Wire electrode electrical discharge machining device and wire electrode electrical discharge machining method

Abstract

Provided are a wire electrode electric discharge machining device and a wire electrode electric discharge machining method with which it is possible to improve the machining accuracy of a corner of a workpiece and to control the feed speed with a relatively small amount of data. Provided is a wire electrode electric discharge machining device provided with: a moving device for driving a moving body while maintaining a prescribed gap formed between a wire electrode and a workpiece on the basis of a prescribed path and a prescribed servo feed speed; the control device is configured so as to set a speed function which divides the path into a straight line portion and a corner portion, the speed function specifying a servo feed speed with respect to a movement distance of the wire electrode along the path of the corner portion, and the servo feed speed specifying a servo feed speed with respect to a movement distance of the wire electrode along the path of the corner portion. The speed function is set using a Bezier curve such that the servo feed speed varies curvilinear with respect to the displacement distance at least in an inner corner R portion of the corner portions.

Description

Technical Field

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

[0002] In the wire discharge machining process, a pulse voltage is applied between the wire and the workpiece to repeatedly generate discharges to remove material from the workpiece. At the same time, the wire and the workpiece are moved relative to each other at a predetermined feed speed and along a path pre-programmed in the NC program. In this way, the workpiece is machined into the desired machining shape. Generally speaking, in order to obtain sufficient machining accuracy in a shorter time, it is necessary to first perform rough machining, which is a first rough cutting when the workpiece is solid and scale-free, and then perform a second machining process on the end face of the workpiece as a finishing process. The higher the required machining accuracy, the more it is necessary to reduce the discharge energy in stages to finish the end face. In order to meet the target machining accuracy, it is sometimes necessary to further perform multiple machining processes such as third machining and fourth machining after the second machining of the finishing process (in other words, the number of cutting times needs to be increased). Since the more cutting times, the longer the machining time becomes, people hope to have a technology that can reduce the number of cutting times while meeting the target machining accuracy.

[0003] When machining a workpiece into a straight line, the wire electrode is usually moved at a predetermined feed rate. When machining a corner R or edge, in order to obtain the desired machining shape accuracy, it is necessary to increase or decrease the feed rate at the straight line according to the machining shape.

[0004] Patent document 1 discloses a wire discharge machining method, which reduces the feed speed of the wire before entering the corner, and after machining the corner at a constant feed speed, increases the feed speed again to the level before the speed reduction. As shown in the example of patent document 1, in the conventional corner machining process, in the speed change process from the speed value in the straight line machining process to the speed value suitable for the corner machining, and in the speed change process returning to the original speed value after the corner machining is completed, the feed speed of the wire changes linearly with respect to the moving distance (changes linearly with the moving distance).

[0005] In the prior art other than the electric discharge machining (e.g., Patent Document 2), a numerical control device for a machining machine tool for cutting machining is also disclosed. In the numerical control device, a parameter curve is generated according to the speed value specified in each instruction block, and the feed speed is changed according to the curve during the acceleration and deceleration process of the tool between the instruction blocks.

[0006] Prior art documents

[0007] Patent document 1: Japanese Patent Application Laid-Open No. 8-39356

[0008] Patent Document 2: Japanese Patent Application Publication No. 2020-9102 Summary of the invention

[0009] As described above, in order to achieve the goal of reducing processing time and energy consumption, it is necessary to achieve the target processing accuracy with fewer processing times (number of cutting times). In the process of processing a corner, when the feed speed of the electrode wire is changed linearly using the previous method described above, reducing the number of cutting times will cause "biting into the workpiece" (excessive removal relative to the working allowance, that is, the removal amount exceeds the working allowance) or residue (insufficient removal relative to the working allowance, that is, the removal amount is less than the working allowance), thereby reducing the processing accuracy. For example, in the case of processing a corner including an inner corner R, when the feed speed of the electrode wire is changed linearly, if the number of cutting times is reduced, it is easy to "bite into the workpiece" due to a short circuit between the electrode wire and the workpiece.

[0010] In order to prevent this kind of reduction in machining accuracy, we can try to divide the path of the electrode wire at the corner into small intervals, and then set a suitable feed speed for each small interval to make the speed change form a smoother curve. However, setting the feed speed for each small interval may cause the data stored in the database used to control the feed speed to become too large.

[0011] The present invention has been made in view of the above circumstances, and an object thereof is to provide a wire discharge machining device and a wire discharge machining method that can improve the machining accuracy of the corner of a workpiece and can control the feed speed with a relatively small amount of data.

[0012] According to the present invention, the following technical solutions are provided:

[0013] [1]: An electrode wire discharge machining device, comprising a moving device for driving a moving body and a control device for controlling the moving device, wherein the moving device maintains a specified gap between the electrode wire and the workpiece according to a specified path and a specified servo feed speed, while moving the electrode wire relative to the workpiece along the path in a machining direction, and processes the workpiece, and the control device is configured to set a speed function, wherein the path is divided into a straight portion and a corner portion, the speed function specifies a servo feed speed relative to a moving distance of the electrode wire along the path of the corner portion, and the speed function is set using a Bezier curve so that in at least the inner corner R portion of the corner portion, the servo feed speed changes in a curve relative to the moving distance.

[0014] [2]: The electrode wire discharge machining device described in [1], wherein the path of the inner corner R portion sequentially includes an approach section, an arc section, and a return section, and the speed functions of the approach section, the arc section, and the return section are respectively set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each section to the servo feed speed at the end point of each section.

[0015] [3]: The electrode wire discharge machining device described in [2], wherein the speed function of the approach interval is set using a third-order Bezier curve, the speed function of the arc interval is set using a second-order Bezier curve, and the speed function of the return interval is set using a third-order Bezier curve.

[0016] [4]: The wire discharge machining device described in [2] or [3], wherein the speed function of the approach interval is set so that the servo feed speed decreases in a curve relative to the moving distance, and the speed function of the return interval is set so that the servo feed speed increases in a curve relative to the moving distance.

[0017] [5]: An electrode wire discharge machining device 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 of the outer corner R portion of the corner portion changes in a curve relative to the moving distance, and the path of the outer corner R portion sequentially includes an approach section, an arc section, and a return section, and the speed functions of the approach section, the arc section, and the return section of the outer corner R portion are respectively set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each section to the servo feed speed at the end point of each section.

[0018] [6]: The electrode wire discharge machining device described in [5], wherein the speed function of the approach interval of the outer corner R part is set using a third-order Bezier curve, the speed function of the arc interval of the outer corner R part is set using a second-order Bezier curve, and the speed function of the return interval of the outer corner R part is set using a third-order Bezier curve.

[0019] [7]: The electrode wire discharge machining device described in [5] or [6], wherein the speed function of the approach interval of the outer corner R part is set so that the servo feed speed increases in a curve relative to the moving distance, and the speed function of the return interval of the outer corner R part is set so that the servo feed speed decreases in a curve relative to the moving distance.

[0020] [8]: An electrode wire discharge machining device as described in any one of [1] to [7], wherein the speed function is set using a Bezier curve so that the servo feed speed in the inner corner edge portion of the corner portion varies in a curve relative to the moving distance, the path of the inner corner edge portion includes an approach interval and a return interval, and the speed functions of the approach interval and the return interval of the inner corner edge portion are set respectively using a Bezier curve so that the servo feed speed varies in a curve relative to the moving distance from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval.

[0021] [9]: The wire discharge machining device described in [8], wherein the velocity functions of the approach section and the return section of the inner corner edge portion are generated using third-order Bezier curves respectively.

[0022]

[10] : An electrode wire discharge machining device as described in [8] or [9], wherein the speed function of the approach interval of the inner corner edge portion is set so that the servo feed speed decreases in a curve relative to the moving distance, and the speed function of the return interval of the inner corner edge portion is set so that the servo feed speed increases in a curve relative to the moving distance.

[0023]

[11] : An electrode wire discharge machining device as described in any one of [1] to

[10] , wherein the speed function is set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance at the outer corner edge portion of the corner portion, and the path of the outer corner edge portion sequentially includes an approach interval, an approach side avoidance interval, a crossing interval, a return side avoidance interval, and a return interval, and the speed functions of the approach interval, the approach side avoidance interval, the return side avoidance interval, and the return interval of the outer corner edge portion are respectively set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval.

[0024]

[12] : The wire discharge machining device described in

[11] , wherein the approach interval of the outer corner edge portion, the approach side avoidance interval, the return side avoidance interval, and the speed function of the return interval are respectively set using a second-order Bezier curve.

[0025]

[13] : An electrode wire discharge machining device as described in

[11] or

[12] , wherein the speed function of the approach section and the approach side avoidance section of the outer corner edge portion is set so that the servo feed speed increases in a curve relative to the moving distance, and the speed function of the return section and the return side avoidance section is set so that the servo feed speed decreases in a curve relative to the moving distance.

[0026]

[14] : The wire discharge machining device according to any one of

[11] to

[13] , wherein the speed function of the crossing interval is set so that the servo feed speed is constant relative to the moving distance.

[0027]

[15] : An electrode wire discharge machining device as described in any one of

[11] to

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

[0028]

[16] : An electrode wire discharge machining device as described in any one of [1] to

[15] , wherein the path includes a continuous corner portion composed of a plurality of the corner portions continuously, the path of the continuous corner portion continuously includes a first corner portion, a connecting portion, and a second corner portion in sequence, and a Bezier curve is used to set the speed function of the connecting portion so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the end point of the first corner portion to the servo feed speed at the starting point of the second corner portion.

[0029]

[17] : The wire discharge machining device described in

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

[0030]

[18] : The wire discharge machining device described in

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

[0031]

[19] : A wire discharge machining method, which comprises maintaining a specified gap between the wire and the workpiece according to a specified path and a specified servo feed speed while moving the wire relative to the workpiece to machine the workpiece, the wire discharge machining method comprising a process of setting a speed function, wherein the path is divided into a straight line portion and a corner portion, the speed function specifies the servo feed speed relative to the moving distance of the wire along the path of the corner portion, and a process of setting the speed function using a Bezier curve so that the servo feed speed varies in a curve relative to the moving distance in at least the inner corner R portion of the corner portion.

[0032]

[20] : The wire discharge machining method described in

[19] further comprises: a process of interpreting an NC program to analyze the type of the corner of the corner part; and when the type of the analyzed corner is an inner corner R part, in the inner corner R part, based on the speed function pre-set using the Bezier curve suitable for the inner corner R part, controlling the servo feed speed in a manner that changes in a curve relative to the moving distance.

[0033]

[21] : The wire discharge machining method described in

[20] further comprises: dividing the corner portion into the inner corner R portion, the outer corner R portion, the inner corner edge portion, and the outer corner edge portion; when the type of the analyzed corner is a corner portion other than the inner corner R portion, respectively in the corner portion, based on the speed function set using the Bezier curve corresponding to the type of each corner portion, controlling the servo feed speed in a manner that changes in a curve relative to the moving distance.

[0034] Effect of the invention:

[0035] In the wire discharge machining device of the present invention, a speed function is set, and the speed is used to specify the servo feed speed at the corner portion by a control device. The speed function is set using a Bezier curve so that at least in the inner corner R portion, the servo feed speed can change in a curve relative to the moving distance. In such a structure, the change of the servo feed speed of the wire electrode is close to a curve, and a suitable servo feed speed can be achieved and obtained at the corner portion, thereby improving the machining accuracy. In addition, by using a Bezier curve to set the speed function, it is possible to avoid the data required to control the servo feed speed from becoming huge. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 1 is a schematic diagram showing a wire electrical discharge machining device 100 according to an embodiment of the present invention.

[0037] Figure 2 This is a block diagram showing a control method of the wire electrical discharge machining device 100 .

[0038] Figure 3 FIG. 1 is an example of a relative movement path of the wire electrode 2 during machining of the inner corner R. FIG.

[0039] Figure 4 It means that the Bezier curve is used to set Figure 3 An example of the speed function of the inner corner R portion L2 is shown.

[0040] Figure 5 An example of the relative movement path of the wire electrode 2 during the outer corner R machining is shown.

[0041] Figure 6 It means that the Bezier curve is used to set Figure 5 An example of the speed function of the outer corner R portion L5 is shown.

[0042] Figure 7 FIG. 1 shows an example of the relative movement path of the wire electrode 2 during the inner corner edge machining process.

[0043] Figure 8 It means that the Bezier curve is used to set Figure 7 An example of the velocity function of the inner corner edge portion L8 is shown.

[0044] Fig. 9 FIG. 1 shows an example of the relative movement path of the wire electrode 2 during the outer corner edge machining process.

[0045] Fig.10 FIG. 2 shows another example of the relative movement path of the wire electrode 2 during the outer corner edge machining process.

[0046] Fig.11 It means that the Bezier curve is used to set Fig. 9 An example of the speed function of the outer corner side portion L12 is shown.

[0047] Fig.12 It means that the Bezier curve is used to set Fig. 9 An example of a stop time function of the outer corner edge portion L12 is shown.

[0048] Fig.13 FIG. 1 shows an example of a relative movement path of the wire electrode 2 during machining of a continuous corner composed of an inner corner R and an outer corner R. FIG.

[0049] Fig.14 It means that the Bezier curve is used to set Fig.13 An example of the velocity function for a continuous corner section is shown.

[0050] Figure numerals: 1: processing machine body; 2: electrode wire; 3: electrode wire guide mechanism; 4: power supply device; 5: moving device; 8: numerical control unit; 9: control device; 10: workbench; 11: workpiece support; 20: saddle; 31: upper guide assembly; 32: lower guide assembly; 33: shell; 34: electrode wire guide part; 35: current-carrying body; 81: input part; 82: interpretation part; 83: servo condition setting part; 84: processing setting part; 85: instruction part; 86: storage part; 91: movement control part; 92: servo control part; 93: power supply control part; 100: electrode wire discharge machining device. DETAILED DESCRIPTION

[0051] Next, embodiments of the present invention will be described with reference to the accompanying drawings. The various features shown in the embodiments described below can be combined with each other. In addition, each feature independently constitutes the present invention.

[0052] 1. Wire EDM Device

[0053] 1.1. Overall structure

[0054] like Figure 1 As shown, a wire electric discharge machining device 100 according to an embodiment of the present invention includes a machining machine body 1 including a wire electrode 2 and a control device 9 .

[0055] The processing machine body 1 includes an electrode wire 2, an electrode wire guide mechanism 3, a power supply device 4, and a moving device 5. The moving device 5 is configured to drive the moving body so that the electrode wire 2 is relatively moved relative to the workpiece W along the path in the processing direction to process the workpiece W while maintaining a predetermined gap (hereinafter referred to as "processing gap") formed between the electrode wire 2 and the workpiece W according to a predetermined path and a predetermined servo feed speed.

[0056] The wire guide mechanism 3 includes an upper guide assembly 31 and a lower guide assembly 32, which are respectively arranged on the upper side and the lower side of the workpiece W placed on the workpiece support 11. The upper guide assembly 31 and the lower guide assembly 32 respectively include a housing 33, a wire guide portion 34, and a current-carrying body 35, and various components are accommodated in the housing 33. The wire electrode 2 is positioned and guided by the wire guide portions 34 of the upper guide assembly 31 and the lower guide assembly 32. The current-carrying body 35 is connected to the power supply device 4. The current-carrying body 35 can move in a direction perpendicular to the extension direction of the wire electrode 2 guided by the wire guide portion 34, and the current-carrying body 35 is powered by contacting the wire electrode 2.

[0057] The moving device 5 includes a plurality of moving bodies in the direction of the control axis for moving the electrode wire 2 relative to the workpiece W, and a servo motor (not shown) for driving each moving body to move it. Under the control of the control device 9, the moving device 5 drives the servo motor of the moving body to move the electrode wire 2 relative to the workpiece W according to a predetermined path and a predetermined servo feed speed. The moving body can be configured in various ways according to the specifications of the electrode wire discharge machining device 100. For example, in Figure 1 In the electrode wire discharge machining device 100 shown, the worktable 10 provided with a workpiece support 11 can be used as a movable body that reciprocates along a horizontal straight line 1-axis direction (X-axis), and the saddle 20 carrying the worktable 10 can be used as a movable body that reciprocates along another horizontal straight line 1-axis direction (Y-axis) perpendicular to the X-axis direction.

[0058] 1.2. Control device 9

[0059] The control device 9 controls the operation of the wire electrical discharge machining device 100. Hereinafter, only the control related to the present invention among the control operations of the control device 9 will be described.

[0060] It should be noted that each component of the control device 9 can be implemented by software or by hardware. When implemented by software, various functions can be implemented by the CPU executing a computer program. The program can be stored in a built-in storage unit or in a non-temporary recording medium that can be read by a computer. In addition, it can also be implemented by reading a program stored in an external storage unit, that is, by the so-called cloud computing method. When implemented by hardware, various circuits such as ASIC (Application Specific Integrated Circuit), FPGA (Field Programmable Gate A rray), or DRP (Dynamically Reconfigurable Processor) can be used to implement it. In this embodiment, various information and concepts included therein are involved, which can all be represented by the high and low signal values ​​of a binary bit set composed of 0 or 1, and communication or calculation can be implemented by the above-mentioned software or hardware.

[0061] like Figure 2 As shown, the control device 9 of the present embodiment includes the numerical control unit 8 , a movement control unit 91 , a servo control unit 92 , and a power supply control unit 93 .

[0062] In the wire discharge machining process of the present embodiment, the wire electrode 2 is moved relative to the workpiece W by a servo method in which the machining gap is kept constant. Specifically, the wire electrode 2 is moved relative to the workpiece W according to the set servo feed speed by setting a suitable servo feed speed while keeping the machining gap constant.

[0063] The numerical control unit 8 includes an input unit 81, an interpretation unit 82, a servo condition setting unit 83, a processing condition setting unit 84, an instruction unit 85, and a storage unit 86 for storing various data required for control. The interpretation unit 82 reads the NC program input by the input unit 81 and obtains NC data, and then outputs it to the instruction unit 85. The instruction unit 85 generates movement instruction data based on the NC data and outputs it to the movement control unit 91. The movement instruction data is, for example, a position coordinate to which the electrode wire 2 should move in each instruction block. The movement control unit 91 controls the moving device 5 according to the movement instruction data. As a result, the electrode wire 2 can move relative to the workpiece W along a specified path.

[0064] The servo control unit 92 determines the appropriate servo feed speed based on the servo condition set by the servo condition setting unit 83 while keeping the size of the machining gap constant, and outputs the servo instruction data corresponding to the servo feed speed to the movement control unit 91. The movement control unit 91 controls the movement device 5 based on the servo instruction data. As a result, the electrode wire 2 can move relative to the workpiece W according to the specified servo feed speed. In other words, the movement control unit 91 controls the movement device 5 based on the movement instruction data and the servo instruction data, so that the electrode wire 2 can move relative to the workpiece W along the specified path in the direction of machining according to the specified servo feed speed while maintaining the specified machining gap.

[0065] An example of a control method for the servo control unit 92 to control the servo feed speed is described below. The servo control unit 92 obtains the average machining voltage detected by the inter-electrode voltage detection device (not shown). The so-called average machining voltage refers to a voltage obtained by averaging the inter-electrode voltage in the machining gap for each predetermined unit time and converting it into a signal. The servo control unit 92 outputs servo instruction data to the movement control unit 91 in accordance with a predetermined speed function set in advance so that the electrode wire 2 can move relatively in the machining direction at an appropriate servo feed speed corresponding to the difference between the servo reference voltage and the average machining voltage. The speed function is a function that represents the change in the servo feed speed based on the servo feed speed on a straight line in the interval from a certain relative position to a certain relative position on the horizontal plane of the electrode wire 2. In short, it is a function that represents the change in the feed speed relative to the moving distance. The speed function is set as a servo condition by the servo condition setting unit 83. For example, it can be set so that the servo feed speed 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, a good machining state can be maintained with a suitable servo feed speed while maintaining a constant machining gap, thereby achieving the desired machining accuracy and advancing the moving electrode wire 2 in the machining direction at a desired speed. It should be noted that when setting the servo feed speed, the discharge frequency (the number of discharges generated per unit time) can also be used instead of the average machining voltage.

[0066] The path (relative movement path) of the relative movement of the wire electrode 2 relative to the workpiece W is divided into a straight portion where the processing area (processing allowance) does not substantially change, and a corner portion where the processing area changes. The corner portion is a relative movement path for processing the workpiece W into a corner shape (angular shape). The straight portion is a portion of the relative movement path other than the corner portion, and is a relative movement path for processing the workpiece W into a straight shape.

[0067] In the straight section, it is preferred to use the speed function mentioned in the above example to control the servo feed speed. In the straight section, the machining load (machining amount per unit discharge machining time, machining amount per unit travel distance along the relative movement path) is usually approximately constant. Therefore, after controlling the servo feed speed as described above, during a period of good machining conditions, the electrode wire 2 moves relatively in the machining direction at a set servo feed speed that is approximately constant.

[0068] In the present invention, in the corner part, based on the change of the processing area caused by the electrode wire 2 moving along the relative movement path of the electrode wire 2 specified according to the processing shape (contour line) and its processing shape, in short, the corner part is divided into 4 types according to the different processing shapes, and the servo feed speed is controlled by different methods. Specifically, the corner part is divided into an arc-shaped "R" and an angle-shaped "side", and then the relative movement path of the electrode wire 2 is divided into an inner corner passing through the inner side of the corner part and an outer corner passing through the outer side in the area of ​​the corner R and the corner side. In the following description, the arc-shaped corner part on the inner side of the corner part through which the relative movement path of the electrode wire 2 passes is called the "inner corner R", the arc-shaped corner part on the outer side of the corner part through which the relative movement path passes is called the "outer corner R", the angular corner part on the inner side of the corner part through which the relative movement path passes is called the "inner corner edge", and the angular corner part on the outer side of the corner part through which the relative movement path passes is called the "outer corner edge".

[0069] At the corner portion, the machining load changes due to the change in the machining area of ​​the discharge machining surface on the surface of the electrode wire 2, depending on the shape of the corner of the machining object. As is well known, when the machining load causes the electrode wire 2 to move relatively at the corner portion at a constant servo feed speed during straight line machining, the machining process is sometimes interrupted due to frequent short circuits, which can lead to a decrease in machining accuracy. In order to improve machining accuracy, it is preferred to change the servo feed speed according to changes in the machining load. Specifically, it is preferred that the servo feed speed be reduced to a lower level than when machining the straight line portion in the portion where the machining load increases in the corner portion, and the servo feed speed be increased to a higher level than when machining the straight line portion in the portion where the machining load decreases.

[0070] The control device 9 sets a speed function, which is used to specify the servo feed speed relative to the moving distance of the electrode wire 2 moving along the relative moving path of the corner part. In the present 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 in at least the inner corner R part of the corner part so that the servo feed speed can change with respect to the moving distance curve. In the present embodiment, by using such a set speed function, the servo control unit 92 sets the servo feed speed of the corner part. The speed function is preferably set so that in the interval where the processing load of the corner part increases, the servo feed speed decreases with respect to the moving distance in a curve. In addition, the speed function can also be preferably set so that in the interval where the processing load at the corner part decreases, the servo feed speed increases with respect to the moving distance in a curve.

[0071] It should be noted that the change in the servo feed speed at the corner portion may start from a point on the straight path before the wire electrode 2 in the relative movement path reaches the corner of the workpiece W. In this case, the corner portion includes the straight path from the point where the speed change starts to occur until the wire electrode 2 reaches the corner. In addition, the change in the servo feed speed at the corner portion may end at a point on the straight path after the wire electrode 2 in the relative movement path passes the corner of the workpiece W. In this case, the corner portion includes the straight path from the wire electrode 2 passing the corner to the point where the speed change ends.

[0072] With such a structure, the servo feed speed of the electrode wire 2 at the corner portion is changed in a curve, so that the appropriate servo feed speed can be better achieved at the corner portion compared to the case where the servo feed speed is changed linearly, thereby improving the processing accuracy. In addition, because the servo feed speed is set using a speed function, the servo feed speed can be changed in a curve using less data compared to the case where the servo feed speed is changed in a curve by dividing the corner portion into a plurality of small intervals and setting the servo feed speed in each small interval.

[0073] In terms of reducing the number of cuts while preventing a decrease in machining accuracy, the control effect of the servo feed speed of the present invention is significant during the machining of the inner corner R where biting is prone to occur. Therefore, the present invention is effective at least when the servo feed speed control method involved in the present invention is used when machining the inner corner R. In addition, in the corner portion other than the inner corner R, by applying the servo feed speed control method of the present invention, an optimal speed distribution can be constructed, thereby improving the accuracy of the corner shape other than the inner corner R. In addition, compared with the case of controlling the servo feed speed only for the inner corner R using a prescribed speed function, the present invention can simplify the configuration of the control software, and at the same time has the advantage of suppressing the complexity of the control software specifications when machining shapes such as machining multiple corner portions continuously.

[0074] The power supply control unit 93 controls the power supply device 4 according to the electrical machining conditions set by the machining condition setting unit 84. In this way, a predetermined voltage can be applied to the machining gap at an appropriate timing.

[0075] 2. Speed ​​function

[0076] The speed function that defines the servo feed speed at the corner portion will be described in detail below.

[0077] 2.1. Inner corner R part

[0078] by Figure 3 The preferred configuration of the speed function of the inner corner R portion is explained by taking the processing of the inner corner R as an example. Figure 3 , Figure 5 , Figure 7 , Fig. 9 , Fig.10 , Fig.13 In the figure, the relative movement path indicated by the solid line with arrows indicates 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 of "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. Figure 3 , Figure 5 , Figure 7 , Fig. 9 , Fig.10 , Fig.13 In the figure, the machining allowance of the workpiece W for each cutting is omitted and not shown, and the outer edge of the workpiece W represents the outer edge after the machining allowance is removed by the discharge machining of the electrode wire 2 along the relative moving path. It should be noted that Figure 3 The center angle θ of the arc shape of the inner corner R Rin Although it is 90°, the center angle θ Rin Not limited to this example, it can be 0°<θ Rin It can be set within the range of <180°.

[0079] In such Figure 3 In the example shown, the relative movement path of the electrode wire 2 includes, in sequence, a straight line portion L1 with a terminal point A1, an inner corner R portion L2 from the terminal point A1 to the terminal point A5, and a straight line portion L3 with the terminal point A5 as the starting point. When the electrode wire 2, which has moved from the straight line portion L1 where the machining load is substantially constant, reaches the terminal point A1 of the straight line portion L1 (the starting point of the inner corner R portion L2), the machining load begins to increase. When the electrode wire 2 reaches the terminal point A3 midway of the inner corner R portion L2, the machining load turns to decrease, and the reduction of the machining load ends at the terminal point A5 of the inner corner R portion L2 (the starting point of the straight line portion L3), and the machining load returns to being substantially constant at the straight line portion L3.

[0080] It is preferred that the relative movement path of the wire electrode 2 at the inner corner R portion L2 includes the approaching sections L 2A 、arc interval L 2C , and return interval L 2R .exist Figure 3 In the example shown, the approximate interval L 2A The linear section from point A1 to point A2, the arc section L 2C It is an arc section from point A2 to point A3 and ends at point A4. 2RIt is a straight line section from point A4 to point A5. It should be noted that point A3 is a section that divides the arc section L into two equal parts. 2C The middle place.

[0081] Approaching interval L 2A 、arc interval L 2C , and return interval L 2R The speed functions at the positions are preferably set using Bezier curves so that the servo feed speed can change in a curve relative to the moving distance of the electrode wire 2 from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval. 2A The speed function is preferably set so that the servo feed speed decreases relative to the moving distance curve. In addition, the return interval L in which the machining load decreases 2R The speed function is preferably set so that the servo feed speed increases relative to the moving distance curve. In addition, the arc interval L is also preferably 2C The speed function at the interval where the machining load increases ( Figure 3 In the example shown, in the interval from point A2 to point A3, the servo feed speed decreases relative to the moving distance curve; in the interval where the machining load decreases ( Figure 3 In the section from point A3 to point A4 in the illustrated example, the servo feed speed increases with respect to the movement distance curve.

[0082] Figure 4 It means that Figure 3 An example of the velocity function of the inner corner R portion L2 set using a Bezier curve. The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path, and the origin of the horizontal axis (X=0) corresponds to the arc section L 2C The vertical axis of the graph represents the relative value SF (unit: %) of the servo feed speed when the servo feed speed of the straight line portion is 100%.

[0083] The Bezier curve is set with n+1 control points P0, P1, ..., P n In this case, the n-th order curve can be expressed by the following formula.

[0084]

[0085] In formula (1) n C k is the binomial coefficient expressed by formula (2).

[0086]

[0087] When the parameter t changes in the range of 0≦t≦1, the curve drawn by P(t) connects the control point P0 and the control point P n It should be noted that in the following description, the control points P0 and P1 at both ends of the Bezier curve are sometimes referred to as n The point equivalent to the control point P0 in is called the starting point of the Bezier curve. n The point is called the end point of the Bezier curve.

[0088] The order of the Bezier curve when setting the speed function is not particularly limited. In the inner corner R portion L2, it is preferred to respectively 2A The velocity function P A (t) Using the third-order Bezier curve, for the arc interval L 2C The velocity function P C (t) Use the second-order Bezier curve to return the interval L 2R The velocity function P R (t) is set using a third-order Bezier curve.

[0089] exist Figure 4 In the example, close to interval L 2A The velocity function P A (t) is P －4 , P －3 , P －2 , P －1 The 4 points are control points, among which the starting point is point P －4 The end point is P －1 The third-order Bezier curve. The arc interval L 2C The velocity function P C (t) is P －1 , P0, P13 points are control points, among which the starting point is point P －1 , a second-order Bezier curve with end point P1. In addition, the interval L is returned 2R The velocity function P R (t) is a third-order Bezier curve with four points P1, P2, P3, and P4 as control points, where the starting point is point P1 and the end point is P4.

[0090] Point P －4 , P －3 , P －2 , P －1 , P0, P1, P2, P3, P4 coordinates are as follows:

[0091] P －4 =(X －4 , Y －4 )=(-D A -D C / 2,100) (3)

[0092]

[0093]

[0094] P －1 =(X －1 , Y －1 )=(-D C / 2,ω A ) (6)

[0095] P0=(X0,Y0)=(0、ω C ) (7)

[0096] P1=(X1,Y1)=(D C / 2,ω R ) (8)

[0097]

[0098]

[0099] P4=(X4,Y4)=(D R +D C / 2,100) (11).

[0100] It is preferred that the slopes of the curves at the connection points are consistent so that adjacent Bezier curves are smoothly connected. －1 The velocity functions P of the adjacent A (t) and velocity function P C (t) is set to point P －1 have the same slope at point P1, so they can be smoothly connected together. C (t) and velocity function P R (t) is set to have the same slope at point P1 so that it can be smoothly connected together. In this case, －1 Set point P on the extension line of P0 and line segment P0P1 －2 , point P2. Point P －2 , the Y coordinate value of point P2 ω －2 , ω2 can be used respectively Figure 4 The triangle P0P in －2 P －2 ' and triangle P0P －1 P －1 The similarity ratio of ' and the similarity ratio of triangle P0P2P2' and triangle P0P1P1' are calculated by the formula shown below.

[0101]

[0102]

[0103]

[0104]

[0105] Among them, D A It means that the interval L is close to 2A Distance (approach distance), D C It represents the arc interval L 2C The distance, D R Indicates the return interval L 2R The distance of the corner section of the present invention refers to the length of the relative moving path within the section (unit: mm). Therefore, the arc section L 2C The distance D C It means: in the arc interval L 2C The length of the arc-shaped relative movement path in. For example, D A 0.12mm, D R The radius R of the inner corner is 0.09 mm. in is 0.15mm, the center angle θ Rin When the angle is 90° and the offset distance (processing gap distance) is 0.105 mm, D C About 0.0707mm. In addition, τ －2 , τ2 is relative to the approach distance D A The relative value (unit: %), which can be 0≦τ －2 ≦100, 0≦τ2≦100, for example, τ －2 =40, τ2 =50. －3 , τ3 is relative to the return distance D R The relative value (unit: %), which can be 0≦τ －3 ≦100, 0≦τ3≦100, for example, τ －3 =50, τ3=60. A ,ω C ,ω R At point P －1 , P0, P1 relative value of the servo feed speed (unit: %), for example, can be ω A =35,ω C =30, and ω R =45.

[0106] By control point P－1 , P0, P1, the arc interval L can be determined 2C The velocity function P C (t) is the formula shown below:

[0107] P C (t) = (X C (t), Y C (t)) (0≦t≦1) (16)

[0108] X C (t) = (1 - t) 2 X －1 +2(1-t)tX0+t 2 X1 (17)

[0109] Y C (t) = (1 - t) 2 Y －1 +2(1-t)tY0+t 2 Y1 (18).

[0110] By control point P －4 , P －3 , P －2 , P －1 , the approximate interval L can be determined 2A The velocity function P A (t) is the formula shown below:

[0111] P A (t) = (X A (t), Y A (t)) (0≦t≦1) (19)

[0112] 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)

[0114] Y A (t) = (1 - t) 3 Y －4 +3(1-t) 2 Y －3 +3(1-t)t 2 Y －2 +t 3 Y －1 (twenty one).

[0116] The return interval L can be determined by the control points P1, P2, P3, and P4. 2R The velocity function P R (t) is the formula shown below:

[0117] P R (t) = (X R (t), Y R (t)) (0≦t≦1) (22)

[0118] X R (t) = (1 - t) 3 X1+3(1-t) 2 tX2+3(1-t)t 2 X3+t 3 X4(23)

[0120] Y R (t) = (1 - t) 3 Y1+3(1-t) 2 tY2+3(1-t)t 2 Y3+t 3 Y4(24).

[0122] It should be noted that －2 , τ2, τ －3 ,τ3,ω A ,ω C , and ω R The setting can be made by searching for an appropriate value for the machining shape accuracy of the corner portion in a test machining performed as a preliminary investigation.

[0123] By using the speed function as described above, the servo feed speed can be specified as a relative value SF. Therefore, even if the reference value of the servo feed speed (for example, the absolute value of the servo feed speed in the straight line portion) as the processing condition for each cutting is different, the appropriate servo feed speed for the corner portion can be set by using the speed function to obtain the correction value of the reference value. In this case, since it is not necessary to set the speed parameter for each instruction block of NC data, the servo feed speed can be controlled with a relatively small amount of data, which can reduce the burden of changing the NC program when changing the control conditions of the servo feed speed.

[0124] 2.2. External corner R part

[0125] The speed function is preferably set using a Bezier curve so that the servo feed speed changes with respect to the moving distance in a curve at the outer corner R portion of the corner portion. Figure 5 Taking the outer corner R shown in the figure as an example, the preferred configuration of the speed function of the outer corner R portion is described. Figure 5The center angle θ of the arc shape of the outer corner R Rout is 90°, but the center angle θ Rout Not limited to this example, it can be 0°<θ Rout It can be set within the range of <180°.

[0126] exist Figure 5 In the example shown, the relative movement path of the electrode wire 2 includes a straight line portion L4 with the point A6 as the end point, a straight line portion L5 from the point A6 to the point A7, and a straight line portion L6 from the point A6 to the point A8. 10 The outer corner R portion L5 to the point A 10 The machining load starts to decrease when the wire electrode 2, which has moved from the straight line section L4 where the machining load is approximately constant, reaches point A6, which is the end point of the straight line section L4 (the starting point of the outer corner R section L5). The machining load starts to increase when the wire electrode 2 reaches point A8 halfway along the outer corner R section L5. 10 At , the increase in machining load ends, and at the straight line portion L6, the machining load becomes substantially constant again.

[0127] The relative movement path of the electrode wire 2 at the outer corner R portion L5 preferably includes the approaching interval L 5A 、arc interval L 5C , and return interval L 5R .exist Figure 5 In the example shown, the interval L 5A The linear section from point A6 to point A7, the arc section L 5C It is an arc section from point A7 to point A9 via point A8, and the return section L 5R It is from point A9 to point A 10 It should be noted that the location A8 is a straight line section that divides the arc section L into two equal parts. 5C The middle place.

[0128] Preferably close to interval L 5A 、arc interval L 5C , and return interval L 5R The speed functions of are set using Bessel so that the servo feed speed can change in a curve relative to the moving distance of the electrode wire 2 from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval. 5A The speed function is preferably set so that the servo feed speed increases relative to the moving distance curve. In addition, the return interval L in which the machining load increases 5RThe speed function is preferably set so that the servo feed speed decreases relative to the moving distance curve. 5C The speed function is preferably set to a range where the machining load decreases (e.g. Figure 5 In the example shown, the servo feed speed increases relative to the moving distance curve, while in the interval where the machining load increases (such as the interval from location A7 to location A8). Figure 5 In the example shown, in the section from point A8 to point A9, the servo feed speed decreases relative to the moving distance curve.

[0129] Figure 6 It means Figure 5 The example shown is an example of the velocity function of the outer corner R portion L5 set using a Bezier curve. The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path, and the origin of the horizontal axis (X=0) corresponds to the arc section L 5C The vertical axis of the graph represents the relative value SF (unit: %) of the servo feed speed when the servo feed speed at the straight line portion is 100%.

[0130] The order of the Bezier curve when setting the speed function is not particularly limited. It is preferred to use a third-order Bezier curve to set the proximity interval L at the outer corner R portion L5. 5A The velocity function P A (t), use the second-order Bezier curve to set the arc interval L 5C The velocity function P C (t), use the third-order Bezier curve to set the return interval L 5R The velocity function P R (t).

[0131] exist Figure 6 In the example, close to interval L 5A The velocity function P A (t) is P －4 , P －3 , P －2 , P －1 The 4 points are control points, among which the starting point is point P －4 The end point is P －1 The third-order Bezier curve. The arc interval L 5C The velocity function P C (t) is P －1 , P0, P13 points are control points, among which the starting point is point P －1 , a second-order Bezier curve with end point P1. In addition, the interval L is returned 5R The velocity function P R(t) is a third-order Bezier curve with four points P1, P2, P3, and P4 as control points, where the starting point is point P1 and the end point is P4.

[0132] Point P －4 , P －3 , P －2 , P －1 , the coordinates of P0, P1, P2, P3, P4, and the velocity function P A (t), P C (t), P R The setting method of (t) is the same as the speed function of the inner corner R portion L2 described above, and its detailed description is omitted. －2 The calculation method of ω2 is the same as that of the inner corner R. 5A The distance D A 、arc interval L 5C The distance D C 、Return interval L 5R The distance D R , for example D A 0.1mm, D R is 0.1mm, the radius Rout of the outer corner R is 0.02mm, and the center angle θ Rout When the angle is 90° and the offset distance is 0.105 mm, D C About 0.196mm. －2 , τ2, for example, is τ －2 =40, τ2 =40. －3 , τ3 is, for example, τ －3 =60, τ3=80. A ,ω C , and ω R For example, ω A =300,ω C =350, and ω R =280.

[0133] 2.3. Inner corner edge

[0134] The speed function is preferably set using a Bezier curve so that at the inner corner edge portion, the servo feed speed changes with respect to the moving distance in a curve. Figure 7 Taking the processing of the inner corner edge shown in the figure as an example, the preferred configuration of the speed function of the inner corner edge portion is described. Figure 7 The corner angle θ of the inner corner edge in Ein (The angle between the two straight lines forming the corner) is 90°, but the corner angle θ Ein Not limited to this example, it can be 0°<θ Ein<180° range for setting.

[0135] exist Figure 7 In the example shown, the relative movement path of the electrode wire 2 includes the following steps: 11 The straight line portion L7 from point A 11 To location A 13 The inner corner edge L8, at location A 13 When the wire electrode 2 moves from the straight line portion L7 where the machining load is substantially constant and reaches the end point of the straight line portion L7 (the starting point of the inner corner side portion L8), 11 After that, the machining load begins to increase. When the electrode wire 2 reaches the edge A halfway along the inner corner edge L8, 12 After that, the machining load turns to decrease, and at the end point A of the inner corner side portion L8 (the starting point of the straight line portion L9), 13 At , the reduction of the machining load ends, and at the straight line portion L9, the machining load becomes substantially constant again.

[0136] It is preferred that the relative movement path of the wire electrode 2 at the inner corner side portion L8 sequentially includes the approaching sections L 8A and return interval L 8R .exist Figure 7 In the example shown, the interval L 8A From location A 11 To location A 12 The linear interval between the two returns the interval L. 8R From location A 12 To location A 13 The straight line interval.

[0137] Approaching interval L 8A and return interval L 8R The speed function is preferably set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance of the electrode wire 2 from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval. 8A The speed function is preferably set so that the servo feed speed decreases relative to the moving distance curve. In addition, the return interval L in which the machining load decreases 8R The speed function is preferably set so that the servo feed speed increases with respect to the moving distance curve.

[0138] Figure 8 It means Figure 7The example shown is an example of the velocity function of the inner corner edge portion L8 set using a Bezier curve. The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path. The origin of the horizontal axis (X=0) is equivalent to the relative moving path, close to the interval L. 8A and return interval L 8R The boundary point A 12 The vertical axis of the graph represents the relative value SF (unit: %) of the servo feed speed when the servo feed speed at the straight line portion is 100%.

[0139] The order of the Bezier curve when setting the speed function is not particularly limited. It is preferred that a third-order Bezier curve be used to set the proximity interval L at the inner corner edge portion L8. 8A The velocity function P A (t), and the return interval L 8R The velocity function P R (t).

[0140] exist Figure 8 In the example, close to interval L 8A The velocity function P A (t) is P －3 , P －2 , P －1 , P04 points are control points, among which the starting point is point P －3 , a 3rd order Bezier curve with end point P0. Returns interval L 8R The velocity function P R (t) is a third-order Bezier curve with four points P0, P1, P2, and P3 as control points, where the starting point is point P0 and the end point is P3.

[0141] Point P －3 , P －2 , P －1 , P0, P1, P2, P3 coordinates are as follows:

[0142] P －3 =(X －3 , Y －3 )=(-D A , 100) (25)

[0143]

[0144]

[0145] P0=(X0,Y0)=(0、ω C ) (28)

[0146]

[0147]

[0148] P3=(X3,Y3)=(D R , 100) (31).

[0149] D A It means that the interval L is close to 8A The distance, D R Indicates the return interval L 8R For example, D A 0.1mm, D R 0.1mm. －1 , τ1 is relative to the approach distance D A The relative value (unit: %), which can be 0≦τ －1 ≦100, 0≦τ1≦100, for example, τ －1 =80, τ1 = 50. τ －2 , τ2 is relative to the return distance D R The relative value (unit: %), which can be 0≦τ －2 ≦100, 0≦τ2≦100, for example, τ －2 =50, τ2 = 50. ω C is the relative value of the servo feed speed at point P0 (unit: %), for example, it can be ω C =5.

[0150] It should be noted that at location A 12 In order to form the vertex of the inner corner edge with high precision, the electrode wire 2 can be stopped for a predetermined dwell time. Figure 8 In the example of 8A The end point A 12 When the servo feed speed is instantly changed from ω C Decrease to 0 (in the figure, the velocity is from point P0 to point T Dowell Reduce), the electrode wire 2 stops, and after the specified dwell time, the servo feed speed is instantly increased to ω C (In the figure, the velocity from point T Dowell Towards point P0), from the return interval L 8R The starting point of the location A 12 Restart the movement. It should be noted that the servo feed speed ω at point P0 can also be C Set to 0. In this case, no 12 Instant speed change.

[0151] By control point P －3 , P－2 , P －1 , P0, we can determine the proximity interval L 8A The velocity function P A (t) is as shown in the following formula:

[0152] P A (t) = (X A (t), Y A (t)) (0≦t≦1) (32)

[0153] X A (t) = (1 - t) 3 X －3 +3(1-t) 2 tX －2 +3(1-t)t 2 X －1 +t 3 X0(33)

[0155] Y A (t) = (1 - t) 3 Y －3 +3(1-t) 2 Y －2 +3(1-t)t 2 Y －1 +t 3 Y0(34).

[0157] From the control points P0, P1, P2, and P3, the return interval L can be determined. 8R The velocity function P R (t) is as shown in the following formula:

[0158] P R (t) = (X R (t), Y R (t)) (0≦t≦1) (35)

[0159] X R (t) = (1 - t) 3 X0+3(1-t) 2 tX1+3(1-t)t 2 X2+t 3 X3(36)

[0161] Y R (t) = (1 - t) 3 Y0+3(1-t) 2 tY1+3(1-t)t 2 Y2+t 3 Y3(37).

[0163] 2.4. Outer corner edge

[0164] The speed function is preferably set using a Bezier curve so that the servo feed speed can change in a curve relative to the moving distance at the outer corner edge. Fig. 9 Taking the processing of the outer corner edge portion shown in FIG. 1 as an example, the preferred configuration of the speed function of the outer corner edge portion is described. It should be noted that, Fig. 9 The corner angle θ of the outer corner edge in Eout (The angle of the contour lines of the two straight lines forming the corner on the workpiece W side) is 75°, but the corner angle θ Eout Not limited to this example, it can be 0°<θ Eout It can be set within the range of <180°.

[0165] exist Fig. 9 In the example shown, the relative movement path of the electrode wire 2 includes the following steps: 14 The straight line portion L is the end point 11 , from location A 14 To location A 20 The outer corner edge portion L 12 , and location A 20 The straight line portion L is the starting point 13 From the straight line portion L where the machining load is approximately constant 11 The moving electrode wire 2 reaches the straight line portion L 11 The end point (outer corner edge part L 12 The starting point of 14 After that, the machining load begins to decrease. The electrode wire 2 is at the outer corner edge L 12 Move, from the vertex of the outer corner edge ( Fig. 9 A point near the intersection of the contour lines of the two straight lines forming the corner in the top view 15 To location A 19 After the machining load on the path up to 0 becomes 0, the machining load starts to increase, and the machining load increases at the outer corner side L 12 The end point (straight line portion L 13 The starting point of 20 At the point where the machining load increases, the increase in the machining load ends and at the straight line portion L 13 At this point, the machining load becomes approximately constant again.

[0166] Outer corner edge part L 12 The relative movement path of the electrode wire 2 preferably includes the approaching intervals L in sequence along the moving direction of the electrode wire 2. 12A , Approaching side avoidance zone L 12AE , crossing the interval L 12S , Return side avoidance zone L 12RE , and return interval L12R .exist Fig. 9 In the example shown, the interval L 12A From location A 14 To location A 15 The linear interval between the approaching side avoidance interval L 12AE From location A 15 To location A 16 The straight line interval between the two, crossing the interval L 12S From location A 16 Passing by Location A 17 Arrive at location A 18 The linear section between the return side and the avoidance section L 12RE From location A 18 To location A 19 The linear interval between the two returns the interval L. 12R From location A 19 To location A 20 It should be noted that location A 17 is bisected across the interval L 12S The middle place.

[0167] It should be noted that Fig. 9 In the example, although it is close to the interval L 12A and approaching side avoidance interval L 12A E , and the return side avoidance zone L 12RE and return interval L 12R Set to be on the same straight line, but the outer corner side L 12 The setting of the relative movement path is not limited to this example. Fig.10 As shown, the approaching side avoidance interval L 12AE and the return side avoidance interval L 12RE The distances L and L can be set to be respectively in the direction away from the workpiece W relative to the approaching zone L. 12A and return interval L 12R The way it bends.

[0168] Approaching interval L 12A , Approaching side avoidance zone L 12AE , Return side avoidance zone L 12RE , and return interval L 12R The speed functions of are preferably set using Bezier curves so that the servo feed speed can change in a curve relative to the moving distance of the electrode wire 2 from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval. 12A and approaching side avoidance interval L 12AEThe speed function is preferably set such that the servo feed speed increases relative to the moving distance curve. In addition, the return side avoidance interval L where the machining load increases 12RE and return interval L 12R The speed function is preferably set so that the servo feed speed can be reduced relative to the moving distance curve.

[0169] Crossing interval L 12S This is a relative movement path set to form the vertex of the outer corner edge with high accuracy. 12S In the embodiment of the present invention, it is preferred to move the electrode wire 2 instantly and at high speed from point A to 16 Move to location A 18 In this embodiment, the interval L is crossed. 12S The velocity function P S (t) is set so that the servo feed speed remains constant relative to the moving distance.

[0170] Fig.11 It means that Fig. 9 In the example shown, the outer corner edge L is set using a Bezier curve. 12 The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path, and the origin of the horizontal axis (X=0) corresponds to the point where the electrode wire 2 crosses the interval L. 12S The middle point A 17 The vertical axis of the graph represents the relative value SF (unit: %) of the servo feed speed when the servo feed speed of the straight line portion is 100%.

[0171] The order of the Bezier curve when setting the speed function is not particularly limited, and the order of the outer corner edge L 12 , preferably close to interval L 12A The velocity function P A (t), approaching side avoidance interval L 12AE The velocity function P AE (t), return side avoidance zone L 12RE The velocity function P RE (t), and the return interval L 12R The velocity function P R (t) The second-order Bezier curve is used for setting.

[0172] exist Fig.11 In the example, close to interval L 12A The velocity function P A (t) is P －5 , P －4 , P －3 The three points are control points, among which the starting point is point P －5 The end point is P －3The second-order Bezier curve. Approaching side avoidance interval L 12AE The velocity function P AE (t) is P －3 , P －2 , P －1 The three points are control points, among which the starting point is point P －3 The end point is P －1 The second-order Bezier curve. Return side avoidance interval L 12RE The velocity function P RE (t) is a second-order Bezier curve with P1, P2, and P3 as control points, where the starting point is P1 and the end point is P3. Return interval L 12R The velocity function P R (t) is a second-order Bezier curve with points P3, P4, and P5 as control points, where the starting point is point P3 and the end point is P5.

[0173] Point P －5 , P －4 , P －3 , P －2 , P －1 , P1, P2, P3, P4, P5's coordinates are as follows:

[0174] P －5 =(X －5 , Y －5 )=(-D A -H1-D S / 2,100) (38)

[0175]

[0176] P －3 =(X －3 , Y －3 )=(-H1-D s / 2,ω A ) (40)

[0177] P －2 =(X －2 , Y －2 )=(-D s / 2,ω －2 ) (41)

[0178] P －1 =(X －1 , Y －1 )=(-D s / 2,ω S ) (42)

[0179] P1=(X1,Y1)=(D s / 2,ω S ) (43)

[0180] P2=(X2,Y2)=(D s / 2,ω2) (44)

[0181] P3=(X3,Y3)=(H1+D s / 2,ω R ) (45)

[0182]

[0183] P5=(X5,Y5)=(D R +H2+D S / 2,100) (47).

[0184] It is preferred that the slopes of the curves at the junctions are consistent so that at point P －3 , the adjacent Bezier curves at point P3 are smoothly connected. Specifically, on line segment P －4 P －3 Set points P on the extension lines of line segments P3P4 and P4 －2 and point P2. Therefore, point P －2 , the Y coordinate value of point P2 ω －2 , ω2 can be calculated by the following formula.

[0185]

[0186]

[0187]

[0188]

[0189] Among them, D A Indicates the proximity interval L 12A The distance, D R Indicates the return interval L 12R The distance. A For example, 0.1 mm, D R For example, it is 0.1 mm. H1 represents the approaching side avoidance zone L 12AE The distance can be set to the proximity interval L 12A The offset distance is equal. H2 represents the return side avoidance interval L 12RE The distance can be set to the return interval L 12R The offset distances are equal. In addition, τ －4 , τ4 are respectively related to the approach distance D A , return distance D RThe corresponding relative value (unit: %) can be 0≦τ －4 ≦100, 0≦τ4≦100 is a suitable value, for example, τ －4 =50, τ4=60. A ,ω R Point P －3 , the relative value of the servo feed speed of P3 (unit: %), for example, can be ω A =300,ω R = 600. The relative value (unit: %) of the servo feed speed from point P-1 to point P1 at ωs, for example, can be ω S =10000.

[0190] By control point P －5 , P －4 , P －3 , we can determine the close interval L 12A The velocity function P A (t) as follows:

[0191] P A (t) = (X A (t), Y A (t)) (0≦t≦1) (52)

[0192] X A (t) = (1 - t) 2 X －5 +2(1-t)tX －4 +t 2 X －3 (53)

[0193] Y A (t) = (1 - t) 2 Y －5 +2(1-t)tY －4 +t 2 Y －3 (54).

[0194] By control point P －3 , P －2 , P －1 , the approaching side avoidance interval L can be determined 12AE The velocity function P AE (t) as follows:

[0195] P AE (t) = (X AE (t), Y AE (t)) (0≦t≦1) (55)

[0196] X AE(t) = (1 - t) 2 X －3 +2(1-t)tX －2 +t 2 X －1 (56)

[0197] Y AE (t) = (1 - t) 2 Y －3 +2(1-t)tY －2 +t 2 Y －1 (57).

[0198] The return side avoidance interval L can be determined by the control points P1, P2, and P3. 12RE The velocity function P R E (t) as follows:

[0199] P RE (t) = (X RE (t), Y RE (t)) (0≦t≦1) (58)

[0200] X RE (t) = (1 - t) 2 X1+2(1-t)tX2+t 2 X3 (59)

[0201] Y RE (t) = (1 - t) 2 Y1+2(1-t)tY2+t 2 Y3 (60).

[0202] From the control points P3, P4, and P5, the return interval L can be determined. 12R The velocity function P R (t) as follows:

[0203] P R (t) = (X R (t), Y R (t)) (0≦t≦1) (61)

[0204] X R (t) = (1 - t) 2 X3+2(1-t)tX4+t 2 X5 (62)

[0205] Y R (t) = (1 - t) 2 Y3+2(1-t)tY4+t 2 Y5 (63).

[0206] Crossing interval L 12S The velocity function P S (t) is defined as follows:

[0207] P S (t) = (X S (t), Y S (t)) (0≦t≦1) (64)

[0208] X S (t) = (1 - t) X －1 +tX1 (65)

[0209] Y S (t) = ω S (66).

[0210] In EDM, after each discharge is completed, a discharge pause time is set to stop applying voltage to the machining gap, so that the machining chips generated in the machining gap can be discharged and cooled. When machining an outer corner, in order to improve machining accuracy, the discharge pause time is sometimes extended to make it longer than the machining straight part. It is preferred to stop the discharge at the outer corner part L 12 , for the outer corner edge L 12 The discharge suspension time function is set based on the movement distance of the electrode wire 2 of the relative movement path, and the discharge suspension time is set based on the outer corner side portion L 12 The discharge pause time set by the pause time function is used to apply a voltage between the wire electrode 2 and the workpiece W. In the present embodiment, the pause time function is set as an electromechanical machining condition by the machining condition setting unit 84 of the control device 9 .

[0211] The suspension time function is preferably set using a Bezier curve so that the discharge suspension time can change in a curve relative to the moving distance of the electrode wire 2 . Fig.12 is Fig. 9 In the example, the outer corner edge portion L is set using a Bezier curve 12 The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path, and the origin of the horizontal axis (X=0) corresponds to the point where the electrode wire 2 crosses the interval L. 12S The middle point A 17 The vertical axis of the graph represents the relative value OFF (unit: %) of the discharge suspension time when the discharge suspension time of the straight line portion is 100%.

[0212] The order of the Bezier curve when setting the stop time function is not particularly limited, but it is preferable to use a second-order Bezier curve to set the approach interval L. 12A The termination time function P AOFF (t), approaching side avoidance interval L 12AE The termination time function P AE OFF (t), return side avoidance zone L 12RE The termination time function P RE OFF (t), and the return interval L 12R The termination time function P R OFF (t).

[0213] exist Fig.12 In the example, close to interval L 12A The termination time function P A OFF (t) is P －5 OFF , P －4 OFF , P －3 OFF The three points are control points, among which the starting point is point P －5 OFF The end point is P －3 OFF The second-order Bezier curve. Approaching side avoidance interval L 12AE The termination time function P AE OFF (t) is P －3 OFF , P －2 OFF , P －1 OFF The three points are control points, among which the starting point is point P －3 OFF The end point is P －1 OFF The second-order Bezier curve. Return side avoidance interval L 12RE The termination time function P RE OFF (t) is based on P1 OFF 、P2 OFF 、P3 OFF The three points are control points, of which the starting point is point P1 OFF , the end point is P3 OFF The second-order Bezier curve of the interval L is returned. 12R The termination time function P R OFF (t) is based on P3 OFF 、P4 OFF 、P5 OFF The three points are control points, of which the starting point is point P3 OFF , the end point is P5OFF A Bezier curve of order 2.

[0214] Point P －5 OFF , P －4 OFF , P －3 OFF , P －2 OFF , P －1 OFF 、P1 OFF 、P2 OFF 、P3 OFF 、P4 OFF 、P5 OFF The coordinates of the termination time function P A OFF (t), P AE OFF (t), P RE OFF (t), P R OFF (t) setting method, and ω －2 OFF ω2 OFF (Point P －2 OFF 、P2 OFF The calculation method of the Y coordinate value of the outer corner edge L described above is the same as that of the outer corner edge L described above. 12 The speed function is the same as that of FIG. 1 , and its detailed description is omitted.

[0215] 2.5. Continuous Corners

[0216] The path of the electrode wire 2 when it moves relative to the workpiece W can also include a continuous corner portion composed of multiple corner portions. When processing a continuous corner composed of two corners (referred to as "the first corner" and "the second corner"), the path of the electrode wire 2 used to process the continuous corner portion of the continuous corner preferably includes the first corner portion, the connecting portion, and the second corner portion in sequence. It should be noted that the continuous corners in the present invention also include the case where there is a linear processing object portion between the corners. Specifically, it is preferred to treat the case where the approach start point of the second corner is ahead of the end point of the return portion of the first corner as a continuous corner. The Bezier curve is used to set the speed distribution connecting the first corner and the second corner at this time, but the most suitable setting method will be different due to the positional relationship between the control points of the first corner and the second corner. In addition, the combination of continuous corners will also exist in various situations due to the different combinations of the repetition order of the inner corner R, the outer corner R, the inner corner side, and the outer corner side. Since it would take a lot of space to explain all the situations, here we will explain the situation where the first corner is the inner corner R, the second corner is the outer corner R, and the approach starting point of the second corner does not enter the arc portion of the first corner.

[0217] by Fig.13 Taking the processing of continuous corners shown in FIG. 1 as an example, the preferred configuration of the speed function of the continuous corner portion is described. In this example, the first corner is the inner corner R (the center angle of the arc shape is θ Ri n =90°), the second corner is the outer corner R (the center angle of the arc shape is θ Rout =90°). From point A 21 To location A 28 The continuous corner portion to the first corner portion L 14 , connection part L 15 , 2nd corner part L 16 Move in sequence and perform discharge machining on the first corner and the second corner in turn.

[0218] 1st corner part L 14 This is the path used to process the first corner. Along the direction of travel of the electrode wire 2, it includes the approach interval L in sequence. 14A and arc interval L 14C . Approaching interval L 14A From location A 21 To location A 22 The linear interval between the arc interval L 14C From location A 22 Passing by Location A 23 Arrival at location A 24 It should be noted that location A23 is the arc interval L that is bisected 14C The middle place.

[0219] 2nd corner part L 16 The path used to process the second corner includes the arc sections L in sequence along the traveling direction of the electrode wire 2. 16C and return interval L 16R . Arc interval L 16C From location A 25 Passing by Location A 26 Arrival at location A 27 The arc-shaped interval up to the return interval L 16R From location A 27 To location A 28 It should be noted that point A 26 is the arc interval L divided into two equal parts 16C The middle place.

[0220] Connection part L 15 Connect the first corner part L 14 and the second corner part L 16 Path. Fig.13 In the example, the connection part L 15 From location A 24 To location A 25 In this example, when the wire electrode 2 reaches the first corner portion L 14 The approach interval L 14A Starting point A 21 After that, the machining load begins to increase, and at the first corner part L 14 The arc interval L 14C The middle point A 23 At the second corner L, the machining load changes from increasing to decreasing. 16 The arc interval L 16C The middle point A 26 Until then, the processing load continues to decrease and reaches the middle point A 26 At the second corner, the machining load changes from decreasing to increasing. 16 The return interval L 16R Location A 28 That is, in the return section of the moving path of the wire electrode 2 when machining the first corner as the single corner, there is a starting point of the approach section of the moving path of the wire electrode 2 when machining the second corner as the single corner.

[0221] Fig.14 It means Fig.13The continuous corner portion L set using the Bezier curve shown in the example s The horizontal axis of the figure represents the moving distance X (unit: mm) of the electrode wire 2 moving along the relative moving path, and the origin of the horizontal axis (X=0) corresponds to the first corner portion L 14 The arc interval L 14C The middle point A 23 The vertical axis of the graph represents the relative value SF (unit: %) of the servo feed speed when the servo feed speed of the straight line portion is 100%.

[0222] 1st corner part L 14 The approach interval L 14A The velocity function P A1 (t) and arc interval L 14C The velocity function P C1 (t) can be set in the same manner as the speed function at the inner corner R portion L2 described above. 16 The arc interval L 16C The velocity function P C2 (t) and return interval L 16R The velocity function P R2 (t) can be set in the same manner as the speed function at the outer corner R portion L5 described above.

[0223] Connection part L 15 The velocity function P J (t) It is preferable to use a Bezier curve to set the first corner portion L 14 The end point A 24 Servo feed speed to the second corner part L 16 The starting point of the location A 25 The servo feed speed varies with respect to the moving distance of the electrode wire 2. Fig.14 In the example, the connection from point P1 to point P －1 The velocity function P J The change line graph of (t) is preferably a curve. Set the speed function P J The order of the Bezier curve at (t) is not particularly limited, but when at least one of the plurality of corner portions constituting the continuous corner portion is an inner corner R portion, it is preferable to use a third-order Bezier curve to set the speed function P J (t).

[0224] In such a structure, the first corner portion L 14 The velocity function and the second corner part L 16 The speed function is connected by the part L 15 The velocity function PJ (t) connected in a smooth curve. Thus, in the continuous corner portion, the servo feed speed of the electrode wire 2 is changed in a curve manner, so that the appropriate servo feed speed can be better achieved, thereby improving the processing accuracy.

[0225] The following describes the connection part L 15 The velocity function P J An example of setting (t). Fig.14 The speed function P is shown by the dashed line R1 (t) is the speed function of the return section of the inner corner R when the first corner is processed as a single inner corner R. Speed ​​function P R1 (t) can be set in the same manner as the velocity function of the inner corner R portion L2 shown above. Fig.14 In the example, the speed function P R1 (t) is a third-order Bezier curve with four points P1, P2, P3, and P4 as control points, where the starting point is point P1 and the end point is P4.

[0226] The coordinates of points P1 and P2 are as follows:

[0227] P1=(X1,Y1)=(D C1 / 2,ω R ) (67)

[0228]

[0229] Among them, D C1 Indicates the first corner part L 14 The arc interval L 14C The distance, D R1 Indicates the distance of the return section when machining the first corner as a single inner corner R. ω R and ω2 are the relative values ​​of the servo feed speed at points P1 and P2, respectively (unit: %). τ2 is a value that can be appropriately set within the range of 0≦τ2≦100.

[0230] exist Fig.14 The dashed line shows the velocity function P A2 (t) is the velocity function of the approach section of the outer corner R portion when the second corner is processed as a single outer corner R. Velocity function P A2 (t) can be set in the same manner as the speed function at the outer corner R portion L5 as shown above. Fig.14 In the example, the speed function P A2 (t) is P －4 , P －3 , P －2 , P －1The 4 points are control points, among which the starting point is point P －4 The end point is P －1 A Bezier curve of degree 3.

[0231] Point P －2 , P －1 The coordinates are as follows:

[0232]

[0233] P －1 =(X －1 , Y －1 )=(D C1 / 2+L、ω A ) (70).

[0234] Among them, D A2 It indicates the distance of the approach interval when the second corner is processed as a separate outer corner R. L indicates the connection part L 15 The distance. －2 and ω A Point P －2 , P －1 The relative value of the servo feed speed at τ (unit: %). －2 It can be 0≦τ －2 A suitable value to be set within the range of ≤100.

[0235] Connection part L 15 The velocity function P J (t) Using four control points P1, P2, P －2 , P －1 The determined third-order Bezier curve is determined as shown in the following formula.

[0236] P J (t) = (X J (t), Y J (t)) (0≦t≦1) (71)

[0237] X J (t) = (1 - t) 3 X1+3(1-t) 2 tX2+3(1-t)t 2 X －2 +t 3 X －1 (72)

[0239] Y J (t) = (1 - t) 3 Y1+3(1-t) 2 tY2+3(1-t)t 2 Y－2 +t 3 Y －1 (73)

[0241] It should be noted that the first corner portion L 14 and the second corner part L 16 For example, the starting point of the approach interval in the moving path of the electrode wire 2 when the second corner is processed as a single corner may fall within the arc interval on the moving path of the electrode wire 2 when the first corner is processed as a single corner.

[0242] In addition, the first corner and the second corner may be any one of an inner corner R, an outer corner R, an inner corner side, and an outer corner side. The continuous corners are not limited to the one consisting of two continuous corners as shown in the above example, but may be one consisting of three or more continuous corners.

[0243] 3. Wire EDM method

[0244] Next, a wire electric discharge machining method of a workpiece W using the wire electric discharge machining device 100 according to the present embodiment will be described.

[0245] The wire discharge machining method of this embodiment includes a function setting process. In the function setting process, a speed function is set, specifically, the path of the wire electrode 2 is divided into a straight part and a corner part, and the speed function is used to specify the servo feed speed relative to the moving distance when the relative movement is performed along the path of the corner part. Specifically, the servo condition setting unit 83 of the control device 9 sets the speed function based on conditions such as the corner shape, size, or number of cuts of the processing object. The servo control unit 92 uses the set speed function to set the servo feed speed at the corner part, and outputs the servo instruction data corresponding to the servo feed speed to the movement control unit 91. The movement control unit 91 controls the moving device 5 according to the servo instruction data and the movement instruction data output from the command unit. As a result, the wire electrode 2 maintains the specified processing gap while moving relative to the workpiece W according to the specified path and servo feed speed.

[0246] In addition, the wire discharge machining method preferably further comprises a step of interpreting the NC program to analyze the type of the corner of the corner portion (corner analysis step), and when the type of the analyzed corner is an inner corner R portion, in the inner corner R portion, based on a speed function that is pre-set using a Bezier curve that is suitable for the inner corner R portion, the step of controlling the servo feed speed so that it changes in a curve with respect to the moving distance. In addition, the wire discharge machining method preferably further comprises dividing the corner portion into an inner corner R portion, an outer corner R portion, an inner corner side portion, and an outer corner side portion, and when the type of the analyzed corner in the above-mentioned corner analysis step is a corner portion other than the inner corner R portion, in each of the different corner portions, based on a speed function that is set using a Bezier curve that is suitable for the type of each corner portion (or that is suitable for the type of each corner portion), the step of controlling the servo feed speed so that it changes in a curve with respect to the moving distance.

[0247] According to such a structure, the most suitable speed distribution can be constructed for the type of corner, so that the reduction of processing accuracy can be further appropriately suppressed. It should be noted that, as an example, the type of corner can be analyzed by the interpretation unit 82 of the control device 9 interpreting the NC program and outputting it to the servo condition setting unit 83, and then the servo condition setting unit 83 sets a speed function suitable for the type of each corner part, and based on the set speed function, the servo control unit 92 controls the servo feed speed to achieve the above control.

[0248] The above contents describe various embodiments of the present invention, but these contents are only given as examples and are not intended to limit the scope of the invention. The novel embodiments may also be implemented in various other ways, and various omissions, substitutions, and changes may be made without departing from the main purpose of the invention. The embodiments and their variations are all included in the scope and main purpose of the present invention, and are included in the invention described in the claims and their equivalents.

Claims

1. A wire discharge machining device comprising a moving device for driving a moving body and a control device for controlling the moving device, wherein: The moving device maintains a predetermined gap between the wire electrode and the workpiece according to a predetermined path and a predetermined servo feed speed, and moves the wire electrode relative to the workpiece along the path in a processing direction to process the workpiece, thereby processing the workpiece. The control device is configured to set a speed function, wherein the path is divided into a straight portion and a corner portion, the speed function prescribes a servo feed speed relative to a moving distance of the wire electrode along the path of the corner portion, The speed function is set using a Bezier curve so that the servo feed speed changes with respect to the moving distance in a curve at least in the inner corner R portion of the corner portion.

2. The wire discharge machining device according to claim 1, wherein: The path of the inner corner R portion includes an approach section, an arc section, and a return section in sequence. The speed functions of the approach section, the arc section, and the return section are respectively set using Bezier curves so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each section to the servo feed speed at the end point of each section.

3. The wire discharge machining device according to claim 2, wherein: The speed function of the approach interval is set using a third-order Bezier curve, The speed function of the arc interval is set using a second-order Bezier curve, The speed function of the return interval is set using a third-order Bezier curve.

4. The wire discharge machining device according to claim 2, wherein: The speed function of the approach section is set so that the servo feed speed decreases in a curve relative to the moving distance. The speed function of the return section is set so that the servo feed speed increases in a curve with respect to the moving distance.

5. The wire discharge machining device according to claim 1, wherein: The speed function is set using a Bezier curve so that the servo feed speed of the outer corner R portion of the corner portion changes in a curve relative to the moving distance, The path of the outer corner R portion includes an approach section, an arc section, and a return section in sequence. The speed functions of the approach interval, the arc interval, and the return interval of the outer corner R part are set respectively using Bezier curves so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval.

6. The wire electrical discharge machining device according to claim 5, wherein: The speed function of the approaching interval of the outer corner R portion is set using a third-order Bezier curve, The speed function of the arc section of the outer corner R is set using a second-order Bezier curve, The speed function of the return section of the outer corner R portion is set using a third-order Bezier curve.

7. The wire electrical discharge machining device according to claim 5, wherein: The speed function of the approach section of the outer corner R portion is set so that the servo feed speed increases in a curve relative to the moving distance. The speed function of the return section of the outer corner R portion is set so that the servo feed speed decreases in a curve with respect to the moving distance.

8. The wire electrical discharge machining device according to claim 1, wherein: The speed function is set using a Bezier curve so that at the inner corner edge portion of the corner portion, the servo feed speed changes with respect to the moving distance in a curve. The path of the inner corner edge portion includes an approach section and a return section, The speed functions of the approach section and the return section of the inner corner side portion are respectively set using Bezier curves so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each section to the servo feed speed at the end point of each section.

9. The wire electrical discharge machining device according to claim 8, wherein: The speed functions of the approach section and the return section of the inner corner side portion are respectively generated using third-order Bezier curves.

10. The wire electrical discharge machining device according to claim 8, wherein: The speed function of the approach section of the inner corner side portion is set so that the servo feed speed decreases in a curve relative to the moving distance. The speed function of the return section of the inner corner side portion is set so that the servo feed speed increases in a curve with respect to the moving distance.

11. The wire electrical discharge machining device according to claim 1, wherein: The speed function is set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance at the outer corner edge of the corner portion. The path of the outer corner side portion includes an approach section, an approach side avoidance section, a crossing section, a return side avoidance section, and a return section in sequence. The approach interval, the approach side avoidance interval, the return side avoidance interval, and the speed function of the return interval of the outer corner edge portion are respectively set using a Bezier curve so that the servo feed speed changes in a curve relative to the moving distance from the servo feed speed at the starting point of each interval to the servo feed speed at the end point of each interval.

12. The wire electrical discharge machining device according to claim 11, wherein: The approach section, the approach side avoidance section, the return side avoidance section, and the speed function of the return section of the outer corner side portion are respectively set using a second-order Bezier curve.

13. The wire electrical discharge machining device according to claim 11, wherein: The speed function of the approach section and the approach side avoidance section of the outer corner side portion is set so that the servo feed speed increases in a curve relative to the moving distance. The speed functions of the return section and the return-side avoidance section are set so that the servo feed speed decreases in a curve with respect to the moving distance.

14. The wire electrical discharge machining device according to claim 11, wherein: The speed function of the crossing section is set so that the servo feed speed is constant with respect to the moving distance.

15. The wire electrical discharge machining device according to claim 11, wherein: The control device is configured to set a pause time function that specifies a discharge pause time relative to a moving distance of the wire electrode along the path of the outer corner edge portion, and is configured to apply a voltage between the wire electrode and the workpiece at the outer corner edge portion based on the discharge pause time. The suspension time function is set using a Bezier curve so that the discharge suspension time varies with respect to the moving distance in a curve.

16. The wire electrical discharge machining device according to claim 1, wherein: The path includes a continuous corner portion formed by a plurality of the corner portions continuously. The path of the continuous corner portion sequentially and continuously includes a first corner portion, a connecting portion, and a second corner portion, The speed function of the connection portion is set using a Bezier curve so that the servo feed speed changes in a curve with respect to the movement distance from the servo feed speed at the end point of the first corner portion to the servo feed speed at the start point of the second corner portion.

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

18. The wire electrical discharge machining device according to claim 17, wherein: The speed function of the connection portion is set using a third-order Bezier curve.

19. A wire discharge machining method, comprising: machining the workpiece by moving the 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 speed, The wire discharge machining method comprises a process of setting a speed function, wherein: the path is divided into a straight portion and a corner portion, the speed function specifies the servo feed speed relative to the moving distance of the electrode wire along the path of the corner portion, The process of setting the speed function using a Bezier curve so that the servo feed speed changes with respect to the moving distance in a curve at least in the inner corner R portion of the corner portion.

20. The wire electrical discharge machining method according to claim 19, further comprising: a step of interpreting an NC program and analyzing the type of the corner of the corner portion; and When the type of corner to be analyzed is an inner corner R portion, a process is provided for controlling the servo feed speed in the inner corner R portion in a manner that changes in a curve relative to the moving distance based on the speed function that is pre-set using the Bezier curve suitable for the inner corner R portion.

21. The wire electrical discharge machining method according to claim 20, further comprising: The corner portion is divided into the inner corner R portion, the outer corner R portion, the inner corner side portion, and the outer corner side portion, When the type of corner to be analyzed is a corner portion other than the inner corner R portion, the process is to control the servo feed speed in a manner that changes in a curve relative to the moving distance, respectively, at the corner portions based on the speed function set using the Bezier curve corresponding to the type of each corner portion.

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