Wire electric discharge machining apparatus and wire electric discharge machining method

Abstract

To provide a wire electric discharge machining device and a wire electric discharge machining method capable of calculating a corner instruction speed for accurately machining a corner part without depending on surface roughness of a previous cut surface.SOLUTION: According to the present invention, there is provided a wire electrical discharge machine comprising a moving device and a controller for controlling the moving device, wherein the moving device is configured to machine a workpiece by moving a wire electrode relative to the workpiece in a machining advancing direction based on a predetermined path and feed rate, wherein the control device includes a movement control device and a corner speed calculation unit, the movement control device is configured to control the movement device by using, as the feed speed, a preset linear instruction speed when a linear portion of the path is machined and a corner instruction speed when a corner portion of the path is machined, and the corner speed calculation unit calculates the corner instruction speed based on the linear instruction speed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a wire electric discharge machining apparatus and a wire electric discharge machining method. [Background technology]

[0002] In wire electrical discharge machining, a voltage pulse is applied between a wire electrode and a workpiece to repeatedly generate discharges and remove material from the workpiece, while the wire electrode and the workpiece are moved relative to each other at a preset speed along a predetermined path preprogrammed into an NC program to machine the workpiece into a desired shape. Generally, to achieve sufficient machining accuracy in a shorter time, a first cut is performed as a rough cut to roughly cut the workpiece in its pure state, followed by a second cut as a finishing cut on the end face of the workpiece. The higher the required machining accuracy, the more machining steps must be performed, such as a second cut, a third cut, and a fourth cut, to achieve the desired machining accuracy.

[0003] Normally, when machining the straight sections of a workpiece, the wire electrode is moved at a specified speed. If the corners are machined at the same specified speed as the straight sections, the machining amounts differ between the straight sections and the corners, resulting in incomplete or over-removed material and making it impossible to machine accurately. Therefore, to machine corners accurately, it is necessary to control the speed so that the machining removal amount per unit time is equal for the straight sections and the corners.

[0004] Patent Document 1 discloses a wire electric discharge machining device equipped with a means for calculating the machining feed speed at corners by multiplying the average feed speed at straight sections by the machining feed speed ratio between straight sections and corner sections. The machining feed speed ratio between straight sections and corner sections is calculated based on the volume ratio between straight sections and corner sections, and therefore the speed can be controlled so that the machining removal amount per unit time at straight sections and corner sections is equal. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 5077433 Summary of the Invention [Problem to be solved by the invention]

[0006] The wire electric discharge machining device in Patent Document 1 uses the average feed rate during machining detected in the straight section to sequentially calculate the machining feed rate for corners in response to changes in the amount of machining that occurs as the wire electrode advances. Because the average feed rate during machining varies depending on the surface roughness of the previously cut surface, the machining feed rate for corners also varies depending on the surface roughness. Furthermore, there was the issue of the need to calculate the speed each time machining is performed, resulting in a heavy computational load.

[0007] The present invention has been made in consideration of the above circumstances, and provides a wire electric discharge machining apparatus and a wire electric discharge machining method that can calculate a corner command speed for machining a corner with high precision, without depending on the surface roughness of the previously cut surface. [Means for solving the problem]

[0008] According to the present invention, the following inventions are provided. [1] A wire electric discharge machining apparatus comprising a moving device and a control device for controlling the moving device, wherein the moving device is configured to machine the workpiece by moving a wire electrode relative to the workpiece in a machining progress direction based on a predetermined path and feed rate, and the control device comprises a movement control device and a corner speed calculation unit, wherein the movement control device is configured to control the moving device using a preset linear command speed as the feed rate when machining a straight portion of the path, and a corner command speed when machining a corner portion of the path, and the corner speed calculation unit calculates the corner command speed based on the linear command speed. [2] The wire electric discharge machining apparatus according to [1], wherein the corner speed calculation unit is configured to calculate the corner instruction speed before the movement device starts machining. [3] A wire electric discharge machining apparatus according to [1] or [2], wherein the corner speed calculation unit calculates the corner instruction speed further based on a volumetric machining speed, which is the amount of removal of the workpiece per unit time at each position of the corner portion. [4] A wire electric discharge machining apparatus according to [3], wherein the corner speed calculation unit includes a calculation formula storage unit and a command speed calculation unit, the calculation formula storage unit stores a calculation formula for the volumetric machining speed of the straight section calculated using the straight-line command speed, and a calculation formula for the volumetric machining speed of the corner section calculated using the corner command speed, and the command speed calculation unit calculates the volumetric machining speed of the straight section using the straight-line command speed, and calculates the corner command speed when the volumetric machining speed of the straight section and the volumetric machining speed of the corner section are equal as the feed speed of the corner section. [5] A wire electric discharge machining apparatus according to any one of [1] to [4], further comprising a position detection device, wherein the control device further comprises a corresponding speed memory unit, wherein the position detection device is configured to be able to detect a current machining position of the wire electrode, and wherein the corresponding speed memory unit stores the position of the straight portion and the linear command speed, and each position of the corner portion and the corner command speed at each position of the corner portion, in correspondence with each other, and wherein the movement control device controls the movement device using the linear command speed or the corner command speed, which is stored in the corresponding speed memory unit in correspondence with the current machining position, as the feed speed. [6] A wire electric discharge machining method for machining a workpiece by moving a wire electrode relative to the workpiece based on a predetermined path and feed rate, comprising a machining step and a corner instruction speed calculation step, wherein in the machining step, the workpiece is machined using a preset linear instruction speed as the feed rate when machining a straight portion of the path, and a corner instruction speed as the feed rate when machining a corner portion of the path, and in the corner instruction speed calculation step, the corner instruction speed is calculated based on the linear instruction speed. [Effects of the Invention]

[0009] In the wire electric discharge machining apparatus according to the present invention, the corner command speed is calculated based on a preset linear command speed, and the corner is machined at the corner command speed. With this configuration, the corner command speed can be obtained at any timing, regardless of the surface roughness of the previously cut surface. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic diagram of a wire electric discharge machining apparatus according to an embodiment of the present invention. [Figure 2] FIG. 2 is a block diagram showing a control mode of the wire electric discharge machining device. [Figure 3] 10A and 10B are diagrams illustrating the amount of processing removal per unit time in a straight section. [Figure 4] 10A and 10B are diagrams illustrating the amount of machining removal per unit time at a corner portion. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following describes embodiments of the present invention. The various features shown in the following embodiments can be combined with one another. Furthermore, each feature can be an independent invention. Furthermore, in the following embodiments, elements not specified in the claims are optional and can be omitted. Any number of "0"s (for example, one or two) may be added to the end of numerical values ​​disclosed in the following description. For example, one or two "0"s may be added after "1.4" to make it "1.40" or "1.400."

[0012] 1. Wire EDM equipment As shown in FIG. 1, a wire electric discharge machining apparatus according to one embodiment of the present invention comprises a machine body 1 including a moving device 5, and a control device 9 that controls the moving device 5.

[0013] 1.1 Processing machine body 1 The processing machine body 1 includes a wire electrode 2, a wire guide mechanism 3, a power supply device 4, a moving device 5, and a position detecting device 6.

[0014] The wire guide mechanism 3 includes an upper guide assembly 31 and a lower guide assembly 32, which are respectively provided above and below the workpiece W placed on the work stand 11. The upper guide assembly 31 and the lower guide assembly 32 each include a housing 33, a wire guide 34, and a current conductor 35, with various components housed within the housing 33. The wire electrode 2 is positioned and guided by the wire guides 34 of the upper guide assembly 31 and the lower guide assembly 32. The current conductor 35 is connected to the power supply 4. The current conductor 35 is movable in a direction approximately perpendicular to the extension direction of the wire electrode 2 guided by the wire guide 34, and is supplied with electricity when the current conductor 35 comes into contact with the wire electrode 2.

[0015] The moving device 5 is configured to drive a moving body (not shown) to move the wire electrode 2 relative to the workpiece W in the machining direction along a predetermined path while maintaining a predetermined gap (hereinafter referred to as the machining gap) formed between the wire electrode 2 and the workpiece W according to a predetermined path and a predetermined feed speed, thereby machining the workpiece W.

[0016] Here, the path of the relative movement of the wire electrode 2 with respect to the workpiece W is divided into a straight section where the machining area does not change substantially and a corner section where the machining area changes. The straight section is the part of the path other than the corner portion, and is a path for machining the workpiece W into a straight shape. The corner section is a path for machining the workpiece W into an arc shape.

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

[0018] The position detection device 6 is configured to be able to detect the current machining position of the wire electrode 2. Specifically, the position detection device 6 is, for example, a linear scale. Note that the "current machining position" includes not only the position strictly during machining, but also the machining position a certain time ahead in the machining progress direction. The current machining position data stored in the position detection device 6 is fed back to the control device 9. The position detection device 6 can be configured in any desired position as long as it has this function.

[0019] 1.2 Control Device 9 The control device 9 controls the operation of the wire electric discharge machining device. The control operation of the control device 9 will be described below.

[0020] Each component of the control device 9 may be realized by software or hardware. When realized by software, various functions can be realized by a CPU executing a computer program. The program may be stored in an internal storage unit or in a computer-readable non-transitory recording medium. Alternatively, the program may be read from an external storage unit and realized by so-called cloud computing.

[0021] When implemented by hardware, it can be implemented by various circuits such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a DRP (Dynamically Reconfigurable Processor). In this embodiment, various information and concepts that encompass them are handled, and these are represented by high and low signal values ​​as a binary bit collection consisting of 0 or 1, and communication and calculation can be performed by the above-mentioned software or hardware aspects.

[0022] As shown in FIG. 2, the control device 9 according to this embodiment includes a numerical control device 40, a movement control device 50, and a power supply control device 60.

[0023] 1.2.1 Numerical Control Device 40 The numerical control device 40 outputs operation commands to the wire electric discharge machining device using an NC program in which data related to machining conditions is recorded. The results of various calculations performed by the numerical control device 40 can be stored in a storage device (not shown). The numerical control device 40 includes a decoding unit 41, a condition acquisition unit 42, a corner speed calculation unit 43, a corresponding speed storage unit 44, and a movement command calculation unit 45.

[0024] (1) Decoding Section 41 An NC program is input to the decoding unit 41. The NC program records various machining data such as the machining path, electrode radius, plate thickness, number of cuts, etc. The decoding unit 41 reads the NC program to obtain NC data, and outputs the NC data to the condition obtaining unit 42, corner speed calculating unit 43, and movement command calculating unit 45.

[0025] (2) Condition acquisition unit 42 The condition acquisition unit 42 acquires a linear command speed based on NC data and acquires machining conditions used to calculate a corner command speed. Here, the linear command speed is a preset reference relative movement speed in the machining progress direction when machining a linear portion, and the corner command speed is a relative movement speed in the machining progress direction when machining a corner portion, and both are used as feed rates. The condition acquisition unit 42 includes a machining condition storage unit 42a, a setting information acquisition unit 42b, and a gap data acquisition unit 42c.

[0026] The machining condition storage unit 42a stores a database of machining conditions. The database stores a plurality of machining condition columns in the form of a data table, for example, by organizing various machining conditions for each combination of the material of the wire electrode 2, the material of the workpiece W, the electrode radius, and the thickness of the workpiece W for each machining step, and stores at least a command linear speed and a machining gap value corresponding to each machining condition column. The command linear speed and machining gap value stored in the database may be, for example, actual measured values ​​from a test cut.

[0027] The setting information acquisition unit 42b acquires machining conditions based on the NC data. The setting information acquisition unit 42b also acquires a linear command speed corresponding to the current machining conditions from the database of the machining condition storage unit 42a. The setting information acquisition unit 42b outputs the linear command speed to the corner speed calculation unit 43, the movement command calculation unit 45, and / or the corresponding speed storage unit 44. The setting information acquisition unit 42b also outputs machining conditions such as the electrode radius and plate thickness to the corner speed calculation unit 43, and outputs electrical machining conditions to the power supply control device 60.

[0028] The gap data acquiring unit 42c acquires a machining gap value corresponding to the current machining conditions from the database of the machining condition storage unit 42a based on the NC data. The gap data acquiring unit 42c outputs the acquired machining gap value to the corner speed calculating unit 43.

[0029] (3) Corner speed calculation unit 43 The corner speed calculation unit 43 calculates the corner command speed based on the linear command speed and the volumetric machining speed at each position of the corner. Here, the volumetric machining speed is the amount of removal (removed volume) of the workpiece W per unit time. The corner speed calculation unit 43 includes a parameter calculation unit 43a, a calculation formula storage unit 43b, and a command speed calculation unit 43c.

[0030] The parameter calculation unit 43a calculates parameters for calculating the corner command speed. Specifically, the parameter calculation unit 43a acquires the machining path, linear command speed, machining gap value, electrode radius, and plate thickness from the NC data and the condition acquisition unit 42. The parameter calculation unit 43a calculates the machining distance of the linear portion per unit time from the linear command speed, and calculates the machining distance of the corner portion per unit time from the machining path and the cut surface radius. The parameter calculation unit 43a also calculates the discharge circle from the acquired machining gap value and electrode radius. Furthermore, the parameter calculation unit 43a calculates the nth cutting path and the (n-1)th cutting path from the machining path and the discharge circle. The parameter calculation unit 43a also calculates the machining allowance from the nth cutting path, the (n-1)th cutting path, and the discharge circle. Each parameter calculated by the parameter calculation unit 43a is output to the command speed calculation unit 43c.

[0031] The calculation formula storage unit 43b stores a calculation formula for the volumetric machining speed of a straight section calculated using a straight line command speed, and a calculation formula for the volumetric machining speed of a corner section calculated using a corner command speed. Specific methods for deriving these calculation formulas will be described later.

[0032] The command speed calculation unit 43c calculates the corner command speed based on the parameters acquired from the parameter calculation unit 43a and the calculation formula stored in the calculation formula storage unit 43b. Specifically, the command speed calculation unit 43c calculates the volumetric machining speed of the straight line portion using the straight line command speed, and calculates the speed when the volumetric machining speed of the straight line portion and the volumetric machining speed of the corner portion are equal as the corner command speed (the detailed calculation method will be described later). By calculating the corner command speed such that the volumetric machining speeds of the straight line portion and the corner portion are equal, the corner portion can be machined with high precision. The command speed calculation unit 43c outputs the calculated corner command speed to the corresponding speed storage unit 44 and the movement command calculation unit 45.

[0033] (4) Corresponding speed memory unit 44 The corresponding speed memory unit 44 stores the positions of straight sections and the straight-line command speeds, as well as the positions of corner sections and the corner command speeds at each corner section, which are output from the setting information acquisition unit 42b and the command speed calculation unit 43c, in association with each other.

[0034] (5) Movement command calculation unit 45 The movement command calculation unit 45 creates a movement command based on the NC data and outputs it to the movement control device 50. The movement command data specifies, for example, the position coordinates to which the wire electrode 2 should move, the initial value of the linear command speed acquired from the setting information acquisition unit 42b, and the corner command speed acquired from the corner speed calculation unit 43 and / or the corresponding speed storage unit 44. A machining method will be described later, but in the case where the command speed is calculated in advance before machining is performed, the movement command calculation unit 45 acquires the linear command speed and the corner command speed from the corresponding speed storage unit 44.

[0035] 1.2.2 Movement control device 50 The movement control device 50 controls the movement device 5 in accordance with the movement command calculation unit 45. As a result, the wire electrode 2 is moved along a predetermined path relative to the workpiece W. Specifically, the movement control device 50 is configured to control the movement device 5 so as to set a linear command speed as the feed rate when machining a linear portion and a corner command speed as the feed rate when machining a corner portion.

[0036] When the command speed is calculated in advance before machining is performed, the movement control device 50 refers to the position detected by the position detection device 6 via the movement command calculation unit 45, and controls the movement device 5 using the straight line command speed or corner command speed stored in correspondence with that position in the corresponding speed memory unit 44 as the feed speed.

[0037] 1.2.3 Power Control Unit 60 The power supply control device 60 controls the power supply device 4 in accordance with the electrical machining conditions acquired from the setting information acquisition unit 42b of the condition acquisition unit 42. As a result, a predetermined voltage is applied to the machining gap at an appropriate time.

[0038] 2. Derivation of corner indication speed Here, a method for deriving the corner command speed will be described. First, the formulas for the volumetric machining speeds of the straight line portion and the corner portion stored in the calculation formula storage unit 43b will be described.

[0039] 2.1 Volumetric processing speed of straight section The method for deriving the volumetric processing speed of the straight portion will be explained using Fig. 3. Fig. 3 is a diagram for explaining the processing removal amount (hereinafter referred to as infinitesimal volume) of the straight portion per unit time (hereinafter referred to as infinitesimal time) in the nth cut after the second cut. s1 and point O s2 The dashed and solid circles centered on indicate the discharge circle. The solid circle indicates the discharge circle after machining for a short time from the dashed discharge circle. P s1(n-1) , P s2(n-1) , P s1(n) , P s2(n) The shaded area surrounded by the circle is the machining area per unit time (hereinafter referred to as the micro area).

[0040] The infinitesimal time is dt, and the infinitesimal volume in the straight section is dV st Then, the volume processing speed in the straight section V c_st can be defined as follows:

number

number

number

[0041] 2.2 Corner volume machining speed A method for deriving the volumetric machining speed of a corner portion will be explained using FIG. 4. FIG. 4 is a diagram for explaining the minute volume of a corner portion in the nth cut after the second cut. FIG. 4 shows an example of machining an inside corner, but the same derivation method as explained below can also be used for an outside corner. Point C is the center of the corner. Point O c1 and point O c2 The dashed and solid circles at the center indicate the discharge circle. The solid circle indicates the discharge circle after a short time of machining from the dashed discharge circle. P c1(n-1) , P c2(n-1) , P c1(n) , P c2(n) The shaded area surrounded by the square is a very small area.

[0042] The infinitesimal time is dt and the infinitesimal volume is dVcn Then, the volumetric machining speed at the corner is V c_cn can be defined as follows:

number

number

number

number

[0043] 2.3 Corner Indication Speed By setting the speed so that the machining removal amount of the straight section and the corner section is equal, the corner section can be machined with high precision. Therefore, it is sufficient to obtain a corner instruction speed that makes the volumetric machining speed of the straight section and the volumetric machining speed of the corner section equal. In this case, the following relationship holds:

number

number

[0044] As described above, the corner command speed is calculated based on the volumetric machining speed. The linear command speed is a preset speed stored in the database of the machining condition storage unit 42a. Therefore, the corner command speed according to one embodiment of the present invention can be configured to be calculated before the movement device 5 starts machining.

[0045] 3. Wire EDM method Here, a method for wire electric discharge machining of a workpiece W using the wire electric discharge machining apparatus according to this embodiment will be described.

[0046] The machining method for the wire electric discharge machining device includes a corner command speed calculation step and a machining step, in this order. The machining method for the wire electric discharge machining device can further include a straight line command speed acquisition step before the corner command speed calculation step.

[0047] 3.1 Linear indicated speed acquisition process In the linear command speed acquisition process, a linear command speed is acquired, which is the feed speed for machining the linear portion. Specifically, in the linear command speed acquisition process, the setting information acquisition unit 42b acquires the machining conditions from the NC data decoded by the decoding unit 41. In addition, the setting information acquisition unit 42b acquires the linear command speed corresponding to the current machining conditions from the database of the machining condition storage unit 42a, and outputs it to the parameter calculation unit 43a.

[0048] 3.2 Corner indication speed calculation process In the corner command speed calculation process, the corner command speed is calculated based on the linear command speed. Specifically, in the corner command speed calculation process, the parameter calculation unit 43a first acquires the machining path, machining gap value, electrode radius, and plate thickness from the NC data and the condition acquisition unit 42, in addition to the linear command speed acquired in the linear command speed acquisition process.

[0049] The parameter calculation unit 43a calculates the linear infinitesimal distance from the linear command speed, and calculates the corner infinitesimal distance from the machining path and the cut surface radius. The parameter calculation unit 43a also calculates the discharge circle from the acquired machining gap value and electrode radius. Furthermore, the parameter calculation unit 43a calculates the nth cutting path and the (n-1)th cutting path from the machining path and the discharge circle. Furthermore, the parameter calculation unit 43a calculates the machining allowance from the nth cutting path, the (n-1)th cutting path and the discharge circle.

[0050] Next, the command speed calculation unit 43c refers to the calculation formula stored in the calculation formula storage unit 43b and calculates the volumetric machining speed of the straight section using the straight section command speed and the various parameters calculated by the parameter calculation unit 43a. The command speed calculation unit 43c calculates the corner command speed using the various parameters calculated by the parameter calculation unit 43a and the volumetric machining speed of the straight section. Specifically, the command speed calculation unit 43c calculates the corner command speed when the volumetric machining speed of the straight section and the volumetric machining speed of the corner section are equal. The command speed calculation unit 43c outputs the calculated corner command speed and each position of the corner corresponding to it to the corresponding speed storage unit 44.

[0051] 3.3 Processing process In the machining process, the workpiece W is machined using a preset linear command speed as the feed rate when machining a linear portion of the path, and a corner command speed as the feed rate when machining a corner portion of the path. Specifically, in a certain finishing machining process in which the workpiece W is actually machined, for example, the movement command calculation unit 45 acquires a linear command speed and a corner command speed corresponding to the path from the corresponding speed memory unit 44 based on current machining position data acquired from the position detection device 6 every predetermined unit time, and generates a movement command to output to the movement control device 50 so that the wire electrode 2 moves relatively in a predetermined machining progress direction at the linear command speed and corner command speed. The movement control device 50 controls the movement device 5 in accordance with the movement command calculation unit 45 to machine the workpiece W. In each machining process, the user may adjust the feed rate according to the actual machining situation based on the command speeds obtained in the linear command speed acquisition process and the corner command speed calculation process.

[0052] Although the method of performing the machining process after the corner command speed calculation process has been described here, the corner command speed calculation process and the machining process may be performed in parallel. For example, the corner command speed calculation process may be performed while machining a straight section in the machining process. Also, for example, the path may be read ahead while machining a corner section, and the corner command speed calculation process may be performed as needed.

[0053] 4. Effects In a wire electrical discharge machining apparatus and wire machining method according to one embodiment of the present invention, a corner indicator speed can be calculated based on a preset linear indicator speed and machining conditions. This configuration allows an ideal corner indicator speed to be obtained without depending on machining results such as the surface roughness of the previously cut surface. Furthermore, in wire electrical discharge machining, a user may adjust the speed depending on the machining status during machining. Therefore, by obtaining an ideal corner indicator speed rather than a corner indicator speed that reflects the previous surface roughness or the actual feed rate during machining, the user can use it as an indicator for speed adjustment. Furthermore, because the corner indicator speed can be obtained before machining begins, the calculation load on the apparatus can be reduced compared to when the corner indicator speed is calculated during machining. [Explanation of symbols]

[0054] 1: Processing machine body 2: Wire electrode 3: Wire guide mechanism 4:Power supply 5: Mobile device 6: Position detection device 9: Control device 10: Table 11: Work stand 20: Saddle 31: Upper guide assembly 32: Lower guide assembly 33: Housing 34: Wire guide 35: Conductor 40: Numerical control device 41: Decoding department 42: Condition acquisition section 42a: Machining condition storage section 42b: Setting information acquisition section 42c: Gap data acquisition section 43: Corner speed calculation section 43a: Parameter calculation unit 43b: Calculation formula storage section 43c: Instruction speed calculation section 44: Corresponding speed memory section 45: Movement command calculation section 50: Movement control device 60: Power supply control device

Claims

1. A wire electric discharge machining apparatus including a moving device and a control device that controls the moving device, the moving device is configured to move the wire electrode relative to the workpiece in a machining progress direction based on a predetermined path and feed speed to machine the workpiece, the control device includes a movement control device and a corner speed calculation unit, the movement control device is configured to control the movement device by setting a preset linear instruction speed as the feed speed when machining a linear portion of the path, and a corner instruction speed as the feed speed when machining a corner portion of the path, The corner speed calculation unit calculates the corner command speed based on the linear command speed.

2. 2. The wire electric discharge machining apparatus according to claim 1, The wire electric discharge machining apparatus, wherein the corner speed calculation unit is configured to calculate the corner instruction speed before the movement device starts machining.

3. 3. The wire electric discharge machining apparatus according to claim 1, The corner speed calculation unit calculates the corner instruction speed based on a volumetric machining speed, which is the amount of removal of the workpiece per unit time, at each position of the corner portion.

4. 4. The wire electric discharge machining apparatus according to claim 3, the corner speed calculation unit includes a calculation formula storage unit and a command speed calculation unit, the calculation formula storage unit stores a calculation formula for the volumetric machining speed of the straight line portion calculated using the straight line command speed, and a calculation formula for the volumetric machining speed of the corner portion calculated using the corner command speed, The command speed calculation unit calculates a volumetric machining speed of the straight line portion using the straight line command speed, and calculates the corner command speed when the volumetric machining speed of the straight line portion and the volumetric machining speed of the corner portion are equal as the feed speed of the corner portion.

5. 2. The wire electric discharge machining apparatus according to claim 1, Further comprising a position detection device, The control device further includes a corresponding speed storage unit, the position detection device is configured to be able to detect a current machining position of the wire electrode; the corresponding speed storage unit stores the position of the straight line portion and the straight line command speed, and the positions of the corner portion and the corner command speed at each position of the corner portion, in association with each other; The movement control device controls the movement device by using the linear instruction speed or the corner instruction speed stored in the corresponding speed storage unit in association with the current machining position as the feed speed.

6. 1. A wire electric discharge machining method for machining a workpiece by moving a wire electrode relative to the workpiece based on a predetermined path and feed speed, comprising: The method includes a machining step and a corner command speed calculation step, In the machining step, the workpiece is machined using a preset linear instruction speed as the feed rate when machining a linear portion of the path, and a corner instruction speed as the feed rate when machining a corner portion of the path, In the corner command speed calculation step, the corner command speed is calculated based on the linear command speed.

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