Control device and control method for wire electric discharge machine

Abstract

According to an aspect of the present disclosure, a control device for a wire electric discharge machine includes: an acquisition unit that acquires a detection value of a machining voltage; a digital low-pass filter that outputs a correction value by removing noise from the detection value; a determination unit that performs at least one of a first determination for determining the degree of noise removal of the digital low-pass filter and a second determination for determining the response delay of the digital low-pass filter on the basis of the shape of a machining path and machining conditions; an adjustment unit that adjusts a parameter of the digital low-pass filter; and a machining control unit that controls electrical discharge machining on the basis of the correction value.

Description

Technical Field

[0001] The present invention relates to a control device and a control method for a wire electrical discharge machining machine. Background Art

[0002] A wire electrical discharge machining machine is disclosed in Japanese Patent Publication No. 6883138. Summary of the Invention

[0003] In a wire electrical discharge machining machine, stable electrical discharge machining is expected.

[0004] A first aspect of the present invention is a control device for a wire electrical discharge machining machine, which performs electrical discharge machining on a workpiece by relatively moving a wire electrode and the workpiece along a machining path while applying a machining voltage between the wire electrode and the workpiece to generate an electrical discharge. The control device is characterized by including: an acquisition unit that acquires a detection value of the machining voltage from a voltage sensor that detects the machining voltage; a digital low-pass filter that outputs a corrected value obtained by removing noise from the detection value; a determination unit that performs at least one of a first determination for determining the noise removal degree of the digital low-pass filter and a second determination for determining the response delay of the digital low-pass filter based on the shape of the machining path and the machining conditions of the electrical discharge machining; an adjustment unit that adjusts parameters of the digital low-pass filter based on a determination result of the determination unit; and a machining control unit that controls the electrical discharge machining based on the corrected value.

[0005] A second aspect of the present invention is a control method for a wire electrical discharge machining machine, which performs electrical discharge machining on a workpiece by relatively moving a wire electrode and the workpiece along a machining path while applying a machining voltage between the wire electrode and the workpiece to generate an electrical discharge. The control method is characterized by including: an acquisition step of acquiring a detection value of the machining voltage from a voltage sensor that detects the machining voltage; an output step of outputting a corrected value obtained by removing noise from the detection value by using a digital low-pass filter; a determination step of performing at least one of a first determination for determining the noise removal degree of the digital low-pass filter and a second determination for determining the response delay of the digital low-pass filter based on the shape of the machining path and the machining conditions of the electrical discharge machining; an adjustment step of adjusting parameters of the digital low-pass filter based on a determination result in the determination step; and a machining control step of controlling the electrical discharge machining based on the corrected value. Brief Description of the Drawings

[0006] Figure 1 It is a block diagram showing a wire electrical discharge machining machine and a control device for the wire electrical discharge machining machine according to the first embodiment. Figure 2This is a diagram for explaining an example of the smoothing process of a digital LPF. Figure 3 This is a diagram exemplifying the detected value of the machining voltage and the corrected value of the detected value. Figure 4 This is a diagram showing an example of a machining path having an inner corner shape. Figure 5 This is a diagram schematically showing a discharge pulse having a specified discharge pulse width and a specified discharge power. Figure 6 This is a flowchart showing an example of the processing procedure related to the machining control of the electric discharge machining of the control device according to the first embodiment. Figure 7A This is a diagram exemplifying the detected value in the case of performing electric discharge machining on a machining path including an inner corner section and the corrected value of the digital LPF output in the case of unadjusted parameters. Figure 7B This is a diagram exemplifying the detected value in the case of performing electric discharge machining on a machining path including an inner corner section and the corrected value of the digital LPF output with parameters adjusted in the first embodiment. Figure 8 This is a diagram showing an example of a machining path having an outer corner shape. Figure 9 This is a flowchart showing an example of the processing procedure related to the machining control of the electric discharge machining of the control device according to the second embodiment. Figure 10A This is a diagram exemplifying the detected value in the case of performing electric discharge machining on a machining path including an outer corner section and the corrected value of the digital LPF output in the case of unadjusted parameters. Figure 10B This is a diagram exemplifying the detected value in the case of performing electric discharge machining on a machining path including an outer corner section and the corrected value of the digital LPF output with parameters adjusted in the second embodiment. Figure 11 This is a diagram for explaining another example of the smoothing process according to the digital LPF. Detailed implementation mode

[0007] The machining voltage during electric discharge machining is detected, and this detected value is used for electric discharge machining control. This detected value contains noise. Therefore, in the electric discharge machining control, a corrected value obtained by reducing this noise through a filter is used. However, when the degree of noise removal by the filter is inappropriate, the electric discharge machining may become unstable.

[0008] (First embodiment) Figure 1is a block diagram showing the wire electrical discharge machining apparatus 10 and the control device 20 of the first embodiment. The control device 20 of the wire electrical discharge machining apparatus 10 controls the wire electrical discharge machining apparatus 10 to perform electrical discharge machining on the workpiece W. In Figure 1 the wire electrical discharge machining apparatus 10, only a part of the configuration related to the electrical discharge machining performed on the workpiece W is shown.

[0009] The wire electrical discharge machining apparatus 10 moves the wire electrode E and the workpiece W relatively along the machining path, and applies a machining voltage to the gap G between the wire electrode E and the workpiece W to generate a discharge. The machining voltage is applied to the gap G by the machining power supply 30. The wire electrical discharge machining apparatus 10 performs electrical discharge machining on the workpiece W by generating a discharge in the gap G. The machining voltage applied to the gap G is detected by the voltage sensor V.

[0010] The wire electrical discharge machining apparatus 10 includes a displacement drive unit 50, a worktable 52, a feed drive unit 60, an upper wire guide unit 62, and a lower wire guide unit 64. The displacement drive unit 50 each has a motor and a drive transmission mechanism (not shown). The drive transmission mechanism converts the rotational motion of the motor into a linear motion. The drive transmission mechanism is, for example, a ball screw and a nut. The workpiece W is supported on the worktable 52. The relative movement between the wire electrode E and the workpiece W is performed, for example, by moving the worktable 52 by the displacement drive unit 50.

[0011] The wire electrode E is supported by the upper wire guide unit 62 and the lower wire guide unit 64. The feed drive unit 60 each has a motor and a roller (not shown). The roller rotates by the motor, and the roller feeds the wire electrode E at a predetermined speed. The wire electrode E is fed from the upper wire guide unit 62 to the lower wire guide unit 64. The wire electrode E forms a gap G with the workpiece W at a position between the upper wire guide unit 62 and the lower wire guide unit 64.

[0012] The control device 20 includes a processing circuit 80 and a storage device 82. The processing circuit 80 includes a processor such as a CPU or a GPU. The storage device 82 includes a volatile memory such as a RAM and a non-volatile memory such as a ROM or a flash memory. The volatile memory is used as a working memory for the processor. The non-volatile memory stores programs executed by the processor and other necessary data. The storage device 82 also stores a machining program for electrical discharge machining.

[0013] The processing circuit 80 includes an acquisition unit 90, a digital LPF (Digital Low-Pass Filter) 92, a determination unit 94, an adjustment unit 96, and a machining control unit 98. By executing the program stored in the storage device 82 by the processing circuit 80, the acquisition unit 90, the digital LPF 92, the determination unit 94, the adjustment unit 96, and the machining control unit 98 are realized. At least a part of the acquisition unit 90, the digital LPF 92, the determination unit 94, the adjustment unit 96, and the machining control unit 98 can be realized by an integrated circuit such as an ASIC or an FPGA, or an electronic circuit including discrete devices.

[0014] The acquisition unit 90 acquires the detection value D of the machining voltage from the voltage sensor V. Noise is generated during the electrical discharge machining. The digital LPF 92 corrects the detection value D by removing noise (such as white noise) from the acquired detection value D. The digital LPF 92 outputs the corrected value C obtained by correcting the detection value D of the machining voltage.

[0015] The determination unit 94 makes a first determination on the noise removal degree of the digital LPF 92 according to the shape of the machining path and the machining conditions of the electrical discharge machining.

[0016] The adjustment unit 96 adjusts the parameters of the digital LPF 92 according to the determination result of the determination unit 94. By adjusting the parameters, the noise removal degree of the digital LPF 92 changes. For example, when it is determined in the first determination of the determination unit 94 that the noise removal degree of the digital LPF 92 is weak, the adjustment unit 96 adjusts the parameters to enhance the noise removal degree.

[0017] The machining control unit 98 reads out the machining path from the machining program stored in the storage device 82. The machining control unit 98 controls the displacement drive unit 50 to relatively move the wire electrode E and the workpiece W along the machining path. The machining control unit 98 controls the feeding drive unit 60 to feed the wire electrode E from the upper wire guide unit 62 to the lower wire guide unit 64. The machining control unit 98 controls the machining power supply 30 to generate a discharge between the electrodes G. Thus, the wire electrical discharge machining machine 10 can perform electrical discharge machining on the workpiece W.

[0018] The machining control unit 98 controls the electrical discharge machining according to the corrected value C. Specifically, the machining control unit 98 controls at least one of the relative speed between the wire electrode E and the workpiece W and the discharge power according to the corrected value C. The relative speed and the discharge power are changed to values corresponding to the shape of the machining path or the machining conditions of the electrical discharge machining, for example.

[0019] Figure 2This is a diagram for illustrating an example of the smoothing process of the digital LPF92. In this smoothing process, the detected value D(t) of the machining voltage obtained at time t is corrected using Equation (1), and the corrected value C(t) is output. According to Equation (1), the corrected value C(t) is the average value of a specified number n of detected values D obtained in the past at a specified time interval i. In other words, the corrected value C(t) is the value obtained by summing the past detected values D(k) = D(t), D(t - i),..., D(t - i×(n - 1)) of the specified number n, each multiplied by an equal weight of 1, and then dividing by the specified number n. [Equation 1]

[0020] Whenever a detected value D(t) is obtained as time t elapses, the average value of the past detected values D of the specified number n is calculated using Equation (1). The digital LPF92 outputs the calculated average value of the detected value D as the corrected value C(t) corresponding to the detected value D(t) obtained at time t. Therefore, the digital LPF92 is a moving average filter. The specified number n is a parameter of the digital LPF92. The adjustment unit 96 adjusts the specified number n according to the judgment result of the determination unit 94.

[0021] By increasing the specified number n, the adjustment unit 96 can enhance the degree of the smoothing process. Through the smoothing process, noise with high-frequency components is removed. That is, by increasing the specified number n, the adjustment unit 96 can enhance the degree of noise removal of the digital LPF92.

[0022] Figure 3 This is a diagram illustrating the detected value D of the machining voltage and the corrected value C of the detected value D. Figure 3 It shows how the detected value D and the corrected value C change as time t elapses. In Figure 3 the example shown, the detected value D contains a lot of noise. This noise is mainly white noise during electrical discharge machining and consists of frequency components with a wide frequency band.

[0023] Figure 4 This is a diagram showing an example of a machining path RT with an inner corner shape. Figure 4 The machining path RT of has an interval path RA with an inner corner shape that is not a straight line section. The shape of the interval path RA is a curved inner corner shape. The workpiece W is located outside this curve. If electrical discharge machining is performed along the interval path RA, the workpiece W will become concave. In addition, in this specification, a curved shape includes a bow-shaped shape and a shape with a straight bend.

[0024] The wire electrical discharge machining apparatus 10 generates discharges by applying a machining voltage to the gap G while relatively moving a wire electrode E and a workpiece W along a machining path RT. The machining amount in the section path RA having an inner corner shape is larger than that in a straight section. The noise generated during electrical discharge machining also tends to become stronger. When the noise removal degree of the digital LPF 92 is weak, if machining control is performed based on the correction value C output from the digital LPF 92, there may be insufficient machining amount.

[0025] In addition, due to insufficient machining amount, there may be a swing of the wire electrode E. In this case, the detected value D of the machining voltage may oscillate. In particular, when the discharge power of the discharge is small and the discharge pulse width of the discharge is also small, in the section path RA having an inner corner shape, a swing of the wire electrode E is likely to occur.

[0026] Figure 5 FIG. is a diagram schematically showing a discharge pulse having a prescribed discharge pulse width PW and a prescribed discharge power. The prescribed discharge pulse width PW corresponds to the width on the time axis for each periodic discharge pulse. The prescribed discharge power is determined based on the machining voltage periodically applied to the gap G.

[0027] When the machining shape is an inner corner shape and a prescribed condition related to the machining conditions based on the discharge pulse width PW and the discharge power PR is satisfied, it is necessary to strengthen the noise removal degree of the digital LPF 92. In the first determination, the determination unit 94 determines that the noise removal degree of the digital LPF 92 is weak when the shape of the machining path RT is an inner corner shape and a prescribed condition related to the machining conditions is satisfied. The prescribed conditions related to the machining conditions are expressed by equations (2) and (3). Equation (2) indicates that the discharge power PR is less than the first prescribed value PR0. Equation (3) indicates that the discharge pulse width PW is less than the second prescribed value PW0. PR<PR0···(2) PW<PW0···(3)

[0028] When it is determined in the first determination that the noise removal degree of the digital LPF 92 is weak, the adjustment unit 96 increases the prescribed number n included in equation (1). In this way, the adjustment unit 96 strengthens the noise removal degree of the digital LPF 92. The next acquired detected value D is corrected by the digital LPF 92 with a stronger noise removal degree. In this way, the noise included in the correction value C output from the digital LPF 92 is reduced. In addition, when at least one of the two conditions expressed by equations (2) and (3) is not satisfied, the prescribed number n included in equation (1) may also be restored to the initial value.

[0029] Figure 6It is a flowchart showing an example of a processing procedure related to the machining control of electric discharge machining of the control device 20 in the first embodiment. This processing procedure is periodically performed by the processing circuit 80 included in the control device 20, for example. When starting this processing procedure, in step S1, the determination unit 94 acquires the electrode position of the wire electrode E and the machining path RT along which the wire electrode E moves from the machining control unit 98. In addition, the machining control unit 98 acquires the machining path RT by analyzing the machining program. In addition, the machining control unit 98 acquires the electrode position of the wire electrode E relative to the workpiece W from an encoder provided on the motor of the feeding drive unit 60.

[0030] In step S2, the determination unit 94 determines whether the machining shape of the machining path RT where the electrode position is located is an inner corner shape. When the electrode position is in the interval path RA (refer to Figure 4 ) of the inner corner shape, it is "Yes" in step S2. When it is "Yes" in step S2, this processing procedure proceeds to step S3. When it is "No" in step S2, this processing procedure proceeds to step S10.

[0031] In step S3, the determination unit 94 acquires the discharge power PR and the discharge pulse width PW from the machining control unit 98. In step S4, the determination unit 94 determines whether the discharge power PR acquired in step S3 is less than the first specified value PR0. When it is "Yes" in step S4, this processing procedure proceeds to step S5. When it is "No" in step S4, this processing procedure proceeds to step S10.

[0032] In step S5, the determination unit 94 determines whether the discharge pulse width PW acquired in step S3 is less than the second specified value PW0. When it is "Yes" in step S5, this processing procedure proceeds to step S6. When it is "No" in step S5, this processing procedure proceeds to step S10. In step S6, the determination unit 94 determines that the degree of noise removal by the digital LPF 92 is weak.

[0033] In step S7, the adjustment unit 96 adjusts the parameters of the digital LPF 92 to enhance the degree of noise removal of the digital LPF 92. When performing the smoothing process represented by Equation (1) ( Figure 2 ) using the digital LPF 92, the adjustment unit 96 adjusts the specified number n included in Equation (1) as the parameter of the digital LPF 92. In the adjustment of the specified number n, the adjustment unit 96 increases the specified number n.

[0034] In step S8, acquisition unit 90 acquires the detected value D of the machining voltage from voltage sensor V. In step S9, digital LPF 92 corrects the detected value D by removing noise from the detected value D detected in step S8. Digital LPF 92 outputs the corrected value C obtained by correcting the detected value D. In step S10, machining control unit 98 controls the electrical discharge machining according to the corrected value C of digital LPF 92 after parameter adjustment. When the process of step S10 ends, this processing procedure ends.

[0035] Figure 7A It is a diagram illustrating the detected value D in the case of performing electrical discharge machining on the machining path RT including the inner corner section and the corrected value C output by digital LPF 92 without parameter adjustment. Figure 7B It is a diagram illustrating the detected value D in the case of performing electrical discharge machining on the machining path RT including the inner corner section and the corrected value C output by digital LPF 92 with parameters adjusted in the present embodiment. Figure 7A and Figure 7B Both represent the variation of the machining voltage corresponding to time t.

[0036] In Figure 4 the interval path RA of the inner corner shape shown, the above-described oscillation of the wire electrode E occurred. Figure 7A It shows the state where the detected value D of the machining voltage oscillates. The corrected value C of the detected value D is affected by the oscillation of the detected value D. In the present embodiment, the parameters of digital LPF 92 are adjusted to enhance the degree of noise removal. Therefore, as Figure 7B shown, the oscillation of the detected value D is suppressed and the corrected value C is stabilized. Since the corrected value C is stabilized, the electrical discharge machining control performed by machining control unit 98 based on this corrected value C can be improved.

[0037] (Second Embodiment) The control device 20 of the second embodiment is also represented by the block diagram shown in Figure 1 Judgment unit 94 makes a second judgment on the response delay of digital LPF 92 according to the shape of the machining path RT and the machining conditions of the electrical discharge machining.

[0038] Adjustment unit 96 adjusts the parameters of digital LPF 92 according to the judgment result of judgment unit 94. By adjusting the parameters, the response delay of digital LPF 92 changes. For example, when it is judged in the second judgment of judgment unit 94 that the response delay of digital LPF 92 is long, adjustment unit 96 adjusts the parameters to shorten the response delay.

[0039] Similar to the first embodiment, the parameter of the digital LPF 92 adjusted by the adjustment unit 96 is the specified number n included in Equation (1). The adjustment unit 96 adjusts the specified number n according to the determination result of the determination unit 94. By reducing the specified number n, the adjustment unit 96 can shorten the response delay of the digital LPF 92.

[0040] Figure 8 FIG. is an example showing a machining path RT having an outer corner shape. Figure 8 The machining path RT has an interval path RB with an outer corner shape that is not a straight line section. The shape of the interval path RB is a curved outer corner shape. The workpiece W is located inside the curve. If electric discharge machining is performed along the interval path RB, the workpiece W becomes a convex shape.

[0041] The wire electric discharge machining machine 10 moves the wire electrode E and the workpiece W relative to each other along the machining path RT, and applies a machining voltage between the electrodes G to generate an electric discharge. The machining amount in the interval path RB with an outer corner shape is less than that in the straight line section. Therefore, when the relative position of the wire electrode E reaches the interval path RB with an outer corner shape, it is preferable to rapidly increase the relative movement speed of the wire electrode E and the workpiece W. Alternatively, it is preferable to rapidly reduce the discharge power of the electric discharge generated between the electrodes G. Therefore, it is preferable to be able to rapidly detect that the relative position of the wire electrode E has reached the interval path RB with an outer corner shape.

[0042] The relative movement speed of the wire electrode E and the workpiece W is determined by PI control based on the machining voltage and the proportional gain KP in the PI control. When the machining shape is an outer corner shape and a specified condition related to the machining condition based on the proportional gain KP is satisfied, it is necessary to shorten the response delay of the digital LPF 92.

[0043] In the second determination, the determination unit 94 determines that the response delay of the digital LPF 92 is long when the shape of the machining path RT is an outer corner shape and a specified condition related to the machining condition is satisfied. The specified condition regarding the machining condition is expressed by Equation (4). Equation (4) indicates that the above-mentioned proportional gain KP is less than the third specified value KP0. KP < KP0 · · · (4)

[0044] When it is determined in the second determination that the response delay of the digital LPF 92 is long, the adjustment unit 96 reduces the specified number n included in Equation (1). In this way, the adjustment unit 96 shortens the response delay of the digital LPF 92. The detection value D obtained next is corrected by the digital LPF 92 with a shorter response delay. In this way, the response delay of the digital LPF 92 that outputs the correction value C is shortened. In addition, when the condition expressed by Equation (4) is not satisfied, the specified number n included in Equation (1) may also be restored to the initial value.

[0045] Figure 9 It is a flowchart showing an example of a processing procedure related to the machining control of electric discharge machining of the control device 20 in the second embodiment. This processing procedure is periodically performed by the processing circuit 80 included in the control device 20, for example. The symbols assigned to Figure 9 the steps of this processing procedure shown and the symbols assigned to Figure 6 the steps of the processing procedure shown partially match. In the steps where the symbols match, the same processing is executed, so the description of the processing in these steps is omitted.

[0046] When the processing in step S1 ends, in step S22, the determination unit 94 determines whether the machining shape of the machining path RT where the electrode position is located is an outer corner shape. When the electrode position is in the section path RB of the outer corner shape (refer to Figure 8 ), it is "Yes" in step S22. When it is "Yes" in step S22, this processing procedure proceeds to step S23. When it is "No" in step S22, this processing procedure proceeds to step S10.

[0047] In step S23, the determination unit 94 acquires the above-mentioned proportional gain KP from the machining control unit 98. In step S24, the determination unit 94 determines whether the proportional gain KP acquired in step S23 is less than the third specified value KP0. When it is "Yes" in step S24, this processing procedure proceeds to step S25. When it is "No" in step S24, this processing procedure proceeds to step S10.

[0048] In step S25, the determination unit 94 determines that the response delay of the digital LPF 92 is long. In step S26, the adjustment unit 96 adjusts the parameters of the digital LPF 92 to shorten the response delay of the digital LPF 92. When performing the smoothing process represented by Equation (1) ( Figure 2 ) using the digital LPF 92, the adjustment unit 96 adjusts the specified number n included in Equation (1) as the parameter of the digital LPF 92. In the adjustment of the specified number n, the adjustment unit 96 decreases the specified number n.

[0049] When the processing in step S26 ends, this processing procedure proceeds to step S8. In step S10, the machining control unit 98 controls the electric discharge machining according to the correction value C of the digital LPF 92 after parameter adjustment. When the processing in step S10 ends, this processing procedure ends.

[0050] Figure 10A It is a diagram illustrating the detected value D in the case of performing electric discharge machining on the machining path RT including the outer corner section and the correction value C output by the digital LPF 92 without adjusting the parameters. Figure 10BThis is a diagram showing the detected value D in the case where electrical discharge machining is performed on a machining path RT including an outer corner section and the corrected value C output by the digital LPF92 whose parameters are adjusted in the present embodiment. Figure 10A And Figure 10B Both represent the variation of the machining voltage corresponding to the time t.

[0051] As Figure 10A And Figure 10B As shown, there is a period during which the magnitude of the detected value D increases. This period is the period during which the relative position of the wire electrode E moves in the section path RB of the outer corner shape. In the section path RB of the outer corner shape, since the discharge frequency decreases, the magnitude of the detected value D of the machining voltage increases. When the magnitude of the detected value D increases, the machining control unit 98 controls at least one of the relative speed between the wire electrode E and the workpiece W and the discharge power according to the corrected value C of the detected value D.

[0052] However, if the response delay of the digital LPF92 is long, as Figure 10A shown, after the magnitude of the detected value D increases, the corrected value C starts to increase with a delay compared to the detected value D. Therefore, without adjusting the parameters of the digital LPF92, the electrical discharge machining control based on the corrected value C of the machining control unit 98 is also delayed. When the outer corner shape of the section path RB is a straight-bending shape, the response delay of the digital LPF92 is more significant compared to the bow shape.

[0053] In the present embodiment, when it is determined that the response delay of the digital LPF92 is long, the adjustment unit 96 adjusts the parameters of the digital LPF92 to shorten the response delay of the digital LPF92. At this time, as Figure 10B shown, as the magnitude of the detected value D increases, the magnitude of the corrected value C also increases. Therefore, when the parameters of the digital LPF92 are adjusted, the electrical discharge machining control based on the corrected value C of the machining control unit 98 can be improved. The electrical discharge machining is performed stably, and high machining accuracy can be maintained.

[0054] [Modification Example] The above-described embodiments can be modified as follows.

[0055] (Modification Example 1) In the smoothing process of the digital LPF92 in the first embodiment and the second embodiment, the exponential smoothing method can also be used. Figure 11This is a diagram for another example of the smoothing process of the digital LPF92. In this smoothing process, the detected value D(t) of the machining voltage obtained at time t is corrected by Equation (5), and the corrected value C(t) is output. The corrected value C(t) is a weighted average of the value obtained by multiplying the detected value D(t) at time t by the weight α (0 ≤ α ≤ 1) and the value obtained by multiplying the previous corrected value C(t - i) obtained at time t - i by the weight 1 - α. In other words, according to Equation (5), the corrected value C(t) is a weighted average of the detected values D obtained in the past at a specified time interval i. C(t) = α × D(t) + (1 - α) × C(t - i) · · · (5)

[0056] Whenever the detected value D(t) is obtained according to the passage of time t, the weighted average of the past detected values D is calculated by Equation (5) using the detected value D(t), the previously detected corrected value C(t - i), and the weight α. The digital LPF92 outputs the calculated weighted average of the detected value D as the corrected value C(t) corresponding to the detected value D(t) obtained at time t. Therefore, the digital LPF92 is a weighted average filter. The weight α is a parameter of the digital LPF92.

[0057] The adjustment unit 96 adjusts the weight α according to the determination result of the determination unit 94. The adjustment unit 96 can enhance the degree of noise removal of the digital LPF92 by reducing the weight α. The adjustment unit 96 can shorten the response delay of the digital LPF92 by increasing the weight α. According to this modification example, the performance of the digital LPF92 can be adjusted relatively simply.

[0058] (Modification Example 2) It is also possible to simultaneously adjust the parameters of the digital LPF92 in the first embodiment and the second embodiment. In this case, the first determination and the second determination are performed according to the shape of the machining path RT and the machining conditions of the electrical discharge machining.

[0059] When it is determined in the first determination that the degree of noise removal of the digital LPF92 is weak, the adjustment unit 96 adjusts the parameters of the digital LPF92 to enhance the degree of noise removal of the digital LPF92. When it is determined in the second determination that the response delay of the digital LPF92 is long, the adjustment unit 96 adjusts the parameters of the digital LPF92 to shorten the response delay of the digital LPF92.

[0060] If the noise reduction level of the digital LPF92 is increased, the response delay of the digital LPF92 becomes longer. If the response delay of the digital LPF92 becomes shorter, the noise reduction level of the digital LPF92 becomes weaker. By adjusting the parameters of the digital LPF92 by the adjustment unit 96, the noise reduction level and the response delay of the digital LPF92 can be appropriately controlled. For example, even when the machining path RT has both an inner corner shape and an outer corner shape, the noise of the detected value D is appropriately removed, and the prolongation of the response delay of the digital LPF92 is prevented. Therefore, according to this modification example, electric discharge machining can be performed more stably. Therefore, a high machining accuracy can be maintained.

[0061] (Modification Example 3) The above-described Modification Example 1 and Modification Example 2 can also be combined.

[0062] In the above-described embodiment and modification examples, at least one of the noise reduction level of the digital LPF92 and the response delay of the digital LPF92 is determined according to the shape of the machining path RT and the machining conditions of the electric discharge machining. The parameters of the digital LPF92 are adjusted according to the determination result. Therefore, the electric discharge machining is stable and the machining accuracy is high.

[0063] Regarding the above-described embodiment and modification examples, the following supplementary notes are also disclosed.

[0064] (Supplementary Note 1) A control device 20 of a wire electric discharge machining machine 10 that performs electric discharge machining on a workpiece W by applying a machining voltage between an electrode wire E and the workpiece W while relatively moving the electrode wire and the workpiece along a machining path RT to generate an electric discharge, the control device 20 includes: an acquisition unit 90 that acquires a detected value D of the machining voltage from a voltage sensor V that detects the machining voltage; a digital low-pass filter 92 that outputs a corrected value C obtained by removing noise from the detected value; a determination unit 94 that performs at least one of a first determination of the noise reduction level of the digital low-pass filter and a second determination of the response delay of the digital low-pass filter according to the shape of the machining path and the machining conditions of the electric discharge machining; an adjustment unit 96 that adjusts parameters n and α of the digital low-pass filter according to the determination result of the determination unit; and a machining control unit 98 that controls the electric discharge machining according to the corrected value.

[0065] (Supplementary Note 2) In the control device of the wire electric discharge machining machine according to Supplementary Note 1, when it is determined in the first determination that the noise reduction level of the digital low-pass filter is weak, the adjustment unit may adjust the parameters to increase the noise reduction level of the digital low-pass filter.

[0066] (Supplementary Note 3) In the control device of the wire electrical discharge machining machine described in Supplementary Note 2, it is also possible that when the shape of the machining path is a curved inner corner shape to make the workpiece into a concave shape, and as the machining condition, the discharge power PR of the discharge is less than a first specified value PR0 and the discharge pulse width PW of the discharge is less than a second specified value PW0, the determination unit determines that the degree of noise removal of the digital low-pass filter is weak in the first determination.

[0067] (Supplementary Note 4) In the control device of the wire electrical discharge machining machine described in any one of Supplementary Notes 1 to 3, it is also possible that when it is determined in the second determination that the response delay of the digital low-pass filter is long, the adjustment unit adjusts the parameter to shorten the response delay of the digital low-pass filter.

[0068] (Supplementary Note 5) In the control device of the wire electrical discharge machining machine described in Supplementary Note 4, it is also possible that the relative movement speed of the wire electrode and the workpiece is determined according to the machining voltage and the proportional gain KP. When the shape of the machining path is a curved outer corner shape to make the workpiece into a convex shape, and as the machining condition, the proportional gain is less than a third specified value KP0, the determination unit determines that the response delay of the digital low-pass filter is long in the second determination.

[0069] (Supplementary Note 6) In the control device of the wire electrical discharge machining machine described in any one of Supplementary Notes 1 to 5, it is also possible that the machining control unit controls at least one of the relative speed of the wire electrode and the workpiece and the discharge power of the discharge according to the correction value.

[0070] (Supplementary Note 7) In the control device of the wire electrical discharge machining machine described in any one of Supplementary Notes 1 to 6, it is also possible that the digital low-pass filter is a moving average filter, which outputs the average value of a specified number n of past detection values as the correction value corresponding to the obtained detection value each time the detection value is obtained, and the parameter is the specified number.

[0071] (Supplementary Note 8) In the control device of the wire electrical discharge machining machine described in any one of Supplementary Notes 1 to 6, it is also possible that the digital low-pass filter is a weighted average filter, which outputs the weighted average value obtained by using the detection value, the correction value output last time, and the weight α as the correction value corresponding to the obtained detection value each time the detection value is obtained, and the parameter is the weight.

[0072] (Supplementary Note 9) A control method for a wire electrical discharge machining apparatus 10, which performs electrical discharge machining on a workpiece W by applying a machining voltage between a wire electrode E and the workpiece W while relatively moving the wire electrode and the workpiece along a machining path RT to generate an electrical discharge, includes: an acquisition step of acquiring a detected value D of the machining voltage from a voltage sensor V that detects the machining voltage; an output step of removing noise from the detected value by a digital low-pass filter 92 and outputting a corrected value C obtained by correcting the detected value; a determination step of performing at least one of a first determination for determining the degree of noise removal of the digital low-pass filter and a second determination for determining the response delay of the digital low-pass filter based on the shape of the machining path and the machining conditions of the electrical discharge machining; an adjustment step of adjusting parameters n and α of the digital low-pass filter according to the determination result in the determination step; and a machining control step of controlling the electrical discharge machining based on the corrected value.

[0073] (Supplementary Note 10) In the control method for the wire electrical discharge machining apparatus described in Supplementary Note 9, when it is determined in the first determination that the degree of noise removal of the digital low-pass filter is weak, the parameters may be adjusted in the adjustment step to enhance the degree of noise removal of the digital low-pass filter.

[0074] (Supplementary Note 11) In the control method for the wire electrical discharge machining apparatus described in Supplementary Note 10, when the shape of the machining path is a curved inner corner shape that makes the workpiece concave, and as the machining conditions, when the discharge power PR of the electrical discharge is less than a first specified value PR0 and the discharge pulse width PW of the electrical discharge is less than a second specified value PW0, it may be determined in the first determination of the determination step that the degree of noise removal of the digital low-pass filter is weak.

[0075] (Supplementary Note 12) In the control method for the wire electrical discharge machining apparatus according to any one of Supplementary Notes 9 to 11, when it is determined in the second determination that the response delay of the digital low-pass filter is long, the parameters may be adjusted in the adjustment step to shorten the response delay of the digital low-pass filter.

[0076] (Supplementary Note 13) In the control method for the wire electrical discharge machining apparatus described in Supplementary Note 12, the relative movement speed of the wire electrode and the workpiece may be determined based on the machining voltage and a proportional gain KP. When the shape of the machining path is a curved outer corner shape that makes the workpiece convex, and as the machining conditions, when the proportional gain is less than a third specified value KP0, it may be determined in the second determination of the determination step that the response delay of the digital low-pass filter is long.

[0077] (Supplementary Note 14) In the control method of the wire electrical discharge machining machine according to any one of Supplementary Notes 9 to 13, it is also possible that in the machining control step, at least one of the relative speed of the wire electrode and the work object and the discharge power of the discharge is controlled according to the correction value.

[0078] Although the present invention has been described in detail, the present invention is not limited to the above-described respective embodiments. These embodiments can be variously added, replaced, changed, partially deleted, etc. within the scope not departing from the gist of the present disclosure, or within the scope not departing from the gist of the present disclosure derived from the content recited in the claims and its equivalents. In addition, these embodiments can also be implemented in combination. For example, in the above embodiments, the order of each operation and the order of each process are shown as an example and are not limited thereto. The same applies to the cases where numerical values or mathematical formulas are used in the description of the above embodiments. Symbol Explanation

[0079] 10... Wire electrical discharge machining machine 20... Control device 30... Machining power supply 50... Displacement drive unit 52... Workbench 60... Feed drive unit 62... Upper wire guide unit 64... Lower wire guide unit 80... Processing circuit 82... Storage device 90... Acquisition unit 92... Digital LPF (Digital Low Pass Filter) 94... Judgment unit 96... Adjustment unit 98... Machining control unit.

Claims

1. A control device for a wire electrical discharge machining machine, which performs electrical discharge machining on a workpiece by relatively moving a wire electrode and the workpiece along a machining path while applying a machining voltage between the wire electrode and the workpiece to generate an electrical discharge. The control device is characterized in that Comprising: An acquisition unit that acquires a detected value of the machining voltage from a voltage sensor that detects the machining voltage; A digital low-pass filter that outputs a corrected value obtained by removing noise from the detected value to correct the detected value; A determination unit that performs at least one of a first determination for determining the degree of noise removal of the digital low-pass filter and a second determination for determining the response delay of the digital low-pass filter according to the shape of the machining path and the machining conditions of the electrical discharge machining; An adjustment unit that adjusts the parameters of the digital low-pass filter according to the determination result of the determination unit; and A machining control unit that controls the electrical discharge machining according to the corrected value.

2. The control device for a wire electrical discharge machining machine according to claim 1, characterized in that In the case where it is determined in the first determination that the degree of the noise removal of the digital low-pass filter is weak, the adjustment unit adjusts the parameters to enhance the degree of the noise removal of the digital low-pass filter.

3. The control device for a wire electrical discharge machining machine according to claim 2, characterized in that In the case where the shape of the machining path is a curved inner corner shape to make the workpiece into a concave shape, and as the machining conditions, the condition that the discharge power of the discharge is less than a first specified value and the discharge pulse width of the discharge is less than a second specified value is satisfied, the determination unit determines in the first determination that the degree of the noise removal of the digital low-pass filter is weak.

4. The control device for a wire electrical discharge machining machine according to any one of claims 1 to 3, characterized in that In the case where it is determined in the second determination that the response delay of the digital low-pass filter is long, the adjustment unit adjusts the parameters to shorten the response delay of the digital low-pass filter.

5. The control device for a wire electrical discharge machining machine according to claim 4, characterized in that The relative movement speed of the wire electrode and the workpiece is determined according to the machining voltage and the proportional gain. In the case where the shape of the machining path is a curved outer corner shape to make the workpiece into a convex shape, and as the machining conditions, the condition that the proportional gain is less than a third specified value is satisfied, the determination unit determines in the second determination that the response delay of the digital low-pass filter is long.

6. The control device for a wire electrical discharge machining machine according to any one of claims 1 to 5, characterized in that The machining control unit controls at least one of the relative speed of the wire electrode and the workpiece and the discharge power of the discharge according to the corrected value.

7. The control device for a wire electrical discharge machining machine according to any one of claims 1 to 6, characterized in that The digital low-pass filter is a moving average filter that, each time the detected value is obtained, outputs the average value of a specified number of past detected values as the corrected value corresponding to the obtained detected value. The parameter is the specified number.

8. The control device for a wire electrical discharge machining machine according to any one of claims 1 to 6, characterized in that The digital low-pass filter is a weighted average filter that, each time the detected value is obtained, outputs the weighted average value obtained by using the detected value, the previously output corrected value, and the weight as the corrected value corresponding to the obtained detected value. The parameter is the weight.

9. A control method for a wire electrical discharge machining machine, which performs electrical discharge machining on a workpiece by relatively moving a wire electrode and the workpiece along a machining path while applying a machining voltage between the wire electrode and the workpiece to generate an electrical discharge. The control method is characterized in that Comprising: An acquisition step of acquiring a detected value of the machining voltage from a voltage sensor that detects the machining voltage; An output step of removing noise from the detected value through a digital low-pass filter and outputting a corrected value obtained by correcting the detected value. Determination step, for determining at least one of a first determination of the noise removal degree of the digital low-pass filter and a second determination of the response delay of the digital low-pass filter according to the shape of the machining path and the machining conditions of the electrical discharge machining; Adjustment step, for adjusting the parameters of the digital low-pass filter according to the determination result in the determination step; and Machining control step, for controlling the electrical discharge machining according to the correction value.

10. The control method of a wire electrical discharge machining machine according to claim 9, wherein, When it is determined in the first determination that the degree of noise removal of the digital low-pass filter is weak, the parameters are adjusted in the adjustment step to enhance the degree of noise removal of the digital low-pass filter.

11. The control method of a wire electrical discharge machining machine according to claim 10, wherein, When the shape of the machining path is a curved inner corner shape to make the workpiece into a concave shape, and as the machining condition, the condition that the discharge power of the discharge is less than a first specified value and the discharge pulse width of the discharge is less than a second specified value is satisfied, it is determined in the first determination of the determination step that the degree of noise removal of the digital low-pass filter is weak.

12. The control method of a wire electrical discharge machining machine according to any one of claims 9 to 11, wherein, When it is determined in the second determination that the response delay of the digital low-pass filter is long, the parameters are adjusted in the adjustment step to shorten the response delay of the digital low-pass filter.

13. The control method of a wire electrical discharge machining machine according to claim 12, wherein, The relative movement speed of the wire electrode and the workpiece is determined according to the machining voltage and the proportional gain, When the shape of the machining path is a curved outer corner shape to make the workpiece into a convex shape, and as the machining condition, the condition that the proportional gain is less than a third specified value is satisfied, it is determined in the second determination of the determination step that the response delay of the digital low-pass filter is long.

14. The control method of a wire electrical discharge machining machine according to any one of claims 9 to 13, wherein, In the machining control step, at least one of the relative speed of the wire electrode and the workpiece and the discharge power of the discharge is controlled according to the correction value.

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