Wire electrical discharge machine, control device, and control method

Abstract

A wire EDM machine (10) includes: an acquisition unit (44) for acquiring the relative movement distance (L) defined by each of the plurality of blocks included in the processing formula (40); a determination unit (48) for determining whether the processing path includes a small part based on the plurality of relative movement distances (L) and a threshold value (TH); and a processing condition modification unit (50) for modifying the processing conditions (42) during the processing of the small part based on the determination result.

Description

Technical Field

[0001] This invention relates to a wire EDM machine, a control device for controlling the wire EDM machine, and a control method performed by the control device. Prior Technology

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

[0003] Generally speaking, processing conditions are set according to the material and thickness of the object being processed. In other words, the same processing conditions are used for both fine-machining paths and non-fine-machining paths.

[0004] However, if the same machining conditions are used for machining fine machining paths and machining non-fine machining paths, the machining accuracy will deteriorate, which is a problem.

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

[0006] The first embodiment of the present invention is a wire electrical discharge machining (EDM) machine, in which a wire electrode moves relative to a workpiece immersed in a processing fluid along a processing path while generating a discharge between the wire electrode and the workpiece according to preset processing conditions, thereby processing the workpiece; the wire EDM machine includes: an acquisition unit that acquires the relative movement distance of "each of the plurality of blocks included in the processing program"; a determination unit that determines whether the processing path includes a minute detail based on the acquired plurality of relative movement distances and a threshold value; and a processing condition modification unit that changes the processing conditions during the processing of the minute detail based on the determination result of the determination unit.

[0007] The second aspect of the present invention is a control device for controlling a wire electrical discharge machining (EDM) machine. The EDM machine moves a wire electrode relative to a workpiece immersed in a processing fluid along a processing path, while simultaneously generating a discharge between the wire electrode and the workpiece according to pre-set processing conditions, thereby processing the workpiece. The control device includes: an acquisition unit that acquires the relative movement distance of "each of the plurality of blocks included in the processing program"; a determination unit that determines whether the processing path contains a minute detail based on a comparison of the acquired plurality of relative movement distances with a threshold value; and a processing condition modification unit that changes the processing conditions during the processing of the minute detail based on the determination result of the determination unit.

[0008] The 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 processing fluid along a processing path, while simultaneously generating a discharge between the wire electrode and the workpiece according to pre-set processing conditions, thereby processing the workpiece. The control method includes: an acquisition step, acquiring relative movement distances defining "each of the plurality of blocks included in the processing formula"; a determination step, determining whether the processing path contains minute details based on a comparison of the acquired plurality of relative movement distances with a critical value; and a processing condition modification step, modifying the processing conditions during the processing of the minute details based on the determination result of the determination step.

[0009] The present invention automatically changes the processing conditions of electrical discharge machining according to the fineness of the processing path.

[0010] The above-mentioned objectives, features, and advantages can be easily understood from the explanation of the following implementation examples with reference to the attached diagrams. Simple Explanation of the Diagram

[0011] Figure 1 is a structural diagram of the wire EDM machine of the first embodiment.

[0012] Figure 2A is a diagram illustrating the positional relationship between the line electrode and the nozzle at a longer straight section of the machining path. Figure 2B is a diagram illustrating the positional relationship between the line electrode and the nozzle at a fine section of the machining path.

[0013] Figure 3 is a configuration diagram of the control device in the first implementation state.

[0014] Figure 4 is a diagram illustrating the functions of a wire EDM machine.

[0015] Figure 5 is a flowchart illustrating the control method of the first implementation state.

[0016] Figure 6 is a structural diagram of the wire EDM machine of the second embodiment.

[0017] Figure 7 is a diagram of the control device configuration for the second implementation.

[0018] Figure 8 is a table showing the results obtained by arranging the relative movement distances of multiple numbers in ascending order of length.

[0019] Figure 9 is a flowchart illustrating the control method of the second implementation state. Implementation

[0020] [First Implementation Example] Figure 1 is a structural diagram of the wire EDM machine 101(10) of the first embodiment.

[0021] Furthermore, Figure 1 shows not only the wire EDM machine 101, but also the X, Y, and Z directions. The X and Y directions are parallel to the horizontal plane. The Z direction is the upward direction. The X, Y, and Z directions are perpendicular to each other.

[0022] The wire electrical discharge machining (EDM) machine 101 includes: a processing 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.

[0023] The machining tank 12 is a tank for housing the first guide block 181, the second guide block 182, and the worktable 14. Furthermore, the machining tank 12 stores machining fluid LQ.

[0024] The worktable 14 is a platform that supports the workpiece W. The worktable 14 and the workpiece W are immersed in the processing fluid LQ inside the processing tank 12.

[0025] Motors 16X and 16Y are motors connected to the worktable 14. The worktable 14 moves in the X direction driven by motor 16X. Also, the worktable 14 moves in the Y direction driven by motor 16Y.

[0026] 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.

[0027] The first guide block 181 is positioned above the worktable 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 remains unchanged. The nozzle 281 is a component for spraying the machining fluid LQ downwards from the nozzle 281. The front end of the nozzle 281 has a spray orifice 28a for spraying the machining fluid LQ. The wire guide 261 is positioned above the spray orifice 28a. The front end of the nozzle 281 (spray orifice 28a) is positioned above the workpiece W and separated from the workpiece W by a predetermined interval S.

[0028] The second guide block 182 is positioned below the worktable 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 remains unchanged. The nozzle 282 sprays the machining fluid LQ upwards. A nozzle orifice 28a is formed at the front end of the nozzle 282 for spraying the machining fluid LQ. The wire guide 262 is located below the nozzle orifice 28a. The front end of the nozzle 282 is positioned below the workpiece W and separated from the workpiece W by a predetermined interval S.

[0029] 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.

[0030] The first guide block 181 and the second guide block 182 can each move horizontally. In order for the first guide block 181 and the second guide block 182 to move horizontally, multiple motors 16 other than motors 16X and motor 16Y can be connected to the first guide block 181 and the second guide block 182 respectively.

[0031] The wire electrode 20 is a conductive wire. A pre-formed machining hole H is formed in the workpiece W. The machining hole H passes through the workpiece W vertically. The wire electrode 20 passes through the machining hole H.

[0032] The wire electrode 20 is supported by metal wire conductors 261 and 262, and is simultaneously delivered from metal wire conductor 261 to metal wire conductor 262. The method of delivering the wire electrode 20 is a method known in the art. Therefore, a description of this method is omitted.

[0033] As mentioned above, the workpiece W (worktable 14) moves horizontally under the drive of motors 16X and 16Y. Therefore, the wire electrode 20 moves horizontally relative to the workpiece W.

[0034] 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 to the control device 241 (see also Figure 3). The control device 241 controls motors 16X and 16Y according to the machining program 40. Therefore, the wire electrode 20 moves relative to the workpiece along the machining path set in the machining program 40.

[0035] Power supply unit 22 is connected to wire electrode 20 and worktable 14 (workpiece W). Power supply unit 22 applies a pulse voltage between the workpiece W and wire electrode 20. Therefore, a discharge is generated between the electrodes. Power supply unit 22 is controlled by control unit 241.

[0036] The workpiece W is cut due to the generation of discharge. Therefore, the wire electrode 20 moves relative to the workpiece along the workpiece path while generating discharge between the electrodes, thereby machining the workpiece W into a shape that follows the workpiece path.

[0037] Furthermore, since the workpiece W is being cut, chips are generated around the electrode spacing. These chips are removed from the electrode spacing using the machining fluid LQ ejected from nozzles 281 and 282. The machining fluid LQ ejected from nozzles 281 and 282 also cools the wire electrode 20. This prevents the wire electrode 20 from overheating due to discharge.

[0038] However, due to the discharge 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 being machined by the wire electrode 20.

[0039] The operator can set the pulse interval of the pulse voltage and the flow rate of the processing fluid LQ ejected from the nozzle 28 per unit time in the control device 241 as processing conditions 42 (see also Figure 3). The operator can set processing conditions 42 based on the material and thickness of the workpiece W. The control device 241 controls the wire electrical discharge machining 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".

[0040] Furthermore, the flow path of the machining fluid LQ ejected from nozzle 28 varies depending on the shape of the workpiece W around the electrode. In simpler sections of the machining path (e.g., longer straight lines), the change in the flow path of the machining fluid LQ ejected from nozzle 28 is smaller. On the other hand, in finer sections of the machining path, the change in the flow path of the machining fluid LQ ejected from nozzle 28 is larger. Therefore, the machining fluid LQ ejected from nozzle 28 is disturbed in the finer sections of the machining path.

[0041] Figure 2A illustrates the positional relationship between P, the line electrode 20, and the nozzle 28 at a relatively long straight section of the machining path. Figure 2B illustrates the positional relationship between Q, the line electrode 20, and the nozzle 28 at a slightly irregular section of the machining path.

[0042] Regarding the examples in Figure 2A and Figure 2B, the change in the flow path of the processing fluid LQ is relatively larger in the example in Figure 2B. Therefore, the processing fluid LQ is disturbed in the example in Figure 2B.

[0043] The disturbance of the machining fluid LQ causes the wire electrode 20 to vibrate significantly. This significant vibration of the wire electrode 20 affects machining accuracy. Therefore, even minor disturbances of the machining fluid LQ along the machining path can impact machining accuracy. Thus, it is preferable to set machining conditions 42 that consider not only the material and thickness of the workpiece W, but also the subtle details of the shape of the workpiece W (machining path).

[0044] However, determining whether a machining path is fine is a significant burden for operators. Furthermore, the criteria for judging whether a machining path is fine may differ between operators. Consequently, when machining multiple objects W using the same machining formula 40, the machining accuracy may vary due to differences in operator skill.

[0045] Based on the above, the detailed technology of the control device 241 of this embodiment will be described below. Furthermore, unless otherwise specified, in the following description, flow rate refers to the flow rate of the processing fluid LQ ejected from the nozzle 28 per unit time.

[0046] Figure 3 is a configuration diagram of the control device 241 in the first embodiment.

[0047] The control device 241 includes a display unit 30, an operation unit 32, a storage unit 34, and a calculation unit 36.

[0048] The display unit 30 is a display device having a display screen 301. The display unit 30 displays, for example, various data stored in the storage unit 34 (described later) on the display screen 301 as needed. The material of the display screen 301 may include, 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 also include organic electroluminescence (OEL) materials.

[0049] 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 through 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 arranged on the display screen 301. Alternatively, the operation unit 32 may also include a keyboard and a mouse.

[0050] The storage unit 34 has one or more memory modules. The storage unit 34 may include, for example, random access memory (RAM) and read-only memory (ROM).

[0051] The storage unit 34 stores the control program 38, the machining program 40, and the machining conditions 42. The control program 38 controls the wire EDM machine 101 (10) according to the machining program 40 and the machining conditions 42.

[0052] Machining program 40 contains instructions representing the machining path. This instruction consists of a plurality of blocks. Each of the plurality of blocks defines the relative movement direction and relative movement distance L of the line electrode 20.

[0053] By sequentially executing multiple blocks, the wire electrode 20 is moved relative to each other along the processing path.

[0054] As mentioned above, processing condition 42 includes conditions related to "the pulse interval of the pulse voltage and the flow rate of the processing fluid LQ ejected from nozzle 28". However, processing condition 42 is not limited to conditions related to pulse interval and flow rate. Processing condition 42 may also include, for example, conditions related to "the offset between the wire electrode 20 and the processing path, and the processing speed of the workpiece W being processed".

[0055] The processing conditions 42 are input by the operator to the control device 241, for example, using the operation unit 32. The operator inputs the processing conditions 42, which takes into account the material and thickness of the object W to be processed, as is the case with conventional techniques. This operation is included in the preparation operation of electrical discharge machining. However, it is not necessary for the operator to input the processing conditions 42, which take into account the fineness of the processing path.

[0056] Furthermore, in addition to storing the control program 38, the processing program 40, and the processing conditions 42, the storage unit 34 can also store various data and programs as needed.

[0057] The arithmetic unit 36 ​​includes processing circuitry. This processing circuitry may include one or more processors. However, the processing circuitry of the arithmetic unit 36 ​​may also include application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), and discrete components.

[0058] 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 the processor of the arithmetic unit 36 ​​executing the control program 38. 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 may also be implemented using the aforementioned ASIC, FPGA, and discrete components.

[0059] The acquisition unit 44 obtains the relative movement distance L of "each of the multiple blocks contained in the processing formula 40" by analyzing the processing formula 40.

[0060] The critical value setting unit 46 sets a critical value TH for determining whether the machining path contains a fine path. The critical value setting unit 46 calculates the critical value TH based on the following mathematical formula (1), for example. In mathematical formula (1), TH represents the critical value TH. D represents the inner diameter of the nozzle 28 (jet outlet 28a). S represents the aforementioned predetermined interval S. φ represents the wire diameter of the wire electrode 20. α, β, and γ represent weighting coefficients, respectively. α, β, and γ are preset through experiments.

[0061]

Mathematical Formula 1

[0062] Furthermore, the operator can specify any threshold value TH. In this case, the operator, for example, inputs any threshold value TH to the control device 241 via the operation unit 32. When the operator has input the threshold value TH, the threshold value setting unit 46 sets the threshold value TH input by the operator.

[0063] The determination unit 48 compares each of the multiple relative movement distances L with the critical value TH. The determination unit 48 determines the part in the processing path that corresponds to the "block that defines a relative movement distance L smaller than the critical value TH" as a minute part.

[0064] The determination unit 48 can sequentially compare the relative movement distances L and the critical value TH according to the progress of the electrical discharge machining, or it can compare the relative movement distances L and the critical value TH of all blocks before the start of the electrical discharge machining.

[0065] The machining condition modification unit 50 changes the machining conditions 42 during the machining of fine details when the machining path contains fine details, so as to avoid deterioration of machining accuracy.

[0066] For example, the processing condition modification unit 50 performs at least one of the following modifications to the processing conditions 42 during the processing of fine details: (1) reducing the flow rate, (2) slowing down the processing speed, (3) changing the offset, and (4) changing the pulse interval. The offset is changed so that the line electrode 20 moves away from the workpiece W. The pulse interval is increased so that the discharge frequency between the electrodes decreases. Therefore, the possibility of deterioration in processing accuracy is reduced.

[0067] Furthermore, the processing condition modification unit 50, when the relative movement distance L is less than the critical value TH, changes the amount of change in processing condition 42 according to the difference between the relative movement distance L and the critical value TH, which is preferable.

[0068] For example, the smaller the relative movement distance L is than the critical value TH, the more the machining condition modification unit 50 significantly reduces the flow rate, significantly slows down the machining speed, significantly deviates the wire electrode 20 from the machining path, or significantly increases the pulse interval, which is preferable. In this way, because the machining conditions are modified with fine detail according to the "corresponding points in the machining path to each block", the machining accuracy is improved.

[0069] 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 42 are changed 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.

[0070] Figure 4 is a diagram illustrating the functions of the wire electrical discharge machining (EDM) machine 101.

[0071] Figure 4 illustrates the machining path R. This machining path R includes simple and relatively long straight sections P (P1, P2) and minor irregularities Q (Q1, Q2). The straight sections P are represented by a single-point chain, and the irregularities Q are represented by a two-point chain.

[0072] The relative movement distance L between P1 and P2 at the straight line is greater than the critical value TH. At this time, the wire EDM machine 101, during the processing of P at the straight line, uses processing conditions 42 "obtained by taking into account the material and thickness of the object W to be processed" as in conventional technology.

[0073] In contrast, the relative movement distance L of each of the "multiple blocks corresponding to the irregularity Q1" is less than the critical value TH. At this time, the wire EDM machine 101 uses different processing conditions 42 than those used at the straight section P during the processing of the irregularity Q.

[0074] As described above, the wire EDM machine 101 can change the processing conditions 42 according to the fineness of the processing path while processing the object W.

[0075] Figure 5 is a flowchart illustrating the control method of the first implementation state.

[0076] The control device 241, for example, executes the control method shown in FIG. 5. This control method includes an acquisition step S1, a threshold value setting step S2, a determination step S3, a processing condition changing step S4, and a processing control step S5. Also, the order of the acquisition step S1 and the threshold value setting step S2 is not fixed.

[0077] In the acquisition step S1, the acquisition unit 44 acquires a plurality of relative movement distances L. The acquisition unit 44 analyzes the machining program 40 to acquire a plurality of relative movement distances L.

[0078] In the threshold value setting step S2, the threshold value setting unit 46 sets a threshold value TH. Here, the threshold value setting unit 46 calculates the threshold value TH based on the aforementioned mathematical formula (1), for example.

[0079] In the determination step S3, the determination unit 48 compares the relative movement distance L with the threshold value TH. The determination unit 48 compares the relative movement distance L of "the block that the machining control unit 52 will continuously execute" with the threshold value TH. When the relative movement distance L is less than the threshold value TH (L < TH), the processing condition changing step S4 and the processing control step S5 are sequentially executed. When the relative movement distance L is greater than or equal to the threshold value TH (L ≧ TH), the processing condition changing step S4 is omitted and the processing control step S5 is executed.

[0080] In the processing condition changing step S4, the processing condition changing unit 50 changes the processing conditions 42. The processing condition changing unit 50 changes the processing conditions 42 in order to reduce the adverse influence of the fineness of the machining path on the machining accuracy. For example, the processing condition changing unit 50 executes at least one of the aforementioned (1) to (4). Here, the greater the difference between the relative movement distance L and the threshold value TH, the better it is that the processing condition changing unit 50 makes the change amount of the processing conditions 42 larger.

[0081] In the processing control step S5, the machining control unit 52 controls the wire electrical discharge machining machine 1 to perform electrical discharge machining on the workpiece W. The machining control unit 52 controls the wire electrical discharge machining machine 101 according to the machining program 40 and the processing conditions 42.

[0082] Also, in the processing control step S5 of this embodiment, it temporarily ends every time the processing of one block is completed. The control device 241 re-executes the process of the determination step S3 to the processing control step S5 as long as the machining program 40 has not ended. In the determination step S3 of the re-execution, the relative movement distance L of "the next block after the last executed block" is compared with the threshold value TH.

[0083] According to this embodiment, the machining conditions 42 are changed to take into account the fineness of the machining path. Therefore, the possibility of "deterioration in machining accuracy due to a finer machining path" is reduced.

[0084] Furthermore, the fineness of the machining path is quantitatively evaluated by comparing each of the "relative movement distances L of the complex numbers included in machining formula 40" with the "critical value TH set by the critical value setting unit 46". Therefore, regardless of the operator, the wire EDM machine 101 can still perform EDM with a certain machining accuracy.

[0085] [Second Implementation Format] The second embodiment will be described below. In the following description, details that are repeated in the first embodiment will be omitted as much as possible. Furthermore, unless otherwise specified, the constituent elements described in the first embodiment will be marked with the same reference numerals as in the first embodiment.

[0086] Figure 6 is a structural diagram of the wire EDM machine 102(10) of the second embodiment.

[0087] The wire electrical discharge machining 102 includes a processing 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).

[0088] Figure 7 is a configuration diagram of the control device 242 in the second embodiment.

[0089] 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 a calculation unit 36.

[0090] 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. Furthermore, the arithmetic unit 36 ​​also includes an exponent calculation unit 54. The exponent calculation unit 54, like the acquisition unit 44, is implemented, for example, by the processor of the arithmetic unit 36 ​​executing the control program 38.

[0091] The index calculation unit 54 calculates the index IDX, which displays the fineness of the processing path, based on the relative movement distance L of the complex number obtained by the acquisition unit 44.

[0092] The index IDX, for example, is the median value of "the relative movement distance L defined by each block contained in processing formula 40". The median value of the relative movement distance L of the complex tends to be smaller as the processing path becomes finer.

[0093] In order to obtain the median value of the relative movement distance L of the complex number, the exponent calculation unit 54 obtains the relative movement distance L defined by each block of the complex number. Then, the exponent calculation unit 54 arranges the "obtained relative movement distance L of the complex number" in order from shortest to longest or from longest to shortest.

[0094] Figure 8 is a table showing the results obtained by arranging the relative movement distances L in ascending order of shortest to longest. In Figure 8, the upper section (order) represents the order of each block. B represents the total number of blocks. The lower section (Li) represents the relative movement distance L that defines each block (1≦i≦B). Lk is above Lk-1 (Lk-1≦Lk, 2≦k≦i). The median value of the relative movement distance L is L(B+1) / 2 in the table of Figure 8.

[0095] The threshold setting unit 46 sets the threshold value TH. Here, the description of the threshold setting unit 46 is omitted (see also the first embodiment).

[0096] The determination unit 48 compares the index IDX calculated by the index calculation unit 54 with the critical value TH. When the index IDX is less than the critical value TH, the determination unit 48 determines that the processing path contains minor details.

[0097] When the machining path contains minute details, the machining condition modification unit 50 changes the machining conditions 42 during the electrical discharge machining process to avoid deterioration of machining accuracy. For example, the machining condition modification unit 50 performs at least one of the following: (1) reducing the flow rate, (2) slowing down the machining speed, (3) changing the offset, and (4) changing the pulse interval (see also the first embodiment).

[0098] Furthermore, it is preferable that the machining condition modification unit 50 changes the amount of machining condition 42 according to the difference between the index IDX and the critical value TH when the index IDX is less than the critical value TH. For example, it is preferable that the machining condition modification unit 50 significantly reduces the flow rate, significantly slows down the machining speed, significantly deviates the wire electrode 20 from the machining path, or significantly increases the pulse interval as the index IDX is less than the critical value TH. In this way, machining accuracy is improved by subtly modifying the machining conditions according to the machining path.

[0099] FIG. 9 is a flowchart illustrating the process of the control method of the second embodiment.

[0100] The control device 242, for example, executes 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 processing condition change step S4, and a processing control step S5. Further, this control method further includes an index calculation step S6.

[0101] 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.

[0102] 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 fine parts.

[0103] In 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 determination unit 48 can make fewer comparisons compared to the case of "comparing each of the plurality of relative movement distances L with the threshold value TH".

[0104] When the index IDX is less than the threshold value TH (IDX < TH), the processing condition change step S4 and the processing control step S5 are sequentially executed. When the index IDX is greater than or equal to the threshold value TH (IDX ≧ TH), the processing control step S5 is executed.

[0105] When the machining path includes fine parts, in the processing condition change step S4, the processing condition 42 is changed to avoid deterioration of machining accuracy (also refer to the first embodiment).

[0106] According to this embodiment, similar to the first embodiment, the processing condition 42 is 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.

[0107] Furthermore, the fineness of the processing path is quantitatively evaluated by comparing the "index IDX calculated by the index calculation unit 54 using a predetermined calculation method" with the "critical value TH set by the critical value setting unit 46". Therefore, regardless of the operator, the wire EDM machine 102 can still perform EDM with a certain processing accuracy.

[0108] [Variation Example] The following describes variations of the above-described embodiments. In the following descriptions, repetitions of the descriptions of the above-described embodiments are omitted as much as possible. Furthermore, unless otherwise specified, constituent elements described in the above-described embodiments are marked with the same reference numerals as in the above-described embodiments.

[0109] (Variation Example 1) The interval between "nozzle 281 and the workpiece W in the vertical direction" and "nozzle 282 and the workpiece W in the vertical direction" may be different. In this case, the threshold setting unit 46 can substitute the average value of "nozzle 281 and the workpiece W in the vertical direction" and "nozzle 282 and the workpiece W in the vertical direction" as a predetermined interval S into the mathematical formula (1).

[0110] (Variation Example 2) In the first implementation state, the processing condition modification unit 50 can change the processing condition 42 to the setting of "pre-determined for fine processing path" when the relative movement distance L is less than the critical value TH, regardless of the size of the difference between the relative movement distance L and the critical value TH.

[0111] Similarly, in the second implementation, the processing condition change unit 50 can change the processing condition 42 to the setting of "pre-defined for fine processing path" when the index IDX is less than the critical value TH, regardless of the size of the difference between the index IDX and the critical value TH.

[0112] For example, a first processing condition 42 for processing simple areas and a second processing condition 42 for processing fine areas are pre-stored in the storage unit 34. When the index IDX is less than the critical value TH, the processing condition modification unit 50 selects the second processing condition 42. On the other hand, when the index IDX is higher than the critical value TH, the processing condition modification unit 50 selects the first processing condition 42.

[0113] (Variation Example 3) The index calculation unit 54 can also calculate the index IDX after the start of electrical discharge machining. For example, whenever one of a plurality of blocks is executed, the index calculation unit 54 can calculate the index IDX based on the relative movement distance L defined for each of the "predetermined number of blocks following the currently executed block". The predetermined number is less than the total number of blocks included in the machining program. The operator can arbitrarily instruct the control device 242 with the specific value of the predetermined number through the operation unit 32.

[0114] The processing condition modification unit 50 modifies the processing conditions 42 during the "period of executing the next block" based on the comparison between the calculated index IDX and the critical value TH. As a result, the processing accuracy is improved.

[0115] (Variation Example 4) The exponent calculation unit 54 can calculate the sum, arithmetic mean, or weighted average of the relative movement distances L of the complex numbers shown in the block as the exponent IDX. The sum, arithmetic mean, and weighted average of the relative movement distances L of the complex numbers, like the median value of the relative movement distance L of the complex numbers, tend to become smaller as the processing path becomes finer.

[0116] The arithmetic mean is derived by dividing the number of blocks by the sum of the relative movement distances L of the complex numbers.

[0117] When calculating the weighted average, a weighting coefficient "multiplied by each relative distance L" is required. The weighting coefficients corresponding to the relative distance L of each complex number are stored in advance, for example, in the storage unit 34. Among the weighting coefficients of the complex numbers, the ones corresponding to shorter relative distances L are larger. Furthermore, the specific values ​​of the weighting coefficients of the complex numbers are set through prior experiments.

[0118] Furthermore, the index calculation unit 54 may also calculate the index IDX based on the following mathematical formula (2). In mathematical formula (2), IDX represents the index IDX. B represents the number of blocks. L1, L2, ..., LB represent the relative movement distance L of the blocks, respectively. W1, W2, ..., WB represent the weighting coefficients corresponding to the blocks, respectively. Similar to the case of calculating the weighted average, among the complex weighting coefficients, those corresponding to shorter relative movement distances L are larger.

[0119]

Mathematical Formula 2

[0120] Furthermore, assuming the case is B = W1 + W2 + ... + WB, mathematical formula (2) represents the formula for "calculating the weighted average of the relative movement distance L of the complex number as the exponent IDX".

[0121] (Combination of examples of complex number variations) The aforementioned variations of complex numbers can be appropriately combined within the scope of not contradicting each other.

[0122] [Invention derived from implementation] The invention described below is understood based on the above embodiments and variations.

[0123] <First Invention> 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) to process the workpiece. The wire electrical discharge machining includes: an acquisition unit (44) that acquires the relative movement distance (L) of "each of the plurality of blocks included in the processing formula (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 value (TH); and a processing condition changing unit (50) that changes the processing conditions during the period when the fine part is processed based on the determination result of the determination unit.

[0124] In this way, the processing conditions of electrical discharge machining can be automatically changed according to the fineness of the processing path.

[0125] The first invention may further include: a nozzle (28) that sprays the processing fluid while moving relative to the workpiece; and a critical value setting unit (46) that sets the critical 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. This allows for quantitative evaluation of the fineness of the processing path.

[0126] The determination unit can identify the part of the processing path that corresponds to "the block that defines the relative movement distance smaller than the threshold value" as the minute detail. In this way, it determines whether the processing path contains minute details on a block-by-block basis.

[0127] The processing condition modification unit can change the amount of processing condition modification based on the difference between the relative movement distance and the critical value. By appropriately modifying the processing conditions according to the fineness corresponding to each block, processing accuracy is improved.

[0128] The first invention further includes: an index calculation unit (54) that calculates an index indicating the fineness of the processing path based on the relative movement distance of the plurality; and a determination unit that, when the index is less than the threshold value, determines the area corresponding to the "block of the plurality of relative movement distances of the plurality" as the fineness. In this way, the determination unit can perform fewer determinations.

[0129] Whenever one of the multiple blocks is executed, the index calculation unit can calculate the index based on the relative movement distance defined for each of the "predetermined number of subsequent blocks in the current block". In this way, the wire EDM machine can perform "determining whether to change the processing conditions used in each block" and "performing EDM" in parallel.

[0130] This index can be the median, weighted average, or arithmetic mean of the relative movement distances of a complex number. In this way, wire EDM machines can use a value that becomes smaller as the machining path becomes finer.

[0131] The processing condition modification unit can change the amount of processing condition modification based on the difference between the index and the critical value. By appropriately modifying the processing conditions according to the fineness corresponding to multiple blocks, processing accuracy is improved.

[0132] The processing conditions include the flow rate of the processing fluid, and the processing condition modification unit can reduce the flow rate during the period when the fine part is processed. Therefore, the possibility of "deterioration in processing accuracy when the processing path is fine" is reduced.

[0133] The processing conditions include the pulse interval of the pulse voltage applied between the electrodes, and the processing condition modification unit can increase the pulse interval during the period when the minute detail is processed. Therefore, the possibility of "processing accuracy deteriorating when the processing path is fine" is reduced.

[0134] The processing conditions include the processing speed at which the workpiece is processed. The processing condition modification unit can slow down the processing speed during the period when the minute detail is processed. Therefore, the possibility of "deterioration in processing accuracy when the processing path is finer" is reduced.

[0135] The processing conditions include the offset of the wire electrode relative to the processing path. The processing condition modification unit can change this offset during the processing period of the minute detail, so that the wire electrode moves away from the object being processed. Therefore, the possibility of "processing accuracy deteriorating when the processing path is fine" is reduced.

[0136] <Second Invention> The second invention is a control device (24) that controls a wire electrical discharge machining (10). The wire electrical discharge machining (10) 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) to process the workpiece. The control device includes: an acquisition unit (44) that acquires the relative movement distance of "each of the plurality of blocks included in the processing formula (40)"; a determination unit (48) that determines whether the processing path contains a fine part based on the acquisition of the plurality of relative movement distances and a comparison with a threshold value (TH); and a processing condition modification unit (50) that changes the processing conditions during the period when the fine part is processed based on the determination result of the determination unit.

[0137] In this way, the processing conditions of electrical discharge machining can be automatically changed according to the fineness of the processing path.

[0138] <Third Invention> The third invention is a control method for controlling a wire electrical discharge machining (10); the wire electrical discharge machining (10) 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) to process the workpiece; the control method includes: an acquisition step (S1) for acquiring the relative movement distance (L) of "each of the multiple blocks defined by the processing formula (40)"; a determination step (S3) for determining whether the processing path contains a small part based on the acquisition of the multiple relative movement distances and a critical value (TH); and a processing condition change step (S4) for changing the processing conditions during the processing of the small part according to the determination result of the determination step.

[0139] In this way, the processing conditions of electrical discharge machining can be automatically changed according to the fineness of the processing path.

[0140] Furthermore, the present invention is not limited to the above-described embodiments and variations, and various configurations can be achieved without departing from the spirit of the present invention.

[0141] 10, 101, 102: Wire EDM machines 12: Machining slot 14: Workbench 16, 16X, 16Y: Motors 181: First guide block 182: Second guide block 20: Line electrode 22: Power supply device 24, 241, 242: Control devices 261, 262: Metal wire conductors 28, 281, 282: Nozzle 28a: Jet nozzle 30: Display Section 301: Display screen 32: Operations Department 321: Operating Panel 322: Touch panel 34: Storage Department 36: Arithmetic Department 38: Control Program 40: Processing method 42: Processing Conditions (First Processing Condition) (Second Processing Condition) 44: Acquisition Department 46: Critical value setting unit 48: Judgment Department 50: Processing Condition Change Department 52: Machining Control Department 54: Index Calculation Department B: Total number of blocks D: Inner diameter of the nozzle H: Start machining the hole IDX: Index L,L i,L 1,L 2,L (B+1) / 2,L B-1,LB,L k,L k-1: Relative distance traveled LQ: Processing Fluid P, P1, P2: Locations along the straight line Q, Q1, Q2: Irregular areas R: Processing path S: Distance between the nozzle and the workpiece S1~S6: Steps TH: Critical value W: Object to be processed W1, W2, WB: Weighting coefficients X, Y, Z: Direction α,β,γ: weighting coefficients φ: 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 a set processing condition (42) to process the workpiece; the wire electrical discharge machining includes: an acquisition unit (44) for acquiring relative movement distances (L) defined by each of a plurality of blocks included in the processing formula (40); a determination unit (48) for determining whether the processing path contains a fine detail based on the acquired plurality of relative movement distances and a threshold value (TH); and a processing condition changing unit (50) for changing the processing conditions during the period when the fine detail is processed according to the determination result of the determination unit.

2. The wire EDM machine of claim 1 further comprises: a nozzle (28) that sprays the processing fluid while moving relative to the workpiece; and a threshold 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.

3. The wire electrical discharge machining machine as requested in item 1 or 2, wherein, The determination unit determines the area in the processing path that corresponds to the block with a relative movement distance smaller than the critical value as the minute detail.

4. The wire electrical discharge machining machine as described in claim 3, wherein, The processing condition changing unit changes the amount of processing condition change based on the difference between the relative movement distance and the critical value.

5. The wire EDM machine of claim 1 or 2 further comprises: an index calculation unit (54) that calculates an index showing the fineness of the processing path based on the plurality of the relative movement distances; and a determination unit that, when the index is less than the threshold value, determines the point corresponding to the block of the plurality of relative movement distances as the fineness.

6. The wire electrical discharge machining machine as described in claim 5, wherein, Whenever one of the multiple blocks is executed, the index calculation unit calculates the index based on the relative movement distance defined by each of the subsequent predetermined number of blocks in the executed block.

7. The wire electrical discharge machining machine as described in claim 5, wherein, The index is the median, weighted average, or arithmetic mean of the relative distances traveled by the complex numbers.

8. The wire electrical discharge machining machine as described in claim 5, wherein, The processing condition change unit adjusts the amount of change in the processing conditions according to the magnitude of the difference between the index and the critical value.

9. The wire electrical discharge machining machine as requested in item 1 or 2, wherein, The processing conditions include the flow rate of the processing fluid; the processing condition change unit reduces the flow rate during the processing of the fine part.

10. The wire electrical discharge machining machine as requested in item 1 or 2, wherein, The processing conditions include the pulse interval of the pulse voltage applied between the electrodes; the processing condition changing unit increases the pulse interval during the processing of the fine part.

11. The wire electrical discharge machining machine as requested in item 1 or 2, wherein, The processing conditions include the processing speed at which the object being processed is processed; the processing condition modification unit slows down the processing speed during the processing of the fine part.

12. The wire electrical discharge machining machine as requested in item 1 or 2, wherein, 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 minute detail so that the wire electrode moves away from the object being processed.

13. A control device (24) for controlling a wire electrical discharge machining (10); the wire electrical discharge machining (10) 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) to process the workpiece; the control device includes: an acquisition unit (44) for acquiring the relative movement distance (L) defined by each of the plurality of blocks included in the processing formula (40); a determination unit (48) for determining whether the processing path contains a minute detail based on a comparison of the acquired plurality of relative movement distances with a threshold value (TH); and a processing condition modification unit (50) for modifying the processing conditions during the period when the minute detail is processed according to the determination result of the determination unit.

14. A control method for controlling a wire electrical discharge machining (10); the wire electrical discharge machining (10) 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) to process the workpiece; the control method includes: an acquisition step (S1) of acquiring the relative movement distance (L) defined by each of the plurality of blocks included in the processing formula (40); a determination step (S3) of determining whether the processing path contains a fine part based on a comparison of the acquired plurality of relative movement distances with a threshold value (TH); and a processing condition change step (S4) of changing the processing conditions during the period when the fine part is processed according to the determination result of the determination step.

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