JP6397699B2 - Control method of multi-wire electric discharge machine - Google Patents

Description

  The present invention relates to a control method for a multi-wire electric discharge machining apparatus.

  Conventionally, a wire saw using abrasive grains is known as a cutting means for cutting a wafer from a cylindrical ingot. However, in such a wire saw, it is necessary to simultaneously supply a processing liquid (slurry) in which processing abrasive grains are mixed, and handling thereof is not easy. In addition, since the wire is in direct contact with the workpiece, particularly in the case of SiC having high hardness, there is a possibility that the wire may be disconnected during processing, and when the disconnection occurs, there is a disadvantage that it takes a long time to recover.

  Therefore, a multi-wire electric discharge machining apparatus has been devised. Since the wire and the ingot are not in contact with each other by electric discharge machining, the load applied to the ingot is very low, and there is no effect of scratches such as scratches due to the slurry.

  However, if the removal of the workpiece due to electric discharge and the relative movement speed of the wire and the ingot do not correspond, the wire and the ingot come into contact with each other, and a short circuit state occurs. If electricity flows concentrated on the short-circuited portion, the wire may break due to high heat. Therefore, the multi-wire electric discharge machining apparatus constantly monitors whether the voltage is short-circuited by monitoring the voltage. And when it will be in a short circuit state, after separating (retracting) a wire from an ingot, it will process again. At this time, whether or not it is separated by a desired distance suitable for processing is determined by applying the same voltage as during processing and the voltage of power flowing in the wire and ingot is a predetermined value or more. A test process is performed to measure the voltage by applying the same voltage as inside.

JP 2012-240128 A

  However, in the test process, if it is not separated by a desired distance for some reason, when the same voltage as that during processing is applied, the discharge is concentrated locally as in the case of a short circuit, and the wire may be disconnected.

  Therefore, the present invention has been made in view of the above, and when the machining is resumed after the wire and the ingot are short-circuited, the control of the multi-wire electric discharge machining apparatus that prevents the wire from being disconnected in the resume process. It aims to provide a method.

In order to solve the above-described problems and achieve the object, the control method of the multi-wire electric discharge machining apparatus according to the present invention is wound around a plurality of guide rollers adjacent to each other at intervals with a plurality of turns in the axial direction. Drive means for relatively processing and feeding the wire and the base portion for fixing the ingot so that the ingot is cut into the wires arranged in parallel, and the wire and the ingot fixed to the base portion. A high-frequency pulse power supply unit that supplies high-frequency pulse power, and the high-frequency pulse power supply unit adjusts the pulse power to be applied to a desired frequency, and voltage adjustment that adjusts the voltage of the pulse power to be applied. Determining means for measuring a voltage of the pulse power flowing through the wire and the ingot and determining an interval between the ingot and the wire based on the voltage And a distance adjusting means for adjusting a distance between the ingot and the wire based on the determined distance, and a control method for a multi-wire electric discharge machining apparatus, wherein the wire and the ingot are applied while applying a predetermined machining voltage. A machining step in which electric discharge machining is performed and the wire and the ingot are in contact with each other or connected via machining scraps during the machining step, and a voltage of a predetermined level or less is measured and it is determined that a short-circuit state has occurred. In addition, a separation step for separating the wire from the ingot to prevent the wire from breaking due to heat generated by a short circuit, and after performing the separation step, a test voltage lower than the machining voltage is applied to eliminate the short circuit state. A test step for determining whether the measured voltage is equal to or greater than a threshold when the predetermined test voltage is applied in the test step. Again performed the processing steps to determine the fault condition has been eliminated, the measured voltage of less than the threshold, implement or該離between steps to implement the test step again again applied at the test step The frequency of the test voltage is higher than that of the machining step, and the number of pulses that can be measured in a predetermined time is larger than that of the machining step .

  Further, in the control method of the multi-wire electric discharge machining apparatus, when the test voltage is gradually adjusted from a low voltage to a predetermined voltage and a voltage equal to or higher than a threshold set corresponding to the applied voltage is measured. It is preferable to apply a higher voltage.

  According to the control method of the multi-wire electric discharge machining apparatus of the present invention, when a short-circuit between the wire and the ingot is determined, after separating both, a test voltage lower than the voltage at the time of machining is applied. Even when the wire and the ingot are in contact with each other, it is possible to prevent the discharge from being intensively generated at a high voltage and to prevent the wire from being disconnected. Further, it is possible to protect a wire that is damaged by contact and is easily broken.

FIG. 1 is a front view illustrating a configuration example of a multi-wire electric discharge machining apparatus according to the first embodiment. FIG. 2 is a side view illustrating an example of forming a wafer according to the first embodiment. FIG. 3 is a diagram illustrating voltages during processing and short-circuiting according to the first embodiment. FIG. 4 is a diagram illustrating a setting example of the test voltage according to the first embodiment. FIG. 5 is a flowchart illustrating a control method of the multi-wire electric discharge machining apparatus according to the first embodiment. FIG. 6 is a diagram illustrating a control example of the frequency of the test voltage according to the second embodiment.

  DESCRIPTION OF EMBODIMENTS Embodiments (embodiments) for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited by the contents described in the following embodiments. The constituent elements described below include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the structures described below can be combined as appropriate. Various omissions, substitutions, or changes in the configuration can be made without departing from the scope of the present invention.

Embodiment 1
A configuration example of the multi-wire electric discharge machining apparatus according to Embodiment 1 will be described with reference to FIG. FIG. 1 is a front view showing a configuration example of a multi-wire electric discharge machining apparatus.

  As shown in FIG. 1, the multi-wire electric discharge machine 1 is an electric discharge machine for an ingot I using a wire R, and a plurality of feed bobbins 20 that feed out the wire R and a plurality of spaced bobbins 20 are provided and fed out by the feed bobbin 20. Cylindrical guide rollers 21 to 24 for guiding the wire R, and a winding bobbin 25 for winding the wire R. The four guide rollers 21 to 24 are each disposed at a corner of the rectangle so as to form a rectangular shape.

  The guide rollers 21 to 24 are arranged so that a line segment formed by the guide roller 21 and the guide roller 22 and a line segment formed by the guide roller 24 and the guide roller 23 are parallel to each other. The guide rollers 21 to 24 are wound around the wire R fed out from the feeding bobbin 20 a plurality of times and sent out to the winding bobbin 25.

  The feeding bobbin 20, the guide rollers 21 to 24, and the take-up bobbin 25 are rotationally driven by a motor (not shown). Note that not all the guide rollers 21 to 24 need to be driven by a motor, and for example, the guide rollers 22 and 24 may be driven rollers.

  A wire R that is a metal wire such as brass used for electric discharge machining is wound around the feeding bobbin 20. The feeding bobbin 20 feeds the wire R to the guide roller 21. The guide roller 21 winds the wire R fed from the feeding bobbin 20 and feeds it to the guide roller 22. The guide roller 22 winds the wire R fed from the guide roller 21 and feeds it to the guide roller 23. The guide roller 23 winds the wire R sent from the guide roller 22 and sends it to the guide roller 24. The guide roller 24 winds the wire R fed from the guide roller 23 and feeds it to the guide roller 21. As a result, the wire R is wound around the guide rollers 21 to 24 once.

  The wire R is wound around the plurality of guide rollers 21 to 24 adjacent to each other at intervals with a plurality of turns at intervals in the axial direction. In this example, it is wound eight times. The wire R wound a plurality of times is finally sent out from the guide roller 22 and taken up on the take-up bobbin 25. As described above, the wire R is wound around the guide rollers 21 to 24 in the axial direction at a plurality of times and travels in parallel between the guide rollers 21 to 24. The wire R constitutes a cutting wire portion 30 formed between a pair of adjacent guide rollers 23 and guide rollers 24.

  The cutting wire portion 30 is a portion for cutting the ingot I. The cutting wire portion 30 is stretched with a certain tension by the guide roller 23 and the guide roller 24, and is disposed in the longitudinal direction of the guide rollers 23, 24 at a predetermined interval. It consists of eight wires R. For example, the interval between the wires R constituting the cutting wire portion 30 is about 0.5 mm to several mm. The ingot I is cut at the intervals of the wires R. The ingot I is a conductive material and is formed of SiC (silicon carbide), single crystal diamond, silicon, GaN (gallium nitride), or the like. In this example, the shape of the ingot I is a cylinder.

  An ingot installation means 40 for installing the ingot I is provided at a position facing the cutting wire portion 30. The ingot installation means 40 includes a base part 41, an attachment part 42, and a drive means 44.

  The base part 41 fixes the ingot I via the attachment part 42. The attachment portion 42 is fixed to the base portion 41 and has an attachment surface 43 that supports the ingot I. The end surface Ia of the ingot I is bonded and fixed to the mounting surface 43 with a conductive adhesive 45 (see FIG. 2).

  The driving means 44 relatively feeds the base 41 and the wire R, which fix the ingot I, so that the ingot I cuts into the parallel wires R. For example, the drive means 44 has a ball screw (not shown) extending in parallel to the vertical direction and a drive source composed of a pulse motor or the like, and a base portion 41 fixed to a nut of the ball screw. Are driven in the machining feed direction. Then, the ingot I is sliced by the wire R of the cutting wire portion 30 to form a wafer. Note that driving means (not shown) for moving the ingot I in the axial direction of the ingot I is provided.

  The nozzle means 50 which removes the processing waste U (refer FIG. 2) produced at the time of the slice of the ingot I is provided, and the moving means 60 which moves the nozzle means 50 is provided. The nozzle means 50 is composed of a pair of members, is arranged before and after the wire R across the ingot I in the traveling direction, and ejects the machining fluid F toward the machining groove of the ingot I. The moving means 60 moves the nozzle means 50 along the shape of the outer peripheral surface of the ingot I while having a certain distance from the outer peripheral surface of the ingot I.

  The multi-wire electric discharge machining is performed in a machining fluid F such as water or oil that is a dielectric, and the cutting wire portion 30 is immersed in a machining tank 70 filled with the machining fluid F. In the processing tank 70, the wire R of the cutting wire portion 30 immersed in the stored processing liquid F processes the ingot I.

  In the processing tank 70, a basket 71 for accommodating a wafer is disposed. The flange 71 is disposed directly below the ingot I, is formed larger than the length of the ingot I in the longitudinal direction and the short direction, and has a certain depth. The wafer separated from the ingot I fixed to the attachment part 42 of the base part 41 is sunk and accommodated in a ridge 71 arranged in the processing tank 70.

  The multi-wire electric discharge machining apparatus 1 includes a high-frequency pulse power supply unit 80 that supplies high-frequency pulse power to the ingot I and the wire R fixed to the base portion 41. The high frequency pulse power supply unit 80 includes control means 81 and an electrode 82. The control means 81 is connected to the drive means 44 and controls the drive means 44 to control the ingot I moving in the machining feed direction or the like.

  The control means 81 is connected to the electrode 82 and supplies high-frequency pulse power to the wire R via the electrode 82. For example, the electrode 82 is connected to a wire R stretched between the guide roller 21 and the guide roller 24, and further connected to a wire R stretched between the guide roller 22 and the guide roller 23. . The control means 81 is connected to the base portion 41 and supplies high frequency pulse power to the ingot I via the base portion 41.

  When high-frequency pulse power is supplied from the control means 81 and a voltage is applied between the electrodes of the wire R and the ingot I, a discharge that is repeated in a short cycle is generated between the wire R and the ingot I of the cutting wire portion 30. . For example, when the distance between the ingot I and the wire R, which are in an insulating state in the liquid, approaches about several tens of μm, the insulation between the two is destroyed and a discharge is generated. By this discharge, the ingot I is heated and melted, and the temperature of the liquid is rapidly increased, whereby the liquid is vaporized, and the melted portion is scattered by volume expansion. In this way, by supplying high-frequency pulse power and applying a voltage between the electrodes, the ingot I is melted and scattered by the wire R, and the ingot I is cut off intermittently.

  The control unit 81 includes a pulse adjustment unit 810, a voltage adjustment unit 811, a determination unit 812, and a distance adjustment unit 813. The pulse adjusting means 810 adjusts the applied pulse power to a desired frequency. For example, the pulse adjusting means 810 is composed of a switching circuit (not shown) composed of a plurality of switching elements such as transistors and a control circuit (not shown) that controls ON / OFF of the switching elements of the switching circuit with a predetermined number of clocks. . For example, the control circuit adjusts the frequency of the applied pulse power to a desired frequency by ON / OFF controlling the switching element with a desired number of clocks.

  In addition, the control circuit changes the polarity of the voltage of the pulse power applied between the electrodes by switching the switching element to be turned on / off. For example, the switching circuit is a full-bridge circuit, and a positive voltage is applied between the electrodes by turning on only the switching element on one side, and a negative voltage is applied by turning on only the switching element on the other side. Apply in between and perform bipolar processing while changing the polarity alternately. Of course, you may make it process only with one polarity, without performing bipolar processing. In this case, ON / OFF control is performed not by a full bridge circuit but by, for example, one switching element.

  The voltage adjusting unit 811 is connected to the pulse adjusting unit 810 and adjusts the voltage of the applied pulse power. For example, the voltage adjusting unit 811 adjusts the voltage during machining (machining voltage) to 200 V, and adjusts the voltage during testing (test voltage) to 100 V to 170 V.

  The discriminating means 812 measures the voltage of the pulse power flowing through the wire R and the ingot I, that is, the potential difference between the poles, and discriminates the interval between the ingot I and the wire R based on the measured potential difference (measured voltage). For example, the determination unit 812 determines whether the wire R and the ingot I are short-circuited based on the measured voltage. For example, the determination unit 812 has a threshold value (120 V) for determining that the wire R and the ingot I are short-circuited, compares this threshold value with the measured voltage, and if the measured voltage is less than the threshold value, the wire R And ingot I are determined to be short-circuited. Further, when the measured voltage is equal to or higher than the threshold value, the determination unit 812 determines that the electric discharge machining is normally performed with a certain interval without short-circuiting the wire R and the ingot I.

  The distance adjustment unit 813 is connected to the determination unit 812 and adjusts the interval between the ingot I and the wire R based on the interval determined by the determination unit 812. For example, when the distance adjustment unit 813 receives short-circuit information indicating that the wire R and the ingot I are short-circuited from the determination unit 812, the distance adjustment unit 813 separates the ingot I from the wire R. For example, the ingot I fixed to the base portion 41 is moved in the machining feed direction so as to be cut into the wire R at a constant machining speed by the driving means 44 during the electric discharge machining. When the short-circuit information is input, the distance adjusting unit 813 temporarily stops the movement in the machining feed direction with respect to the driving unit 44, and further moves the ingot I slightly in the direction opposite to the machining feed direction to stop the ingot I. Is separated from the wire R.

  Next, based on FIGS. 2-5, the control method of the multi-wire electric discharge machining apparatus 1 which concerns on Embodiment 1 is demonstrated. FIG. 2 is a side view illustrating an example of forming a wafer according to the first embodiment. FIG. 3 is a diagram illustrating voltages during processing and short-circuiting according to the first embodiment. FIG. 4 is a diagram illustrating a setting example of the test voltage according to the first embodiment. FIG. 5 is a flowchart illustrating a control method of the multi-wire electric discharge machining apparatus according to the first embodiment.

  In step ST1 shown in FIG. 5, the control means 81 performs machining control so that the wire R and the ingot I are fed and subjected to electric discharge machining while applying a predetermined machining voltage (machining step). For example, the voltage adjusting unit 811 applies a machining voltage of 200V. Further, the control means 81 controls the drive means 44 to move the ingot I in the machining feed direction so as to cut into the wire R at a constant machining speed. Next, the process proceeds to step ST2.

  In step ST2, the control means 81 determines whether or not electric discharge machining has been completed. For example, based on the diameter of the ingot I to be machined, a movement amount for moving the ingot I in the machining feed direction is set in advance, and the control unit 81 sets the movement amount of the ingot I to the set movement amount. When it reaches, it is determined that the electric discharge machining is finished, and the electric discharge machining is finished. When the movement amount of the ingot I has not reached the set movement amount, the process proceeds to step ST3.

  In step ST3, the control means 81 determines whether or not the wire R and the ingot I are in contact with each other or connected via the processing waste U during the above-described processing control, and a voltage equal to or lower than a predetermined value is measured to cause a short circuit. To do. For example, when the ingot I is subjected to electric discharge machining by the wire R, as shown in the enlarged view of FIG. 2A, the interval between the ingot I and the wire R (discharge gap G) in the machining groove D of the ingot I. Is present. On the other hand, when the ingot I and the wire R are short-circuited, the gap between the ingot I and the wire R (discharge gap G) is zero in the machining groove D of the ingot I as shown in the enlarged view of FIG. Or the wire R and the ingot I are connected via the processing waste U.

When the ingot I and the wire R is short-circuited, as shown in FIG. 3, short circuit the measurement voltage V _m at time t1 generated, it becomes less than the threshold Th voltage. In FIG. 3, the vertical axis indicates voltage, the horizontal axis indicates time, and a reference for determining whether or not the threshold Th is a short circuit. For example, the machining voltage to be applied is 200V, the threshold Th is 120V, and a short circuit occurs at time t1.

Prior to time t1 when the short circuit occurs, the measured voltage _{V m} is made to a voltage higher than the threshold value Th (120V). The short-circuit time t1 after that occurred, the measured voltage _{V m} is adapted to a voltage lower than the threshold value Th (120V). Discriminating means 812, a result of comparing the measured voltage V _m and the threshold value Th, if the measured voltage V _m is less than the threshold Th, and determine the wire R and the ingot I and is shorted proceeds to step ST4. Moreover, determination unit 812, when the measured voltage V _m is equal to or greater than a threshold Th, the normal discharge machining a wire R and regular intervals and the ingot I is not short-circuited (discharge gap G) is carried out It is determined that the electric discharge machining is performed and the process returns to step ST1 to continue the electric discharge machining.

  In step ST4, the control means 81 performs the separation control when it is determined that the short circuit state has occurred during the machining control (step ST3 determines YES). In the separation control, the wire R is separated from the ingot I to prevent the wire R from being broken by heat generated by a short circuit (separation step). For example, the distance adjusting unit 813 temporarily stops the movement of the ingot I in the machining feed direction with respect to the driving unit 44, and further moves the ingot I slightly in the direction opposite to the machining feed direction to stop the ingot I. Is separated from the wire R. Next, the process proceeds to step ST5.

  In step ST5, the control means 81 performs test control. After performing the separation control, the control means 81 applies a test voltage lower than the machining voltage and determines whether or not the short circuit state has been eliminated (test step). For example, the voltage adjustment unit 811 gradually adjusts the test voltage from a low voltage to a predetermined voltage. The voltage adjusting unit 811 applies a higher voltage when a voltage equal to or higher than a threshold set corresponding to the applied voltage is measured. For example, the voltage adjusting unit 811 first applies a test voltage of 100V, then applies a test voltage of 150V, and finally applies a test voltage of 170V.

For each test voltage, threshold values Th _t 1 to Th _t 3 for determining whether or not the ingot I and the wire R are short-circuited are set. For example, a 60V threshold Th _t 1 is set for the 100V test voltage, a 100V threshold Th _t 2 is set for the 150V test voltage, and a 120V threshold Th _t 3 is set for the 170V test voltage. Yes.

When the test voltage of 100 V is first applied, the determination unit 812 compares the measured voltage V _t 1 shown in FIG. 4 with the threshold Th _t 1 (60 V), and the measured voltage V _t 1 is _{equal to} or higher than the threshold Th _t 1. In this case, it is determined that the ingot I and the wire R are not short-circuited, and information indicating that they are not short-circuited is output to the voltage adjusting unit 811. The voltage adjusting means 811 then applies a test voltage of 150V. The determination unit 812 compares the measured voltage V _t 2 with the threshold Th _t 2 (100 V), and determines that the ingot I and the wire R are not short-circuited when the measured voltage V _t 2 is greater than or _equal to the threshold Th _t 2. Then, information indicating that no short circuit has occurred is output to the voltage adjusting means 811. The voltage adjusting unit 811 finally applies a test voltage of 170V. The determining unit 812 compares the measured voltage V _t 3 with the threshold Th _t 3 (120 V), and determines that the ingot I and the wire R are not short-circuited when the measured voltage V _t 3 is _{equal to} or higher than the threshold Th _t 3. To end the test control. Moreover, determination unit 812, one of the measurement voltage _V t 1 to V _t 3 is, if less than the corresponding threshold value _{Th t 1~Th} t 3, to determine and the ingot I and the wire R is short-circuited End test control. Next, the process proceeds to step ST6.

  In step ST6, when a predetermined test voltage is applied in the test control, the control unit 81 determines that the short-circuit state has been resolved if the measured voltage is equal to or greater than the corresponding threshold value, and returns to step ST1 to control the machining. Control to resume. Moreover, when the measured voltage is less than a corresponding threshold value, it transfers to step ST7.

  In step ST7, the control means 81 counts up the counter. For example, the controller 81 initializes the count value “n” of the counter by setting it to zero at the time of electric discharge machining (n = 0). The control means 81 adds 1 to the count value “n” of the counter when the short circuit is not resolved in step ST6 (n = n + 1). Next, the process proceeds to step ST8.

  In step ST8, the control means 81 determines whether or not the count value “n” of the counter exceeds the reference value. The reference value determines the number of times that the separation control and the test control are performed again. In this example, the reference value is set to “3” and the number of times that the separation control and the test control are performed again is set to three. doing. If the count value “n” is equal to or less than the reference value “3”, the process proceeds to step ST4 to perform separation control, and the process proceeds to step ST5 to perform test control again. If the count value “n” is larger than the reference value “3”, the separation control and the test control are ended. In this way, the number of times that the separation control and the test control are performed again is limited.

  In addition, in step ST6, ST8, when trying to cancel the short circuit again without canceling the short circuit, even if it shifts to step ST5 and performs the test control again without shifting to step ST4 for performing the separation control. Good. For example, when the machining waste U is short-circuited, the machining waste U may be naturally removed and the short circuit may be resolved, so even if it is determined that the short circuit has occurred after the separation control, the shift to the separation control is not immediately performed. It is effective to perform the test control again. In this case, since the short circuit is eliminated without performing the separation control, the process of separating the ingot I from the wire R becomes unnecessary, and the processing time can be shortened. If the short circuit is not resolved even after performing the test control again, the process proceeds to step ST4 and the separation control is performed.

  If the cause of the short circuit is that the discharge gap G becomes zero or if the machining waste U is not removed naturally, the short circuit is not resolved even if the test control is performed again without performing the separation control. Processing time can be shortened by performing separation control immediately without performing test control.

  As described above, according to the control method of the multi-wire electric discharge machining apparatus 1 according to the first embodiment, when it is determined that the wire R and the ingot I are short-circuited, the wire R and the ingot I are separated and then machined. By applying a test voltage lower than the voltage at the time, even if the wire R and the ingot I are in contact with each other, it is possible to prevent discharge from being concentrated at a high voltage and to prevent the wire R from being disconnected. . Further, it is possible to protect the wire R that is easily damaged due to contact and breaks. If the wire R is disconnected due to a short circuit, it is necessary to remove the disconnected wire R from the guide rollers 21 to 24 and the like, and to set the wire R by paying out from the pay-out bobbin 20. Work does not occur.

  In addition, since a plurality of test voltages are prepared and the test voltage is gradually adjusted from a low voltage to a predetermined voltage, it is possible to accurately determine whether the short circuit has been eliminated, as compared with the case where one test voltage is used. The damage given can be suppressed. That is, even if the wire R and the ingot I are short-circuited in the test control, the short-circuit can be found at the lowest test voltage (100 V), and thus damage to the wire R can be suppressed. .

[Embodiment 2]
Next, a control example of the frequency of the test voltage according to the second embodiment will be described based on FIG. FIG. 6 is a diagram illustrating a control example of the frequency of the test voltage according to the second embodiment. The pulse adjusting means 810 makes the frequency of the test voltage applied by the test control higher than the frequency of the test voltage applied by the machining control. For example, in the test control, the pulse adjustment unit 810 makes the number of clocks for turning on / off the switching elements of the switching circuit higher than the number of clocks shown in FIG. Thereby, the pulse interval of the measured voltage _{V t 1'~ V} t 3 'shown in FIG. 6 is shorter than the pulse interval of the measured voltage _{V t 1~ V} t 3 shown in FIG.

  As described above, according to the method for controlling the frequency of the test voltage according to the second embodiment, the number of pulses that can be measured in a predetermined time in the test control is larger than that in the machining control. As described above, by performing the test control at a higher frequency than at the time of processing, the test control can be completed in a short time, and the processing time can be prevented from being unnecessarily extended.

  In addition, although the ingot I is disposed above the wire R of the cutting wire portion 30 and the ingot I is moved from above to below, it is not limited to such a configuration. For example, the ingot I may be disposed below the wire R of the cutting wire portion 30, and the ingot I may be moved upward from below the wire R to perform electric discharge machining.

  Further, it is not always necessary to use a plurality of voltages as the test voltage. One test voltage lower than the machining voltage may be used.

DESCRIPTION OF SYMBOLS 1 Multi-wire electric discharge machine 20 Feeding bobbin 21-24 Guide roller 30 Cutting wire part 40 Ingot installation means 41 Base part 42 Attachment part 44 Driving means 70 Processing tank 71 籠 80 High-frequency pulse power supply unit 82 Electrode F Processing liquid I Ingot R wire G discharge gap D kerf _{V m, V} t _1~V t 3 measured voltage _{Th, Th t 1~Th} t 3 threshold

Claims (2)

A wire wound around a plurality of guide rollers adjacent to each other at an interval in the axial direction and a base portion that fixes the wire and the ingot so that the ingot is cut into the wires arranged in parallel with each other. Driving means for automatically processing and feeding, and a high-frequency pulse power supply unit that supplies high-frequency pulse power to the wire and the ingot fixed to the base part,
The high-frequency pulse power supply unit includes a pulse adjusting unit that adjusts a pulse power to be applied to a desired frequency, a voltage adjusting unit that adjusts a voltage of the pulse power to be applied, and a voltage of the pulse power that has flowed through the wire and the ingot. A multi-wire comprising: a discriminating means for measuring the gap between the ingot and the wire based on the voltage; and a distance adjusting means for adjusting the gap between the ingot and the wire based on the discriminated gap A method for controlling an electric discharge machine,
A machining step of machining and feeding the wire and the ingot while applying a predetermined machining voltage, and electric discharge machining;
When it is determined that the wire and the ingot are in contact with each other or are in contact with each other during the processing step, and a voltage of a predetermined voltage or less is measured and a short-circuit state is detected, the wire is separated from the ingot to generate heat due to the short-circuit. A spacing step to prevent the wire from breaking;
A test step of applying a test voltage lower than the machining voltage and determining whether or not the short-circuit state has been eliminated after performing the separation step;
When the predetermined test voltage is applied in the test step and the measured voltage is equal to or greater than the threshold value, it is determined that the short-circuit state has been resolved, and the processing step is performed again. The measured voltage is less than the threshold value. In this case, the test step is performed again or the separation step is performed again .
A method of controlling a multi-wire electric discharge machining apparatus, wherein the frequency of the test voltage applied in the test step is higher than that of the machining step, and the number of pulses that can be measured in a predetermined time is larger than that of the machining step . The test voltage is adjusted to be gradually higher from a low voltage to a predetermined voltage, and when a voltage equal to or higher than a threshold value set corresponding to the applied voltage is measured, a higher voltage is applied. Item 8. A control method for a multi-wire electric discharge machining apparatus according to Item 1 .

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