Wire electric discharge machine and control method for wire electric discharge machine

Abstract

The wire electric discharge machine (10) of the present invention has: an average interelectrode voltage calculation section (32) that calculates an average interelectrode voltage of an interelectrode; a correction section (34) that obtains a corrected average interelectrode voltage in accordance with a machining speed of a wire electrode (12) with respect to a workpiece (14); and a motor control section (36) that controls an X-axis motor (24) and a Y-axis motor (26) in accordance with the corrected average interelectrode voltage to make the size of the interelectrode during machining constant, and the correction section (34) obtains the corrected average interelectrode voltage in accordance with a formula that has the average interelectrode voltage as a numerator and a value obtained by multiplying the machining speed by a coefficient as a denominator.

Description

Technical Field

[0001] This invention relates to a wire electrical discharge machining (EDM) machine for machining workpieces by generating an inter-electrode discharge between an online electrode and a workpiece, and its control method. Background Technology

[0002] International Publication No. 2015 / 145484 discloses a wire electrical discharge machining (EDM) machine. The EDM machine includes a control unit that controls the machining speed (the relative speed of the machining electrode to the workpiece). The difference between the machining speed and the set speed is related to the distance (side clearance) between the machining electrode and the workpiece. Therefore, the control unit corrects the average machining voltage between the machining electrode and the workpiece based on the difference between the machining speed and the set speed. The control unit controls the machining speed based on the corrected average machining voltage. Thus, the wire EDM machine can maintain a constant side clearance during EDM, thereby improving the machining accuracy of the workpiece. Summary of the Invention

[0003] The correlation between the difference between the machining speed and the set speed and the size of the side clearance decreases as the difference between the machining speed and the set speed increases. Therefore, in the wire electrical discharge machining (EDM) machine disclosed in International Publication No. 2015 / 145484, there is a problem that the larger the difference between the machining speed and the set speed, the lower the machining accuracy of the workpiece.

[0004] The purpose of this invention is to solve the above-mentioned problems.

[0005] The first aspect of the present invention is a wire electrical discharge machining (EDM) machine that processes the workpiece by generating an inter-electrode discharge between a wire electrode and a workpiece. The machine comprises: a discharge state value acquisition unit that acquires a discharge state value based on any one of the following: the time average of the voltage between the electrodes (i.e., average inter-electrode voltage), the reciprocal of the number of discharge pulses between the electrodes per unit time, and the discharge delay time from the application of voltage to the inter-electrode until a discharge occurs; a discharge state value correction unit that corrects the discharge state value based on the relative speed of the wire electrode relative to the workpiece (i.e., processing speed) and calculates a correction value; a drive unit that moves the wire electrode relative to the workpiece; and a control unit that controls the drive unit based on the correction value to keep the size of the inter-electrode distance constant during processing. The discharge state value correction unit calculates the correction value using a formula with the discharge state value as the numerator and the processing speed multiplied by a coefficient as the denominator.

[0006] The second aspect of the present invention is a control method for a wire electrical discharge machining (EDM) machine, which processes the workpiece by generating an inter-electrode discharge between a wire electrode and a workpiece. The method comprises: a discharge state value acquisition step, which acquires a discharge state value by taking any one of the following: the time average of the voltage between the electrodes (i.e., average inter-electrode voltage), the reciprocal of the number of discharge pulses between the electrodes per unit time, and the discharge delay time from the application of voltage to the inter-electrode until the discharge occurs; a discharge state value correction step, which corrects the discharge state value based on the relative speed of the wire electrode relative to the workpiece (i.e., processing speed) to calculate a correction value; a driving step, which moves the wire electrode relative to the workpiece by a driving unit; and a control step, which controls the driving unit based on the correction value to keep the size of the inter-electrode distance constant during processing. The discharge state value correction step calculates the correction value using the discharge state value as the numerator and the processing speed multiplied by a coefficient as the denominator.

[0007] With the help of this invention, wire electrical discharge machining can improve the machining accuracy of workpieces. Attached Figure Description

[0008] Figure 1 This is a schematic diagram illustrating a wire electrical discharge machining (EDM) machine.

[0009] Figure 2 A diagram illustrating the discharge gap.

[0010] Figure 3A as well as Figure 3B A graph showing the voltage applied between the electrodes and the average voltage between the electrodes.

[0011] Figure 4 This is a schematic diagram illustrating a wire electrical discharge machining (EDM) machine.

[0012] Figure 5 This is a schematic diagram illustrating a wire electrical discharge machining (EDM) machine. Detailed Implementation

[0013] [First Implementation]

[0014] Figure 1 This is a schematic diagram illustrating a wire electrical discharge machining (EDM) machine 10. The EDM machine 10 is a machine tool that performs electrical discharge machining on a workpiece 14 by applying a voltage between a wire electrode 12 and the workpiece 14 (hereinafter sometimes referred to as the inter-electrode). The wire electrode 12 is made of, for example, tungsten-based, copper alloy-based, or brass-based metals. The workpiece 14 is made of, for example, ferrous-based or superhard materials. The EDM machine 10 includes a machining body 16 and a control device 18.

[0015] The machining machine body 16 includes a machining power supply 20, an inter-electrode voltage detection unit 22, an X-axis motor 24, and a Y-axis motor 26. The machining power supply 20 applies voltage between the electrodes. The inter-electrode voltage detection unit 22 is a voltage sensor that detects the voltage between the electrodes (hereinafter sometimes referred to as inter-electrode voltage). The X-axis motor 24 and the Y-axis motor 26 move a workpiece stage (not shown). As the workpiece 14, which is fixed to the workpiece stage, moves together with the workpiece stage, the wire electrode 12 moves relative to the workpiece 14.

[0016] The control device 18 includes an arithmetic unit 28 and a storage unit 30. The arithmetic unit 28 is configured as a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit). The arithmetic unit 28 includes an average inter-electrode voltage calculation unit 32, a correction unit 34, a motor control unit 36, and a processing power supply control unit 38. The average inter-electrode voltage calculation unit 32, the correction unit 34, the motor control unit 36, and the processing power supply control unit 38 are implemented by the arithmetic unit 28 executing a program stored in the storage unit 30. At least one of the average inter-electrode voltage calculation unit 32, the correction unit 34, the motor control unit 36, and the processing power supply control unit 38 can also be implemented using integrated circuits such as ASICs (Application Specific Integrated Circuits) or FPGAs (Field-Programmable Gate Arrays). At least one of the average inter-electrode voltage calculation unit 32, the correction unit 34, the motor control unit 36, and the processing power supply control unit 38 can also be configured using electronic circuits containing discrete components.

[0017] The storage unit 30 comprises volatile memory (not shown) and non-volatile memory (not shown). The volatile memory is, for example, RAM (Random Access Memory). For example, temporarily used data is stored in the volatile memory. The non-volatile memory is, for example, ROM (Read Only Memory), flash memory, etc. For example, programs, tables, mappings, etc., are stored in the non-volatile memory. At least a portion of the storage unit 30 may also be disposed within the aforementioned processor, integrated circuit, etc.

[0018] The average inter-electrode voltage calculation unit 32 calculates the time average of the inter-electrode voltage detected by the inter-electrode voltage detection unit 22. Hereinafter, the time average of the inter-electrode voltage is sometimes referred to as the average inter-electrode voltage. The average inter-electrode voltage calculation unit 32 corresponds to the discharge state value acquisition unit of the present invention. The correction unit 34 corrects the average inter-electrode voltage based on the relative speed of the line electrode 12 relative to the workpiece 14. Hereinafter, the relative speed of the line electrode 12 relative to the workpiece 14 is sometimes referred to as the machining speed. The correction of the average inter-electrode voltage performed in the correction unit 34 will be described in detail later. The correction unit 34 corresponds to the discharge state value correction unit of the present invention. The motor control unit 36 ​​controls the X-axis motor 24 and the Y-axis motor 26 to make the machining speed the target machining speed. The target machining speed is set based on the average inter-electrode voltage after correction in the correction unit 34. Hereinafter, the average inter-electrode voltage after correction in the correction unit 34 is sometimes referred to as the corrected average inter-electrode voltage. The motor control unit 36 ​​corresponds to the control unit of the present invention. The machining power supply control unit 38 controls the machining power supply 20 to apply voltage to the inter-electrode.

[0019] Furthermore, the motor control unit 36 ​​can also perform proportional control, integral control, and derivative control (PID control) on the X-axis motor 24 and the Y-axis motor 26. The motor control unit 36 ​​can also control the X-axis motor 24 and the Y-axis motor 26 according to a target machining speed set based on the average inter-electrode voltage before correction. In this case, the motor control unit 36 ​​can also set at least one of the proportional gain, integral time, and derivative time based on the corrected average inter-electrode voltage.

[0020] [About the Calibration Department]

[0021] Figure 2 This is a diagram illustrating the discharge gap. In this embodiment, the size of the electrode spacing in the direction orthogonal to the moving direction of the wire electrode 12 relative to the workpiece 14 during the electrical discharge machining of the workpiece 14 is called the discharge gap. In order to improve the machining accuracy of the workpiece 14 processed by the wire electrical discharge machining machine 10, the motor control unit 36 ​​controls the X-axis motor 24 and the Y-axis motor 26 to keep the discharge gap approximately constant during the electrical discharge machining of the workpiece 14.

[0022] In the electrical discharge machining of workpiece 14, it is difficult to directly detect the discharge gap using the wire electrical discharge machining machine 10. Therefore, in this embodiment, the motor control unit 36 ​​controls the X-axis motor 24 and Y-axis motor 26 based on the average inter-pole voltage, rather than based on the discharge gap.

[0023] However, even if the average inter-electrode voltage during the electrical discharge machining of workpiece 14 remains constant, the discharge gap will become smaller as the machining speed increases. Therefore, in this embodiment, the correction unit 34 corrects the average inter-electrode voltage based on the machining speed to obtain a corrected average inter-electrode voltage. The motor control unit 36 ​​controls the X-axis motor 24 and the Y-axis motor 26 based on the corrected average inter-electrode voltage. As a result, the discharge gap during the electrical discharge machining of workpiece 14 is kept approximately constant.

[0024] The corrected average inter-electrode voltage is calculated using the following equation (1). In the equation, “Ec” represents the corrected average inter-electrode voltage. In the equation, “E” represents the average inter-electrode voltage. In the equation, “α1” represents a coefficient. In the equation, “V” represents the processing speed.

[0025] …(1)

[0026] Figure 3A as well as Figure 3B It is a graph representing the voltage applied between the electrodes and the average voltage between them. For example... Figure 3A as well as Figure 3B As shown, even if the number of discharge pulses per unit time is equal and the discharge delay time from the application of voltage between the electrodes to the generation of discharge between the electrodes is equal, the average electrode voltage will vary depending on the voltage applied between the electrodes. Therefore, the correction unit 34 changes the coefficient "α1" of equation (1) according to the voltage applied between the electrodes.

[0027] [Effects]

[0028] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the correction unit 34 calculates the corrected average inter-electrode voltage using a formula with the average inter-electrode voltage as the numerator and the machining speed multiplied by a coefficient as the denominator. The motor control unit 36 ​​controls the X-axis motor 24 and the Y-axis motor 26 based on the corrected average inter-electrode voltage to keep the size of the discharge gap constant during machining. As a result, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0029] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the correction unit 34 calculates the corrected average inter-electrode voltage according to the above formula (1). As a result, the wire EDM machine 10 can keep the size of the discharge gap constant during the EDM of the workpiece 14, regardless of the processing speed.

[0030] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the motor control unit 36 ​​sets at least one of the following based on the corrected average inter-electrode voltage: the proportional gain of proportional control, the integral time of integral control, the derivative time of derivative control, and the target machining speed. As a result, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0031] [Second Implementation]

[0032] In the first embodiment, the motor control unit 36 ​​sets the target machining speed based on the average inter-electrode voltage. In contrast, in this embodiment, the target machining speed is set based on the reciprocal of the number of discharge pulses per unit time. Figure 3A and Figure 3B In the example shown, the number of discharge pulses per unit time is "4", and the reciprocal of the number of discharge pulses per unit time is "1 / 4". Hereinafter, the number of discharge pulses per unit time will sometimes be simply referred to as the discharge pulse count.

[0033] Figure 4 This is a schematic diagram showing the wire electrical discharge machining (EDM) machine 10. The structure of the machine body 16 is the same as that of the machine body 16 in the first embodiment. The arithmetic unit 28 of the control device 18 includes a discharge pulse count calculation unit 40, a correction unit 42, a motor control unit 44, and a machining power supply control unit 38. The machining power supply control unit 38 is the same as that in the first embodiment.

[0034] The discharge pulse count calculation unit 40 calculates the number of discharge pulses per unit time based on the inter-electrode voltage detected by the inter-electrode voltage detection unit 22, and calculates the reciprocal of the discharge pulse count. When a voltage is applied between the electrodes, and the insulation between the electrodes breaks, resulting in a discharge, the inter-electrode voltage decreases. The discharge pulse count calculation unit 40 calculates the number of discharge pulses based on the number of times the inter-electrode voltage drops below a predetermined voltage after a voltage is applied between the electrodes. The discharge pulse count calculation unit 40 corresponds to the discharge state value acquisition unit of the present invention. The correction unit 42 corrects the reciprocal of the discharge pulse count based on the processing speed and calculates the corrected reciprocal of the discharge pulse count. The correction of the reciprocal of the discharge pulse count performed in the correction unit 42 will be described in detail later. The correction unit 42 corresponds to the discharge state value correction unit of the present invention. The motor control unit 44 controls the X-axis motor 24 and the Y-axis motor 26 to make the processing speed the target processing speed. The target processing speed is set based on the reciprocal of the discharge pulse count after correction performed in the correction unit 42. Hereinafter, the corrected discharge pulse count will sometimes be referred to as the corrected discharge pulse count. The motor control unit 44 corresponds to the control unit of this invention. The reciprocal of the correction discharge pulse number corresponds to the correction value of this invention.

[0035] Furthermore, the motor control unit 44 can also perform proportional control, integral control, and derivative control (PID control) on the X-axis motor 24 and the Y-axis motor 26. The motor control unit 44 can also control the X-axis motor 24 and the Y-axis motor 26 based on a target machining speed set according to the reciprocal of the number of discharge pulses before correction. In this case, the motor control unit 44 can also set at least one of the proportional gain, integral time, and derivative time based on the reciprocal of the number of correction discharge pulses.

[0036] The correction unit 42 calculates the reciprocal of the correction discharge pulse number according to the following formula (2). In the formula, “Nc” represents the reciprocal of the correction discharge pulse number. In the formula, “N” represents the reciprocal of the discharge pulse number. In the formula, “α2” represents a coefficient. In the formula, “V” represents the processing speed.

[0037] …(2)

[0038] like Figure 3A as well as Figure 3B As shown, the average inter-electrode voltage varies depending on the voltage applied between the electrodes. Therefore, the correction unit 34 in the first embodiment changes the coefficient "α1" of equation (1) according to the voltage applied between the electrodes. On the other hand, as Figure 3A as well as Figure 3B As shown, the number of discharge pulses does not change with the voltage applied between the electrodes. Therefore, the correction unit 42 in this embodiment does not need to change the coefficient "α2" of equation (2) according to the voltage applied between the electrodes.

[0039] [Effects]

[0040] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the correction unit 42 calculates the reciprocal of the number of corrected discharge pulses using a formula where the numerator is the reciprocal of the number of discharge pulses per unit time and the denominator is the value obtained by multiplying the machining speed by a coefficient. The motor control unit 44 controls the X-axis motor 24 and the Y-axis motor 26 based on the reciprocal of the corrected discharge pulse number, keeping the size of the discharge gap constant during machining. As a result, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0041] In the wire EDM machine 10 of this embodiment, the correction unit 42 calculates the reciprocal of the correction discharge pulse number according to the above formula (2). As a result, the wire EDM machine 10 can keep the size of the discharge gap constant during the EDM of the workpiece 14, regardless of the processing speed.

[0042] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the discharge pulse count calculation unit 40 calculates the number of discharge pulses per unit time based on the inter-electrode voltage detected by the inter-electrode voltage detection unit 22, and calculates the reciprocal of the discharge pulse count. The correction unit 42 calculates the reciprocal of the corrected discharge pulse count based on the above formula (2). Since the number of discharge pulses per unit time does not change with the voltage applied between the electrodes, the correction unit 42 does not need to change the coefficient "α2" in formula (2) according to the voltage applied between the electrodes, thus reducing the processing load of the correction unit 42.

[0043] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the motor control unit 44 sets at least one of the following based on the reciprocal of the number of correction discharge pulses: the proportional gain of proportional control, the integral time of integral control, the derivative time of derivative control, and the target machining speed. As a result, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0044] [Third Implementation Method]

[0045] In the first embodiment, the discharge gap is estimated based on the average inter-electrode voltage. In contrast, in this embodiment, the discharge gap is estimated based on the discharge delay time. Figure 3A as well as Figure 3B As shown, the discharge delay time is the time from when a voltage is applied between the electrodes until a discharge occurs between them.

[0046] Figure 5 This is a schematic diagram showing the wire electrical discharge machining (EDM) machine 10. The structure of the machine body 16 is the same as that of the machine body 16 in the first embodiment. The arithmetic unit 28 of the control device 18 includes a discharge delay time calculation unit 46, a correction unit 48, a motor control unit 50, and a machining power supply control unit 38. The machining power supply control unit 38 is the same as that in the first embodiment.

[0047] The discharge delay time calculation unit 46 calculates the discharge delay time based on the inter-electrode voltage detected by the inter-electrode voltage detection unit 22. If a discharge occurs after applying voltage to the inter-electrode, the inter-electrode voltage decreases. The discharge delay time calculation unit 46 calculates the discharge delay time based on the time from when voltage is applied to the inter-electrode until the inter-electrode voltage becomes below a predetermined voltage. The discharge delay time calculation unit 46 corresponds to the discharge state value acquisition unit of the present invention. The correction unit 48 corrects the discharge delay time based on the processing speed. The correction of the discharge delay time performed in the correction unit 48 will be described in detail later. The correction unit 48 corresponds to the discharge state value correction unit of the present invention. The motor control unit 50 controls the X-axis motor 24 and the Y-axis motor 26 to make the processing speed a target processing speed. The target processing speed is set based on the discharge delay time corrected in the correction unit 48. Hereinafter, the discharge delay time corrected in the correction unit 48 will sometimes be referred to as the corrected discharge delay time. The motor control unit 50 corresponds to the control unit of the present invention.

[0048] Furthermore, the motor control unit 50 can also perform proportional control, integral control, and derivative control (PID control) on the X-axis motor 24 and the Y-axis motor 26. The motor control unit 50 can also control the X-axis motor 24 and the Y-axis motor 26 based on a target machining speed set based on the discharge delay time before correction. In this case, the motor control unit 50 can also set at least one of the proportional gain, integral time, and derivative time based on the correction discharge delay time.

[0049] The correction unit 48 calculates the correction discharge delay time according to the following formula (3). In the formula, "Tc" represents the correction discharge delay time. In the formula, "T" represents the discharge delay time. In the formula, "α3" represents a coefficient. In the formula, "V" represents the processing speed.

[0050] …(3)

[0051] like Figure 3A as well as Figure 3B As shown, the average inter-electrode voltage varies depending on the voltage applied between the electrodes. Therefore, the correction unit 34 in the first embodiment changes the coefficient "α1" of equation (1) according to the voltage applied between the electrodes. On the other hand, as Figure 3A as well as Figure 3B As shown, the discharge delay time does not change with the inter-electrode voltage. Therefore, the correction unit 48 does not need to change the coefficient "α3" of equation (3) according to the inter-electrode voltage.

[0052] [Effects]

[0053] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the correction unit 48 calculates the corrected discharge delay time using a formula with the discharge delay time as the numerator and the machining speed multiplied by a coefficient as the denominator. The motor control unit 50 controls the X-axis motor 24 and the Y-axis motor 26 based on the corrected discharge delay time, ensuring that the size of the discharge gap during the EDM machining of the workpiece 14 remains constant. Therefore, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0054] In the wire EDM machine 10 of this embodiment, the correction unit 48 calculates the correction discharge delay time according to the above formula (3). As a result, the wire EDM machine 10 can keep the size of the discharge gap constant during processing, regardless of the processing speed.

[0055] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the discharge delay time calculation unit 46 calculates the discharge delay time based on the inter-electrode voltage detected by the inter-electrode voltage detection unit 22. The correction unit 48 calculates the corrected discharge delay time based on the above formula (3). Since the discharge delay time does not change with the voltage applied between the electrodes, the correction unit 48 does not need to change the coefficient "α3" in formula (3) according to the voltage applied between the electrodes, thus reducing the processing load of the correction unit 48.

[0056] In the wire electrical discharge machining (EDM) machine 10 of this embodiment, the motor control unit 50 sets at least one of the following based on the correction discharge delay time: the proportional gain of proportional control, the integral time of integral control, the derivative time of derivative control, and the target machining speed. As a result, the wire EDM machine 10 can improve the machining accuracy of the workpiece 14.

[0057] Furthermore, the present invention is not limited to the above-described embodiments, and various configurations may be adopted without departing from the spirit of the present invention.

[0058] [Technical Ideas Obtained from Implementation Methods]

[0059] The following describes the technical concepts that can be grasped from the above implementation methods.

[0060] A wire electrical discharge machining (EDM) machine (10) processes a workpiece by generating an inter-electrode discharge between an electrode (12) and a workpiece (14). It comprises: a discharge state value acquisition unit (32) that acquires a discharge state value based on one of the following: the time average of the voltage between the electrodes (i.e., the average inter-electrode voltage), the reciprocal of the number of discharge pulses between the electrodes per unit time, and the discharge delay time from the application of voltage to the inter-electrode until a discharge occurs; a discharge state value correction unit (34) that corrects the discharge state value based on the relative speed of the electrode to the workpiece (i.e., the processing speed) to obtain a correction value; drive units (24) and (26) that move the electrode relative to the workpiece; and a control unit (36) that controls the drive unit based on the correction value to keep the size of the inter-electrode distance constant during processing. The discharge state value correction unit obtains the correction value using a formula with the discharge state value as the numerator and the processing speed multiplied by a coefficient as the denominator. Thus, the wire EDM machine can improve the processing accuracy of the workpiece.

[0061] In the aforementioned wire electrical discharge machining (EDM) machine, the discharge state value correction unit can also adjust the setting based on the following conditions: the correction value is set to Sc, the discharge state value is set to S, the coefficient is set to α, and the machining speed is set to V. The correction value is obtained by applying the formula. Therefore, the wire electrical discharge machining (EDM) machine can maintain a constant discharge gap size during machining, regardless of the machining speed.

[0062] In the aforementioned wire electrical discharge machining (EDM) machine, the discharge state value acquisition unit can also acquire the discharge state value as the reciprocal of the number of discharge pulses per unit time or the discharge delay time. Therefore, the discharge state value correction unit does not need to change the coefficient α based on the voltage applied between the electrodes, thus reducing the processing load on the discharge state value correction unit.

[0063] In the aforementioned wire electrical discharge machining (EDM) machine, the control unit can also perform proportional control, integral control, and derivative control on the drive unit to make the machining speed a target machining speed. Based on the correction value, at least one of the proportional gain of the proportional control, the integral time of the integral control, the derivative time of the derivative control, and the target machining speed is set. Therefore, the wire EDM machine can improve the machining accuracy of the workpiece.

[0064] A control method for a wire electrical discharge machining (EDM) machine (10) is provided, which processes the workpiece by generating an inter-electrode discharge between an electrode (12) and a workpiece (14). The method comprises: a discharge state value acquisition step, which acquires a discharge state value by taking any one of the following: the time average of the voltage between the electrodes (i.e., the average inter-electrode voltage), the reciprocal of the number of discharge pulses between the electrodes per unit time, and the discharge delay time from the application of voltage to the inter-electrode until the discharge occurs; a discharge state value correction step, which corrects the discharge state value based on the relative speed of the electrode to the workpiece (i.e., the processing speed) and calculates a correction value; a driving step, which moves the electrode relative to the workpiece by driving units (24) and (26); and a control step, which controls the driving unit based on the correction value to keep the size of the inter-electrode distance constant during processing. In the discharge state value correction step, the correction value is calculated using a formula with the discharge state value as the numerator and the processing speed multiplied by a coefficient as the denominator. Therefore, the wire EDM machine can improve the processing accuracy of the workpiece.

[0065] In the above-described control method for a wire electrical discharge machining (EDM) machine, the discharge state value correction step can also be based on setting the correction value to Sc, the discharge state value to S, the coefficient to α, and the machining speed to V. The correction value is obtained by applying the formula. Therefore, the wire electrical discharge machining (EDM) machine can maintain a constant discharge gap size during machining, regardless of the machining speed.

[0066] In the above-described control method for a wire electrical discharge machining (EDM) machine, the discharge state value acquisition step can also use the reciprocal of the number of discharge pulses per unit time or the discharge delay time as the discharge state value. Therefore, in the discharge state value correction step, it is not necessary to change the coefficient α based on the voltage applied between the electrodes, thus reducing the processing load in the discharge state value correction step.

[0067] In the above-described control method for a wire electrical discharge machining (EDM) machine, the drive unit can also be subjected to proportional control, integral control, and derivative control in the control steps to make the machining speed a target machining speed. At least one of the following—the proportional gain of the proportional control, the integral time of the integral control, the derivative time of the derivative control, and the target machining speed—is set according to the correction value. Therefore, the wire EDM machine can improve the machining accuracy of the workpiece.

[0068] Symbol Explanation

[0069] 10… Wire EDM machine, 12… Wire electrode, 14… Workpiece, 24… X-axis motor (drive unit), 26… Y-axis motor (drive unit), 32… Average inter-electrode voltage calculation unit (discharge state value acquisition unit), 34… Correction unit (discharge state value correction unit), 36… Motor control unit (control unit).

Claims

1. A wire electrical discharge machining (10) for machining a workpiece by generating an electrical discharge between a wire electrode (12) and a workpiece (14), the wire electrical discharge machining being characterized by comprising: The discharge state value acquisition unit (32) acquires any one of the following as a discharge state value: the time average of the voltage between the electrodes, i.e., the average voltage between the electrodes; the reciprocal of the number of discharge pulses between the electrodes per unit time; and the time from the application of voltage to the electrodes until discharge occurs between the electrodes, i.e., the discharge delay time. The discharge state value correction unit (34) corrects the discharge state value based on the relative speed of the line electrode relative to the workpiece, i.e. the processing speed, and calculates the correction value. Drive units (24, 26) that cause the wire electrode to move relative to the workpiece; and The control unit (36) controls the drive unit according to the correction value to keep the size of the interpole spacing constant during processing. The discharge state value correction unit calculates the correction value based on a formula that uses the discharge state value as the numerator and the value obtained by multiplying the processing speed by a coefficient as the denominator.

2. The wire electrical discharge machining machine according to claim 1, characterized in that, The discharge state value correction unit determines the discharge state value based on the following conditions: the correction value is set to Sc, the discharge state value is set to S, the coefficient is set to α, and the processing speed is set to V. The formula is used to calculate the correction value.

3. The wire electrical discharge machining machine according to claim 2, characterized in that, The discharge state value acquisition unit acquires the discharge state value by taking the reciprocal of the number of discharge pulses per unit time or the discharge delay time.

4. The wire electrical discharge machining machine according to any one of claims 1 to 3, characterized in that, In the control unit, The drive unit is subjected to proportional control, integral control, and derivative control to make the processing speed reach the target processing speed. Based on the correction value, at least one of the following is set: the proportional gain of the proportional control, the integral time of the integral control, the derivative time of the derivative control, and the target processing speed.

5. A control method for a wire electrical discharge machining (10) wherein the wire electrical discharge machining generates an inter-electrode discharge between a wire electrode (12) and a workpiece (14) to process the workpiece, the control method of the wire electrical discharge machining is characterized by comprising: The discharge state value acquisition step involves acquiring any one of the following as the discharge state value: the time average of the voltage between the electrodes (i.e., the average voltage between the electrodes), the reciprocal of the number of discharge pulses between the electrodes per unit time, and the discharge delay time from the time when the voltage is applied to the electrodes until the discharge occurs between the electrodes. The discharge state value correction step involves correcting the discharge state value based on the relative speed of the line electrode to the workpiece, i.e., the processing speed, and then calculating the correction value. In the driving step, the driving unit (24, 26) moves the wire electrode relative to the workpiece. as well as The control step involves controlling the drive unit based on the correction value to keep the distance between the poles constant during processing. In the discharge state value correction step, the correction value is calculated using a formula with the discharge state value as the numerator and the processing speed multiplied by a coefficient as the denominator.

6. The control method for a wire electrical discharge machining machine according to claim 5, characterized in that, In the discharge state value correction step, based on setting the correction value to Sc, the discharge state value to S, the coefficient to α, and the processing speed to V, The formula is used to calculate the correction value.

7. The control method for a wire electrical discharge machining machine according to claim 6, characterized in that, In the step of obtaining the discharge state value, the reciprocal of the number of discharge pulses per unit time or the discharge delay time is used as the discharge state value.

8. The control method for a wire electrical discharge machining machine according to any one of claims 5 to 7, characterized in that, In the control step, The drive unit is subjected to proportional control, integral control, and derivative control to make the processing speed reach the target processing speed. Based on the correction value, at least one of the following is set: the proportional gain of the proportional control, the integral time of the integral control, the derivative time of the derivative control, and the target processing speed.

Images