Wire electric discharge machine control device and method for controlling a wire electric discharge machine

Abstract

In a control device (18) for a wire electric-discharge machining machine (10), if it has been determined that the length of a route defined by two blocks is equal to or less than the diameter of a wire electrode (12), a route shape determination unit (32) determines whether the shape of the route defined by the two blocks is a right corner or a left corner on the basis of the coordinates of three points established from origin points and end points of the two blocks. If it has been determined that the shape of the route is a left corner or a right corner, an inner / outer corner determination unit (36) determines whether the shape of the route is an inner corner or an outer corner on the basis of an offset direction.

Description

[Technical field]

[0001] The present invention relates to a control device for a wire electric discharge machine and a control method for a wire electric discharge machine. [Background technology]

[0002] Japanese Patent Application Laid-Open No. 2021-041475 discloses a wire electric discharge machine. The wire electric discharge machine changes machining conditions according to a path shape defined by a machining program, thereby improving the machining accuracy of the workpiece. Summary of the Invention

[0003] A curved path shape may be defined by combining multiple blocks that define a very short path. In this case, the machining shape cannot be determined from the movement command of each block. Therefore, the wire electric discharge machine disclosed in JP 2021-041475 A has a problem that the machining accuracy of the workpiece is low.

[0004] The present invention aims to solve the above-mentioned problems.

[0005] A first aspect of the present invention is a control device for a wire electric discharge machine that performs electric discharge machining on a workpiece by applying a voltage between the wire electrode and the workpiece while moving the wire electrode relative to the workpiece in accordance with a machining program that defines a program path, the control device including a minimum block determination unit that determines whether or not a length of a path defined by each of two consecutive blocks is equal to or less than a diameter of the wire electrode, and a minimum block determination unit that, when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, determines whether or not the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode based on the coordinates of three points determined by start points and end points of the two consecutive blocks. the machining program includes a path shape determination unit that determines whether the path shape defined by two consecutive blocks is a right corner that bends to the right in the direction of travel of the wire electrode, or a left corner that bends to the left in the direction of travel; an offset direction acquisition unit that acquires the offset direction in the two consecutive blocks from the machining program; an inside / outside corner determination unit that determines whether the path shape is an inside corner or an outside corner based on the offset direction when it is determined that the path shape is a left corner or a right corner; and an electric discharge machining control unit that controls electric discharge machining based on the determination result of the inside / outside corner determination unit.

[0006] A second aspect of the present invention is a control method for a wire electric discharge machine that performs electric discharge machining on a workpiece by applying a voltage between the wire electrode and the workpiece while moving the wire electrode relative to the workpiece in accordance with a machining program that defines a program path, the control method including a very small block determination step of determining whether or not a length of a path defined by each of two consecutive blocks is equal to or less than a diameter of the wire electrode, and a step of determining whether or not a length of the path defined by each of two consecutive blocks is equal to or less than a diameter of the wire electrode when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode based on the coordinates of three points determined from start points and end points of two consecutive blocks. the path shape determination step determining whether the path shape defined by two of the blocks is a right corner that bends to the right in the direction of travel of the wire electrode, or a left corner that bends to the left in the direction of travel; an offset direction acquisition step acquiring an offset direction in two successive blocks from the machining program; an inside / outside corner determination step determining whether the path shape is an inside corner or an outside corner based on the offset direction when it is determined that the path shape is a left corner or a right corner; and an electric discharge machining control step controlling the electric discharge machining based on a result of the determination in the inside / outside corner determination step.

[0007] According to the present invention, the machining accuracy of the workpiece can be improved. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram showing a wire electric discharge machine. [Diagram 2] FIG. 2 is a table showing combinations of G codes indicating circular interpolation and G codes indicating offset directions, and the correspondence between inner corners and outer corners. [Diagram 3] FIG. 3 is a schematic diagram showing an example of a path having an outer corner shape. [Figure 4] FIG. 4 is a diagram for explaining a method for determining a route shape. [Diagram 5] FIG. 5 is a diagram for explaining a method for determining a route shape. [Figure 6]FIG. 6 is a diagram for explaining a method for determining a route shape. [Figure 7] FIG. 7 is a flowchart showing the flow of a route shape determination process performed by the control device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] [First embodiment] [Wire EDM machine configuration] 1 is a schematic diagram showing a wire electric discharge machine 10. The wire electric discharge machine 10 applies a voltage between a wire electrode 12 and a workpiece 14 (hereinafter sometimes referred to as an electrode gap) to generate an electric discharge. This causes the workpiece 14 to be machined by electric discharge. The wire electric discharge machine 10 has a machine body 16 and a control device 18.

[0010] The processing machine body 16 has a processing power supply 20, an X-axis motor 22, and a Y-axis motor 24. The processing power supply 20 applies a voltage between the poles. The X-axis motor 22 and the Y-axis motor 24 move a work table (not shown). The workpiece 14 fixed to the work table moves together with the work table, whereby the wire electrode 12 moves relative to the workpiece 14.

[0011] The control device 18 has a calculation unit 26 and a storage unit 28. The calculation unit 26 is a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The calculation unit 26 has a minimal block determination unit 30, a path shape determination unit 32, an offset direction acquisition unit 34, an inside / outside corner determination unit 36, and an electric discharge machining control unit 38. The minimal block determination unit 30, the path shape determination unit 32, the offset direction acquisition unit 34, the inside / outside corner determination unit 36, and the electric discharge machining control unit 38 are realized by the calculation unit 26 executing a program stored in the storage unit 28. At least a part of the minimal block determination unit 30, the path shape determination unit 32, the offset direction acquisition unit 34, the inside / outside corner determination unit 36, and the electric discharge machining control unit 38 may be realized by an integrated circuit such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array). At least a portion of the minimum block determination unit 30, the path shape determination unit 32, the offset direction acquisition unit 34, the inside / outside corner determination unit 36 ​​and the electric discharge machining control unit 38 may be realized by electronic circuits including discrete devices.

[0012] The memory unit 28 is composed of a volatile memory (not shown) and a non-volatile memory (not shown). The volatile memory is, for example, a random access memory (RAM). The non-volatile memory is, for example, a read only memory (ROM) or a flash memory. Data, for example, is stored in the volatile memory. Programs, tables, maps, for example, are stored in the non-volatile memory. At least a part of the memory unit 28 may be provided in the above-mentioned processor, integrated circuit, etc. At least a part of the memory unit 28 may be mounted on a device connected to the wire electric discharge machine 10 via a network.

[0013] [About paths with corner shapes] A path with a corner shape is usually defined by a block having the G code "G02" or "G03" which indicates circular interpolation. A path shape defined by a block having the G code "G02" is a right corner. A path shape defined by a block having the G code "G03" is a left corner. A right corner is a path shape that curves to the right in the direction of travel of the wire electrode 12. A left corner is a path shape that curves to the left in the direction of travel of the wire electrode 12.

[0014] In this case, it is possible to determine whether the path shape is an inside corner or an outside corner by the combination of a G code indicating circular interpolation and a G code indicating an offset direction. Fig. 2 is a table showing the combination of a G code indicating circular interpolation and a G code indicating an offset direction, and the correspondence between the inside corner and the outside corner. An inside corner is a path shape in which the surface of the workpiece 14 after machining is convex toward the inside of the workpiece 14. An outside corner is a path shape in which the surface of the workpiece 14 after machining is convex toward the outside of the workpiece 14.

[0015] As shown in FIG. 2, the combination of the G code "G03" indicating a left corner and the G code "G41" indicating a left offset determines that the path shape is an inside corner. As shown in FIG. 2, the combination of the G code "G03" indicating a left corner and the G code "G42" indicating a right offset determines that the path shape is an outside corner. As shown in FIG. 2, the combination of the G code "G02" indicating a right corner and the G code "G41" indicating a left offset determines that the path shape is an outside corner. As shown in FIG. 2, the combination of the G code "G02" indicating a right corner and the G code "G42" indicating a right offset determines that the path shape is an inside corner.

[0016] The electric discharge machining control unit 38 adjusts the machining conditions according to the path shape. The electric discharge machining control unit 38 outputs command values ​​to the machining power supply 20, the X-axis motor 22, the Y-axis motor 24, etc. based on the adjusted machining conditions. This controls the electric discharge machining of the workpiece 14. Specifically, the electric discharge machining control unit 38 controls the machining speed, the number of applications, etc. according to the path shape. The machining speed is the relative movement speed of the wire electrode 12 with respect to the workpiece 14. The number of applications is the number of times a voltage is applied between the electrodes per unit time.

[0017] For example, when the path shape is an inner corner, the electric discharge machining control unit 38 slows down the machining speed compared to when the path shape is a straight line. Also, when the path shape is an inner corner, the electric discharge machining control unit 38 slows down the machining speed the greater the curvature of the path shape. When the path shape is an inner corner, the electric discharge machining control unit 38 increases the number of applications compared to when the path shape is a straight line. Also, when the path shape is an inner corner, the electric discharge machining control unit 38 increases the number of applications the greater the curvature of the path shape.

[0018] For example, when the path shape is an outer corner, the electric discharge machining control unit 38 increases the machining speed compared to when the path shape is a straight line. Also, when the path shape is an outer corner, the electric discharge machining control unit 38 increases the machining speed as the curvature of the path shape decreases. When the path shape is an outer corner, the electric discharge machining control unit 38 reduces the number of applications compared to when the path shape is a straight line. Also, when the path shape is an outer corner, the electric discharge machining control unit 38 reduces the number of applications as the curvature of the path shape decreases.

[0019] FIG. 3 is a schematic diagram showing an example of a path whose shape is an outer corner. The path shown in FIG. 3 is defined by a plurality of blocks having a G-code "G01" indicating linear interpolation. The length of the path defined by each block is equal to or less than the diameter of the wire electrode 12. Hereinafter, a block whose defined path length is equal to or less than the diameter of the wire electrode 12 may be referred to as a very small block. Furthermore, a G-code "G42" indicating a right offset is set in each block defining the path shown in FIG. 3.

[0020] The path shape shown in Fig. 3 is an outer corner. However, since the G code of each block is "G01" indicating linear interpolation, the electric discharge machining control unit 38 determines that the path shape is a straight line. The electric discharge machining control unit 38 performs electric discharge machining by adjusting the machining conditions to those for when the path shape is a straight line. Therefore, there is a risk that the accuracy of the machined surface of the workpiece 14 after machining will deteriorate.

[0021] It is also possible to define a path shape equivalent to that shown in Figure 3 from multiple minimal blocks having the G code "G02" indicating circular interpolation of the right corner. The G code "G42" indicating the right offset is set in each block.

[0022] The path shape shown in Fig. 3 is an outside corner. However, since the G code of each block is "G02" indicating circular interpolation of a right corner and "G42" indicating a right offset is set, the electric discharge machining control unit 38 determines that the path shape is an inside corner. The electric discharge machining control unit 38 performs electric discharge machining by adjusting the machining conditions to those for when the path shape is an inside corner. Therefore, there is a risk that the accuracy of the machined surface of the workpiece 14 after machining will deteriorate.

[0023] A path shape equivalent to that shown in Figure 3 can be defined from multiple minimal blocks having the G code "G03" indicating circular interpolation of the left corner. Each block has the G code "G42" set to indicate a right offset.

[0024] The path shape shown in FIG. 3 is an outer corner. Since the G code of each block is "G03" indicating circular interpolation of a left corner and "G42" indicating a right offset is set, the electric discharge machining control unit 38 determines that the path shape is an outer corner. The electric discharge machining control unit 38 performs electric discharge machining by adjusting the machining conditions to those for when the path shape is an outer corner. However, the curvature of the path shape of the outer corner shown in FIG. 3 cannot be obtained from the G code of each block. Therefore, there is a risk that the accuracy of the machined surface of the workpiece 14 after machining will deteriorate.

[0025] Therefore, the route shape determination unit 32 of the present embodiment determines the route shape based on the coordinates of three points determined by the start points and end points of two consecutive blocks. Specifically, the route shape determination unit 32 determines the route shape by the method described below.

[0026] [Judgment method (1)] 4 is a diagram illustrating a method for determining a route shape. In the determination method (1), the route shape determination unit 32 determines the route shape based on the cross product of a vector extending from the start point to the end point of the first block and a vector extending from the start point to the end point of the second block, out of a first block and a second block that are consecutive.

[0027] Let the starting point of the first block be P0, the end point of the first block be P1, and the vector from starting point P0 to end point P1 be a. Let the coordinates of starting point P0 be (x0, y0), and the coordinates of end point P1 be (x1, y1). The starting point of the second block, which is the block after the first block, coincides with the end point P1 of the first block. Let the end point of the second block be P2, and the vector from starting point P1 to end point P2 be b. Let the coordinates of end point P2 be (x2, y2). The cross product a×b of vectors a and b can be calculated using the following formula.

[0028]

number

[0029] When the value of the cross product of vector a and vector b is 0, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a straight line. When the value of the cross product of vector a and vector b is positive, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a left corner. When the value of the cross product of vector a and vector b is negative, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a right corner. In addition, the route shape determination unit 32 determines that the greater the absolute value of the cross product of vector a and vector b, the greater the curvature.

[0030] [Judgment method (2)] 5 is a diagram illustrating a method for determining a route shape. In the determination method (2), the route shape determination unit 32 determines the route shape based on the curvature of a line passing through the start points and end points of a first block and a second block that are consecutive.

[0031] Let the start point of the first block be P0, and the end point of the first block be P1. Let the coordinates of the start point P0 be (x0, y0), and the coordinates of the end point P1 be (x1, y1). The start point of the second block, which is the block next to the first block, coincides with the end point P1 of the first block. Let the end point of the second block be P2. Let the coordinates of the end point P2 be (x2, y2).

[0032] The route shape determination unit 32 sets a function f(x) that indicates a line that passes through the start points and end points of the first block and the second block. The function f(x) is a function that can be differentiated twice. In other words, the function f(x) is a quadratic or higher function or a trigonometric function. The number of coefficients of the function f(x) is three or less. The curvature κ of the line that passes through the start points and end points of the first block and the second block is calculated by the following formula.

[0033]

number

[0034] When the value of curvature κ is 0, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a straight line. When the value of curvature κ is positive, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a left corner. When the value of curvature κ is negative, the route shape determination unit 32 determines that the route shape defined by the first block and the second block is a right corner.

[0035] [Judgment method (3)] 6 is a diagram illustrating a method for determining a route shape. In the determination method (3), the route shape determination unit 32 determines the route shape based on the perpendicular bisector of the line segment connecting the start point and the end point of the first block and the perpendicular bisector of the line segment connecting the start point and the end point of the second block, among the first block and the second block that are consecutive.

[0036] Let the start point of the first block be P0, and the end point of the first block be P1. Let the coordinates of the start point P0 be (x0, y0), and the coordinates of the end point P1 be (x1, y1). The start point of the second block, which is the block next to the first block, coincides with the end point P1 of the first block. Let the end point of the second block be P2. Let the coordinates of the end point P2 be (x2, y2).

[0037] The route shape determination unit 32 determines the perpendicular bisector L1 of the line segment connecting the start point P0 and the end point P1 of the first block. The route shape determination unit 32 determines the perpendicular bisector L2 of the line segment connecting the start point P1 and the end point P2 of the second block. The perpendicular bisector L1 and the perpendicular bisector L2 can each be expressed by the following equations.

[0038]

number

[0039]

number

[0040] The judgment value J is calculated using the coefficients a1 and b1 of the perpendicular bisector L1 and the coefficients a2 and b2 of the perpendicular bisector L2. The judgment value J is calculated using the following formula.

[0041]

number

[0042] When the judgment value J is 0, the route shape judgment unit 32 judges that the route shape defined by the first block and the second block is a straight line. When the judgment value J is positive, the route shape judgment unit 32 judges that the route shape defined by the first block and the second block is a left corner. When the judgment value J is negative, the route shape judgment unit 32 judges that the route shape defined by the first block and the second block is a right corner.

[0043] When the path shape defined by the first block and the second block is a left corner or a right corner, the curvature κ is calculated by the following formula.

[0044]

number

[0045] In the above formula, xc and yc are coordinates at the intersection O of the perpendicular bisector L1 and the perpendicular bisector L2.

[0046] [Route shape determination] 7 is a flow chart showing the flow of processing for determining the path shape performed by the control device 18. The processing for determining the path shape is repeatedly executed at a predetermined cycle while the wire electric discharge machine 10 is performing electric discharge machining. In the following, the first block refers to the block that is to be processed next among the blocks of the machining program. The second block refers to the block that is to be processed next after the first block.

[0047] In step S1, the minimum block determination unit 30 determines whether or not the length of the path of the first block is equal to or less than the diameter of the wire electrode 12. If the length of the path of the first block is equal to or less than the diameter of the wire electrode 12, the process proceeds to step S2. If the length of the path of the first block is longer than the diameter of the wire electrode 12, the path shape determination is terminated.

[0048] In step S2, the minimum block determination unit 30 determines whether or not the length of the path of the second block is equal to or less than the diameter of the wire electrode 12. If the length of the path of the second block is equal to or less than the diameter of the wire electrode 12, the process proceeds to step S3. If the length of the path of the second block is longer than the diameter of the wire electrode 12, the path shape determination is terminated.

[0049] In step S3, the route shape determination unit 32 determines the route shape defined by the first block and the second block. The route shape determination unit 32 determines whether the route shape is a straight line, a left corner, or a right corner. Then, the process proceeds to step S4.

[0050] In step S4, the route shape determination unit 32 determines whether the route shape defined by the first block and the second block is a straight line. If the route shape is a straight line, the route shape determination ends. If the route shape is not a straight line, the process proceeds to step S5.

[0051] In step S5, the offset direction acquisition unit 34 acquires the offset directions in the first block and the second block, and then the process proceeds to step S6.

[0052] In step S6, the inside / outside corner determination unit 36 ​​determines whether the path shape defined by the first block and the second block is an inside corner or an outside corner, and then ends the path shape determination.

[0053] The electric discharge machining control unit 38 adjusts the machining conditions according to the result of the path shape determination. Furthermore, if the result of the path shape determination is either an inner corner or an outer corner, the electric discharge machining control unit 38 adjusts the machining conditions according to the curvature of the path shape. The electric discharge machining control unit 38 outputs command values ​​to the machining power source 20, the X-axis motor 22, the Y-axis motor 24, etc., based on the adjusted machining conditions. This controls the electric discharge machining of the workpiece 14. Note that the electric discharge machining control unit 38 may adjust items other than the machining conditions according to the result of the path shape determination.

[0054] [Effects] When a path shape is defined by a plurality of minimal blocks, the control device 18 may erroneously determine the path shape defined by the plurality of minimal blocks. If the path shape is erroneously determined, the electric discharge machining control unit 38 may not be able to properly adjust the machining conditions, and the accuracy of the machined surface of the workpiece 14 may deteriorate.

[0055] In the control device 18 of this embodiment, the minimal block determination unit 30 determines whether the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode 12. When it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode 12, the path shape determination unit 32 determines whether the path shape is a right corner or a left corner. The path shape determination unit 32 performs the above determination based on the coordinates of three points determined by the start and end points of the two consecutive blocks. The offset direction acquisition unit 34 acquires the offset direction in the two consecutive blocks from the machining program. After that, when it is determined that the path shape is a left corner or a right corner, the inside / outside corner determination unit 36 ​​determines whether the path shape is an inside corner or an outside corner based on the offset direction. The electric discharge machining control unit 38 controls the electric discharge machining based on the determination result in the inside / outside corner determination unit 36. This makes it possible to improve the accuracy of the machined surface of the workpiece 14 after machining on a path of an inner corner or an outer corner defined by a plurality of extremely small blocks.

[0056] In addition, in the control device 18 of this embodiment, the route shape determination unit 32 determines the route shape based on the cross product of two vectors obtained from two consecutive blocks. The two vectors are a vector extending from the start point to the end point of one of the two consecutive blocks, and a vector extending from the start point to the end point of the other of the two consecutive blocks. This makes it possible to determine the route shape defined by multiple minimal blocks.

[0057] In addition, in the control device 18 of this embodiment, the route shape determination unit 32 determines the route shape based on a function that indicates a line passing through three points determined by the start points and end points of two consecutive blocks. The function has three or less coefficients. The function is also twice differentiable. This makes it possible to determine the route shape defined by multiple minimal blocks.

[0058] Furthermore, in the control device 18 of this embodiment, the route shape determination unit 32 determines the route shape based on the perpendicular bisector of the line segment connecting the start point and end point of each of two consecutive blocks. Specifically, the route shape determination unit 32 determines the route shape based on the coefficients of an equation indicating the perpendicular bisector of the line segment connecting the start point and end point of one of the two consecutive blocks and the coefficients of an equation indicating the perpendicular bisector of the line segment connecting the start point and end point of the other of the two consecutive blocks. This makes it possible to determine the route shape defined by a plurality of minimal blocks.

[0059] The present invention is not limited to the above-described embodiment, and various configurations can be adopted without departing from the gist of the present invention.

[0060] [Invention Obtained from the Embodiments] The invention that can be understood from the above embodiment will be described below.

[0061] A control device (18) of a wire electric discharge machine (10) which performs electric discharge machining of a workpiece (14) by applying a voltage between the wire electrode and the workpiece while moving the wire electrode (12) relative to the workpiece in accordance with a machining program that defines a program path, includes a minimum block determination unit (30) that determines whether or not the length of a path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, and a minimum block determination unit (30) that determines whether or not the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, based on the coordinates of three points determined by the start points and end points of the two consecutive blocks. The machining program further comprises a path shape determination unit (32) for determining whether the path shape defined by the two blocks is a right corner that curves to the right in the advancing direction of the wire electrode or a left corner that curves to the left in the advancing direction, an offset direction acquisition unit (34) for acquiring an offset direction in the two successive blocks from the machining program, an inside / outside corner determination unit (36) for determining whether the path shape is an inside corner or an outside corner based on the offset direction when the path shape is determined to be a left corner or a right corner, and an electric discharge machining control unit (38) for controlling electric discharge machining based on the determination result by the inside / outside corner determination unit. This makes it possible to improve the accuracy of the machined surface of a machined object after machining in a path with an inside corner or an outside corner defined by a plurality of extremely small blocks.

[0062] In the control device for the wire electric discharge machine, the path shape determination unit may determine the path shape based on a cross product of a vector extending from a start point to an end point of one of the two consecutive blocks and a vector extending from a start point to an end point of the other of the two consecutive blocks. This makes it possible to determine the path shape defined by a plurality of minimal blocks.

[0063] In the control device for the wire electric discharge machine described above, the path shape determination unit may determine the path shape based on a curvature calculated from a function having three or less coefficients, the function being a function indicating a line passing through three points determined by the start points and end points of two consecutive blocks. This makes it possible to determine the path shape defined by a plurality of minimal blocks.

[0064] In the above-mentioned control device for a wire electric discharge machine, the function may be a function that is twice differentiable, thereby making it possible to determine a path shape defined by a plurality of minimal blocks.

[0065] In the control device for the wire electric discharge machine, the path shape determination unit may determine the path shape based on a coefficient of an equation that represents a perpendicular bisector of a line segment connecting a start point and an end point of one of the two consecutive blocks and a coefficient of an equation that represents a perpendicular bisector of a line segment connecting a start point and an end point of the other of the two consecutive blocks. This makes it possible to determine a path shape defined by a plurality of minimal blocks.

[0066] A control method for a wire electric discharge machine which applies an electric discharge to a workpiece by applying a voltage between the wire electrode and the workpiece while moving the wire electrode relative to the workpiece in accordance with a machining program that defines a program path, includes a very small block determination step of determining whether or not the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, and when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, a very small block determination step of determining whether or not the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, The method includes a path shape determination step of determining whether the path shape defined by the lock is a right corner that turns right in the advancing direction of the wire electrode or a left corner that turns left in the advancing direction, an offset direction acquisition step of acquiring offset directions in two consecutive blocks from the machining program, an inside / outside corner determination step of determining whether the path shape is an inside corner or an outside corner based on the offset direction when the path shape is determined to be a left corner or a right corner, and an electric discharge machining control step of controlling electric discharge machining based on the determination result in the inside / outside corner determination step. This makes it possible to improve the accuracy of the machined surface of a machined object after machining in a path with an inside corner or an outside corner defined by a plurality of extremely small blocks.

[0067] In the above-mentioned method for controlling a wire electric discharge machine, the path shape determination step may determine the path shape based on a cross product of a vector extending from a start point to an end point of one of the two consecutive blocks and a vector extending from a start point to an end point of the other of the two consecutive blocks. This makes it possible to determine a path shape defined by a plurality of minimal blocks.

[0068] In the above-mentioned method for controlling a wire electric discharge machine, the path shape determining step may determine the path shape based on a curvature calculated from a function having three or less coefficients, the function being a line passing through three points determined by the start points and end points of two consecutive blocks. This makes it possible to determine the path shape defined by a plurality of minimal blocks.

[0069] In the above-mentioned method for controlling a wire electric discharge machine, the function may be a function that is twice differentiable, thereby making it possible to determine a path shape defined by a plurality of minimal blocks.

[0070] In the above-mentioned method for controlling a wire electric discharge machine, the path shape determination step may determine the path shape based on a coefficient of an equation that represents a perpendicular bisector of a line segment connecting a start point and an end point of one of the two consecutive blocks and a coefficient of an equation that represents a perpendicular bisector of a line segment connecting a start point and an end point of the other of the two consecutive blocks. This makes it possible to determine a path shape defined by a plurality of minimal blocks. [Explanation of symbols]

[0071] 10... Wire electric discharge machine 12... Wire electrode 14...Workpiece to be processed 18...Control device 30: Minimum block determination unit 32: Route shape determination unit 34: offset direction acquisition unit 36: inside / outside corner determination unit 38... Electric discharge machining control section

Claims

1. A control device (18) for a wire electric discharge machine (10) that performs electric discharge machining on a workpiece (14) by applying a voltage between the wire electrode (12) and the workpiece while moving the wire electrode (12) relative to the workpiece (14) in accordance with a machining program that defines a program path, comprising: a minimal block determination unit (30) that determines whether or not a length of a path defined by each of two consecutive blocks is equal to or less than a diameter of the wire electrode; a path shape determination unit (32) that, when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, determines whether the path shape defined by the two consecutive blocks is a right corner that turns right toward the advancing direction of the wire electrode, or a left corner that turns left toward the advancing direction, based on the coordinates of three points determined by the start points and end points of the two consecutive blocks; an offset direction acquisition unit (34) that acquires an offset direction in two consecutive blocks from the machining program; an inside / outside corner determination unit (36) that, when the path shape is determined to be a left corner or a right corner, determines whether the path shape is an inside corner or an outside corner based on the offset direction; an electric discharge machining control unit (38) for controlling electric discharge machining based on a result of the determination by the inside / outside corner determination unit; A control device for a wire electric discharge machine comprising:

2. 2. The control device for a wire electric discharge machine according to claim 1, The control device for a wire electric discharge machining machine, wherein the path shape determination unit determines the path shape based on the cross product of a vector extending from the start point to the end point of one of the two consecutive blocks and a vector extending from the start point to the end point of the other of the two consecutive blocks.

3. 2. The control device for a wire electric discharge machine according to claim 1, The path shape determination unit is a control device for a wire electric discharge machining machine, and determines the path shape based on a curvature obtained from a function having three or less coefficients, the function indicating a line passing through three points determined by the start points and end points of two consecutive blocks.

4. 4. The control device for a wire electric discharge machine according to claim 3, A control device for a wire electric discharge machine, wherein the function is a twice differentiable function.

5. 2. The control device for a wire electric discharge machine according to claim 1, The path shape determination unit is a control device for a wire electric discharge machining machine that determines the path shape based on the coefficients of an equation that represents the perpendicular bisector of a line segment connecting a start point and an end point of one of the two consecutive blocks, and the coefficients of an equation that represents the perpendicular bisector of a line segment connecting a start point and an end point of the other of the two consecutive blocks.

6. A control method for a wire electric discharge machine that performs electric discharge machining on a workpiece by applying a voltage between the wire electrode and the workpiece while moving the wire electrode relative to the workpiece in accordance with a machining program that defines a program path, comprising the steps of: a very small block determination step of determining whether or not a length of a path defined by each of two consecutive blocks is equal to or less than a diameter of the wire electrode; a path shape determination step of determining, when it is determined that the length of the path defined by each of two consecutive blocks is equal to or less than the diameter of the wire electrode, whether the path shape defined by the two consecutive blocks is a right corner that turns to the right in the advancing direction of the wire electrode or a left corner that turns to the left in the advancing direction, based on the coordinates of three points determined by the start points and end points of the two consecutive blocks; an offset direction acquisition step of acquiring an offset direction in two consecutive blocks from the machining program; an inside / outside corner determination step of determining whether the path shape is an inside corner or an outside corner based on the offset direction when the path shape is determined to be a left corner or a right corner; an electric discharge machining control step of controlling electric discharge machining based on a result of the determination step of the inner and outer corners; A method for controlling a wire electric discharge machine comprising:

7. 7. The method for controlling a wire electric discharge machine according to claim 6, A control method for a wire electric discharge machine, in which the path shape determination step determines the path shape based on the cross product of a vector extending from a start point to an end point of one of the two consecutive blocks and a vector extending from the start point to the end point of the other of the two consecutive blocks.

8. 7. The method for controlling a wire electric discharge machine according to claim 6, The path shape determination step is a control method for a wire electric discharge machine, in which the path shape is determined based on a curvature obtained from a function having three or less coefficients, the function indicating a line passing through three points determined by the start points and end points of two consecutive blocks.

9. 9. The method for controlling a wire electric discharge machine according to claim 8, The method for controlling a wire electric discharge machine, wherein the function is a twice differentiable function.

10. 7. The method for controlling a wire electric discharge machine according to claim 6, A control method for a wire electric discharge machine, in which the path shape determination step determines the path shape based on the coefficients of an equation that represents the perpendicular bisector of a line segment connecting a start point and an end point of one of the two consecutive blocks, and the coefficients of an equation that represents the perpendicular bisector of a line segment connecting the start point and the end point of the other of the two consecutive blocks.

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