Wire electrical discharge machining device and wire electrical discharge machining method

Abstract

To provide a wire electrical discharge machining device and a wire electrical discharge machining method that can improve machining accuracy at corners of a workpiece and control a feed rate with a relatively small data amount.SOLUTION: A wire electrical discharge machining device comprises a movement device that drives a moving body, and a control device. The movement device is configured to relatively move a wire electrode relative to the workpiece in a machining progress direction along a path and machine the workpiece while maintaining a prescribed gap between the wire electrode and the workpiece according to a prescribed path and a prescribed servo feed rate. The control device is configured to set a speed function of regulating the servo feed rate relative to a movement distance of the wire electrode at corner sections of the path. The speed function is set by using Bezier curves such that the servo feed rate curvilinearly changes relative to the movement distance at an inner corner R section of the corner section.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a wire electric discharge machining apparatus and a wire electric discharge machining method for performing electric discharge machining on a workpiece using a wire electrode. [Background technology]

[0002] In wire electric discharge machining, a voltage pulse is applied between the wire electrode and the workpiece to repeatedly generate electric discharges to remove material from the workpiece, while the wire electrode and the workpiece are moved relative to each other at a predetermined feed rate along a predetermined path previously programmed in an NC program, thereby machining the workpiece into a desired machining shape. Generally, in order to obtain sufficient machining accuracy in a shorter time, a first cut is performed as a rough machining process in which the workpiece is roughly cut in a pure state, and then a second cut is performed on the end face of the workpiece as a finishing process. The higher the required machining accuracy, the more the discharge energy needs to be gradually reduced while finishing the end face, and it is necessary to perform more machining steps according to the target machining accuracy, such as the second cut, third cut, and force cut, after the finishing process, in other words, the number of cuts needs to be increased. On the other hand, since the machining time increases as the number of cuts increases, it is desired to reduce the number of cuts relative to the target machining accuracy.

[0003] Normally, when machining a workpiece in a straight line, the wire electrode is moved at a predetermined feed speed, but when machining a corner R or edge, the feed speed in the straight line is increased or decreased depending on the machining shape in order to obtain the desired machining shape accuracy.

[0004] Patent Document 1 discloses a wire electric discharge machining method in which the feed speed of the wire electrode is reduced just before a corner, and after the corner is machined at a constant feed speed, the feed speed is increased to the feed speed before the speed reduction. As shown in the example of Patent Document 1, in conventional corner machining, the feed speed of the wire electrode is changed linearly with respect to the moving distance when changing the speed from a speed value for straight line machining to a speed value suitable for corner machining, and when changing the speed to return to the original speed value after corner machining.

[0005] As a prior art in a field other than electric discharge machining, for example, Patent Document 2 discloses a numerical control device for a cutting machine tool. In this numerical control device, a parametric curve is generated from a speed value specified for each command block, and the feed speed is changed in a curved manner when accelerating and decelerating the tool between command blocks. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 8-39356 [Patent Document 2] JP 2020-9102 A Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, it is required to achieve the target machining accuracy with fewer machining times (number of cuts) in order to reduce machining time and energy consumption. In machining corners, when the feed speed of the wire electrode is changed linearly as in the conventional method described above, it has been found that reducing the number of cuts can cause bites into the workpiece (a phenomenon in which the amount of material removed is excessive compared to the amount of material removed) or leftover material (a phenomenon in which the amount of material removed is insufficient compared to the amount of material removed) and result in a decrease in machining accuracy. For example, when machining corners including an inner corner R, when the feed speed of the wire electrode is changed linearly, reducing the number of cuts can easily cause a short circuit between the wire electrode and the workpiece, which can easily cause bites.

[0008] In order to avoid such a decrease in machining accuracy, it is conceivable to divide the path of the wire electrode in the corner portion into small sections, set an appropriate feed speed for each small section, and make the speed change a smoother curve. However, setting a feed speed for each small section may result in a huge amount of data to be stored in a database for controlling the feed speed.

[0009] The present invention has been made in consideration of the above-mentioned circumstances, and has as its object to provide a wire electric discharge machining apparatus and a wire electric discharge machining method that are capable of improving the machining accuracy of corners of a workpiece and capable of controlling the feed speed with a relatively small amount of data. [Means for solving the problem]

[0010] According to the present invention, the following inventions are provided. [1] A wire electric discharge machining apparatus comprising a moving device that drives a moving body and a control device that controls the moving device, wherein the moving device is configured to machine the workpiece by moving the wire electrode relative to the workpiece along a predetermined path in a machining progress direction while maintaining a predetermined gap formed between the wire electrode and the workpiece in accordance with a predetermined path and a predetermined servo feed speed, and the control device is configured to divide the path into a straight portion and a corner portion and set a speed function that specifies the servo feed speed with respect to the movement distance of the wire electrode along the path in the corner portion, and the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance at least in the corner R portion of the corner portion. [2] A wire electric discharge machining apparatus as described in [1], wherein the path in the corner R portion includes an approach section, an arc section, and a return section, in that order, and the speed functions in the approach section, the arc section, and the return section are each set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the travel distance from the servo feedrate at a start point of each section to the servo feedrate at an end point of each section. [3] A wire electric discharge machining apparatus as described in [2], wherein the speed function in the approach section is set using a third-order Bezier curve, the speed function in the arc section is set using a second-order Bezier curve, and the speed function in the return section is set using a third-order Bezier curve. [4] A wire electric discharge machining apparatus as described in [2] or [3], wherein the speed function in the approach section is set so that the servo feed rate decreases curvilinearly with respect to the travel distance, and the speed function in the return section is set so that the servo feed rate increases curvilinearly with respect to the travel distance. [5] A wire electric discharge machining apparatus as described in any one of [1] to [4], wherein the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance in an outer corner R portion of the corner portion, the path in the outer corner R portion includes an approach section, an arc section, and a return section, in that order, and the speed functions in the approach section, the arc section, and the return section of the outer corner R portion are each set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance from the servo feed speed at a start point of each section to the servo feed speed at an end point of each section. [6] A wire electric discharge machining apparatus as described in [5], wherein the speed function in the approach section of the outer corner R portion is set using a third-order Bezier curve, the speed function in the arc section of the outer corner R portion is set using a second-order Bezier curve, and the speed function in the return section of the outer corner R portion is set using a third-order Bezier curve. [7] A wire electric discharge machining apparatus as described in [5] or [6], wherein the speed function in the approach section of the outer corner R portion is set so that the servo feed speed increases curvilinearly with respect to the travel distance, and the speed function in the return section of the outer corner R portion is set so that the servo feed speed decreases curvilinearly with respect to the travel distance. [8] A wire electric discharge machining apparatus according to any one of [1] to [7], wherein the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance at an inner corner edge portion of the corner portion, the path at the inner corner edge portion includes an approach section and a return section, and the speed functions in the approach section and the return section of the inner corner edge portion are each set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance from the servo feed speed at a start point of each section to the servo feed speed at an end point of each section. [9] [8] A wire electric discharge machining apparatus according to the above item, wherein the speed functions in the approach section and the return section of the corner edge portion are each created using a third-order Bezier curve.

[10] A wire electric discharge machining apparatus as described in [8] or [9], wherein the speed function in the approach section of the corner edge portion is set so that the servo feed speed decreases curvilinearly with respect to the travel distance, and the speed function in the return section of the corner edge portion is set so that the servo feed speed increases curvilinearly with respect to the travel distance.

[11] A wire electric discharge machining apparatus according to any one of [1] to

[10] , wherein the speed function is set using a Bezier curve so that the servo feedspeed changes curvilinearly with respect to the travel distance at the outer corner edge of the corner portion, the path at the outer corner edge portion includes an approach section, an approach side avoidance section, a skip section, a return side avoidance section, and a return section, in this order, and the speed functions in the approach section, the approach side avoidance section, the return side avoidance section, and the return section of the outer corner edge portion are each set using a Bezier curve so that the servo feedspeed changes curvilinearly with respect to the travel distance from the servo feedspeed at a start point of each section to the servo feedspeed at an end point of each section.

[12]

[11] A wire electric discharge machining apparatus according to the above-mentioned embodiment, wherein the speed functions in the approach section, the approach side avoidance section, the return side avoidance section, and the return section of the outer corner edge portion are each set using a quadratic Bezier curve.

[13] A wire electric discharge machining apparatus as described in

[11] or

[12] , wherein the speed function in the approach section and the approach side avoidance section of the outer corner edge portion is set so that the servo feed speed increases curvilinearly with respect to the travel distance, and the speed function in the return section and the return side avoidance section is set so that the servo feed speed decreases curvilinearly with respect to the travel distance.

[14] A wire electric discharge machining apparatus according to any one of

[11] to

[13] , wherein the speed function in the skip section is set so that the servo feed speed is constant with respect to the travel distance.

[15] A wire electric discharge machining apparatus as described in any one of

[11] to

[14] , wherein the control device is configured to set a pause time function that specifies a discharge pause time with respect to a moving distance of the wire electrode along the path in the outer corner edge portion, and to apply a voltage between the wire electrode and the workpiece in the outer corner edge portion based on the discharge pause time, and the pause time function is set using a Bezier curve so that the discharge pause time changes curvilinearly with respect to the moving distance.

[16] A wire electric discharge machining apparatus according to any one of [1] to

[15] , wherein the path includes a continuous corner portion formed by a plurality of the corner portions being consecutive, the path in the continuous corner portion includes a first corner portion, a connection portion, and a second corner portion being consecutive in this order, and the speed function in the connection portion is set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the travel distance from the servo feedrate at the end point of the first corner portion to the servo feedrate at the start point of the second corner portion.

[17] The wire electric discharge machining apparatus according to

[16] , wherein at least one of the plurality of corner portions is an inner corner R portion.

[18] The wire electric discharge machining apparatus according to

[17] , wherein the velocity function in the connection portion is set using a third-order Bezier curve.

[19] A wire electric discharge machining method for machining a workpiece by moving a wire electrode relative to the workpiece while maintaining a predetermined gap between the wire electrode and the workpiece in accordance with a predetermined path and a predetermined servo feed speed, the method comprising the steps of dividing the path into a straight portion and a corner portion, and setting a speed function that defines the servo feed speed with respect to the movement distance of the wire electrode along the path in the corner portion, the speed function being set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance at least in the corner R portion of the corner portion.

[20] A wire electric discharge machining method as described in

[19] , comprising the steps of: decoding an NC program to analyze the type of corner in the corner portion; and, when the analyzed type of corner is an inner corner R portion, controlling the servo feed speed so that it changes curvilinearly with respect to the travel distance based on the speed function that is set in advance using the Bezier curve suitable for the inner corner R portion.

[21] The wire electric discharge machining method according to

[20] , further comprising a step of: dividing the corner portion into an inner corner R portion, an outer corner R portion, an inner corner edge portion, and an outer corner edge portion; and when the type of the analyzed corner is a corner portion other than the inner corner R, controlling the servo feed speed so that it changes curvilinearly with respect to the travel distance in each of the corner portions based on the speed function that is set using the Bezier curve appropriate for the type of each of the corner portions. Effect of the Invention

[0011] In the wire electric discharge machining apparatus according to the present invention, a speed function for defining a servo feed speed in a corner portion is set by the control device, and the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the moving distance at least in the corner R portion. In this configuration, the change in the servo feed speed of the wire electrode is brought closer to a curve, and a more suitable servo feed speed is realized in the corner portion, thereby improving the machining accuracy. Furthermore, by setting the speed function using a Bezier curve, it is possible to avoid a situation in which data required for controlling the servo feed speed becomes enormous. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a wire electric discharge machining apparatus 100 according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a block diagram showing a control mode of the wire electric discharge machining apparatus 100. [Diagram 3] FIG. 4 is a diagram showing an example of a relative movement path of a wire electrode 2 in machining an inner corner R. [Figure 4] 4 is a graph showing an example of a speed function of the corner R portion L2 shown in FIG. 3, which is set using a Bezier curve. [Diagram 5] 11 is a diagram showing an example of a relative movement path of a wire electrode 2 in machining an outer corner R. FIG. [Figure 6] 6 is a graph showing an example of a speed function of the outside corner R portion L5 shown in FIG. 5, which is set using a Bezier curve. [Figure 7] FIG. 4 is a diagram showing an example of a relative movement path of a wire electrode 2 in machining an inside corner edge. [Figure 8] 8 is a graph showing an example of a speed function of the inside corner edge portion L8 shown in FIG. 7, which is set using a Bezier curve. [Figure 9] 11 is a diagram showing an example of a relative movement path of a wire electrode 2 in machining an outer corner edge. FIG. [Figure 10] 13 is a diagram showing another example of the relative movement path of the wire electrode 2 in machining the outer corner edge. FIG. [Figure 11] 10 is a graph showing an example of a speed function of the outside corner edge portion L12 shown in FIG. 9, which is set using a Bezier curve. [Figure 12] 10 is a graph showing an example of a dwell time function of the outside corner edge portion L12 shown in FIG. 9, which is set using a Bezier curve. [Figure 13] 1 is a diagram showing an example of a relative movement path of a wire electrode 2 in machining a continuous corner in which an inner corner R and an outer corner R are formed in succession. FIG. [Figure 14] 14 is a graph showing an example of a velocity function for the continuous corner portion shown in FIG. 13 set using a Bezier curve. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Each feature described in the following embodiment can be combined with each other. Also, each feature can be an invention independently.

[0014] 1. Wire EDM equipment 1.1. Overall structure As shown in FIG. 1, a wire electric discharge machining apparatus 100 according to one embodiment of the present invention includes a machining unit 1 including a wire electrode 2, and a control device 9.

[0015] The processing machine body 1 includes a wire electrode 2, a wire guide mechanism 3, a power supply unit 4, and a moving unit 5. The moving unit 5 is configured to drive the moving body to move the wire electrode 2 relative to the workpiece W in the machining progress direction along a predetermined path while maintaining a predetermined gap (hereinafter referred to as machining gap) formed between the wire electrode 2 and the workpiece W in accordance with a predetermined path and a predetermined servo feed speed, thereby machining the workpiece W.

[0016] The wire guide mechanism 3 includes an upper guide assembly 31 and a lower guide assembly 32, which are provided above and below the workpiece W placed on the work stand 11, respectively. Each of the upper guide assembly 31 and the lower guide assembly 32 includes a housing 33, a wire guide 34, and a current conductor 35, and various components are accommodated within the housing 33. The wire electrode 2 is positioned and guided by the wire guides 34 of the upper guide assembly 31 and the lower guide assembly 32. The current conductor 35 is connected to the power supply unit 4. The current conductor 35 is movable in a direction approximately perpendicular to the extension direction of the wire electrode 2 guided by the wire guide 34, and is supplied with electricity when the current conductor 35 comes into contact with the wire electrode 2.

[0017] The moving device 5 includes a plurality of movable bodies in control axis directions for moving the wire electrode 2 relative to the workpiece W, and a servo motor (not shown) for driving and moving each movable body. The moving device 5 drives the servo motors of the movable bodies under the control of the control device 9, whereby the wire electrode 2 moves relative to the workpiece W along a predetermined path and a predetermined servo feed speed. Various configurations of the movable bodies can be applied depending on the specifications of the wire electric discharge machining apparatus 100. For example, in the wire electric discharge machining apparatus 100 shown in FIG. 1, a table 10 on which a work stand 11 is erected is configured as a movable body that moves back and forth in one horizontal linear axis direction (X-axis), and a saddle 20 on which the table 10 is mounted is configured as a movable body that moves back and forth in another horizontal linear axis direction (Y-axis) perpendicular to the X-axis direction.

[0018] 1.2.Control device 9 The control device 9 controls the operation of the wire electric discharge machining device 100. The following description will be limited to the control operations of the control device 9 that are relevant to the present invention.

[0019] Each component of the control device 9 may be realized by software or hardware. When realized by software, various functions can be realized by a CPU executing a computer program. The program may be stored in a built-in storage unit or a computer-readable non-transitory recording medium. In addition, the program may be read from an external storage unit and realized by so-called cloud computing. When realized by hardware, it can be realized by various circuits such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a DRP (Dynamically Reconfigurable Processor). In this embodiment, various information and concepts including the information are handled, and these are represented by high and low signal values ​​as a binary bit collection consisting of 0 or 1, and communication and calculation can be performed by the above-mentioned software or hardware aspects.

[0020] As shown in FIG. 2, the control device 9 of this embodiment includes a numerical control unit 8, a movement control unit 91, a servo control unit 92, and a power supply control unit 93.

[0021] In the wire electric discharge machining of this embodiment, the wire electrode 2 is moved relative to the workpiece W by a servo system that maintains a constant machining gap size. Specifically, a servo feed speed suitable for maintaining a constant machining gap is set, and the wire electrode 2 moves relative to the workpiece W in accordance with the set servo feed speed.

[0022] The numerical control unit 8 includes an input unit 81, an interpretation unit 82, a servo condition setting unit 83, a machining condition setting unit 84, a command unit 85, and a memory unit 86 that stores various data required for control. The interpretation unit 82 reads the NC program input from the input unit 81 to obtain NC data, and outputs it to the command unit 85. The command unit 85 creates movement command data based on the NC data, and outputs it to the movement control unit 91. The movement command data specifies, for example, position coordinates to which the wire electrode 2 should move for each command block. The movement control unit 91 controls the moving device 5 in accordance with the movement command data. As a result, the wire electrode 2 is moved relatively to the workpiece W along a predetermined path.

[0023] The servo control unit 92 determines a servo feed speed suitable for maintaining the size of the machining gap constant in accordance with the servo conditions set by the servo condition setting unit 83, and outputs servo command data in accordance with the servo feed speed to the movement control unit 91. The movement control unit 91 controls the movement device 5 in accordance with the servo command data. As a result, the wire electrode 2 is moved relatively to the workpiece W in accordance with the predetermined servo feed speed. In other words, the movement control unit 91 controls the movement device 5 based on the movement command data and the servo command data, so that the wire electrode 2 moves relatively to the workpiece W in the machining progress direction along a predetermined path in accordance with the predetermined servo feed speed while maintaining a predetermined machining gap.

[0024] An example of a method for controlling the servo feed rate by the servo control unit 92 will be described. The servo control unit 92 acquires an average machining voltage detected by a gap voltage detection device (not shown). The average machining voltage is obtained by averaging the gap voltage in the machining gap for each predetermined unit time and converting it into a signal. The servo control unit 92 outputs servo command data to the movement control unit 91 so that the wire electrode 2 moves relatively in the machining progress direction at a suitable servo feed rate according to the difference between the servo reference voltage and the average machining voltage according to a predetermined speed function set in advance. The speed function is a function that represents a change in the servo feed rate based on the servo feed rate in a straight line in a certain section from one relative position to another relative position on the horizontal plane of the wire electrode 2, or, simply put, a function that represents a change in the feed rate with respect to the moving distance. The speed function is set by the servo condition setting unit 83 as a servo condition, and is set, for example, so that the servo feed rate increases as the difference between the servo reference voltage set as a reference and the average machining voltage increases. By using such a servo function, it becomes possible to advance the wire electrode 2 in the machining progress direction at a desired speed while maintaining a good machining state at a servo feed speed suitable for keeping the machining gap constant and obtaining the expected machining accuracy. Note that, in setting the servo feed speed, the discharge frequency, which is the number of discharge occurrences per unit time, may be used instead of the average machining voltage.

[0025] The path of the relative movement of the wire electrode 2 with respect to the workpiece W (relative movement path) is divided into straight sections where the machining area (removal allowance) does not change substantially, and corner sections where the machining area changes. The corner sections are the relative movement path for machining the workpiece W into a corner shape. The straight sections are the parts of the relative movement path other than the corner sections, and are the relative movement path for machining the workpiece W into a straight line.

[0026] In the straight section, it is preferable to control the servo feed speed using the speed function as in the above example. In the straight section, the machining load (machining amount per unit electric discharge machining time, or machining amount per unit progress distance along the relative movement path) is usually almost constant, so when the servo feed speed is controlled as described above, the wire electrode 2 moves relatively in the machining progress direction at a nearly constant set servo feed speed while the machining state is good.

[0027] In the present invention, in the corner portion, based on the machining shape (contour line) and the way in which the machining area changes as the wire electrode 2 advances along the relative movement path of the wire electrode 2 defined based on the machining shape, the corner portion is divided into four types according to the difference in machining shape, and the servo feed speed is controlled by a different method for each type. Specifically, the corner portion is divided into an arc-shaped "R" and an angular "edge", and further divided into an in-corner where the relative movement path of the wire electrode 2 passes through the inside of the corner portion and an out-corner where the relative movement path passes through the outside of the corner portion for each corner R and corner edge. In the following description, an arc-shaped corner portion where the relative movement path of the wire electrode 2 passes through the inside of the corner portion is called an in-corner R, an arc-shaped corner portion where the relative movement path passes through the outside of the corner portion is called an out-corner R, an angular corner portion where the relative movement path passes through the inside of the corner portion is called an in-corner edge, and an angular corner portion where the relative movement path passes through the outside of the corner portion is called an out-corner edge.

[0028] In the corner portion, the machining load changes because the machining area of ​​the discharge machining surface on the surface of the wire electrode 2 changes according to the shape of the corner of the workpiece. It is known that if the wire electrode 2 is moved relatively in the corner portion at the servo feed speed for straight line machining with a constant machining load, short circuits occur frequently, interrupting the machining, and the machining accuracy decreases. In order to improve the machining accuracy, it is preferable to change the servo feed speed according to the change in the machining load. Specifically, it is preferable to reduce the servo feed speed in the corner portion where the machining load increases compared to when machining the straight line portion, and to increase the servo feed speed in the corner portion where the machining load decreases compared to when machining the straight line portion.

[0029] The control device 9 is configured to set a speed function that specifies the servo feed speed with respect to the moving distance of the wire electrode 2 along the relative moving path in the corner portion. In this embodiment, the speed function is set by the servo condition setting unit 83 of the control device 9 as a servo condition. The speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the moving distance at least in the inner corner R portion of the corner portion. In this embodiment, the servo control unit 92 sets the servo feed speed in the corner portion using the speed function set in this manner. It is preferable that the speed function is set so that the servo feed speed decreases curvilinearly with respect to the moving distance in a section where the machining load increases in the corner portion. It is also preferable that the speed function is set so that the servo feed speed increases curvilinearly with respect to the moving distance in a section where the machining load decreases in the corner portion.

[0030] The change in the servo feed speed in the corner portion may be started from a point on the linear path of the relative movement path before the wire electrode 2 reaches the corner of the workpiece W. In this case, the corner portion includes the linear path from the point where the speed change starts to the point where the wire electrode 2 reaches the corner. The change in the servo feed speed in the corner portion may be ended at a point on the linear path of the relative movement path after the wire electrode 2 has passed the corner of the workpiece W. In this case, the corner portion includes the linear path from the point where the wire electrode 2 has passed the corner to the point where the speed change ends.

[0031] In this configuration, the servo feed speed of the wire electrode 2 changes in a curved manner at the corner, so that a more suitable servo feed speed can be achieved at the corner and machining accuracy can be improved compared to when the servo feed speed is changed linearly. Also, since the servo feed speed is set using a speed function, it is possible to change the servo feed speed in a curved manner with less data compared to when the corner is divided into many small sections and the servo feed speed is set for each small section to change the servo feed speed in a curved manner.

[0032] In terms of preventing a decrease in machining accuracy while reducing the number of cuts, the effect of the servo feed speed control of the present invention is particularly noticeable when machining an inner corner R where biting is likely to occur. Therefore, the present invention is effective by applying the servo feed speed control method of the present invention at least when machining an inner corner R. In addition, by applying the servo feed speed control method of the present invention to corner portions other than the inner corner R, an optimal speed distribution can be established, so that the accuracy of corner shapes other than the inner corner R can also be improved. In addition, the configuration of the control software can be simplified compared to when the servo feed speed is controlled using a predetermined speed function only for the inner corner R, and it is also advantageous in that the specifications of the control software do not become complicated, for example, when machining a machining shape in which multiple corner portions are successively formed.

[0033] The power supply control unit 93 controls the power supply device 4 in accordance with the electrical machining conditions set by the machining condition setting unit 84. This allows a predetermined voltage to be applied to the machining gap at an appropriate time.

[0034] 2. Speed ​​Function The velocity function that defines the servo feed velocity in the corner portion will now be described in detail.

[0035] 2.1. Corner R section A preferred configuration of the speed function in the corner R portion will be described by taking the machining of the corner R shown in FIG. 3 as an example. In FIG. 3, FIG. 5, FIG. 7, FIG. 9, FIG. 10, and FIG. 13, the relative movement path indicated by the solid line with an arrow indicates, in detail, the path along which the center of the cross section of the wire electrode 2 moves relative to the workpiece W. In the following description, the description that the wire electrode 2 reaches a point on the relative movement path means that the center of the cross section of the wire electrode 2 reaches the point. In FIG. 3, FIG. 5, FIG. 7, FIG. 9, FIG. 10, and FIG. 13, the machining allowance of the workpiece W for each cut is omitted, and the outer edge of the workpiece W indicates the outer edge after the wire electrode 2 performs electric discharge machining along the relative movement path to remove the machining allowance. In FIG. 3, the central angle θ of the arc shape of the corner R is Rin is 90°, but the central angle θ Rin is not limited to this example, and 0°<θ Rin Can be set in the range of <180°.

[0036] In the example shown in FIG. 3, the relative movement path of the wire electrode 2 is 1 Linear segment L ending at 1 , point A 1 From point A 5 Corner R part L up to 2 , point A 5 Linear segment L starting from 3 In this order, the linear portion L where the processing load is approximately constant 1 The wire electrode 2 moving along the straight line L 1 End point (corner R part L 2 Point A, which is the start point of 1When the wire electrode 2 reaches the corner R part L, the machining load starts to increase. 2 Point A on the way 3 When it reaches L, the machining load starts to decrease, and the corner R part L 2 End point of the straight line segment L 3 Point A, which is the start point of 5 The reduction in the machining load ends at the linear portion L 3 At this point, the processing load becomes substantially constant again.

[0037] Corner R part L 2 The relative movement path of the wire electrode 2 in the approach section L 2A and the circular arc section L 2C and the return section L 2R In the example shown in FIG. 2A is point A 1 From point A 2 The straight section between the arc section L 2C is point A 2 From point A 3 via point A 4 The return section L 2R is point A 4 From point A 5 It is a straight section up to point A. 3 is the circular arc section L 2C It is the midpoint that divides the area into two equal parts.

[0038] Approach section L 2A , circular arc section L 2C , and the return section L 2R The speed functions in the approach section L where the machining load increases are preferably set using a Bezier curve so that the servo feed speed changes in a curved manner from the servo feed speed at the start point of each section to the servo feed speed at the end point of each section with respect to the moving distance of the wire electrode 2. 2A It is preferable that the speed function in the return section L where the servo feed speed decreases in a curved manner with respect to the moving distance is set. 2RIt is preferable that the speed function in the circular arc section L be set so that the servo feed speed increases in a curved manner with respect to the moving distance. 2C The speed function in the section where the processing load increases (in the example of Figure 3, point A 2 From point A 3 In the section where the servo feed rate decreases in a curved manner with respect to the moving distance, the machining load decreases (in the example of Fig. 3, point A 3 From point A 4 In the section up to the position where the servo feed speed is increased, it is preferable that the servo feed speed is set so as to increase in a curved manner with respect to the moving distance.

[0039] FIG. 4 shows the corner radius portion L set using a Bezier curve in the example shown in FIG. 2 1 is a graph showing an example of a velocity function of the wire electrode 2. The horizontal axis of the graph indicates the moving distance X (unit: mm) of the wire electrode 2 along the relative moving path, and the origin of the horizontal axis (X=0) is located within the circular arc section L 2C Midpoint A 3 The vertical axis of the graph indicates the relative value SF (unit: %) of the servo feed speed when the servo feed speed in the straight line portion is set to 100%.

[0040] A Bézier curve is made up of n+1 control points P 0 ,P 1 ,......,P n When is set, it is an n-th order curve expressed by the following formula. JPEG2025019967000002.jpg8128 In equation (1) n C k is the binomial coefficient expressed by equation (2). JPEG2025019967000003.jpg857 When the parameter t is changed in the range of 0≦t≦1, the curve drawn by P(t) is the control point P 0 and control point P n In the following explanation, the control points P 0 ,P n Of these, control point P 0 The point corresponding to the start point of the Bezier curve, the control point P nThe point corresponding to is sometimes called the end point of the Bézier curve.

[0041] The degree of the Bezier curve when setting the speed function is not particularly limited, but the corner R part L 2 Regarding the approach section L 2A The velocity function P A (t) is expressed as a cubic Bezier curve in the circular arc section L 2C The velocity function P C (t) is expressed as a quadratic Bezier curve, and the return interval L 2R The velocity function P R It is preferable to set each of (t) using a cubic Bezier curve.

[0042] In the example of Figure 4, the approach section L 2A The speed function P A (t) is the four points P -4 ,P -3 ,P -2 ,P -1 is the control point, and the starting point is point P -4 and the end point is P -1 The cubic Bezier curve is given by the circular arc segment L 2C The speed function P C (t) is the three points P -1 ,P 0 ,P 1 is the control point, and the starting point is point P -1 and the end point is P 1 In addition, the return interval L 2R The speed function P R (t) is the four points P 1 ,P 2 ,P 3 ,P 4 is the control point, and the starting point is point P 1 and the end point is P 4 is a cubic Bézier curve.

[0043] point P -4 ,P -3 ,P -2 ,P -1 ,P 0 ,P 1 ,P 2 ,P3 ,P 4 The coordinates of are as follows: JPEG2025019967000004.jpg75128

[0044] Here, it is preferable to make the slopes of the curves at the tangent points of adjacent Bezier curves the same so that they are smoothly connected. -1 In the adjacent velocity functions P A (t) and the velocity function P C (t) is point P -1 It is preferable that the points P and P have the same slope and are smoothly connected. 1 In the adjacent velocity functions P C (t) and the velocity function P R (t) is point P 1 It is preferable that the line segments P have the same slope and are smoothly connected. -1 P 0 , line segment P 0 P 1 On the extension of -2 , point P 2 Therefore, point P -2 , point P 2 ω is the Y coordinate value of -2 ,ω 2 is the triangle P in Figure 4. 0 P -2 P -2 ' and triangle P 0 P -1 P -1 Similarity ratio of ' and triangle P 0 P 2 P 2 ' and triangle P 0 P 1 P 1 Using the similarity ratio of ', the following formulas are used to calculate each. JPEG2025019967000005.jpg45128

[0045] Here, D A is the approach section L 2A The distance (approach distance) is D C is the circular arc section L 2CThe distance between R is the return section L 2R In the present invention, the distance of the section of the corner portion means the length (unit: mm) of the relative movement path in that section. Therefore, the circular arc section L 2C Distance D C is the circular arc section L 2C For example, D A is 0.12 mm, D R is 0.09mm, and the radius of the corner R is R in is 0.15mm, central angle θ Rin When the offset distance (machining gap distance) is 0.105 mm, D C is about 0.0707 mm. -2 , τ 2 is the approach distance D A Relative value (unit: %) to τ -2 ≦100,0≦τ 2 ≦100, for example, τ -2 = 40, τ 2 = 50. -3 , τ 3 is the return distance D R Relative value (unit: %) to τ -3 ≦100,0≦τ 3 ≦100, for example, τ -3 = 50, τ 3 = 60. ω A ,ω C ,ω R are the points P -1 ,P 0 ,P 1 The relative value of the servo feed rate (unit: %) at ω A =35, ω C = 30, and ω R =45.

[0046] Control point P -1 ,P 0 ,P 1 Therefore, the arc section L 2C The speed function P C(t) is defined as follows: P C (t)=(X C (t), Y C (t)) (0≦t≦1) (16) X C (t) = (1-t) 2 X -1 +2(1-t)tX 0 +t 2 X 1 (17) Y C (t) = (1-t) 2 Y -1 +2(1-t)tY 0 +t 2 Y 1 (18)

[0047] Control point P -4 ,P -3 ,P -2 ,P -1 Therefore, the approach section L 2A The speed function P A (t) is defined as follows: P A (t)=(X A (t), Y A (t)) (0≦t≦1) (19) X A (t) = (1-t) 3 X -4 +3(1-t) 2 tX -3 +3(1-t)t 2 X -2 +t 3 X -1 (20) Y A (t) = (1-t) 3 Y -4 +3(1-t) 2 tY -3 +3(1-t)t 2 Y -2 +t 3 Y -1 (twenty one)

[0048] Control point P 1 ,P 2 ,P 3 ,P4 Therefore, the return section L 2R The speed function P R (t) is defined as follows: P R (t)=(X R (t), Y R (t)) (0≦t≦1) (22) X R (t) = (1-t) 3 X 1 +3(1-t) 2 tX 2 +3(1-t)t 2 X 3 +t 3 X 4 (twenty three) Y R (t) = (1-t) 3 Y 1 +3(1-t) 2 tY 2 +3(1-t)t 2 Y 3 +t 3 Y 4 (twenty four)

[0049] In addition, τ -2 , τ 2 , τ -3 , τ 3 ,ω A ,ω C , and ω R can be set, for example, by searching for a value that provides an appropriate machining shape accuracy for the corner portion in test machining performed as a preliminary investigation.

[0050] In the speed function described above, the servo feedspeed is defined as a relative value SF. Therefore, even if the reference value of the servo feedspeed (for example, the absolute value of the servo feedspeed in a straight portion) differs for each cut as a machining condition, it is possible to set a suitable servo feedspeed for a corner portion by finding a correction value for the reference value using the speed function. In this case, since there is no need to set a speed parameter for each command block of the NC data, it is possible to control the servo feedspeed with a relatively small amount of data, and the burden of changing the NC program when changing the control conditions for the servo feedspeed is reduced.

[0051] 2.2.Outside corner R part The speed function is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner with respect to the moving distance in the outer corner R portion of the corner ^ portion. A preferred configuration of the speed function in the outer corner R portion will be described using the machining of the outer corner R shown in Figure 5 as an example. Note that the central angle θ of the circular arc shape of the outer corner R in Figure 5 Rout is 90°, but the central angle θ Rout is not limited to this example, and 0°<θ Rout Can be set in the range of <180°.

[0052] In the example shown in FIG. 5, the relative movement path of the wire electrode 2 is 6 Linear segment L ending at 4 , point A 6 From point A 10 Out corner R part L 5 , point A 10 Linear segment L starting from 6 In this order, the linear portion L where the processing load is approximately constant 4 The wire electrode 2, which was moving along the straight line L 4 End point of (out corner R part L 5 Point A, which is the start point of 6 When the wire electrode 2 reaches the outer corner R part L 5 Point A on the way 8 When it reaches , the machining load starts to increase, and the outer corner R part L 5 End point of the straight line segment L 6 Point A, which is the start point of 10 The increase in the machining load ends at the linear portion L 6 At this point, the processing load becomes substantially constant again.

[0053] Out corner R part L 5 The relative movement path of the wire electrode 2 in the approach section L 5A and the circular arc section L 5C and the return section L5R In the example shown in FIG. 5A is point A 6 From point A 7 The straight section between the arc section L 5C is point A 7 From point A 8 via point A 9 The return section L 5R is point A 9 From point A 10 It is a straight section up to point A. 8 is the circular arc section L 5C It is the midpoint that divides the area into two equal parts.

[0054] Approach section L 5A , circular arc section L 5C , and the return section L 5R The speed function in each section is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner from the servo feed speed at the start point of each section to the servo feed speed at the end point of each section with respect to the moving distance of the wire electrode 2. Here, in the approach section L 5A It is preferable that the speed function in the return section L where the processing load increases is set so that the servo feed speed increases in a curved manner with respect to the moving distance. 5R It is preferable that the speed function in the circular arc section L be set so that the servo feed speed decreases in a curved manner with respect to the moving distance. 5C The speed function in the section where the machining load decreases (in the example of Figure 5, point A 7 From point A 8 In the section where the servo feed rate increases in a curved manner with respect to the moving distance, the machining load increases (in the example of Fig. 5, point A 8 From point A 9 In the section up to the position where the servo feed speed is set, it is preferable that the servo feed speed is set so as to decrease in a curved manner with respect to the moving distance.

[0055] FIG. 6 shows the outer corner R portion L set using a Bezier curve in the example shown in FIG.5 1 is a graph showing an example of a velocity function of the wire electrode 2. The horizontal axis of the graph indicates the moving distance X (unit: mm) of the wire electrode 2 along the relative moving path, and the origin of the horizontal axis (X=0) is located within the circular arc section L 5C Midpoint A 8 The vertical axis of the graph indicates the relative value SF (unit: %) of the servo feed speed when the servo feed speed in the straight line portion is set to 100%.

[0056] The degree of the Bezier curve when setting the speed function is not particularly limited, but the out corner R part L 5 Regarding the approach section L 5A The velocity function P A (t) is expressed as a cubic Bezier curve in the circular arc section L 5C The velocity function P C (t) is expressed as a quadratic Bezier curve, and the return interval L 5R The velocity function P R It is preferable to set each of (t) using a cubic Bezier curve.

[0057] In the example of FIG. 6, the approach section L 5A The speed function P A (t) is the four points P -4 ,P -3 ,P -2 ,P -1 is the control point, and the starting point is point P -4 and the end point is P -1 The cubic Bezier curve is given by the circular arc segment L 5C The speed function P C (t) is the three points P -1 ,P 0 ,P 1 is the control point, and the starting point is point P -1 and the end point is P 1 In addition, the return interval L 5R The speed function P R (t) is the four points P 1 ,P 2 ,P 3 ,P 4 is the control point, and the starting point is point P 1 and the end point is P 4is a cubic Bézier curve.

[0058] point P -4 ,P -3 ,P -2 ,P -1 ,P 0 ,P 1 ,P 2 ,P 3 ,P 4 coordinates, and the velocity function P A (t),P C (t),P R The method for setting (t) is as described above for the corner radius part L 2 Since this is the same as the velocity function of ω, we will not explain it in detail. -2 ,ω 2 The calculation method is the same as for the corner radius. 5A Distance D A , circular arc section L 5C Distance D C , return section L 5R Distance D R For example, D A is 0.1 mm, D R is 0.1 mm, and the radius of the outer corner R is R out is 0.02mm, central angle θ Rout When the offset is 90° and the offset distance is 0.105 mm, D C is about 0.196 mm. -2 , τ 2 For example, τ -2 = 40, τ 2 = 40. -3 , τ 3 For example, τ -3 = 60, τ 3 = 80. ω A ,ω C , and ω R For example, ω A = 300, ω C = 350, and ω R =280.

[0059] 2.3. Corner edge part The speed function is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner with respect to the moving distance at the inside corner edge portion. A preferred configuration of the speed function at the inside corner edge portion will be described using the machining of the inside corner edge shown in FIG. 7 as an example. Note that the corner angle θ of the inside corner edge in FIG. Ein (the angle between the two straight contour lines that form the corner) is 90°, but the corner angle θ Ein is not limited to this example, and 0°<θ Ein Can be set in the range of <180°.

[0060] In the example shown in FIG. 7, the relative movement path of the wire electrode 2 is 11 Linear segment L ending at 7 , point A 11 From point A 13 Corner edge part L up to 8 , point A 13 Linear segment L starting from 9 In this order, the linear portion L where the processing load is approximately constant 7 The wire electrode 2, which was moving along the straight line L 7 End point (corner edge part L 8 Point A, which is the start point of 11 When the wire electrode 2 reaches the corner edge part L 8 Edge A in the middle 12 When it reaches L, the machining load starts to decrease. 8 End point of the straight line segment L 9 Point A, which is the start point of 13 The reduction in the machining load ends at the linear portion L 9 At this point, the processing load becomes substantially constant again.

[0061] In-corner edge part L 8 The relative movement path of the wire electrode 2 in the approach section L 8A and the return section L 8R In the example shown in FIG. 8A is point A11 From point A 12 The return section L is a straight section between 8R is point A 12 From point A 13 It is a straight section up to.

[0062] Approach section L 8A and return section L 8R The speed function in each section is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner from the servo feed speed at the start point of each section to the servo feed speed at the end point of each section with respect to the moving distance of the wire electrode 2. Here, in the approach section L where the machining load increases, 8A It is preferable that the speed function in the return section L where the servo feed speed decreases in a curved manner with respect to the moving distance is set. 8R The speed function in is preferably set so that the servo feed rate increases curvilinearly with respect to the travel distance.

[0063] FIG. 8 shows the inner corner edge portion L set using a Bezier curve in the example shown in FIG. 8 1 is a graph showing an example of a velocity function of the wire electrode 2. The horizontal axis of the graph indicates the moving distance X (unit: mm) of the wire electrode 2 along the relative movement path, and the origin of the horizontal axis (X=0) is the approach section L 8A and return section L 8R Point A, which is the border with 12 The vertical axis of the graph indicates the relative value SF (unit: %) of the servo feed speed when the servo feed speed in the straight line portion is set to 100%.

[0064] The degree of the Bezier curve when setting the speed function is not particularly limited, but the corner edge part L 8 Regarding the approach section L 8A The velocity function P A (t), and the return section L 8R The velocity function P R It is preferable to set (t) using a third-order Bezier curve.

[0065] In the example of FIG. 8, the approach section L 8A The speed function P A (t) is the four points P -3 ,P -2 ,P -1 ,P 0 is the control point, and the starting point is point P -3 and the end point is P 0 In addition, the return section L 8R The speed function P R (t) is the four points P 0 ,P 1 ,P 2 ,P 3 is the control point, and the starting point is point P 0 and the end point is P 3 is a cubic Bézier curve.

[0066] point P -3 ,P -2 ,P -1 ,P 0 ,P 1 ,P 2 ,P 3 The coordinates of are as follows: JPEG2025019967000006.jpg64128

[0067] Here, D A is the approach section L 8A The distance between R is the return section L 8R For example, D A is 0.1 mm, D R is 0.1 mm. Also, τ -1 , τ 1 is the approach distance D A Relative value (unit: %) to τ -1 ≦100,0≦τ 1 ≦100, for example, τ -1 = 80, τ 1 = 50. -2 , τ 2 Return Distance D RRelative value (unit: %) to τ -2 ≦100,0≦τ 2 ≦100, for example, τ -2 = 50, τ 2 = 50. ω C is the point P 0 The relative value of the servo feed rate (unit: %) at ω C =5.

[0068] In addition, point A 12 In order to form the apex of the inside corner edge with high accuracy, the wire electrode 2 may be stopped for a predetermined dwell time. In the example of FIG. 8, the wire electrode 2 is in the approach section L 8A Point A, the end point of 12 When it reaches ω, the servo feed rate is instantly C to 0 (point P on the graph) 0 From point T Dowell After the predetermined dwell time has elapsed, the servo feed speed is instantly reduced to ω C (on the graph, point T Dowell From point P 0 ), and in the return section L 8R Point A, the starting point of 12 The movement is resumed from point P 0 Servo feed rate ω C can be set to 0. In this case, point A 12 This eliminates the need for instantaneous gear changes.

[0069] Control point P -3 ,P -2 ,P -1 ,P 0 Therefore, the approach section L 8A The speed function P A (t) is defined as follows: P A (t)=(X A (t), Y A (t)) (0≦t≦1) (32) X A (t) = (1-t)3 X -3 +3(1-t) 2 tX -2 +3(1-t)t 2 X -1 +t 3 X 0 (33) Y A (t) = (1-t) 3 Y -3 +3(1-t) 2 tY -2 +3(1-t)t 2 Y -1 +t 3 Y 0 (34)

[0070] Control point P 0 ,P 1 ,P 2 ,P 3 Therefore, the return section L 8R The speed function P R (t) is defined as follows: P R (t)=(X R (t), Y R (t)) (0≦t≦1) (35) X R (t) = (1-t) 3 X 0 +3(1-t) 2 tX 1 +3(1-t)t 2 X 2 +t 3 X 3 (36) Y R (t) = (1-t) 3 Y 0 +3(1-t) 2 tY 1 +3(1-t)t 2 Y 2 +t 3 Y 3 (37)

[0071] 2.4.Outside corner edge The speed function is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner with respect to the moving distance at the outside corner edge. A preferred configuration of the speed function at the outside corner edge will be described using the machining of the outside corner edge shown in Figure 9 as an example. Note that the corner angle θ of the outside corner edge in Figure 9 is Eout (The angle between the two straight contour lines that form the corner, on the workpiece W side) is 75°, but the corner angle θ Eout is not limited to this example, and 0°<θ Eout Can be set in the range of <180°.

[0072] In the example shown in FIG. 9, the relative movement path of the wire electrode 2 is 14 Linear segment L ending at 11 , point A 14 From point A 20 Outer corner edge part L up to 12 , point A 20 Linear segment L starting from 13 In this order, the linear portion L where the processing load is approximately constant 11 The wire electrode 2, which was moving along the straight line L 11 End point (out corner edge part L 12 Point A, which is the start point of 14 When the wire electrode 2 reaches the outer corner edge L 12 and move to point A near the vertex of the outside corner edge (the intersection of the two straight lines that form the corner in the plan view of Figure 9). 15 From point A 19 After the machining load becomes 0 on the path up to, the machining load starts to increase and the outer corner edge part L 12 End point of the straight line segment L 13 Point A, which is the start point of 20 The increase in the machining load ends at the linear portion L 13 At this point, the processing load becomes substantially constant again.

[0073] Outer corner edge L 12The relative movement path of the wire electrode 2 in the approach section L 12A and the approach side avoidance section L 12AE and the skip section L 12S and the return side avoidance section L 12RE and the return section L 12R In the example shown in FIG. 12A is point A 14 From point A 15 The approach side avoidance section L is a straight section between 12AE is point A 15 From point A 16 The straight section between 12S is point A 16 From point A 17 via point A 18 The return side avoidance section L 12RE is point A 18 From point A 19 The return section L is a straight section between 12R is point A 19 From point A 20 It is a straight section up to point A. 17 is the skip section L 12S It is the midpoint that divides the area into two equal parts.

[0074] In the example of FIG. 9, the approach section L 12A and approach side avoidance section L 12AE and the return side avoidance section L 12RE and return section L 12R and are set to be on the same straight line, but the outside corner edge part L 12 The setting of the relative movement path in the approach side avoidance section L 12AE and return side avoidance section L 12RE However, the approach section L 12A and return section L 12R Alternatively, the curve may be set so as to bend with respect to the curve .

[0075] Approach section L 12A , Avoidance section on approach side L 12AE , return side avoidance section L 12RE , and the return section L 12R The speed function in each section is preferably set using a Bezier curve so that the servo feed speed changes in a curved manner from the servo feed speed at the start point of each section to the servo feed speed at the end point of each section with respect to the moving distance of the wire electrode 2. Here, in the approach section L 12A and approach side avoidance section L 12AE The speed function in the return side avoidance section L where the machining load increases is preferably set so that the servo feed speed increases in a curved manner with respect to the moving distance. 12RE and return section L 12R The speed function in is preferably set so that the servo feed rate decreases curvilinearly with respect to the travel distance.

[0076] Skip section L 12S is a relative movement path provided to form the apex of the outside corner edge with high accuracy. 12S In this case, the wire electrode 2 is moved quickly and instantaneously to point A. 16 From point A 18 In this embodiment, it is preferable to move the skip section L 12S The velocity function P S (t) is set so that the servo feedrate is constant with respect to the travel distance.

[0077] FIG. 11 shows the outer corner edge portion L set using a Bezier curve in the example shown in FIG. 12 1 is a graph showing an example of a speed function of the wire electrode 2. The horizontal axis of the graph indicates the moving distance X (unit: mm) of the wire electrode 2 along the relative moving path, and the origin of the horizontal axis (X=0) is the skip section L 12S Midpoint A 17 The vertical axis of the graph indicates the relative value SF (unit: %) of the servo feed speed when the servo feed speed in the straight line portion is set to 100%.

[0078] The degree of the Bezier curve when setting the speed function is not particularly limited, but the out-corner edge part L 12 Regarding the approach section L 12A The velocity function P A (t), approach side avoidance section L 12AE The velocity function P AE (t), return side avoidance section L 12RE The velocity function P RE (t), and the return section L 12R The velocity function P R It is preferable to set (t) using a quadratic Bezier curve.

[0079] In the example of FIG. 11, the approach section L 12A The speed function P A (t) is the three points P -5 ,P -4 ,P -3 is the control point, and the starting point is point P -5 and the end point is P -3 It is a quadratic Bezier curve. 12AE The speed function P AE (t) is the three points P -3 ,P -2 ,P -1 is the control point, and the starting point is point P -3 and the end point is P -1 It is a quadratic Bezier curve. The return side avoidance section L 12RE The speed function P RE (t) is the three points P 1 ,P 2 ,P 3 is the control point, and the starting point is point P 1 and the end point is P 3 A quadratic Bezier curve with the return interval L 12R The speed function P R (t) is the three points P 3 ,P 4 ,P 5 is the control point, and the starting point is point P 3 and the end point is P 5 is a quadratic Bézier curve.

[0080] point P -5 ,P -4 ,P -3 ,P -2 ,P -1 ,P 1 ,P 2 ,P 3 ,P 4 ,P 5 The coordinates of are as follows: JPEG2025019967000007.jpg70128

[0081] Here, point P -3 , point P 3 It is preferable to make the slopes of the curves at the tangent points of the line segment P consistent so that the adjacent Bezier curves are smoothly connected. -4 P -3 , line segment P 3 P 4 On the extension of -2 , point P 2 Therefore, point P -2 , point P 2 ω is the Y coordinate value of -2 ,ω 2 can be calculated using the following formulas, respectively. JPEG2025019967000008.jpg45128

[0082] Here, D A is the approach section L 12A The distance between R is the return section L 12R For example, D A is 0.1 mm, D R is 0.1 mm. 1 is the approach side avoidance section L 12AE This indicates the distance of, for example, the approach section L 12A The offset distance can be set equal to the offset distance in H 2 is the return side avoidance section L 12RE This indicates the distance of, for example, the return section L 12R The offset distance in the τ -4 , τ 4are the approach distances D A , return distance D R Relative value (unit: %) to τ -4 ≦100,0≦τ 4 ≦100, for example, τ -4 = 50, τ 4 = 60. ω A ,ω R are the points P -3 ,P 3 The relative value of the servo feed rate (unit: %) at ω A = 300, ω R = 600. ωs is the relative value (unit: %) of the servo feed speed from point P-1 to point P1. For example, ω S =10000.

[0083] Control point P -5 ,P -4 ,P -3 Therefore, the approach section L 12A The speed function P A (t) is defined as follows: P A (t)=(X A (t), Y A (t)) (0≦t≦1) (52) X A (t) = (1-t) 2 X -5 +2(1-t)tX -4 +t 2 X -3 (53) Y A (t) = (1-t) 2 Y -5 +2(1-t)tY -4 +t 2 Y -3 (54)

[0084] Control point P -3 ,P -2 ,P -1 Therefore, the approach side avoidance section L 12AE The speed function P AE (t) is defined as follows: PAE (t)=(X AE (t), Y AE (t)) (0≦t≦1) (55) X AE (t) = (1-t) 2 X -3 +2(1-t)tX -2 +t 2 X -1 (56) Y AE (t) = (1-t) 2 Y -3 +2(1-t)tY -2 +t 2 Y -1 (57)

[0085] Control point P 1 ,P 2 ,P 3 Therefore, the return side avoidance section L 12RE The speed function P RE (t) is defined as follows: P RE (t)=(X RE (t), Y RE (t)) (0≦t≦1) (58) X RE (t) = (1-t) 2 X 1 +2(1-t)tX 2 +t 2 X 3 (59) Y RE (t) = (1-t) 2 Y 1 +2(1-t)tY 2 +t 2 Y 3 (60)

[0086] Control point P 3 ,P 4 ,P 5 Therefore, the return section L 12R The speed function P R (t) is defined as follows: P R (t)=(X R (t), Y R (t)) (0≦t≦1) (61) X R (t) = (1-t) 2 X 3 +2(1-t)tX 4 +t 2 X 5 (62) Y R (t) = (1-t) 2 Y 3 +2(1-t)tY 4 +t 2 Y 5 (63)

[0087] In addition, the skip section L 12S The velocity function P S (t) is defined as follows: P S (t)=(X S (t), Y S (t)) (0≦t≦1) (64) X S (t)=(1-t)X -1 +tX 1 (65) Y S (t)=ω S (66)

[0088] In electrical discharge machining, after each discharge, a discharge rest period is provided during which the application of voltage to the machining gap is stopped to allow for the discharge and cooling of machining debris generated in the machining gap. In machining of the outer corner edge, the discharge rest period may be extended more than when machining a straight section in order to improve machining accuracy. Outer corner edge portion L 12 In the outer corner edge part L 12 A pause time function is set to define the discharge pause time for the distance traveled by the wire electrode 2 along the relative movement path in the outer corner edge portion L 12 In the embodiment, it is preferable to apply a voltage between the wire electrode 2 and the workpiece W based on the discharge pause time set using the pause time function. In the present embodiment, the pause time function is set by the machining condition setting unit 84 of the control device 9 as an electrical machining condition.

[0089] The pause time function is preferably set using a Bezier curve so that the discharge pause time changes in a curved manner with respect to the moving distance of the wire electrode 2. FIG. 12 shows the relationship between the outer corner edge portion L and the discharge pause time function set using a Bezier curve in the example shown in FIG. 12 1 is a graph showing an example of a pause time function of the relative movement path of the wire electrode 2. The horizontal axis of the graph indicates the movement distance X (unit: mm) of the wire electrode 2 along the relative movement path, and the origin of the horizontal axis (X=0) is the skip section L 12S Midpoint A 17 The vertical axis of the graph indicates the relative value OFF (unit: %) of the discharge pause time when the discharge pause time in the straight line portion is set to 100%.

[0090] The degree of the Bezier curve when setting the rest time function is not particularly limited, but the approach section L 12A The pause time function P A OFF (t), approach side avoidance section L 12AE The pause time function P AE OFF (t), return side avoidance section L 12RE The pause time function P RE OFF (t), and the return section L 12R The pause time function P R OFF It is preferable to set (t) using a quadratic Bezier curve.

[0091] In the example of FIG. 12, the approach section L 12A The pause time function P A OFF (t) is the three points P -5 OFF ,P -4 OFF ,P -3 OFF is the control point, and the starting point is point P -5 OFF and the end point is P -3 OFF It is a quadratic Bezier curve. 12AE The pause time function P AE OFF(t) is the three points P -3 OFF ,P -2 OFF ,P -1 OFF is the control point, and the starting point is point P -3 OFF and the end point is P -1 OFF It is a quadratic Bezier curve. The return side avoidance section L 12RE The pause time function P RE OFF (t) is the three points P 1 OFF ,P 2 OFF ,P 3 OFF is the control point, and the starting point is point P 1 OFF and the end point is P 3 OFF A quadratic Bezier curve with the return interval L 12R The pause time function P R OFF (t) is the three points P 3 OFF ,P 4 OFF ,P 5 OFF is the control point, and the starting point is point P 3 OFF and the end point is P 5 OFF is a quadratic Bézier curve.

[0092] point P -5 OFF ,P -4 OFF ,P -3 OFF ,P -2 OFF ,P -1 OFF ,P 1 OFF ,P 2 OFF ,P 3 OFF ,P 4 OFF ,P 5 OFF The coordinates of the dwell time function P AOFF (t),P AE OFF (t),P RE OFF (t),P R OFF How to set (t) and ω -2 OFF ,ω 2 OFF (Point P -2 OFF ,P 2 OFF The calculation method for the Y coordinate value of the outer corner edge part L 12 Since this is similar to the velocity function of

[0093] 2.5.Continuous corners The path of the wire electrode 2 moving relative to the workpiece W may include a continuous corner portion consisting of a plurality of consecutive corner portions. In machining a continuous corner consisting of two consecutive corners (referred to as a first corner and a second corner, respectively), the path of the wire electrode 2 in the continuous corner portion for machining the continuous corner preferably includes a first corner portion, a connection portion, and a second corner portion in this order. Note that the continuous corner in the present invention also includes a case where a linear machining target portion exists between the corners. Specifically, it is preferable to treat a case where the approach start point of the second corner is before the end point of the return portion of the first corner as a continuous corner. In this case, the speed distribution connecting the first corner and the second corner is set using a Bezier curve, but the optimal setting method varies depending on the positional relationship of the control points of the first corner and the second corner. In addition, the combination of continuous corners is a combination of a duplicated permutation of an in-corner R, an out-corner R, an in-corner edge, and an out-corner edge, so there are multiple patterns. Explaining all the patterns would require an enormous amount of space, so this time we will limit our explanation to the case where the first corner has an inside R and the second corner has an outside R, and the starting point of the approach to the second corner does not fit within the arc portion of the first corner.

[0094] A preferred configuration of the speed function in the continuous corner portion will be described with reference to the machining of the continuous corners shown in FIG. 13. In this example, the first corner is an inner corner R (central angle θ Rin =90°), and the second corner is the outside corner R (the central angle θ Rout = 90°). The wire electrode 2 is at point A 21 From point A 28 The continuous corners up to the first corner L 14 , connection part L 15 , second corner part L 16 The tool moves in this order, and EDM processing is performed on the first corner and then the second corner.

[0095] First corner part L 14 is a path for machining the first corner, and the approach section L 14A and the circular arc section L 14C Approach section L 14A is point A 21 From point A 22 The straight section between the arc section L 14C is point A 22 From point A 23 via point A 24 It is an arc-shaped section up to point A. 23 is the circular arc section L 14C It is the midpoint that divides the area into two equal parts.

[0096] Second corner part L 16 is a path for machining the second corner, and is a circular arc section L along the advancing direction of the wire electrode 2. 16C and the return section L 16R The circular arc section L includes 16C is point A 25 From point A 26 via point A 27 The return section L 16R is point A 27 From point A 28 It is a straight section up to point A. 26 is the circular arc section L 16CIt is the midpoint that divides the area into two equal parts.

[0097] Connection part L 15 is the first corner part L 14 and the second corner part L 16 In the example of FIG. 13, the connection part L 15 is point A 24 From point A 25 In this example, the wire electrode 2 passes through the first corner portion L 14 Approach section L 14A Point A, the starting point of 21 When it reaches the first corner part L, the machining load starts to increase. 14 The circular arc section L 14C Midpoint A 23 At the second corner L, the machining load changes from increasing to decreasing. 16 The circular arc section L 16C Midpoint A 26 The processing load continues to decrease until the intermediate point A 26 The machining load changes from decreasing to increasing at the second corner L 16 Return section L 16R Point A 28 In other words, the start point of the approach section in the movement path of the wire electrode 2 when machining the second corner as an independent corner is located in the return section in the movement path of the wire electrode 2 when machining the first corner as an independent corner.

[0098] FIG. 14 shows the continuous corner portion L set using a Bezier curve in the example shown in FIG. s 1 is a graph showing an example of a velocity function of the wire electrode 2. The horizontal axis of the graph indicates the moving distance X (unit: mm) of the wire electrode 2 along the relative moving path, and the origin of the horizontal axis (X=0) is the first corner portion L 14 The circular arc section L 14C Midpoint A 23 The vertical axis of the graph indicates the relative value SF (unit: %) of the servo feed speed when the servo feed speed in the straight line portion is set to 100%.

[0099] First corner part L 14 Approach section L 14A The speed function P A1 (t) and the arc section L 14C The speed function P C1 Regarding (t), the above-mentioned corner R part L 2 The speed function in the second corner part L 16 The circular arc section L 16C The speed function P C2 (t) and return section L 16R The speed function P R2 Regarding (t), the above-mentioned outer corner R part L 5 It can be set in the same way as the speed function in

[0100] Connection part L 15 The velocity function P J (t) is the first corner part L 14 Point A, the end point of 24 From the servo feed rate at the second corner part L 16 Point A, the starting point of 25 It is preferable that the servo feed speed is set using a Bezier curve so that the servo feed speed changes in a curved manner with respect to the moving distance of the wire electrode 2 up to the servo feed speed at point P 1 From point P -1 The speed function P J It is preferable that the graph of (t) be a curve. J The degree of the Bezier curve when setting (t) is not particularly limited, but if at least one of the multiple corner parts that make up the continuous corner part is an inner corner R part, a third-order Bezier curve is used to set the speed function P J It is preferable to set (t).

[0101] In this configuration, the first corner portion L 14 Velocity function of the second corner part L 16 The speed function of the connecting part L 15 The speed function P JIn this way, the servo feed speed of the wire electrode 2 can be changed in a curved manner in the continuous corner portions, thereby realizing a more suitable servo feed speed and improving the machining accuracy.

[0102] Connection part L 15 The velocity function P J An example of the setting of (t) is described below. In FIG. 14, the velocity function P R1 (t) is the speed function in the return section of the corner R portion when machining the first corner as a single corner R. The speed function P R1 (t) is the above-mentioned corner R part L 2 In the example of FIG. 14, the speed function P R1 (t) is the four points P 1 ,P 2 ,P 3 ,P 4 is the control point, and the starting point is point P 1 and the end point is P 4 is a cubic Bézier curve.

[0103] point P 1 ,P 2 The coordinates of are as follows: JPEG2025019967000009.jpg17128, where D C1 is the first corner part L 14 The circular arc section L 14C The distance between R1 indicates the distance of the return section when machining the first corner as a single inner corner R. ω R and ω 2 are the points P 1 ,P 2 is the relative value of the servo feed speed (unit: %) at τ 2 , 0≦τ 2 The value is appropriately set within the range of ≦100.

[0104] In FIG. 14, the velocity function P A2(t) is the speed function in the approach section of the outside corner R portion when machining the second corner as a single outside corner R. The speed function P A2 (t) is the above-mentioned outside corner R part L 5 In the example of FIG. 14, the speed function P A2 (t) is the four points P -4 ,P -3 ,P -2 ,P -1 is the control point, and the starting point is point P -4 and the end point is P -1 is a cubic Bézier curve.

[0105] point P -2 ,P -1 The coordinates of are as follows: JPEG2025019967000010.jpg16128, where D A2 indicates the distance of the approach section when machining the second corner as a single outside corner R. L is the connection part L 15 ω -2 and ω A are the points P -2 ,P -1 is the relative value of the servo feed speed (unit: %) at τ -2 , 0≦τ -2 The value is appropriately set within the range of ≦100.

[0106] Connection part L 15 The velocity function P J (t) is the four control points P 1 ,P 2 ,P -2 ,P -1 It is defined as follows using a cubic Bézier curve: P J (t)=(X J (t), Y J (t)) (0≦t≦1) (71) X J (t) = (1-t) 3 X 1 +3(1-t) 2 tX 2+3(1-t)t 2 X -2 +t 3 X -1 (72) Y J (t) = (1-t) 3 Y 1 +3(1-t) 2 tY 2 +3(1-t)t 2 Y -2 +t 3 Y -1 (73)

[0107] In addition, the first corner part L 14 and the second corner part L 16 The connection manner is not limited to the above example. For example, the start point of the approach section in the movement path of the wire electrode 2 when machining the second corner as an independent corner may be located in the circular arc section in the movement path of the wire electrode 2 when machining the first corner as an independent corner.

[0108] The first corner and the second corner may be an inner corner R, an outer corner R, an inner corner edge, or an outer corner edge, respectively. The consecutive corners are not limited to those consisting of two consecutive corners as in the above example, but may be those consisting of three or more consecutive corners.

[0109] 3. Wire EDM method Next, a method for wire electric discharge machining of a workpiece W using the wire electric discharge machining apparatus 100 according to this embodiment will be described.

[0110] The wire electric discharge machining method of this embodiment includes a function setting step. In the function setting step, the path of the wire electrode 2 is divided into a straight portion and a corner portion, and a speed function is set that specifies the servo feed speed for the moving distance along the path at the corner portion. Specifically, the servo condition setting unit 83 of the control device 9 sets the speed function based on conditions such as the corner shape and size of the machining target, the number of cuts, etc. The servo control unit 92 sets the servo feed speed at the corner portion using the set speed function, and outputs servo command data according to the servo feed speed to the movement control unit 91. The movement control unit 91 controls the movement device 5 according to the servo command data and the movement command data output from the command unit. As a result, the wire electrode 2 moves relatively to the workpiece W according to a predetermined path and servo feed speed while maintaining a predetermined machining gap.

[0111] The wire electric discharge machining method preferably includes a step of decoding the NC program to analyze the type of corner in the corner portion (corner analysis step), and, when the analyzed type of corner is an inner corner R portion, a step of controlling the servo feed speed so that it changes curvilinearly with respect to the travel distance in the inner corner R portion based on a speed function that is set in advance using a Bezier curve suitable for the inner corner R portion.More preferably, the wire electric discharge machining method includes a step of dividing the corner portion into an inner corner R portion, an outer corner R portion, an inner corner edge portion, and an outer corner edge portion, and, when the type of corner analyzed in the corner analysis step is a corner portion other than an inner corner R portion, controlling the servo feed speed so that it changes curvilinearly with respect to the travel distance in each corner portion based on a speed function that is set in advance using a Bezier curve suitable for the type of each corner portion.

[0112] In such a configuration, it is possible to construct an optimal speed distribution according to the type of corner, and more suitably suppress the deterioration of machining accuracy. As an example, the decoding unit 82 of the control device 9 decodes the NC program to analyze the type of corner and outputs the result to the servo condition setting unit 83, which sets a speed function suitable for the type of each corner portion, and the servo control unit 92 sets the servo feed speed based on the set speed function, thereby performing the above-mentioned control.

[0113] Various embodiments of the present invention have been described above, but these are presented as examples and are not intended to limit the scope of the invention. The novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and modifications thereof are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0114] 1: Processing machine body 2: Wire electrode 3: Wire guide mechanism 4:Power supply 5: Mobile device 8: Numerical control section 9: Control device 10: Table 11: Work stand 20: Saddle 31: Upper guide assembly 32: Lower guide assembly 33: Housing 34: Wire guide 35: Conductor 81: Input section 82: Decoding Department 83: Servo condition setting section 84: Processing setting section 85: Command department 86: Storage section 91: Movement control unit 92: Servo control unit 93: Power supply control section 100: Wire electric discharge machining device

Claims

1. A wire electric discharge machining apparatus including a moving device that drives a moving body and a control device that controls the moving device, the moving device is configured to move the wire electrode relative to the workpiece along a predetermined path in a machining progress direction while maintaining a predetermined gap between the wire electrode and the workpiece in accordance with a predetermined path and a predetermined servo feed rate, to machine the workpiece; the control device is configured to divide the path into a straight portion and a corner portion, and to set a speed function that defines the servo feed speed with respect to a moving distance of the wire electrode along the path in the corner portion; The wire electric discharge machining apparatus according to claim 1, wherein the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the moving distance at least in an inner corner R portion of the corner portion.

2. 2. The wire electric discharge machining apparatus according to claim 1, the path in the corner R portion includes an approach section, an arc section, and a return section in this order, the speed functions in the approach section, the arc section, and the return section are each set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the movement distance from the servo feedrate at the start point of each section to the servo feedrate at the end point of each section.

3. 3. The wire electric discharge machining apparatus according to claim 2, the speed function in the approach section is set using a third-order Bezier curve; the velocity function in the arc section is set using a quadratic Bezier curve; A wire electric discharge machining apparatus, wherein the velocity function in the return section is set using a third-order Bezier curve.

4. 3. The wire electric discharge machining apparatus according to claim 2, the speed function in the approach section is set so that the servo feed speed decreases in a curved manner with respect to the moving distance; A wire electric discharge machining apparatus, wherein the speed function in the return section is set so that the servo feed speed increases curvilinearly with respect to the movement distance.

5. 2. The wire electric discharge machining apparatus according to claim 1, the speed function is set using a Bezier curve such that the servo feed speed changes in a curved manner with respect to the movement distance at an outer corner R portion of the corner portion, the path in the out-corner R portion includes an approach section, an arc section, and a return section in this order, a wire electric discharge machining apparatus, wherein the speed functions in the approach section, the arc section, and the return section of the outer corner R portion are each set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the travel distance from the servo feedrate at the start point of each section to the servo feedrate at the end point of each section.

6. 6. The wire electric discharge machining apparatus according to claim 5, the speed function in the approach section of the outer corner R portion is set using a third-order Bezier curve, the speed function in the arc section of the outer corner R portion is set using a quadratic Bezier curve, The speed function in the return section of the outer corner R portion is set using a third order Bezier curve. This is a wire electric discharge machining device.

7. 6. The wire electric discharge machining apparatus according to claim 5, the speed function in the approach section of the outer corner R portion is set so that the servo feed speed increases curvilinearly with respect to the movement distance, A wire electric discharge machining apparatus, wherein the speed function in the return section of the outer corner R portion is set so that the servo feed speed decreases curvilinearly with respect to the movement distance.

8. 2. The wire electric discharge machining apparatus according to claim 1, the speed function is set using a Bezier curve such that the servo feed speed changes in a curved manner with respect to the moving distance at an inside corner edge portion of the corner portion; the path in the inside corner edge portion includes an approach section and a return section, the speed functions in the approach section and the return section of the corner edge portion are each set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the movement distance from the servo feedrate at the start point of each section to the servo feedrate at the end point of each section.

9. 9. The wire electric discharge machining apparatus according to claim 8, a speed function in the approach section and the return section of the inside corner edge portion is created using a third-order Bezier curve,

10. 9. The wire electric discharge machining apparatus according to claim 8, the speed function in the approach section of the corner edge portion is set so that the servo feed speed decreases curvilinearly with respect to the moving distance; A wire electric discharge machining apparatus, wherein the speed function in the return section of the corner edge portion is set so that the servo feed speed increases curvilinearly with respect to the movement distance.

11. 2. The wire electric discharge machining apparatus according to claim 1, the speed function is set using a Bezier curve such that the servo feed speed changes in a curved manner with respect to the movement distance at the outer corner edge portion of the corner portion; the path in the out-corner edge portion includes, in this order, an approach section, an approach-side avoidance section, a skip section, a return-side avoidance section, and a return section; a wire electric discharge machining apparatus, wherein the speed functions in the approach section, the approach side avoidance section, the return side avoidance section, and the return section of the outer corner edge portion are each set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the movement distance from the servo feedrate at the start point of each section to the servo feedrate at the end point of each section.

12. The wire electric discharge machining apparatus according to claim 11, a speed function in the approach section, the approach side avoidance section, the return side avoidance section, and the return section of the outer corner edge portion is set using a quadratic Bezier curve, respectively.

13. The wire electric discharge machining apparatus according to claim 11, the speed function in the approach section and the approach-side avoidance section of the outer corner edge portion is set so that the servo feed speed increases curvilinearly with respect to the moving distance, The speed function in the return section and the return-side avoidance section is set so that the servo feed speed decreases curvilinearly with respect to the moving distance.

14. The wire electric discharge machining apparatus according to claim 11, The speed function in the skip section is set so that the servo feed speed is constant with respect to the movement distance.

15. The wire electric discharge machining apparatus according to claim 11, the control device is configured to set a pause time function that defines a discharge pause time with respect to a moving distance of the wire electrode along the path at the outer corner edge portion, and to apply a voltage between the wire electrode and the workpiece at the outer corner edge portion based on the discharge pause time; A wire electric discharge machining apparatus, wherein the pause time function is set using a Bezier curve so that the discharge pause time changes curvilinearly with respect to the movement distance.

16. 2. The wire electric discharge machining apparatus according to claim 1, the path includes a continuous corner portion formed by a plurality of the corner portions being successively arranged, the path in the successive corner portions includes a first corner portion, a connection portion, and a second corner portion in this order; a wire electric discharge machining apparatus, wherein the speed function in the connection portion is set using a Bezier curve so that the servo feedrate changes curvilinearly with respect to the movement distance from the servo feedrate at the end point of the first corner portion to the servo feedrate at the start point of the second corner portion.

17. 17. The wire electric discharge machining apparatus according to claim 16, At least one of the plurality of corner portions is an inner corner R portion.

18. 18. The wire electric discharge machining apparatus according to claim 17, A wire electric discharge machining apparatus, wherein the velocity function in the connection portion is set using a third-order Bezier curve.

19. 1. A wire electric discharge machining method for machining a workpiece by moving a wire electrode relative to the workpiece while maintaining a predetermined gap between the wire electrode and the workpiece according to a predetermined path and a predetermined servo feed rate, comprising: dividing the path into a straight portion and a corner portion, and setting a speed function that defines the servo feed speed with respect to a moving distance of the wire electrode along the path at the corner portion; A wire electric discharge machining method, wherein the speed function is set using a Bezier curve so that the servo feed speed changes curvilinearly with respect to the movement distance at least in a corner R portion of the corner portion.

20. Decoding an NC program to analyze a type of corner in the corner portion; a step of controlling a servo feed speed in the inner corner R portion so that the servo feed speed changes curvilinearly with respect to the moving distance based on the speed function that is set in advance by using the Bezier curve suited to the inner corner R portion when the analyzed type of corner is an inner corner R portion; 20. The wire electric discharge machining method of claim 19, comprising:

21. The corner portion is divided into an inner corner R portion, an outer corner R portion, an inner corner edge portion, and an outer corner edge portion, a step of controlling the servo feed speed so as to change curvilinearly with respect to the moving distance based on the speed function set by using the Bezier curve suited to the type of each of the corner portions when the analyzed corner type is a corner portion other than the inner corner R portion; 21. The wire electric discharge machining method of claim 20, comprising:

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