Wire electrical discharge machine, control device, and control method

Abstract

A wire electric discharge machine (10) has an acquisition section (44) that acquires a relative movement distance (L) specified in each of a plurality of program blocks included in a machining program (40), a determination section (48) that determines whether a machining path includes a fine portion based on the plurality of relative movement distances (L) and a threshold value (TH), and a machining condition change section (50) that changes a machining condition (42) for a period during which a fine portion is machined based on a determination result.

Description

Technical Field

[0001] This invention relates to a wire electrical discharge machining (EDM) machine, a control device for controlling the EDM machine, and a control method performed by the control device. Background Technology

[0002] A wire electrical discharge machining (EDM) machine moves a wire electrode relative to the workpiece along a machining path set in the machining program. Furthermore, the EDM machine generates a discharge between the wire electrode and the workpiece according to set machining conditions. Thus, the wire EDM machine processes the workpiece (see also Japanese Patent Application Publication No. 2017-127918). Summary of the Invention

[0003] Generally, processing conditions are set based on the material and thickness of the object being processed. In other words, the same processing conditions are used when processing fine processing paths and when processing non-fine processing paths.

[0004] However, when machining fine machining paths, if the same machining conditions are used as when machining non-fine machining paths, there is a problem of decreased machining accuracy.

[0005] The purpose of this invention is to solve the above-mentioned problems.

[0006] The first aspect of the present invention is a wire electrical discharge machining (EDM) machine in which a wire electrode is moved relative to a workpiece immersed in a processing fluid along a processing path, and a discharge is generated between the wire electrode and the workpiece according to set processing conditions, thereby processing the workpiece. The EDM machine includes: an acquisition unit that acquires a relative movement distance specified in each of a plurality of program blocks included in a processing program; a determination unit that determines whether the processing path contains a fine part based on the acquired relative movement distances and a threshold value; and a processing condition modification unit that changes the processing conditions during the processing of the fine part 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 (EDM) machine, wherein the EDM machine moves a wire electrode relative to a workpiece immersed in a machining fluid along a machining path and generates a discharge between the wire electrode and the workpiece according to set machining conditions, thereby machining the workpiece. The control device comprises: an acquisition unit that acquires a relative movement distance specified in each of a plurality of program blocks included in a machining program; a determination unit that determines whether the machining path contains a minute part based on a comparison of the acquired relative movement distances with a threshold; and a machining condition modification unit that changes the machining conditions during the machining of the minute part 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 (EDM) machine. The EDM machine moves a wire electrode relative to a workpiece immersed in a machining fluid along a machining path and generates a discharge between the wire electrode and the workpiece according to set machining conditions, thereby machining the workpiece. The control method includes the following steps: an acquisition step, acquiring a specified relative movement distance in each of a plurality of program blocks included in a machining program; a determination step, determining whether the machining path contains minute parts based on a comparison of the acquired relative movement distances with a threshold; and a machining condition modification step, modifying the machining conditions during the machining of the minute parts based on the determination result of the determination step.

[0009] According to the method of the present invention, the processing conditions of electrical discharge machining are automatically changed according to the fineness of the processing path. Attached Figure Description

[0010] Figure 1 This is a structural diagram of the wire electrical discharge machining machine according to the first embodiment.

[0011] Figure 2A It is a diagram illustrating the positional relationship between long straight sections, line electrodes, and nozzles in the machining path.

[0012] Figure 2B It is a diagram illustrating the positional relationships of fine details, wire electrodes, and nozzles in the machining path.

[0013] Figure 3 This is a structural diagram of the control device according to the first embodiment.

[0014] Figure 4 This diagram illustrates the functions performed by a wire electrical discharge machining (EDM) machine.

[0015] Figure 5 This is a flowchart illustrating the control method of the first embodiment.

[0016] Figure 6 This is a structural diagram of the wire electrical discharge machining machine according to the second embodiment.

[0017] Figure 7 This is a structural diagram of the control device according to the second embodiment.

[0018] Figure 8 It is a table that represents the result of arranging multiple relative movement distances in ascending order.

[0019] Figure 9 This is a flowchart illustrating the control method of the second embodiment. Detailed Implementation

[0020] [First Implementation Method]

[0021] Figure 1 This is a structural diagram of the wire electrical discharge machining machine 101(10) according to the first embodiment.

[0022] In addition, Figure 1 In this context, besides the wire electrical discharge machine 101, the X, Y, and Z directions are also indicated. The X and Y directions represent directions parallel to the horizontal plane. The Z direction represents the upward direction. The X, Y, and Z directions are orthogonal to each other.

[0023] The wire electrical discharge machining (EDM) machine 101 includes: a machining tank 12, a worktable 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.

[0024] The machining tank 12 is a tank that houses the first guide block 181, the second guide block 182, and the worktable 14. Additionally, machining fluid LQ is stored in the machining tank 12.

[0025] The worktable 14 is a platform that supports the workpiece W. The worktable 14 and the workpiece W are immersed in the machining fluid LQ inside the machining tank 12.

[0026] Motors 16X and 16Y are motors connected to the worktable 14. The worktable 14 moves along the X direction driven by motor 16X. Additionally, the worktable 14 moves along the Y direction driven by motor 16Y.

[0027] Motors 16X and 16Y are controlled by control device 241. That is, the horizontal movement of the worktable 14 is controlled by control device 241.

[0028] The first guide block 181 is positioned above the worktable 14. The first guide block 181 has 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 remains unchanged. The nozzle 281 is a component for spraying machining fluid LQ downwards. A nozzle orifice 28a for spraying machining fluid LQ is formed at the front end of the nozzle 281. The wire guide 261 is located above the nozzle orifice 28a. The front end of the nozzle 281 (nozzle 28a) is separated from the workpiece W upwards by a predetermined interval S.

[0029] The second guide block 182 is positioned below the worktable 14. The second guide block 182 has 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 remains unchanged. The nozzle 282 sprays machining fluid LQ upwards. A nozzle orifice 28a for spraying machining fluid LQ is formed at the front end of the nozzle 282. The wire guide 262 is located below the nozzle orifice 28a. The front end of the nozzle 282 is separated from the workpiece W downwards by a predetermined interval S.

[0030] The flow rate of the processing fluid LQ ejected from nozzles 281 and 282 per unit time is controlled by control device 241. Alternatively, one of nozzles 281 and 282 may be omitted.

[0031] The first guide block 181 and the second guide block 182 can move horizontally. In order for the first guide block 181 and the second guide block 182 to move horizontally, multiple motors 16, different from motors 16X and 16Y, can be connected to the first guide block 181 and the second guide block 182 respectively.

[0032] The wire electrode 20 is a conductive wire. A machining start hole H is pre-formed in the workpiece W. The machining start hole H extends vertically through the workpiece W. The wire electrode 20 passes through the machining start hole H.

[0033] The wire electrode 20 is supported by wire guides 261 and 262, and is delivered from wire guide 261 toward wire guide 262. The method of delivering the wire electrode 20 is known in the art. Therefore, a description of this method is omitted.

[0034] Furthermore, as described above, the workpiece W (worktable 14) moves horizontally under the drive of motors 16X and 16Y. Consequently, the wire electrode 20 moves horizontally relative to the workpiece W.

[0035] The operator pre-creates a machining program 40 that describes the movement path (machining path) of the wire electrode 20 relative to the workpiece W. The machining program 40 is input into the control device 241 (see also...). Figure 3 The control device 241 controls motors 16X and 16Y according to the machining program 40. As a result, the wire electrode 20 moves relative to each other along the machining path set in the machining program 40.

[0036] The power supply unit 22 is connected to the wire electrode 20 and the worktable 14 (workpiece W). The power supply unit 22 applies a pulse voltage between the workpiece W and the wire electrode 20. This generates a discharge between the electrodes. The power supply unit 22 is controlled by the control unit 241.

[0037] The workpiece W is cut by the discharge. Therefore, the wire electrode 20 moves relative to each other along the machining path and a discharge is generated between the electrodes, thereby machining the workpiece W into the shape along the machining path.

[0038] Furthermore, chips are generated around the electrode space when the workpiece W is cut. The machining fluid LQ sprayed from nozzles 281 and 282 removes these chips from the periphery of the electrode space. Additionally, the machining fluid LQ sprayed from nozzles 281 and 282 cools the wire electrode 20. This prevents the wire electrode 20 from overheating due to discharge.

[0039] However, due to the discharge generated between the electrodes and the flow of the processing fluid LQ, the wire electrode 20 deforms (vibrates, bends). The deformation of the wire electrode 20 causes changes in the machining accuracy of the workpiece W processed by the wire electrode 20.

[0040] The operator can set the pulse interval of the pulse voltage, the flow rate of the processing fluid LQ sprayed from nozzle 28 per unit time, etc., as processing conditions 42 to the control device 241 (see also...). Figure 3 The operator sets the processing conditions 42 based on factors such as the material and thickness of the workpiece W. The control device 241 controls the wire electrical discharge machine 101 according to the set processing conditions 42, thereby reducing the possibility of deterioration in processing accuracy due to deformation of the wire electrode 20.

[0041] However, the flow of the machining fluid LQ ejected from nozzle 28 varies depending on the shape of the workpiece W being machined around the electrode. The flow of the machining fluid LQ ejected from nozzle 28 varies little in simple sections of the machining path (e.g., long straight lines). On the other hand, the flow of the machining fluid LQ ejected from nozzle 28 varies greatly in fine sections of the machining path. Therefore, the machining fluid LQ ejected from nozzle 28 experiences turbulence in the fine sections of the machining path.

[0042] Figure 2AThis is a diagram illustrating the positional relationship between the long straight section P, the line electrode 20, and the nozzle 28 in the machining path. Figure 2B This is a diagram illustrating the positional relationship between the minute irregularities Q, the wire electrode 20, and the nozzle 28 in the machining path.

[0043] exist Figure 2A Examples and Figure 2B In the example, Figure 2B In this example, the flow of the processing fluid LQ varies greatly. Therefore, in Figure 2B In the example, the processing fluid LQ undergoes turbulence.

[0044] The turbulence of the machining fluid LQ causes the wire electrode 20 to vibrate significantly. This large vibration of the wire electrode 20 affects the machining accuracy. Therefore, the turbulence of the machining fluid LQ in the minute parts of the machining path affects the machining accuracy. For this reason, it is preferable to set the machining conditions 42 by considering not only the material and thickness of the workpiece W, but also the minuteness of the shape (machining path) of the workpiece W.

[0045] However, judging whether the machining path is subtle is a burden for the operator. Furthermore, the criteria for judging whether the machining path is subtle may differ from operator to operator. As a result, when machining multiple workpieces W according to the same machining program 40, the machining accuracy may deviate depending on the operator in charge.

[0046] Based on the above, the control device 241 of this embodiment will be described in detail below. Furthermore, unless otherwise specified, in the following description, the liquid volume refers to the volume of the processing fluid LQ sprayed from the nozzle 28 per unit time.

[0047] Figure 3 This is a structural diagram of the control device 241 in the first embodiment.

[0048] The control device 241 includes a display unit 30, an operation unit 32, a storage unit 34, and an arithmetic unit 36.

[0049] Display unit 30 is a display device having a display screen 301. Display unit 30 displays various data stored in storage unit 34 (described later) on display screen 301 as needed. The material of display screen 301 may include liquid crystal, for example. However, the material of display screen 301 is not limited to liquid crystal. For example, the material of display screen 301 may include OEL (Organic Electro-Luminescence).

[0050] The operation unit 32 is an input device that accepts information input from the operator. The operator can input information (instructions) to the control device 241 via the operation unit 32. The operation unit 32 may include, for example, an operation panel 321 and a touch panel 322. The touch panel 322 is provided on the display screen 301. In addition, the operation unit 32 may include a keyboard, mouse, etc.

[0051] The storage unit 34 has one or more memories. The storage unit 34 may include, for example, RAM (Random Access Memory) or ROM (Read Only Memory).

[0052] The storage unit 34 stores the control program 38, the machining program 40, and the machining conditions 42. The control program 38 is a program that controls the wire electrical discharge machine 101 (10) according to the machining program 40 and the machining conditions 42.

[0053] The machining program 40 contains instructions indicating the machining path. These instructions consist of multiple program blocks. Within each program block, the relative movement direction and relative movement distance L of the wire electrode 20 are specified.

[0054] By executing multiple program blocks in sequence, the wire electrode 20 moves relative to each other along the machining path.

[0055] As described above, processing condition 42 includes conditions related to the pulse interval of the pulse voltage and the volume of the processing fluid LQ ejected from nozzle 28. However, processing condition 42 is not limited to conditions related to the pulse interval and fluid volume. Processing condition 42 may also include, for example, conditions related to the offset of the wire electrode 20 and the processing path, the processing speed of the workpiece W, etc.

[0056] The processing conditions 42 are input by the operator to the control device 241 via the operation unit 32, for example. The operator inputs the processing conditions 42, taking into account the material, thickness, etc., of the object being processed, as is customary. This operation is included in the preparation work for the electrical discharge machining. However, the operator does not need to input the processing conditions 42, which take into account the fine details of the processing path.

[0057] In addition to the control program 38, the processing program 40, and the processing conditions 42, the storage unit 34 can also store various data, programs, etc. as needed.

[0058] The arithmetic unit 36 ​​has processing circuitry. This processing circuitry includes one or more processors. However, the processing circuitry of the arithmetic unit 36 ​​may also include an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), a discrete device, etc.

[0059] The arithmetic unit 36 ​​includes an acquisition unit 44, a threshold setting unit 46, a determination unit 48, a processing condition modification unit 50, and a processing control unit 52. The acquisition unit 44, threshold setting unit 46, determination unit 48, processing condition modification unit 50, and processing control unit 52 are implemented by executing a control program 38 through the processor of the arithmetic unit 36. However, at least some of the acquisition unit 44, threshold setting unit 46, determination unit 48, processing condition modification unit 50, and processing control unit 52 can also be implemented using the aforementioned ASIC, FPGA, discrete devices, etc.

[0060] The acquisition unit 44 obtains the relative movement distance L specified in each of the multiple program blocks contained in the machining program 40 by analyzing the machining program 40.

[0061] The threshold setting unit 46 sets a threshold TH for determining whether the processing path contains a fine path. The threshold setting unit 46 calculates the threshold TH, for example, according to the following mathematical formula (1). In the mathematical formula (1), TH represents the threshold TH. D represents the inner diameter of the nozzle 28 (jet outlet 28a). S represents the aforementioned specified interval S. This indicates the wire diameter of line electrode 20. α, β, and γ represent weighting coefficients. α, β, and γ are determined in advance based on experiments.

[0062] [Mathematical Expression 1]

[0063]

[0064] Furthermore, the operator can specify any threshold TH. In this case, the operator, for example, inputs any threshold TH to the control device 241 via the operation unit 32. When the operator inputs the threshold TH, the threshold setting unit 46 sets the input threshold TH.

[0065] The determination unit 48 compares each of the plurality of relative movement distances L with a threshold TH. The determination unit 48 determines the part corresponding to the program block in the machining path that specifies a relative movement distance L smaller than the threshold TH as a fine part.

[0066] The determination unit 48 can compare each of the multiple relative movement distances L with the threshold TH in sequence according to the progress of the electrical discharge machining, or it can compare the relative movement distance L of each of the program blocks with the threshold TH before the electrical discharge machining begins.

[0067] When the machining path includes fine parts, the machining condition change unit 50 changes the machining conditions 42 during the machining of the fine parts so as not to degrade the machining accuracy.

[0068] For example, the machining condition modification unit 50 performs at least one of the following modifications during machining of a fine part: (1) reducing the liquid volume, (2) decreasing the machining speed, (3) changing the offset, and (4) changing the pulse interval. Changing the offset moves the wire electrode 20 away from the workpiece W. Increasing the pulse interval reduces the discharge frequency between the electrodes. This reduces the possibility of machining accuracy deterioration.

[0069] Furthermore, preferably, when the relative movement distance L is less than the threshold TH, the processing condition changing unit 50 changes the amount of change in the processing condition 42 according to the difference between the relative movement distance L and the threshold TH.

[0070] For example, preferably, the smaller the relative movement distance L is than the threshold TH, the more significantly the machining condition modification unit 50 reduces the liquid volume, significantly reduces the machining speed, significantly shifts the wire electrode 20 off the machining path, or significantly extends the pulse interval. Thus, by modifying the machining conditions according to the fineness of the parts corresponding to each program block in the machining path, machining accuracy is improved.

[0071] The machining control unit 52 controls the wire electrical discharge machine 101 according to the machining program 40 and the machining conditions 42. When the machining conditions change the machining conditions 42 by the machining conditions change unit 50, the machining control unit 52 controls the wire electrical discharge machine 101 according to the changed machining conditions 42.

[0072] Figure 4 This diagram illustrates the functions implemented by the wire electrical discharge machining (EDM) machine 101.

[0073] Figure 4 Example of a machining path R. This machining path R consists of simple, long straight sections P (P1, P2) and fine, uneven sections Q (Q1, Q2). The straight sections P are represented by single-dotted lines, and the uneven sections Q are represented by double-dotted lines.

[0074] The relative movement distance L between the straight sections P1 and P2 is greater than the threshold TH. At this time, during the machining of the straight section P, the wire EDM machine 101 uses machining conditions 42 that take into account the material, thickness, etc. of the workpiece W, as always.

[0075] In contrast, the relative movement distance L of each of the multiple program blocks corresponding to the concave-convex portion Q1 is less than the threshold TH. At this time, the wire EDM machine 101 uses different processing conditions 42 than those for the straight portion P during the processing of the concave-convex portion Q.

[0076] In this way, the wire electrical discharge machine 101 can change the processing conditions 42 according to the fineness of the processing path and process the object W.

[0077] Figure 5This is a flowchart illustrating the control method of the first embodiment.

[0078] Control device 241, for example, performs Figure 5 The control method shown includes: an acquisition step S1, a threshold setting step S2, a judgment step S3, a processing condition change step S4, and a processing control step S5. Furthermore, the acquisition step S1 and the threshold setting step S2 are in different orders.

[0079] Step S1 is the step in which the acquisition unit 44 acquires multiple relative movement distances L. The acquisition unit 44 acquires multiple relative movement distances L by analyzing the machining program 40.

[0080] The threshold setting step S2 is the step in which the threshold setting unit 46 sets the threshold TH. Here, the threshold setting unit 46 calculates the threshold TH, for example, according to the mathematical formula (1) described above.

[0081] Determination step S3 is the 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 program block to be executed next by the machining control unit 52 with the threshold TH. When the relative movement distance L is less than the threshold TH (L<TH), the machining condition change step S4 and the machining control step S5 are executed sequentially. When the relative movement distance L is greater than or equal to the threshold TH (L≥TH), the machining condition change step S4 is skipped, and the machining control step S5 is executed.

[0082] The processing condition change step S4 is the step in which the processing condition change unit 50 changes the processing condition 42. The processing condition change unit 50 changes the processing condition 42 to reduce the adverse effects of the fineness of the processing path on processing accuracy. For example, the processing condition change unit 50 performs at least one of steps (1) to (4) described above. Preferably, the greater the difference between the relative movement distance L and the threshold TH, the greater the change in processing condition 42 by the processing condition change unit 50.

[0083] Machining control step S5 is the step in which the machining control unit 52 controls the wire electrical discharge machine 101 to perform electrical discharge machining on the workpiece W. The machining control unit 52 controls the wire electrical discharge machine 101 according to the machining program 40 and the machining conditions 42.

[0084] Furthermore, the processing control step S5 of this embodiment temporarily ends whenever a program block is completed. If the processing program 40 has not ended, the control device 241 executes the process from determination step S3 to processing control step S5 again. In the re-executed determination step S3, the relative movement distance L of the next program block after the last executed program block is compared with the threshold TH.

[0085] According to this embodiment, the machining conditions 42 are modified considering the fineness of the machining path. Therefore, the possibility of machining accuracy deteriorating due to the fineness of the machining path is reduced.

[0086] Furthermore, the fineness of the machining path is quantitatively evaluated by comparing each of the multiple relative movement distances L included in the machining program 40 with the threshold TH set by the threshold setting unit 46. Therefore, the wire EDM machine 101 can perform EDM with a fixed machining accuracy regardless of the operator.

[0087] [Second Implementation]

[0088] The second embodiment will be described below. However, descriptions that are repeated in the first embodiment will be omitted as much as possible. Unless otherwise specified, the constituent elements described in the first embodiment will be labeled with the same reference numerals as those in the first embodiment.

[0089] Figure 6 This is a structural diagram of the wire electrical discharge machining machine 102(10) according to the second embodiment.

[0090] The wire electrical discharge machining (EDM) machine 102 includes: a machining tank 12, a worktable 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).

[0091] Figure 7 This is a structural diagram of the control device 242 according to the second embodiment.

[0092] 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.

[0093] The arithmetic unit 36 ​​includes: an acquisition unit 44, a threshold setting unit 46, a determination unit 48, a processing condition modification unit 50, and a processing control unit 52. Additionally, the arithmetic unit 36 ​​also includes an exponent calculation unit 54. Like the acquisition unit 44, the exponent calculation unit 54 is implemented, for example, by executing a control program 38 through the processor of the arithmetic unit 36.

[0094] The index calculation unit 54 calculates the index IDX, which represents the fineness of the processing path, based on the multiple relative movement distances L obtained by the acquisition unit 44.

[0095] The index IDX is, for example, the median of the relative movement distances L represented by the program blocks contained in machining program 40. The median of multiple relative movement distances L tends to be smaller as the machining path becomes finer.

[0096] In order to calculate the median of multiple relative movement distances L, the exponent calculation unit 54 obtains the relative movement distance L specified in each of the multiple program blocks. Then, the exponent calculation unit 54 arranges the obtained multiple relative movement distances L in ascending order or descending order.

[0097] Figure 8 This is a table representing the result of arranging multiple relative movement distances L in ascending order. Figure 8 The upper segment (position) in the code indicates the position of each program block. B represents the total number of program blocks. The lower segment (L) i The ) represents the relative movement distance L (1≤i≤B) specified for each program block. k For L k-1 The above (L) k-1 ≤L k (2≤k≤i). The median of multiple relative movement distances L is Figure 8 L in the table (B+1) / 2 .

[0098] The threshold setting unit 46 sets the threshold TH. (The description of the threshold setting unit 46 is omitted; see also the first embodiment.)

[0099] The determination unit 48 compares the index IDX calculated by the index calculation unit 54 with the threshold TH. When the index IDX is less than the threshold TH, the determination unit 48 determines that the processing path contains a small part.

[0100] When the machining path includes fine details, the machining condition modification unit 50 modifies the machining conditions 42 during the execution of electrical discharge machining to prevent the machining accuracy from deteriorating. For example, the machining condition modification unit 50 performs at least one of the following: (1) reducing the liquid volume, (2) reducing the machining speed, (3) changing the offset, and (4) changing the pulse interval (see also the first embodiment).

[0101] Furthermore, preferably, when the index IDX is less than the threshold TH, the processing condition modification unit 50 changes the amount of change in the processing condition 42 based on the difference between the index IDX and the threshold TH. For example, preferably, the smaller the index IDX is than the threshold TH, the more significantly the processing condition modification unit 50 reduces the liquid volume, significantly reduces the processing speed, significantly deviates the wire electrode 20 from the processing path, or significantly extends the pulse interval. Thus, by changing the processing conditions according to the fineness of the processing path, the processing accuracy is improved.

[0102] Figure 9 This is a flowchart illustrating the control method of the second embodiment.

[0103] Control device 242, for example, performs Figure 9The control method shown includes: an acquisition step S1, a threshold setting step S2, a judgment step S3, a processing condition change step S4, and a processing control step S5. Additionally, the control method also includes an index calculation step S6.

[0104] Between the acquisition step S1 and the determination step S3, the exponent calculation step S6 is performed. The exponent calculation step S6 is the step in which the exponent calculation unit 54 calculates the exponent IDX. The exponent calculation unit 54 calculates the exponent IDX based on the multiple relative movement distances L obtained in the acquisition step S1.

[0105] In determination step S3, determination unit 48 compares the index IDX with the threshold TH. Based on the comparison result, determination unit 48 determines whether the processing path contains minute parts.

[0106] In this embodiment, the exponent IDX based on multiple relative travel distances L is compared with a threshold TH. Therefore, according to this embodiment, the determination unit 48 performs fewer comparisons compared to the case where each of the multiple relative travel distances L is compared with the threshold TH.

[0107] When the index IDX is less than the threshold TH (IDX < TH), the processing condition change step S4 and the processing control step S5 are executed sequentially. When the index IDX is greater than or equal to the threshold TH (IDX ≥ TH), the processing control step S5 is executed.

[0108] In the processing condition change step S4, when the processing path includes fine parts, the processing condition 42 is changed so that the processing accuracy does not deteriorate (see also the first embodiment).

[0109] According to this embodiment, as in the first embodiment, the machining conditions 42 are modified considering the fineness of the machining path. Therefore, the possibility of machining accuracy deterioration due to the fineness of the machining path can be reduced.

[0110] Furthermore, the precision of the machining path is quantitatively evaluated by comparing the index IDX calculated by the index calculation unit 54 through a predetermined calculation with the threshold TH set by the threshold setting unit 46. Therefore, the wire EDM machine 102 can perform EDM with a fixed machining accuracy regardless of the operator.

[0111] [Variation Example]

[0112] Hereinafter, variations of the above embodiments are described. However, descriptions that are repeated in the above embodiments will be omitted as much as possible. Unless otherwise specified, structural elements described in the above embodiments will be labeled with the same reference numerals as those in the above embodiments.

[0113] (Variation Example 1)

[0114] Sometimes the vertical distance between nozzle 281 and the workpiece W is different from the vertical distance between nozzle 282 and the workpiece W. In this case, the threshold setting unit 46 can substitute the average value of the vertical distance between nozzle 281 and the workpiece W and the vertical distance between nozzle 282 and the workpiece W as the specified distance S into the mathematical formula (1).

[0115] (Variation Example 2)

[0116] The processing condition changing unit 50 of the first embodiment can change the processing condition 42 to a setting predetermined for a fine processing path, regardless of the difference between the relative movement distance L and the threshold TH, when the relative movement distance L is less than the threshold TH.

[0117] Similarly, the processing condition changing unit 50 of the second embodiment can change the processing condition 42 to a setting predetermined for a fine processing path when the exponent IDX is less than the threshold TH, regardless of the difference between the exponent IDX and the threshold TH.

[0118] For example, a first processing condition 42 for processing simple parts and a second processing condition 42 for processing fine parts are pre-stored in the storage unit 34. When the index IDX is less than the threshold TH, the processing condition changing unit 50 selects the second processing condition 42. On the other hand, when the index IDX is higher than the threshold TH, the processing condition changing unit 50 selects the first processing condition 42.

[0119] (Variation Example 3)

[0120] The index calculation unit 54 can calculate the index IDX after the start of electrical discharge machining. For example, the index calculation unit 54 can calculate the index IDX each time one of a plurality of program blocks is executed, based on the relative movement distance L specified in each of a specified number of program blocks following the currently executed program block. The specified number is less than the total number of program blocks included in the machining program. The operator can arbitrarily instruct the specific value of the specified number to the control device 242 via the operation unit 32.

[0121] The machining condition modification unit 50 modifies the machining conditions 42 during the execution of the next program block based on the comparison result of the calculated exponent IDX and the threshold TH. As a result, the machining accuracy is improved.

[0122] (Variation Example 4)

[0123] The index calculation unit 54 can calculate the sum, arithmetic mean, or weighted average of multiple relative movement distances L represented by multiple program blocks as the index IDX. The sum, arithmetic mean, and weighted average of the multiple relative movement distances L, like the median of the multiple relative movement distances L, tend to be smaller as the processing path becomes finer.

[0124] The arithmetic mean is derived by dividing the sum of multiple relative movement distances L by the number of program blocks.

[0125] When calculating the weighted average, weighting coefficients are needed to multiply each relative distance L. These weighting coefficients, corresponding to each of the multiple relative distances L, are stored in advance, for example, by the storage unit 34. The weighting coefficients are larger the ones corresponding to shorter relative distances L. Furthermore, the specific values ​​of the weighting coefficients are determined based on prior experiments.

[0126] Additionally, the exponent calculation unit 54 can calculate the exponent IDX according to the following mathematical formula (2). In mathematical formula (2), IDX represents the exponent IDX. B represents the number of program blocks. L1, L2, ..., L B These represent the relative movement distance L of the program blocks. W1, W2, ..., W B These represent the weight coefficients corresponding to the program blocks. Similar to the case of calculating the weighted average, the weight coefficients are larger the closer they are to the shorter the relative movement distance L.

[0127] [Mathematical Expression 2]

[0128]

[0129] Furthermore, assuming B = W1 + W2 + ... + W B When, mathematical formula (2) represents the formula for calculating the weighted average of multiple relative movement distances L as the exponent IDX.

[0130] (A combination of multiple variations)

[0131] The aforementioned variations can be appropriately combined within a non-contradictory range.

[0132] [Invention derived from implementation methods]

[0133] The invention described below can be understood from the above embodiments and variations.

[0134] <First Invention>

[0135] The first invention is a wire electrical discharge machining (10) that moves a wire electrode (20) relative to a workpiece (W) immersed in a processing fluid (LQ) along a processing path and generates a discharge between the wire electrode and the workpiece according to a set processing condition (42), thereby processing the workpiece. The wire electrical discharge machining (10) includes: an acquisition unit (44) that acquires a relative movement distance (L) specified in each of a plurality of program blocks included in a processing program (40); a determination unit (48) that determines whether the processing path contains a fine part based on the acquired plurality of relative movement distances and a threshold (TH); and a processing condition changing unit (50) that changes the processing conditions during the processing of the fine part according to the determination result of the determination unit.

[0136] Therefore, the processing conditions of electrical discharge machining are automatically changed according to the fineness of the processing path.

[0137] Alternatively, the first invention may also include: a nozzle (28) that moves relative to the workpiece and sprays the processing fluid; and 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 workpiece, and the diameter of the wire electrode. The threshold is set accordingly. This allows for a quantitative evaluation of the fineness of the processing path.

[0138] Alternatively, the determination unit may identify the portion corresponding to the following program blocks in the processing path as the "minor portion": the program block that specifies a relative movement distance smaller than the threshold. Thus, the processing path is determined on a program block basis to determine whether it contains a minor portion.

[0139] Alternatively, the processing condition modification unit may vary the amount of change in the processing conditions based on the difference between the relative movement distance and the threshold. This allows for appropriate modification of the processing conditions according to the subtlety of the parts corresponding to each program block, thereby improving processing accuracy.

[0140] Alternatively, the first invention may also include an index calculation unit (54) that calculates an index representing the fineness of the processing path based on a plurality of the relative movement distances, and when the index is less than the threshold, the determination unit determines the part corresponding to the plurality of program blocks that define the plurality of the relative movement distances as the fine part. This reduces the number of determinations performed by the determination unit.

[0141] Alternatively, whenever one of the multiple program blocks is executed, the index calculation unit calculates the index based on the relative movement distance specified in each of the following program blocks: a predetermined number of program blocks following the currently executing program block. Thus, the wire EDM machine can determine whether to change the machining conditions used during the execution of each program block while simultaneously performing the EDM.

[0142] Alternatively, the index can be the median, weighted average, or arithmetic mean of the relative movement distances. Thus, the wire electrical discharge machining (EDM) machine can use a value that decreases as the machining path becomes finer as the index.

[0143] Alternatively, the processing condition modification unit may vary the amount of change in the processing conditions based on the difference between the index and the threshold. This allows for appropriate modification of the processing conditions according to the subtlety of the parts corresponding to multiple program blocks, thereby improving processing accuracy.

[0144] Alternatively, the processing conditions may include the volume of the processing fluid, and the processing condition modification unit reduces the volume of fluid during the processing of the fine parts. This reduces the possibility of deterioration in processing accuracy when the processing path is fine.

[0145] Alternatively, the processing conditions may include the pulse interval of the pulse voltage applied between the electrodes, and the processing condition modification unit may extend the pulse interval during the processing of the fine parts. This reduces the possibility of processing accuracy degradation when the processing path is fine.

[0146] Alternatively, the processing conditions may include a processing speed for processing the workpiece, and the processing condition change unit reduces the processing speed during the processing of the fine parts. This reduces the possibility of deterioration in processing accuracy when the processing path is fine.

[0147] Alternatively, the processing conditions may include an offset of the wire electrode relative to the processing path, and the processing condition modification unit may change this offset during the processing of the fine portion to move the wire electrode away from the workpiece. This reduces the likelihood of processing accuracy degradation when the processing path is fine.

[0148] <Second Invention>

[0149] The second invention is a control device (24) that controls a wire electrical discharge machining (10) to move a wire electrode (20) relative to a workpiece (W) immersed in a processing fluid (LQ) along a processing path and to generate a discharge between the wire electrode and the workpiece according to a set processing condition (42), thereby processing the workpiece. The control device (24) includes: an acquisition unit (44) that acquires a relative movement distance specified in each of a plurality of program blocks included in a processing program (40); a determination unit (48) that determines whether the processing path contains a fine part based on a comparison of the acquired plurality of relative movement distances with a threshold (TH); and a processing condition changing unit (50) that changes the processing conditions during the processing of the fine part based on the determination result of the determination unit.

[0150] Therefore, the processing conditions of electrical discharge machining are automatically changed according to the fineness of the processing path.

[0151] <Third Invention>

[0152] The third invention is a control method for controlling a wire electrical discharge machining (10) that moves a wire electrode (20) relative to a workpiece (W) immersed in a machining fluid (LQ) along a machining path and generates a discharge between the wire electrode and the workpiece according to set machining conditions (42), thereby machining the workpiece. The control method includes the following steps: an acquisition step (S1) of acquiring a relative movement distance (L) specified in each of a plurality of program blocks included in a machining program (40); a determination step (S3) of determining whether the machining path contains a fine part based on a comparison of the acquired plurality of relative movement distances with a threshold (TH); and a machining condition change step (S4) of changing the machining conditions during the machining of the fine part based on the determination result of the determination step.

[0153] Therefore, the processing conditions of electrical discharge machining are automatically changed according to the fineness of the processing path.

[0154] Symbol Explanation

[0155] 10… wire EDM machine, 20… wire electrode

[0156] 24…control device 28…nozzle

[0157] 40…Machining program 42…Machining conditions

[0158] 44…Acquisition Unit 46…Threshold Setting Unit

[0159] 48… Judgment Department 50… Processing Condition Change Department

[0160] 54… Index Calculation Section D… Nozzle Inner Diameter

[0161] IDX… Index LQ… Processing Fluid

[0162] S… Nozzle-to-work distance; TH… Threshold

[0163] W…processing object …wire diameter.

Claims

1. A wire electrical discharge machining (10) wherein a wire electrode (20) is moved relative to a workpiece (W) immersed in a processing fluid (LQ) along a processing path, and a discharge is generated between the wire electrode and the workpiece according to set processing conditions (42), thereby processing the workpiece, characterized in that, The wire electrical discharge machining (10) has the following features: The acquisition unit (44) acquires the relative movement distance (L) specified in each of the multiple program blocks included in the machining program (40). The determination unit (48) determines, based on the acquired relative movement distances and thresholds (TH), whether the processing path contains minute parts; and The processing condition modification unit (50) modifies the processing conditions during the processing of the fine part based on the determination result of the determination unit. The determination unit determines the part corresponding to the following program blocks in the processing path as the fine part: the program block that specifies a relative movement distance smaller than the threshold; or, determines the part corresponding to the following multiple program blocks as the fine part: multiple program blocks that specify multiple relative movement distances when the index representing the fineness of the processing path calculated based on multiple relative movement distances is less than the threshold.

2. The wire electrical discharge machining machine according to claim 1, characterized in that, The wire electrical discharge machining machine also has the following features: The nozzle (28) moves relative to the workpiece and sprays the processing fluid; and The threshold setting unit (46) sets the threshold 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.

3. The wire electrical discharge machining machine according to claim 1, characterized in that, When the determination unit determines the part corresponding to the program block in the processing path that has a relative movement distance smaller than the threshold as the fine part, the processing condition change unit changes the amount of processing condition change based on the difference between the relative movement distance and the threshold.

4. The wire electrical discharge machining machine according to claim 1, characterized in that, The wire electrical discharge machining machine further includes an index calculation unit that calculates the index based on a plurality of relative movement distances. When the index is less than the threshold, the determination unit determines the part corresponding to the plurality of program blocks that define the plurality of relative movement distances as the fine part. Whenever one of the plurality of program blocks is executed, the index calculation unit calculates the index based on the relative movement distance defined in the following program blocks: each of the program blocks in the specified number of program blocks following the program block that is being executed.

5. The wire electrical discharge machining machine according to claim 4, characterized in that, The index is the median, weighted average, or arithmetic mean of the relative distances traveled.

6. The wire electrical discharge machining machine according to claim 4, characterized in that, The processing condition modification unit adjusts the amount of change in the processing conditions based on the difference between the index and the threshold.

7. The wire electrical discharge machining machine according to claim 1 or 2, characterized in that, The processing conditions include the volume of the processing fluid. The processing condition modification unit reduces the amount of liquid used during the processing of the fine parts.

8. The wire electrical discharge machining machine according to claim 1 or 2, characterized in that, The processing conditions include the pulse interval of the pulse voltage applied between the electrodes. The pulse interval is extended during the processing of the fine parts by the processing condition change unit.

9. The wire electrical discharge machining machine according to claim 1 or 2, characterized in that, The processing conditions include the processing speed for processing the object being processed. The processing condition change unit reduces the processing speed during the processing of the fine parts.

10. The wire electrical discharge machining machine according to claim 1 or 2, characterized in that, The processing conditions include the offset of the wire electrode relative to the processing path. The processing condition changing unit changes the offset during the processing of the fine part so that the wire electrode is moved away from the object being processed.

11. A control device (24) that controls a wire electrical discharge machining (10) to move a wire electrode (20) relative to a workpiece (W) immersed in a machining fluid (LQ) along a machining path, and to generate a discharge between the wire electrode and the workpiece according to set machining conditions (42), thereby machining the workpiece, characterized in that, The control device (24) has: The acquisition unit (44) acquires the relative movement distance (L) specified in each of the multiple program blocks included in the machining program (40). The determination unit (48) determines whether the processing path contains minute parts based on a comparison of the acquired relative movement distances with a threshold (TH); and The processing condition modification unit (50) modifies the processing conditions during the processing of the fine part based on the determination result of the determination unit. The determination unit determines the part corresponding to the following program blocks in the processing path as the fine part: the program block that specifies a relative movement distance smaller than the threshold; or, determines the part corresponding to the following multiple program blocks as the fine part: multiple program blocks that specify multiple relative movement distances when the index representing the fineness of the processing path calculated based on multiple relative movement distances is less than the threshold.

12. A control method for controlling a wire electrical discharge machining (10) that moves a wire electrode (20) relative to a workpiece (W) immersed in a machining fluid (LQ) along a machining path and generates a discharge between the wire electrode and the workpiece according to set machining conditions (42), thereby machining the workpiece, characterized in that, The control method includes the following steps: In step S1, the relative movement distance (L) specified in each of the multiple program blocks included in the machining program (40) is obtained. The determination step (S3) involves comparing the obtained relative movement distances with a threshold (TH) to determine whether the processing path contains minute parts; and Processing condition change step (S4): Based on the determination result of the determination step, the processing conditions during the processing of the fine part are changed. In the determination step, the parts corresponding to the following program blocks in the processing path are determined to be the fine parts: program blocks that specify a relative movement distance smaller than the threshold; or, the parts corresponding to the following multiple program blocks are determined to be the fine parts: multiple program blocks that specify multiple relative movement distances when the index representing the fineness of the processing path calculated based on multiple relative movement distances is less than the threshold.

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