Wire Electrical Discharge Machine, Control Device, and Control Method

Abstract

A wire electrical discharge machine (10) comprises: an acquisition unit (44) that acquires a relative moving distance (L) defined for each of a plurality of blocks included in a machining program (40); a determination unit (48) that determines, on the basis of the plurality of relative moving distances (L) and a threshold value (TH), whether or not a machining route includes a minute part; and a machining condition changing unit (50) that changes, on the basis of the determination result, a machining condition (42) during machining of the minute part.

Description

Technical Field

[0001] The present invention relates to a wire electrical discharge machining machine, a control device for controlling the wire electrical discharge machining machine, and a control method executed by the control device.

Background Art

[0002] A wire electrical discharge machining machine relatively moves a wire electrode with respect to a workpiece along a machining path set in a machining program. Further, the wire electrical discharge machining machine generates a discharge between the wire electrode and the workpiece according to set machining conditions. Thereby, the wire electrical discharge machining machine machines the workpiece (see also Japanese Unexamined Patent Application Publication No. 2017-127918).

Summary of the Invention

[0003] The machining conditions are generally set based on the material, thickness, etc. of the workpiece. In other words, the same machining conditions are used when machining a fine machining path and when machining a non-fine machining path.

[0004] However, when machining a fine machining path, there is a problem that the machining accuracy deteriorates when the same machining conditions as those for machining a non-fine machining path are used.

[0005] An object of the present invention is to solve the above-described problems.

[0006] A first aspect of the present invention is a wire electrical discharge machining apparatus that processes a workpiece by relatively moving a wire electrode along a machining path with respect to the workpiece immersed in a machining fluid and generating a discharge between the wire electrode and the workpiece according to set machining conditions. The wire electrical discharge machining apparatus includes: an acquisition unit that acquires a relative movement distance defined for each of a plurality of blocks included in a machining program; a determination unit that determines whether the machining path includes a fine portion based on the plurality of acquired relative movement distances and a threshold value; and a machining condition changing unit that changes the machining conditions during machining of the fine portion based on the determination result of the determination unit.

[0007] A second aspect of the present invention is a control device that controls a wire electrical discharge machining apparatus that processes a workpiece by relatively moving a wire electrode along a machining path with respect to the workpiece immersed in a machining fluid and generating a discharge between the wire electrode and the workpiece according to set machining conditions. The control device includes: an acquisition unit that acquires a relative movement distance defined for each of a plurality of blocks included in a machining program; a determination unit that determines whether the machining path includes a fine portion based on a comparison between the plurality of acquired relative movement distances and a threshold value; and a machining condition changing unit that changes the machining conditions during machining of the fine portion based on the determination result of the determination unit.

[0008] A third aspect of the present invention is a control method for controlling a wire electrical discharge machining apparatus that processes a workpiece by relatively moving a wire electrode along a machining path with respect to the workpiece immersed in a machining fluid and generating a discharge between the wire electrode and the workpiece according to set machining conditions. The control method includes: an acquisition step of acquiring a relative movement distance defined for each of a plurality of blocks included in a machining program; a determination step of determining whether the machining path includes a fine portion based on a comparison between the plurality of acquired relative movement distances and a threshold value; and a machining condition changing step of changing the machining conditions during machining of the fine portion based on the determination result of the determination step.

[0009] According to an aspect of the present invention, the machining conditions of electrical discharge machining are automatically changed according to the fineness of the machining path.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 9

Modes for Carrying Out the Invention

[0011] [First Embodiment] FIG. 1 is a configuration diagram of a wire electrical discharge machining machine 101(10) according to the first embodiment.

[0012] Note that FIG. 1 shows not only the wire electrical discharge machining machine 101 but also the X direction, the Y direction, and the Z direction. The X direction and the Y direction indicate directions parallel to the horizontal plane. The Z direction indicates the upward direction. The X direction, the Y direction, and the Z direction are orthogonal to each other.

[0013] The wire electrical discharge machining machine 101 includes a machining tank 12, a table 14, a motor 16X, a motor 16Y, a first guide block 181, a second guide block 182, a wire electrode 20, a power supply device 22, and a control device 241 (24). The control device 241 is, for example, a numerical control device.

[0014] The machining tank 12 is a tank that houses the first guide block 181, the second guide block 182, and the table 14. Further, a machining fluid LQ is stored in the machining tank 12.

[0015] The table 14 is a table that supports the workpiece W. The table 14 and the workpiece W are immersed in the machining fluid LQ inside the machining tank 12.

[0016] Each of the motor 16X and the motor 16Y is a motor connected to the table 14. The table 14 moves in the X direction in response to the drive of the motor 16X. Further, the table 14 moves in the Y direction in response to the drive of the motor 16Y.

[0017] The motor 16X and the motor 16Y are controlled by the control device 241. That is, the horizontal movement of the table 14 is controlled by the control device 241.

[0018] The first guide block 181 is disposed above the table 14. The first guide block 181 includes a wire guide 261 and a nozzle 281 (28). The wire guide 261 supports the wire electrode 20 so that its position in the XY plane does not fluctuate. The nozzle 281 is a member for jetting the machining fluid LQ downward from the nozzle 281. A jet port 28a for jetting the machining fluid LQ is formed at the tip of the nozzle 281. The wire guide 261 is located above the jet port 28a. The tip of the nozzle 281 (jet port 28a) is separated from above the workpiece W by a predetermined interval S.

[0019] The second guide block 182 is disposed below the table 14. The second guide block 182 includes a wire guide 262 and a nozzle 282 (28). The wire guide 262 supports the wire electrode 20 so that its position in the XY plane does not vary. The nozzle 282 jets the machining liquid LQ upward from the nozzle 282. A jet port 28a for jetting the machining liquid LQ is formed at the tip of the nozzle 282. The wire guide 262 is located below the jet port 28a. The tip of the nozzle 282 is separated from the workpiece W by a predetermined distance S below the workpiece W.

[0020] The liquid volume per unit time of the machining liquid LQ jetted from each of the nozzle 281 and the nozzle 282 is controlled by the control device 241. Note that one of the nozzle 281 and the nozzle 282 may be omitted.

[0021] Each of the first guide block 181 and the second guide block 182 may move in the horizontal direction. In order to move each of the first guide block 181 and the second guide block 182 in the horizontal direction, a plurality of motors 16 different from the motor 16X and the motor 16Y may be connected to each of the first guide block 181 and the second guide block 182.

[0022] The wire electrode 20 is a conductive wire material. A machining start hole H is formed in advance in the workpiece W. The machining start hole H penetrates the workpiece W in the vertical direction. The wire electrode 20 is passed through the machining start hole H.

[0023] The wire electrode 20 is supported by the wire guide 261 and the wire guide 262 and is fed from the wire guide 261 toward the wire guide 262. The method of feeding the wire electrode 20 is known in the art. Therefore, the description of the method is omitted.

[0024] Also, as described above, the object to be processed W (table 14) moves horizontally in response to the driving of the motors 16X and 16Y. As a result, the wire electrode 20 moves relatively horizontally with respect to the object to be processed W.

[0025] The operator creates in advance a machining program 40 that describes the movement path (machining path) of the wire electrode 20 with respect to the object to be processed W. The machining program 40 is input to the control device 241 (see also FIG. 3). The control device 241 controls the motors 16X and 16Y based on the machining program 40. As a result, the wire electrode 20 moves relatively along the machining path set in the machining program 40.

[0026] The power supply device 22 is connected to the wire electrode 20 and the table 14 (object to be processed W). The power supply device 22 applies a pulsed voltage between the electrodes of the object to be processed W and the wire electrode 20. As a result, discharge occurs between the electrodes. The power supply device 22 is controlled by the control device 241.

[0027] The object to be processed W is cut in response to the discharge. Therefore, by generating a discharge between the electrodes while the wire electrode 20 moves relatively along the machining path, the object to be processed W is machined into a shape along the machining path.

[0028] Note that when the object to be processed W is cut, chips are generated around the electrodes. The chips are removed from around the electrodes by the machining fluid LQ jetted from each of the nozzles 281 and 282. Also, the machining fluid LQ jetted from each of the nozzles 281 and 282 cools the wire electrode 20. As a result, it is possible to prevent the wire electrode 20 from being overheated in response to the generation of the discharge.

[0029] However, the wire electrode 20 deforms (vibrates, bends) in response to the discharge generated between the electrodes and the flow of the machining fluid LQ. The deformation of the wire electrode 20 changes the machining accuracy with which the wire electrode 20 machines the object to be processed W.

[0030] The operator can set, as processing conditions 42, the pulse interval of the pulsed voltage, the amount of the machining fluid LQ jetted from the nozzle 28 per unit time, etc. to the control device 241 (see also FIG. 3). The operator sets the processing conditions 42 based on, for example, the material, thickness, etc. of the workpiece W. The control device 241 controls the wire electrical discharge machining machine 101 based on the set processing conditions 42, thereby reducing the risk of deterioration of machining accuracy due to deformation of the wire electrode 20.

[0031] Incidentally, the flow of the machining fluid LQ jetted from the nozzle 28 changes according to the shape of the workpiece W in the vicinity between the electrodes. In a simple portion (for example, a long straight line) of the machining path, the change in the flow of the machining fluid LQ jetted from the nozzle 28 is small. On the other hand, in a fine portion of the machining path, the change in the flow of the machining fluid LQ jetted from the nozzle 28 is large. Therefore, the machining fluid LQ jetted from the nozzle 28 becomes turbulent in the fine portions of the machining path.

[0032] FIG. 2A is a diagram illustrating the positional relationship among a long straight portion P in the machining path, the wire electrode 20, and the nozzle 28. FIG. 2B is a diagram illustrating the positional relationship among a fine uneven portion Q in the machining path, the wire electrode 20, and the nozzle 28.

[0033] In the example of FIG. 2A and the example of FIG. 2B, the change in the flow of the machining fluid LQ is larger in the example of FIG. 2B. Therefore, in the example of FIG. 2B, the machining fluid LQ becomes turbulent.

[0034] The turbulent flow of the machining fluid LQ greatly vibrates the wire electrode 20. The large vibration of the wire electrode 20 affects the machining accuracy. Therefore, the turbulent flow of the machining fluid LQ in the fine portions of the machining path affects the machining accuracy. For this reason, it is desirable that the processing conditions 42 be set in consideration of not only the material and thickness of the workpiece W but also the fineness of the shape (machining path) of the workpiece W.

[0035] However, the task of determining whether the machining path is fine or not is a burden on the operator. Also, the criteria for determining whether the machining path is fine may vary from operator to operator. As a result, when a plurality of workpieces W are machined based on the same machining program 40, there is a possibility that the machining accuracy may vary depending on the operator in charge.

[0036] Based on the above, the details of the control device 241 according to the present embodiment will be described below. In the following description, the liquid amount refers to the amount of the machining liquid LQ jetted from the nozzle 28 per unit time, unless otherwise specified.

[0037] FIG. 3 is a configuration diagram of the control device 241 according to the first embodiment.

[0038] The control device 241 includes a display unit 30, an operation unit 32, a storage unit 34, and a calculation unit 36.

[0039] The display unit 30 is a display device including a display screen 301. The display unit 30 displays various data stored in the storage unit 34 described later on the display screen 301 as necessary. The material of the display screen 301 includes, for example, liquid crystal. However, the material of the display screen 301 is not limited to liquid crystal. For example, the material of the display screen 301 may include OEL (Organic Electro-Luminescence).

[0040] The operation unit 32 is an input device that receives information input by the operator. The operator can input information (instructions) to the control device 241 via the operation unit 32. The operation unit 32 has, for example, an operation panel 321 and a touch panel 322. The touch panel 322 is installed on the display screen 301. Note that the operation unit 32 may have a keyboard, a mouse, or the like.

[0041] The storage unit 34 includes one or more memories. The storage unit 34 includes, for example, RAM (Random Access Memory), ROM (Read Only Memory), and the like.

[0042] The storage unit 34 stores a control program 38, a machining program 40, and machining conditions 42. The control program 38 is a program for controlling the wire electrical discharge machining machine 101(10) based on the machining program 40 and the machining conditions 42.

[0043] The machining program 40 includes commands indicating a machining path. This command consists of a plurality of blocks. In each of the plurality of blocks, the relative movement direction of the wire electrode 20 and the relative movement distance L are defined.

[0044] By sequentially executing the plurality of blocks, the wire electrode 20 moves relatively along the machining path.

[0045] As described above, the machining conditions 42 include conditions regarding the pulse interval of the pulse voltage and the liquid volume of the machining liquid LQ jetted by the nozzle 28. However, the machining conditions 42 are not limited to the conditions regarding the pulse interval and the liquid volume. The machining conditions 42 may include, for example, conditions regarding the offset amount between the wire electrode 20 and the machining path, the machining speed at which the workpiece W is machined, and the like.

[0046] The machining conditions 42 are input into the control device 241 by the operator via the operation unit 32, for example. The operator inputs the machining conditions 42 that take into account the material, thickness, etc. of the workpiece W as before. This operation is included in the setup operation of the electrical discharge machining. However, it is not necessary for the operator to input the machining conditions 42 that take into account the fineness of the machining path.

[0047] Note that in addition to the control program 38, the machining program 40, and the machining conditions 42, the storage unit 34 may store various data, programs, etc. as necessary.

[0048] The calculation unit 36 includes a processing circuit. This processing circuit includes one or more processors. However, the processing circuit of the calculation unit 36 may include an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), discrete devices, etc.

[0049] The calculation unit 36 includes an acquisition unit 44, a threshold setting unit 46, a determination unit 48, a processing condition change unit 50, and a processing control unit 52. The acquisition unit 44, the threshold setting unit 46, the determination unit 48, the processing condition change unit 50, and the processing control unit 52 are realized by the processor of the calculation unit 36 executing the control program 38. However, at least a part of the acquisition unit 44, the threshold setting unit 46, the determination unit 48, the processing condition change unit 50, and the processing control unit 52 may be realized by the aforementioned ASIC, FPGA, discrete devices, etc.

[0050] The acquisition unit 44 acquires the relative movement distance L defined for each of a plurality of blocks included in the processing program 40 by analyzing the processing program 40.

[0051] The threshold setting unit 46 sets a threshold TH for determining whether the processing path includes a fine path. The threshold setting unit 46 calculates the threshold TH based on, for example, the following mathematical formula (1). In mathematical formula (1), TH indicates the threshold TH. D indicates the inner diameter of the nozzle 28 (jet orifice 28a). S indicates the aforementioned predetermined interval S. φ indicates the wire diameter of the wire electrode 20. Each of α, β, and γ indicates a weighting coefficient. α, β, and γ are determined in advance based on experiments.

[0052]

Equation

[0053] Note that the operator may specify any threshold value TH. In this case, the operator inputs any threshold value TH to the control device 241 via, for example, the operation unit 32. When the operator inputs the threshold value TH, the threshold value setting unit 46 sets the input threshold value TH.

[0054] The determination unit 48 compares each of the plurality of relative movement distances L with the threshold value TH. The determination unit 48 determines that a location corresponding to a block that defines a relative movement distance L smaller than the threshold value TH in the machining path is a fine location.

[0055] The determination unit 48 may sequentially compare each of the plurality of relative movement distances L with the threshold value TH according to the progress of the electrical discharge machining, or may compare the relative movement distance L of each block with the threshold value TH before the start of the electrical discharge machining.

[0056] When the machining path includes fine locations, the machining condition changing unit 50 changes the machining condition 42 while the fine locations are being machined so that the machining accuracy does not deteriorate.

[0057] For example, the machining condition changing unit 50 performs at least one of (1) reducing the liquid volume, (2) decreasing the machining speed, (3) changing the offset amount, and (4) changing the pulse interval for the machining condition 42 during the period when the fine locations are being machined. The offset amount is changed so that the wire electrode 20 moves away from the workpiece W. The pulse interval is extended so that the discharge frequency between the electrodes decreases. Thereby, the possibility of deterioration of the machining accuracy is reduced.

[0058] Note that when the relative movement distance L is smaller than the threshold value TH, it is preferable that the machining condition changing unit 50 changes the amount of change of the machining condition 42 according to the magnitude of the difference between the relative movement distance L and the threshold value TH.

[0059] For example, it is preferable that the machining condition changing unit 50 increases the reduction of the liquid amount, greatly reduces the machining speed, greatly offsets the wire electrode 20 from the machining path, or greatly extends the pulse interval as the relative movement distance L is smaller than the threshold value TH. Thereby, since the machining conditions are changed according to the fineness of the portion corresponding to each block in the machining path, the machining accuracy is improved.

[0060] The machining control unit 52 controls the wire electrical discharge machining machine 101 based on the machining program 40 and the machining conditions 42. When the machining condition changing unit 50 changes the machining conditions 42, the machining control unit 52 controls the wire electrical discharge machining machine 101 based on the changed machining conditions 42.

[0061] FIG. 4 is a diagram for explaining the functions realized by the wire electrical discharge machining machine 101.

[0062] In FIG. 4, a machining path R is illustrated. This machining path R includes a simple long straight portion P (P1, P2) and a fine uneven portion Q (Q1, Q2). The straight portion P is represented by a one-dot chain line, and the uneven portion Q is represented by a two-dot chain line.

[0063] The relative movement distance L between each of the straight portions P1 and P2 is larger than the threshold value TH. In this case, during the period when the straight portion P is machined, the wire electrical discharge machining machine 101 uses the machining conditions 42 considering the material, thickness, etc. of the workpiece W as before.

[0064] On the other hand, the relative movement distance L of each of the plurality of blocks corresponding to the uneven portion Q1 is smaller than the threshold value TH. In this case, during the period when the uneven portion Q is machined, the wire electrical discharge machining machine 101 uses machining conditions 42 different from those of the straight portion P.

[0065] In this way, the wire electrical discharge machining machine 101 can machine the workpiece W while changing the machining conditions 42 according to the fineness of the machining path.

[0066] FIG. 5 is a flowchart exemplifying the flow of the control method according to the first embodiment.

[0067] The control device 241 executes, for example, the control method shown in FIG. 5. This control method includes an acquisition step S1, a threshold setting step S2, a determination step S3, a processing condition change step S4, and a processing control step S5. Note that the acquisition step S1 and the threshold setting step S2 may be performed in any order.

[0068] The acquisition step S1 is a step in which the acquisition unit 44 acquires a plurality of relative movement distances L. The acquisition unit 44 acquires a plurality of relative movement distances L by analyzing the machining program 40.

[0069] The threshold setting step S2 is a step in which the threshold setting unit 46 sets a threshold TH. Here, the threshold setting unit 46 calculates the threshold TH based on, for example, the aforementioned formula (1).

[0070] The determination step S3 is a step in which the determination unit 48 compares the relative movement distance L with the threshold TH. The determination unit 48 compares the relative movement distance L of the block that the machining control unit 52 will execute next with the threshold TH. When the relative movement distance L is smaller than the threshold TH (L < TH), the processing condition change step S4 and the processing control step S5 are executed in this order. When the relative movement distance L is greater than or equal to the threshold TH (L ≧ TH), the processing condition change step S4 is skipped and the processing control step S5 is executed.

[0071] The processing condition change step S4 is a step in which the processing condition change unit 50 changes the processing conditions 42. The processing condition change unit 50 changes the processing conditions 42 in order to reduce the adverse effect of the fineness of the machining path on the machining accuracy. For example, the processing condition change unit 50 executes at least one of the aforementioned (1) to (4). Here, it is preferable that the processing condition change unit 50 increases the amount of change in the processing conditions 42 as the difference between the relative movement distance L and the threshold TH increases.

[0072] The machining control step S5 is a step in which the machining control unit 52 controls the wire electrical discharge machining machine 101 to perform electrical discharge machining on the workpiece W. The machining control unit 52 controls the wire electrical discharge machining machine 101 based on the machining program 40 and the machining conditions 42.

[0073] Note that the machining control step S5 of the present embodiment ends once the processing of one block is completed. If the machining program 40 has not ended, the control device 241 executes the flow of the determination step S3 to the machining control step S5 again. In the determination step S3 that is executed again, the relative movement distance L of the next block after the last executed block is compared with the threshold value TH.

[0074] According to the present embodiment, the machining conditions 42 are changed in consideration of the fineness of the machining path. Therefore, the possibility of deterioration of machining accuracy due to the fineness of the machining path is reduced.

[0075] Further, the fineness of the machining path is quantitatively evaluated based on the comparison between each of the plurality of relative movement distances L included in the machining program 40 and the threshold value TH set by the threshold value setting unit 46. Therefore, the wire electrical discharge machining machine 101 can perform electrical discharge machining with a certain machining accuracy regardless of the difference in the operator in charge.

[0076] [Second Embodiment] The second embodiment will be described below. However, the description overlapping with the first embodiment is omitted as much as possible in the following description. The components described in the first embodiment are given the same reference numerals as those in the first embodiment unless otherwise specified.

[0077] FIG. 6 is a configuration diagram of a wire electrical discharge machining machine 102(10) according to the second embodiment.

[0078] The wire electrical discharge machining machine 102 includes a machining tank 12, a table 14, a motor 16X, a motor 16Y, a first guide block 181, a second guide block 182, a wire electrode 20, a power supply device 22, and a control device 242(24).

[0079] FIG. 7 is a configuration diagram of the control device 242 according to the second embodiment.

[0080] The control device 242 is, for example, a numerical control device. The control device 242 includes a display unit 30, an operation unit 32, a storage unit 34, and an arithmetic unit 36.

[0081] The arithmetic unit 36 includes an acquisition unit 44, a threshold setting unit 46, a determination unit 48, a processing condition changing unit 50, and a processing control unit 52. Further, the arithmetic unit 36 further includes an exponent calculation unit 54. The exponent calculation unit 54 is realized, for example, when a processor of the arithmetic unit 36 executes the control program 38, similar to the acquisition unit 44 and the like.

[0082] The exponent calculation unit 54 calculates an exponent IDX indicating the fineness of the machining path based on a plurality of relative movement distances L acquired by the acquisition unit 44.

[0083] The exponent IDX is, for example, the median of the relative movement distances L indicated by each block included in the machining program 40. The median of the plurality of relative movement distances L tends to become smaller as the machining path is finer.

[0084] The exponent calculation unit 54 acquires the relative movement distance L defined for each of the plurality of blocks in order to obtain the median of the plurality of relative movement distances L. Next, the exponent calculation unit 54 arranges the acquired plurality of relative movement distances L in ascending or descending order.

[0085] FIG. 8 is a table showing the result of arranging a plurality of relative movement distances L in ascending order. In FIG. 8, the upper row (rank) indicates the rank of each block. B indicates the total number of blocks. The lower row (L i ) indicates the relative movement distance L defined by each block (1 ≦ i ≦ B). L k is L k-1 or more (L k-1 ≦ L k , 2 ≦ k ≦ i). The median of the plurality of relative movement distances L is L (B+1) / 2 in the table of FIG. 8.

[0086] The threshold setting unit 46 sets a threshold TH. The description of the threshold setting unit 46 is omitted (see also the first embodiment).

[0087] The determination unit 48 compares the index IDX calculated by the index calculation unit 54 with the threshold TH. When the index IDX is smaller than the threshold TH, the determination unit 48 determines that the machining path includes a fine portion.

[0088] When the machining path includes a fine portion, the machining condition changing unit 50 changes the machining condition 42 during the execution of the electrical discharge machining so that the machining accuracy does not deteriorate. For example, the machining condition changing unit 50 performs at least one of (1) a decrease in the liquid amount, (2) a decrease in the machining speed, (3) a change in the offset amount, and (4) a change in the pulse interval (see also the first embodiment).

[0089] Note that when the index IDX is smaller than the threshold TH, it is preferable that the machining condition changing unit 50 changes the amount of change in the machining condition 42 according to the magnitude of the difference between the index IDX and the threshold TH. For example, it is preferable that the machining condition changing unit 50 greatly decreases the liquid amount, greatly reduces the machining speed, greatly offsets the wire electrode 20 from the machining path, or greatly extends the pulse interval as the index IDX is smaller than the threshold TH. Thereby, since the machining condition is changed according to the fineness of the machining path, the machining accuracy is improved.

[0090] FIG. 9 is a flowchart illustrating the flow of the control method according to the second embodiment.

[0091] The control device 242 executes, for example, the control method shown in FIG. 9. This control method includes an acquisition step S1, a threshold setting step S2, a determination step S3, a machining condition change step S4, and a machining control step S5. Further, this control method further includes an index calculation step S6.

[0092] The index calculation step S6 is executed between the acquisition step S1 and the determination step S3. The index calculation step S6 is a step in which the index calculation unit 54 calculates the index IDX. The index calculation unit 54 calculates the index IDX based on the plurality of relative movement distances L acquired in the acquisition step S1.

[0093] In the determination step S3, the determination unit 48 compares the index IDX with the threshold value TH. Based on the comparison result, the determination unit 48 determines whether the machining path includes a fine portion.

[0094] In the case of this embodiment, the index IDX based on the plurality of relative movement distances L is compared with the threshold value TH. Therefore, according to this embodiment, the number of comparisons performed by the determination unit 48 can be reduced compared to the case of comparing each of the plurality of relative movement distances L with the threshold value TH.

[0095] When the index IDX is smaller than the threshold value TH (IDX < TH), the machining condition change step S4 and the machining control step S5 are executed in this order. When the index IDX is greater than or equal to the threshold value TH (IDX ≧ TH), the machining control step S5 is executed.

[0096] In the machining condition change step S4, when the machining path includes a fine portion, the machining condition 42 is changed so that the machining accuracy does not deteriorate (see also the first embodiment).

[0097] According to this embodiment, similarly to the first embodiment, the machining condition 42 is changed in consideration of the fineness of the machining path. Therefore, the possibility that the machining accuracy deteriorates due to the fineness of the machining path is reduced.

[0098] Also, the fineness of the machining path is quantitatively evaluated based on the comparison between the index IDX calculated by the index calculation unit 54 by a predetermined calculation and the threshold value TH set by the threshold setting unit 46. Therefore, the wire electrical discharge machine 102 can perform electrical discharge machining with a certain machining accuracy regardless of the difference in the operator in charge.

[0099] [Modification Example] The following describes modifications related to the above embodiment. However, descriptions overlapping with the above embodiment are omitted as much as possible in the following description. Components described in the above embodiment are given the same reference numerals as those in the above embodiment unless otherwise specified.

[0100] (Modification 1) There may be a case where the vertical distance between the nozzle 281 and the workpiece W is different from the vertical distance between the nozzle 282 and the workpiece W. In this case, the threshold setting unit 46 may substitute the average value of the vertical distance between the nozzle 281 and the workpiece W and the vertical distance between the nozzle 282 and the workpiece W as a predetermined distance S into the formula (1).

[0101] (Modification 2) When the relative movement distance L is smaller than the threshold TH, the machining condition changing unit 50 according to the first embodiment may change the machining condition 42 to a setting determined in advance for a fine machining path regardless of the difference between the relative movement distance L and the threshold TH.

[0102] Similarly, when the index IDX is smaller than the threshold TH, the machining condition changing unit 50 according to the second embodiment may change the machining condition 42 to a setting determined in advance for a fine machining path regardless of the difference between the index IDX and the threshold TH.

[0103] For example, a first machining condition 42 for machining a simple portion and a second machining condition 42 for machining a fine portion are stored in the storage unit 34 in advance. When the index IDX is smaller than the threshold TH, the machining condition changing unit 50 selects the second machining condition 42. On the other hand, when the index IDX is higher than the threshold TH, the machining condition changing unit 50 selects the first machining condition 42.

[0104] (Modification 3) The index calculation unit 54 may calculate an index IDX after the electrical discharge machining is started. For example, each time one of a plurality of blocks is executed, the index calculation unit 54 may calculate the index IDX based on the relative movement distance L defined for each of a predetermined number of blocks following the next block of the block being executed. The predetermined number is smaller than the total number of blocks included in the machining program. The operator may arbitrarily instruct the control device 242 of the specific value of the predetermined number via the operation unit 32.

[0105] The machining condition change unit 50 changes the machining condition 42 during the execution of the next block based on the comparison result between the calculated index IDX and the threshold value TH. Thereby, the machining accuracy is improved.

[0106] (Modification Example 4) The index calculation unit 54 may calculate the sum, arithmetic mean value, or weighted mean value of a plurality of relative movement distances L indicated by a plurality of blocks as the index IDX. The sum, arithmetic mean value, and weighted mean value of the plurality of relative movement distances L tend to become smaller as the machining path is finer, similar to the median value of the plurality of relative movement distances L.

[0107] The arithmetic mean value is derived by dividing the sum of the plurality of relative movement distances L by the number of blocks.

[0108] When obtaining the weighted mean value, a weight coefficient to be multiplied by each relative movement distance L is required. A plurality of weight coefficients corresponding to each of the plurality of relative movement distances L are stored in advance by the storage unit 34, for example. The plurality of weight coefficients are larger as the weight coefficient corresponding to a shorter relative movement distance L is. Note that the specific values of the plurality of weight coefficients are determined based on experiments performed in advance.

[0109] Further, the index calculation unit 54 may calculate the index IDX based on the following formula (2). In formula (2), IDX indicates the index IDX. B indicates the number of blocks. L1, L2, …, L B each indicates the relative movement distance L of the block. W1, W2, …, W BEach of them indicates a weight coefficient corresponding to a block. Similar to the case of obtaining a weighted average value, the larger the plurality of weight coefficients, the more they correspond to a short relative movement distance L.

[0110] [Number]

[0111] Incidentally, if B = W1 + W2 + … + W B in the case of, Equation (2) represents an equation for calculating the weighted average value of a plurality of relative movement distances L as the index IDX.

[0112] (Combination of multiple modification examples) The plurality of modification examples described above may be appropriately combined within a non - conflicting range.

[0113] [Invention obtained from the embodiment] The following describes the inventions that can be grasped from the above - mentioned embodiment and modification examples.

[0114] <The first invention> The first invention is a wire electrical discharge machining machine (10) for machining a workpiece (W) immersed in a machining fluid (LQ) by causing a discharge to occur between the wire electrode (20) and the workpiece along the machining path while relatively moving the wire electrode along the machining path according to set machining conditions (42), the wire electrical discharge machining machine comprising: an acquisition unit (44) that acquires a relative movement distance (L) defined for each of a plurality of blocks included in a machining program (40); a determination unit (48) that determines whether or not the machining path includes a fine portion based on the plurality of acquired relative movement distances and a threshold value (TH); and a machining condition changing unit (50) that changes the machining conditions during machining of the fine portion based on the determination result of the determination unit.

[0115] Thereby, the machining conditions of the electrical discharge machining are automatically changed according to the fineness of the machining path.

[0116] The first invention may further include a nozzle (28) that jets the machining fluid while relatively moving with respect to the object to be machined, a threshold setting unit (46) that sets the threshold based on the inner diameter (D) of the nozzle, the distance (S) between the nozzle and the object to be machined, and the wire diameter (φ) of the wire electrode. Thereby, the fineness of the machining path is quantitatively evaluated.

[0117] The determination unit may determine, as the fine portion, a portion corresponding to the block that defines the relative movement distance smaller than the threshold value among the machining paths. Thereby, whether or not the machining path includes a fine portion is determined in block units.

[0118] The machining condition changing unit may change the amount of change in the machining conditions according to the magnitude of the difference between the relative movement distance and the threshold value. Thereby, since the machining conditions are appropriately changed according to the fineness of the portion corresponding to each block, the machining accuracy is improved.

[0119] The first invention further includes an index calculation unit (54) that calculates an index indicating the fineness of the machining path based on a plurality of the relative movement distances, and the determination unit determines, when the index is smaller than the threshold value, a portion corresponding to the plurality of blocks that define the plurality of the relative movement distances as the fine portion. Thereby, the number of determinations made by the determination unit can be reduced.

[0120] The index calculation unit may calculate the index based on the relative movement distances defined for each of a predetermined number of blocks subsequent to the block being executed each time one of the plurality of blocks is executed. Thereby, the wire electrical discharge machining machine can make a determination as to whether or not to change the machining conditions used during the execution of each block in parallel with the execution of the electrical discharge machining.

[0121] The index may be a median value, a weighted average value, or an arithmetic mean value of the plurality of relative movement distances. Thereby, the wire electrical discharge machining machine can use, as the index, a value that becomes smaller as the machining path is finer.

[0122] The machining condition changing unit may change the amount of change in the machining conditions according to the magnitude of the difference between the exponent and the threshold value. Thereby, since the machining conditions are appropriately changed according to the fineness of the portions corresponding to the plurality of blocks, the machining accuracy is improved.

[0123] The machining conditions include the amount of the machining fluid, and the machining condition changing unit may decrease the amount of the fluid during machining of the fine portion. Thereby, the possibility that the machining accuracy deteriorates when the machining path is fine is reduced.

[0124] The machining conditions include the pulse interval of the pulse voltage applied between the electrodes, and the machining condition changing unit may extend the pulse interval during machining of the fine portion. Thereby, the possibility that the machining accuracy deteriorates when the machining path is fine is reduced.

[0125] The machining conditions include the machining speed at which the object to be machined is machined, and the machining condition changing unit may decrease the machining speed during machining of the fine portion. Thereby, the possibility that the machining accuracy deteriorates when the machining path is fine is reduced.

[0126] The machining conditions include the offset amount of the wire electrode with respect to the machining path, and the machining condition changing unit may change the offset amount during machining of the fine portion so that the wire electrode moves away from the object to be machined. Thereby, the possibility that the machining accuracy deteriorates when the machining path is fine is reduced.

[0127] <Second Invention> The second invention is a control device (24) for controlling a wire electrical discharge machining apparatus (10) that machines a workpiece (W) by relatively moving a wire electrode (20) along a machining path with respect to the workpiece (W) immersed in a machining fluid (LQ) and generating a discharge between the wire electrode and the workpiece according to set machining conditions (42). The control device (24) includes an acquisition unit (44) that acquires the relative movement distance defined for each of a plurality of blocks included in a machining program (40), a determination unit (48) that determines whether or not the machining path includes a fine portion based on a comparison between the acquired plurality of relative movement distances and a threshold value (TH), and a machining condition change unit (50) that changes the machining conditions during machining of the fine portion based on the determination result of the determination unit.

[0128] Thereby, the machining conditions of the electrical discharge machining are automatically changed according to the fineness of the machining path.

[0129] <The third invention> The third invention is a control method for controlling a wire electrical discharge machining apparatus (10) that machines a workpiece (W) by relatively moving a wire electrode (20) along a machining path with respect to the workpiece (W) immersed in a machining fluid (LQ) and generating a discharge between the wire electrode and the workpiece according to set machining conditions (42). The control method includes an acquisition step (S1) of acquiring the relative movement distance (L) defined for each of a plurality of blocks included in a machining program (40), a determination step (S3) of determining whether or not the machining path includes a fine portion based on a comparison between the acquired plurality of relative movement distances and a threshold value (TH), and a machining condition change step (S4) of changing the machining conditions during machining of the fine portion based on the determination result of the determination step.

[0130] Thereby, the machining conditions of the electrical discharge machining are automatically changed according to the fineness of the machining path.

Explanation of reference numerals

[0131] 10…Wire electrical discharge machining apparatus, 20…Wire electrode 24... Control device 28... Nozzle 40... Processing program 42... Processing conditions 44... Acquisition unit 46... Threshold setting unit 48... Judgment unit 50... Processing condition change unit 54... Index calculation unit D... Inner diameter of the nozzle IDX... Index LQ... Processing fluid S... Distance between the nozzle and the object to be processed TH... Threshold value W... Object to be processed φ... Wire diameter

Claims

1. A wire electrical discharge machining machine (10) for machining a workpiece (W) immersed in a machining fluid (LQ) by relatively moving a wire electrode (20) along a machining path while generating a discharge between the wire electrode and the workpiece according to set machining conditions (42), an acquisition unit (44) that acquires a relative movement distance (L) defined for each of a plurality of blocks included in a machining program (40), a determination unit (48) that determines whether or not the machining path includes a fine portion based on the plurality of acquired relative movement distances and a threshold value (TH), a machining condition changing unit (50) that changes the machining conditions while the fine portion is being machined based on the determination result of the determination unit, and a wire electrical discharge machining machine comprising the same.

2. The wire electrical discharge machining machine according to Claim 1, a nozzle (28) that jets the machining fluid while relatively moving with respect to the workpiece, and a threshold value setting unit (46) that sets the threshold value based on the inner diameter (D) of the nozzle, the distance (S) between the nozzle and the workpiece, and the wire diameter (φ) of the wire electrode, and further comprising a wire electrical discharge machining machine.

3. The wire electrical discharge machining machine according to Claim 1 or 2, wherein the determination unit determines a location corresponding to the block that defines the relative movement distance smaller than the threshold value among the machining paths as the fine portion.

4. The wire electrical discharge machining machine according to Claim 3, wherein the machining condition changing unit changes the amount of change of the machining conditions according to the magnitude of the difference between the relative movement distance and the threshold value.

5. The wire electrical discharge machining machine according to Claim 1 or 2, Further provided is an index calculation unit (54) that calculates an index indicating the fineness of the machining path based on the plurality of relative movement distances. The determination unit determines, as the fine portion, a portion corresponding to each of the plurality of blocks that define the plurality of relative movement distances when the index is smaller than the threshold value. A wire electrical discharge machining machine.

6. The wire electrical discharge machining machine according to claim 5, The index calculation unit calculates the index based on the relative movement distances defined for each of a predetermined number of blocks following the currently executed block each time one of the plurality of blocks is executed. A wire electrical discharge machining machine.

7. The wire electrical discharge machining machine according to claim 5 or 6, The index is a median value, a weighted average value, or an arithmetic average value of the plurality of relative movement distances. A wire electrical discharge machining machine.

8. The wire electrical discharge machining machine according to any one of claims 5 to 7, The machining condition changing unit changes the amount of change in the machining conditions according to the magnitude of the difference between the index and the threshold value. A wire electrical discharge machining machine.

9. The wire electrical discharge machining machine according to any one of claims 1 to 8, The machining conditions include the amount of the machining fluid, The machining condition changing unit decreases the amount of the fluid while the fine portion is being machined. A wire electrical discharge machining machine.

10. The wire electrical discharge machining machine according to any one of claims 1 to 9, The machining conditions include the pulse interval of the pulse voltage applied between the electrodes, The machining condition changing unit extends the pulse interval while the fine portion is being machined. A wire electrical discharge machining machine.

11. The wire electrical discharge machining machine according to any one of claims 1 to 10, The machining conditions include the machining speed at which the object to be machined is machined. The machining condition changing unit is a wire electrical discharge machining machine that reduces the machining speed while the fine portion is being machined.

12. A wire electrical discharge machining machine according to any one of claims 1 to 11, The machining conditions include the offset amount of the wire electrode with respect to the machining path, The machining condition changing unit is a wire electrical discharge machining machine that changes the offset amount while the fine portion is being machined so that the wire electrode moves away from the object to be machined.

13. A control device (24) for controlling a wire electrical discharge machining machine (10) that machines an object to be machined (W) by generating a discharge between the wire electrode and the object to be machined while relatively moving a wire electrode (20) along a machining path with respect to the object to be machined (W) immersed in a machining fluid (LQ) according to set machining conditions (42), An acquisition unit (44) that acquires the relative movement distance (L) defined for each of a plurality of blocks included in a machining program (40); A determination unit (48) that determines whether or not the machining path includes a fine portion based on a comparison between the acquired plurality of relative movement distances and a threshold value (TH); A machining condition changing unit (50) that changes the machining conditions while the fine portion is being machined based on the determination result of the determination unit; A control device comprising:

14. A control method for controlling a wire electrical discharge machining machine (10) that machines an object to be machined (W) by generating a discharge between the wire electrode and the object to be machined while relatively moving a wire electrode (20) along a machining path with respect to the object to be machined (W) immersed in a machining fluid (LQ) according to set machining conditions (42), An acquisition step (S1) of acquiring the relative movement distance (L) defined for each of a plurality of blocks included in a machining program (40); A determination step (S3) of determining whether or not the machining path includes a fine portion based on a comparison between the plurality of obtained relative movement distances and a threshold value (TH); A machining condition changing step (S4) of changing the machining conditions during machining of the fine portion based on the determination result of the determination step; A control method including the above.

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