fluid supply device 7, machining head 8, machining power supply unit 81, machining power supply circuit 9, NC Unit 91, arithmetic unit 911, main arithmetic unit 912, corner discriminating unit 913, offset path correcting unit 92, storage device EL, wire electrode WP, workpiece WD, processed product CP, corner vertex PN, NC program locus PO, Offset path GP, discharge gap L, maximum amplitude O ₃ , O ₆ , changes

Claims (6)

[Claims] 1. An intersection of an NC program trajectory representing a desired machining shape with a vertical line lowered from a vertex of an acute angle of an out-corner of the NC program trajectory on the offset path on which the correction path is corrected by a predetermined correction amount. The first auxiliary path and the second auxiliary path which extend from the neighboring points to the outside of the NC program trajectory and do not intersect with each other, and the outside of an arc having the predetermined correction amount as a radius with the vertex of the out corner as the center. Positioning the wire electrode and the workpiece relative to each other along an offset path that is located and corrected by a third auxiliary path that connects the first auxiliary path and the second auxiliary path. Characteristic wire cut electric discharge machining method. 2. The wire-cut electric discharge machining method according to claim 1, wherein the first auxiliary path and the second auxiliary path have the same length. 3. The wire according to claim 1, wherein at least one of the first auxiliary path, the second auxiliary path, and the third auxiliary path is a straight line. Cut electric discharge machining method. 4. A step of setting an offset path in which an NC program trajectory representing a desired machining shape is corrected by a predetermined correction amount, a step of searching for an acute out corner included in the NC program trajectory, and a step of searching for the acute out corner. Calculating the intersection between the offset path on the offset path and a vertical line lowered from the vertex of the acute angle out corner, and connecting the intersection to the intersection at a predetermined angle set in advance. Setting a first auxiliary path and a second auxiliary path having a length obtained by multiplying the predetermined correction amount located outside of the image by a predetermined predetermined magnification; and setting the first auxiliary path and the second auxiliary path. Setting a third auxiliary path connecting to the auxiliary path, and correcting the offset path by the first to third auxiliary paths. A wire electrode and a workpiece based on the corrected offset path. 5. The wire according to claim 3, wherein an angle formed between the first correction path, the second correction path, and the offset path is 10 ° or more. Cut electric discharge machining method. 6. A means for calculating an NC program trajectory representing a desired machining shape and an offset path obtained by correcting the NC program trajectory by a predetermined correction amount, and determining whether or not the NC program trajectory includes an acute out corner. Means, at a predetermined angle set in advance from a point near or near an intersection of the offset path on the offset path with a vertical line lowered from the vertex of the out corner when the acute angle out corner exists. The first auxiliary path and the second auxiliary path which extend outside the NC program trajectory and do not intersect with each other are located outside an arc centered on the apex of the out corner and having a radius of the predetermined correction amount and the first auxiliary path. Means for calculating a third auxiliary path connected to the second auxiliary path and a third auxiliary path connected to the second auxiliary path; A wire cut electric discharge machining apparatus comprising: an arithmetic unit including: means for correcting the relative movement command value based on the corrected offset path; and means for calculating and outputting a relative movement command value based on the corrected offset path.