JP2019181617A - Wire electric discharge machine and wire electric discharge machining method - Google Patents

Abstract

To provide a wire electric discharge machine and a wire electric discharge machining method by which it is prevented that electric discharge machining becomes unstable by a stray capacitance which is fluctuated due to a shape and a size of a machining object.SOLUTION: A wire electric discharge machine 10, which performs electric discharge machining for a machining object 14 by occurrence of electric discharge by applying a voltage to an electrode gap 16 which is formed between a wire electrode 12 and the machining object 14, comprises: a power supply unit 18 which applies a prescribed voltage to the electrode gap 16; and a power source control part 20 which controls the power supply unit 18, and changes an application time T of the prescribed voltage according to a shape and a size of the machining object 14 so that a peak voltage Vp of the electrode gap 16 becomes a predetermined reference voltage Vb.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wire electric discharge machine and a wire electric discharge machining method for machining an object to be machined using a wire electrode.

  Patent Document 1 shown below discloses a wire electric discharge machine that processes a workpiece by applying a voltage between electrodes formed between the wire electrode and the workpiece to generate electric discharge. ing.

Japanese Patent No. 3245087

  Here, the stray capacitance generated between the wire electrode and the workpiece varies depending on the shape and size of the workpiece. When this stray capacitance fluctuates, the voltage waveform between the poles fluctuates, and machining becomes unstable.

  Therefore, an object of the present invention is to provide a wire electric discharge machine and a wire electric discharge machining method that prevent machining from becoming unstable due to fluctuations in stray capacitance.

  A first aspect of the present invention is a wire discharge for performing electric discharge machining on the workpiece by applying a voltage between the electrodes formed between the wire electrode and the workpiece to generate electric discharge. A processing machine, wherein a power supply unit that applies a predetermined voltage between the electrodes and the power supply unit is controlled to apply the predetermined voltage so that a peak voltage between the electrodes becomes a predetermined reference voltage. And a power supply controller that changes the shape according to the shape and size of the workpiece.

  According to a second aspect of the present invention, there is provided a wire electric discharge machine having a power supply unit that applies a predetermined voltage between electrodes formed between a wire electrode and a workpiece, and performs electric discharge machining on the workpiece. In the wire electric discharge machining method to be performed, the power source unit is controlled so that the application time of the predetermined voltage is set so that the peak voltage between the poles becomes a predetermined reference voltage, and the shape and size of the workpiece. The power supply control step is changed according to the height.

  According to the present invention, it is possible to prevent processing from becoming unstable due to fluctuations in stray capacitance.

It is a figure which illustrates the schematic structure of the wire electric discharge machine which concerns on embodiment. FIG. 2A is a diagram illustrating the stray capacitance and the interelectrode voltage when the workpiece is small, and FIG. 2B is a diagram illustrating the stray capacitance and the interelectrode voltage when the workpiece is large. It is a flowchart of the process by the wire electric discharge machine which concerns on embodiment.

  DESCRIPTION OF EMBODIMENTS A wire electric discharge machine and a wire electric discharge machining method according to the present invention will be described in detail below with reference to the accompanying drawings with preferred embodiments.

[Embodiment]
FIG. 1 is a diagram illustrating a schematic configuration of a wire electric discharge machine 10 according to the present embodiment. The wire electric discharge machine 10 applies electrical discharge to the workpiece 14 by applying a voltage to the gap 16 formed between the wire electrode 12 and the workpiece (workpiece) 14 to generate electric discharge. It is a machine tool to be applied.

  The wire electric discharge machine 10 includes a power supply unit 18, a power supply control unit 20, a table 22, and the like. The table 22 is made of a conductive member, for example, metal.

  The power supply unit 18 applies a predetermined voltage (constant voltage) to the gap 16. The power supply unit 18 can apply a positive voltage and a negative voltage to the gap 16.

  The power supply unit 18 includes a DC power supply 24 and four switches 26A, 26B, 26C, and 26D. In the present embodiment, the voltage of the DC power supply 24 is set to a predetermined voltage.

  The switch 26 </ b> A is connected to the negative electrode terminal of the DC power supply 24 and the wire electrode 12, and the switch 26 </ b> B is connected to the negative electrode terminal of the DC power supply 24 and the table 22. The switch 26C is connected to the positive terminal of the DC power supply 24 and the table 22, and the switch 26D is connected to the positive terminal of the DC power supply 24 and the wire electrode 12.

  When the switches 26 </ b> A and 26 </ b> C are turned on, a positive voltage is applied to the gap 16. On the other hand, when the switches 26 </ b> B and 26 </ b> D are turned on, a negative voltage is applied to the gap 16. The time during which both the switches 26A and 26C are turned on is the application time T during which a predetermined voltage is applied between the electrodes 16. Further, the time when the switches 26B and 26D are turned on is the application time T during which a predetermined voltage is applied to the gap 16.

  The power supply control unit 20 controls the power supply unit 18 to change the application time T for applying a predetermined voltage. Specifically, the power supply control unit 20 changes the application time T for applying a predetermined voltage by controlling on / off of the switches 26 </ b> A to 26 </ b> D of the power supply unit 18. Note that the power supply control unit 20 may control the power supply unit 18 so that a positive voltage and a negative voltage are alternately applied to the gap 16. The case where the unit 20 applies a positive voltage to the gap 16 will be described as an example.

  The power supply control unit 20 controls the power supply unit 18 to change the application time T of the predetermined voltage according to the shape and size of the workpiece 14 so that the peak voltage Vp between the electrodes 16 becomes the reference voltage Vb. . The reference voltage Vb is a predetermined voltage, and is determined according to a predetermined processing speed and the surface roughness of the processed surface after processing. Note that, as described above, the size of the stray capacitance generated between the wire electrode 12 and the workpiece 14 changes depending on the shape and size of the workpiece 14, and the voltage waveform of the gap 16 changes. Therefore, it is necessary to change the application time T for applying a predetermined voltage to the gap 16. Although stray capacitance can also occur between the wire electrode 12 and the table 22, since the shape and size of the table 22 are constant, the stray capacitance generated between the wire electrode 12 and the table 22 is here. The capacity will be described without considering it.

  Hereinafter, control of the power supply control unit 20 will be described with reference to FIGS. 2A and 2B. FIG. 2A is a diagram illustrating a stray capacitance and a voltage between the electrodes 16 (also referred to as an electrode voltage) when the workpiece 14 is small. FIG. 2B is a diagram illustrating the stray capacitance and the interelectrode voltage when the workpiece 14 is large. 2A and 2B, the shape of the workpiece 14 is a rectangular parallelepiped for easy understanding.

  In the case shown in FIG. 2A, the stray capacitance generated between the wire electrode 12 and the workpiece 14 is small, but in the case shown in FIG. 2B, the wire electrode 12 and the workpiece are compared with the case shown in FIG. 2A. 14 is large.

In the case of FIG. 2A, since the stray capacitance is small, the time from when the predetermined voltage is applied to the gap 16 to when the gap voltage becomes the reference voltage Vb is short. T ₀ in FIG. 2A indicates the application start time. t ₁ indicates the time when the interelectrode voltage becomes the reference voltage Vb and the application end time. Accordingly, when the workpiece 14 is small, the application time T until the interelectrode voltage becomes the reference voltage Vb is T = t ₁ −t ₀ . Voltage of the machining gap 16 in this application end time _{t 1} is the peak voltage Vp.

In the case of FIG. 2B, since the stray capacitance is large, it takes a long time after the predetermined voltage is applied to the gap 16 until the gap voltage becomes the reference voltage Vb. T ₀ in FIG. 2B indicates the application start time. t ₂ represents the application end time with indicating the time when the machining gap voltage is the reference voltage Vb. Time t ₂ as shown in Figure 2B is the time after time t _1. At time t _1, the machining gap voltage does not reach the reference voltage Vb. Therefore, when the workpiece 14 is large, the application time T until the interelectrode voltage becomes the reference voltage Vb is T = t ₂ −t ₀ , and the application time until the interelectrode voltage becomes the reference voltage Vb. T is longer than in the case of FIG. 2A. Voltage of the machining gap 16 in this application end time _{t 2} becomes the peak voltage Vp.

  The stray capacitance generated in the gap 16 can also change depending on the shape of the workpiece 14. For this reason, the application time T until the inter-electrode voltage becomes the reference voltage Vb can also vary depending on the shape of the workpiece 14. For this reason, the power supply control part 20 changes the application time T of the predetermined voltage to the space | interval 16 not only according to the magnitude | size of the workpiece 14 but the shape. Here, the size and shape of the workpiece 14 are those when placed on the table 22.

  As a functional block for performing the above control, the power supply control unit 20 includes a switch control unit 28, a storage unit 30, and the like as shown in FIG.

  The storage unit 30 stores an application time (information indicating the application time) T according to the shape and size of the workpiece 14.

  The switch control unit 28 acquires the shape and size of the processing target 14 to be processed based on an operation of an input unit (not shown) by the operator or based on an image captured by a camera that captures the processing target 14. To do. The switch control unit 28 reads the application time T corresponding to the shape and size of the workpiece 14 from the storage unit 30. Then, the switch control unit 28 controls the switches 26A and 26C so that the voltage is applied for the read application time T.

  Hereinafter, a method for determining the application time T according to the shape and size of the workpiece 14 stored in the storage unit 30 will be described.

  In order to determine the application time T, as shown in FIG. 1, the wire electric discharge machine 10 further includes a voltage detection unit 32, and the power supply control unit 20 further includes a determination unit 34.

  The voltage detector 32 is a sensor that detects the voltage between the electrodes 16. The voltage detection unit 32 outputs the detected voltage between the electrodes 16 to the power supply control unit 20 (determination unit 34).

  The determination unit 34 determines the application time T using the voltage between the electrodes 16 obtained from the voltage detection unit 32 and the amount of change over time. The determination unit 34 calculates the slope of increase of the acquired interelectrode voltage V. From the calculated slope, the determination unit 34 calculates to what point the voltage V is applied to reach the reference voltage Vb. When the value of the interelectrode voltage V acquired from the voltage detection unit 32 cannot be approximated as a straight line, the determination unit 34 approximates the interelectrode voltage V as a curve, and the interelectrode voltage V is Vb on this curve. And the application time T may be determined.

  In addition to the determination of the application time T as described above, the determination unit 34 continues until the interelectrode voltage V reaches Vb (until the voltage detection unit 32 detects that the interelectrode voltage V has reached Vb). The application time T may be obtained by measuring the time of time with a timer (not shown).

  The determination unit 34 stores the application time T in the storage unit 30 in association with the shape and size of the workpiece 14. For obtaining the shape and size of the workpiece 14, an operation content from an operator via an input unit (not shown), a camera, and the like are used. The determination unit 34 acquires the shape and size of the workpiece 14 when placed on the table 22.

  Next, the machining process performed by the wire electric discharge machine 10 using the application time T determined and stored as described above will be described with reference to the flowchart shown in FIG. FIG. 3 is a flowchart of the machining process performed by the wire electric discharge machine 10. The switch control unit 28 acquires the shape and size of the workpiece 14 placed on the table 22 (step S1). The switch control unit 28 acquires, from the storage unit 30, the application time T associated with the shape and size of the workpiece 14 acquired in step S1 (step S2).

  The switch control unit 28 turns on the switches 26A and 26C during the acquired application time T. As a result, a predetermined voltage is applied from the power supply unit 18 to the gap 16 to perform the processing (step S3).

  The power supply control unit 20 in the present embodiment is realized using, for example, a processor, a memory, a switch drive circuit, and the like. The processor is, for example, a single core, dual core, or multi-core processor. The memory is a memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), and a flash memory, for example. The switch drive circuit is an existing circuit for executing a switch ON / OFF switching operation.

  The function of the storage unit 30 is realized by the memory. The function of the determination part 34 is implement | achieved when a processor performs a process using information, such as the application time T and the program which were memorize | stored in memory. Further, the processor performs processing using information stored in the memory and controls the switch drive circuit, whereby the function of the switch control unit 28 is realized. The power supply control unit 20 may be configured by dedicated hardware or the like other than the above configuration.

  As described above, the wire electric discharge machine 10 according to the present embodiment changes the application time T for applying a predetermined voltage in accordance with the shape and size of the workpiece 14. Thereby, even if it is a case where the stray capacitance which arises in the gap | interval 16 according to the shape and magnitude | size of the workpiece 14 is fluctuate | varied, it can prevent that processing becomes unstable.

  In addition, that processing becomes unstable means that the surface roughness and processing speed of the processing surface fluctuate. Specifically, if the applied voltage is constant, the peak voltage Vp between the electrodes 16 is deviated from the desired reference voltage Vb, so that the surface roughness of the processed surface does not become the desired surface roughness. sell. In addition, when the peak voltage Vp is lower than the reference voltage Vb, it is difficult for electric discharge to occur and the wire electrode 12 may be disconnected. If the processing speed is lowered so as not to disconnect, the processing time becomes longer.

[Modification]
The above embodiment can be modified as follows.
The storage unit 30 in the above embodiment stores the application time T itself as information indicating the application time T. However, any information may be used as long as the information indicates the application time T. For example, the storage unit 30 may store a correction value (information indicating the application time) for correcting the reference application time Tb. The reference application time Tb is a predetermined time and is determined according to the reference voltage Vb. The reference application time Tb is stored in the storage unit 30.

  The correction value for correcting the reference application time Tb is for correcting the reference application time Tb so as to be the application time T according to the shape and size of the workpiece 14. For example, the correction value may be information indicating the difference between the application time T corresponding to the shape and size of the workpiece 14 and the reference application time Tb. Further, the correction value may be information indicating a ratio between the application time T and the reference application time Tb according to the shape and size of the workpiece 14. The storage unit 30 stores correction values according to the shape and size of the workpiece 14.

  The switch control unit 28 controls the power supply unit 18 to apply a predetermined voltage to the gap 16 during the application time T obtained using the reference application time Tb and the correction value.

  According to the wire electric discharge machine 10 according to the present embodiment, the amount of information to be stored in the storage unit 30 can be reduced.

[Technical idea obtained from the embodiment]
The technical idea that can be grasped from the above embodiment will be described below.

<First technical idea>
Electric discharge machining is performed on the workpiece (14) by applying a voltage to the gap (16) formed between the wire electrode (12) and the workpiece (14) to generate electric discharge. The wire electric discharge machine (10) controls the power supply unit (18) for applying a predetermined voltage between the electrodes (16) and the power supply unit (18) so that the peak voltage (Vp) between the electrodes (16) is set in advance. And a power supply control unit (20) that changes the application time (T) of the predetermined voltage according to the shape and size of the workpiece (14) so that the determined reference voltage (Vb) is obtained.

  Thereby, it is possible to prevent the processing from becoming unstable due to the fluctuation of the stray capacitance.

  The wire electric discharge machine (10) may include a storage unit (30) that stores information indicating an application time (T) according to the shape and size of the workpiece (14). 20) may acquire information indicating the application time (T) according to the shape and size of the workpiece (14) from the storage unit (30). Thereby, it is not necessary to determine how much the application time (T) is made each time the workpiece (14) is machined, and the processing load during machining can be reduced.

  In the wire electric discharge machine (10), the information indicating the application time (T) stored in the storage unit (30) may be a correction value for correcting a predetermined reference application time (Tb), The power supply controller (20) may apply a predetermined voltage between the electrodes (16) for the reference application time (Tb) corrected based on the information indicating the application time (T). Thereby, compared with the case where application time (T) itself is memorize | stored, the reduction of the data amount memorize | stored in a memory | storage part (30) can be aimed at.

<Second technical idea>
A wire electric discharge machine (10) having a power supply unit (18) for applying a predetermined voltage to a gap (16) formed between a wire electrode (12) and a workpiece (14) is a workpiece ( In the wire electric discharge machining method for performing electric discharge machining on 14), the power supply unit (18) is controlled so that the peak voltage (Vp) between the electrodes (16) becomes a predetermined reference voltage (Vb). A power supply control step is included in which the application time (T) of the predetermined voltage is changed according to the shape and size of the workpiece (14).

  Thereby, it is possible to prevent the processing from becoming unstable due to the fluctuation of the stray capacitance.

  The wire electric discharge machining method may include a storage step of storing information indicating an application time (T) according to the shape and size of the workpiece (14) in the storage unit (30). You may acquire the information which shows the application time (T) according to the shape and magnitude | size of a process target object (14) from a part (30). Thereby, it is not necessary to determine how much the application time (T) is made each time the workpiece (14) is machined, and the processing load during machining can be reduced.

  In the wire electric discharge machining method, the information indicating the application time (T) stored in the storage unit (30) may be a correction value for correcting a predetermined reference application time (Tb). May be a step of applying a predetermined voltage to the gap (16) for the reference application time (Tb) corrected based on the information indicating the application time (T). Thereby, compared with the case where application time (T) itself is memorize | stored, the reduction of the data amount memorize | stored in a memory | storage part (30) can be aimed at.

DESCRIPTION OF SYMBOLS 10 ... Wire electric discharge machine 12 ... Wire electrode 14 ... Work object 16 ... Electrode 18 ... Power supply part 20 ... Power supply control part 22 ... Table 24 ... DC power supply 26A, 26B, 26C, 26D ... Switch 28 ... Switch control part 30 ... storage unit 32 ... voltage detection unit 34 ... determination unit T ... application time Tb ... reference application time V ... voltage between electrodes Vb ... reference voltage Vp ... peak voltage

Claims (6)

A wire electric discharge machine that performs electric discharge machining on the workpiece by applying a voltage between the electrodes formed between the wire electrode and the workpiece to generate electric discharge,
A power supply unit for applying a predetermined voltage between the electrodes;
A power supply control unit that controls the power supply unit to change the application time of the predetermined voltage in accordance with the shape and size of the workpiece so that the peak voltage between the electrodes becomes a predetermined reference voltage. When,
A wire electric discharge machine. The wire electric discharge machine according to claim 1,
A storage unit that stores information indicating the application time according to the shape and size of the workpiece;
The power supply control unit is a wire electric discharge machine that acquires information indicating the application time according to the shape and size of the workpiece from the storage unit. The wire electric discharge machine according to claim 2,
Information indicating the application time stored in the storage unit is a correction value for correcting a predetermined reference application time,
The power supply control unit causes the predetermined voltage to be applied between the electrodes for the reference application time corrected based on information indicating the application time. A wire electric discharge machine having a power supply unit that applies a predetermined voltage between electrodes formed between a wire electrode and a workpiece is a wire electric discharge machining method for performing electric discharge machining on the workpiece,
A power supply control step of controlling the power supply unit to change the application time of the predetermined voltage according to the shape and size of the workpiece so that the peak voltage between the electrodes becomes a predetermined reference voltage A wire electric discharge machining method. The wire electric discharge machining method according to claim 4,
A storage step of storing in the storage unit information indicating the application time according to the shape and size of the workpiece;
In the wire electric discharge machining method, the power control step acquires information indicating the application time according to the shape and size of the workpiece from the storage unit. The wire electric discharge machining method according to claim 5,
Information indicating the application time stored in the storage unit is a correction value for correcting a predetermined reference application time,
In the wire electric discharge machining method, the power supply control step applies the predetermined voltage between the electrodes for the reference application time corrected based on the information indicating the application time.

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