Wire electrical discharge machining device, wire electrical discharge machining method, and wafer manufacturing method

Abstract

This wire electrical discharge machining device comprises: a wire electrode that cuts out a plurality of plate-like members by electrical discharge machining from a workpiece (W) immersed in a machining liquid (23); a swing stage (20) that moves the workpiece back and forth in a wire traveling direction that is the direction for feeding and winding the wire electrode; an inter-electrode monitoring unit that determines a discharge state between electrodes of the workpiece and the wire electrode on the basis of the pulse current value of a current applied between the electrodes; and a control unit (300) that controls the back and forth movement of the workpiece on the basis of a result of the determination by the inter-electrode monitoring unit, wherein the control unit controls the swing stage, thereby controlling the position of the workpiece in the wire traveling direction with respect to the position of the deflection shape in a primary vibration mode of the wire electrode stretched between parallel wire guide rollers (51a, 51b).

Description

Wire electric discharge machining apparatus, wire electric discharge machining method, and wafer manufacturing method

[0001] The present disclosure relates to a wire electric discharge machining apparatus, a wire electric discharge machining method, and a wafer manufacturing method that simultaneously cut out multiple wafers from a workpiece using a wire electrode.

[0002] Multi-wire electric discharge machining devices generate electric discharges between multiple wire electrodes and the workpiece, and simultaneously cut multiple plate-shaped members (wafers) from the workpiece. Multi-wire electric discharge machining devices are used, for example, in the semiconductor manufacturing process, for slicing multiple wafers from an ingot of semiconductor material.

[0003] If the shape accuracy (flatness) of the sliced ​​wafer is poor, the burden of shape correction processing in the grinding process after slicing increases. For this reason, it is desirable to cut out wafers with a uniform thickness in multi-wire EDM.

[0004] The electric discharge machining device described in Patent Document 1 includes a tool electrode unit having a thin plate electrode, a tensioning mechanism that applies tension to the thin plate electrode, and a drive mechanism that moves the thin plate electrode and the workpiece relative to each other, and cuts out a wafer using the tensioned thin plate electrode.

[0005] International Publication No. 2014 / 084277

[0006] However, in the technology of Patent Document 1, the thin plate electrode is worn away by the electrical discharge machining, so the width of the portion of the thin plate electrode used in the electrical discharge machining is locally reduced, making it difficult to continue applying the tension to the thin plate electrode at the start of machining. As a result, the tension acting within the surface of the thin plate electrode gradually becomes uneven, causing the problem of uneven wafer thickness as machining progresses.

[0007] The present disclosure has been made in view of the above, and has an object to provide a wire electric discharge machining apparatus that can cut out wafers with a uniform thickness even as machining progresses.

[0008] To solve the above-mentioned problems and achieve the object, the presently disclosed wire electric discharge machining apparatus includes a wire electrode that uses electric discharge machining to cut out multiple plate-shaped members from a workpiece immersed in a machining fluid, and a swing stage that moves the workpiece back and forth in the wire travel direction, which is the direction in which the wire electrode is paid out and wound up. The presently disclosed wire electric discharge machining apparatus also includes a gap monitor that determines the state of discharge between the workpiece and the wire electrode based on the value of a pulse current applied to the gap between the workpiece and the wire electrode, and a control unit that controls the reciprocating movement of the workpiece based on the determination result by the gap monitor. The control unit controls the swing stage to control the position of the workpiece in the wire travel direction relative to the position of the deflection shape of the wire electrode in a primary vibration mode, which is stretched between guide rollers.

[0009] The wire electric discharge machining apparatus according to the present disclosure has the effect of being able to cut out wafers with a uniform thickness even as machining progresses.

[0010] FIG. 1 is a diagram showing a configuration example of a wire electric discharge machining apparatus according to a first embodiment; FIG. 2 is a diagram showing a configuration example of a thin plate machining unit and a variable nozzle provided in the wire electric discharge machining apparatus according to the first embodiment; FIG. 3 is a diagram showing components of the thin plate machining unit provided in the wire electric discharge machining apparatus according to the first embodiment; FIG. 4 is a diagram showing a configuration example of a cutting wire unit provided in the wire electric discharge machining apparatus according to the first embodiment; FIG. 5 is a diagram for explaining the machining direction of machining performed by the wire electric discharge machining apparatus according to the first embodiment; FIG. 6 is a diagram for explaining the shape of the variable nozzle when the wire electric discharge machining apparatus according to the first embodiment swings the swing stage;

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A wire electric discharge machining apparatus, a wire electric discharge machining method, and a wafer manufacturing method according to embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0012] First embodiment Fig. 1 is a diagram showing a configuration example of a wire electric discharge machining apparatus according to a first embodiment. Fig. 2 is a schematic diagram showing a configuration example of a thin plate machining unit and a variable nozzle provided in the wire electric discharge machining apparatus according to the first embodiment. Fig. 3 is a schematic diagram showing components of the thin plate machining unit provided in the wire electric discharge machining apparatus according to the first embodiment. Fig. 4 is a schematic diagram showing a configuration example of a cutting wire unit provided in the wire electric discharge machining apparatus according to the first embodiment.

[0013] The wire electric discharge machining apparatus 1000 is a multi-wire electric discharge machining apparatus that performs electric discharge cutting using the cutting wire portion 1b of the wire electrode 1. Hereinafter, the electric discharge cutting performed by the wire electric discharge machining apparatus 1000 may be referred to as electric discharge machining or machining.

[0014] As shown in Fig. 1, the wire electric discharge machining apparatus 1000 includes a thin plate machining unit 70. A workpiece W is disposed in the thin plate machining unit 70, and the workpiece W is machined by the cutting wire 1b within the thin plate machining unit 70. Fig. 2 shows the configuration of components disposed between the power supply unit 6a and the power supply unit 6b in the wire electric discharge machining apparatus 1000 shown in Fig. 1.

[0015] Figure 3 shows a schematic diagram of the shapes of the components of the thin plate machining unit 70 provided in the wire electric discharge machining apparatus 1000, and some parts differ in shape, size, etc. from the components shown in Figure 2 etc. In the wire electric discharge machining apparatus 1000, the thin plate machining unit 70 is formed by assembling the components shown in Figure 3. As shown in Figure 4, in the cutting wire portion 1b, a plurality of wire electrodes 1 are arranged in parallel and spaced apart from each other at positions facing the workpiece W.

[0016] 1 to 4 show the x-axis, y-axis, and z-axis of a three-axis Cartesian coordinate system. The y-axis direction corresponds to the traveling direction of the wire electrode 1 on the workpiece W, i.e., the traveling direction of the wire electrode 1 relative to the workpiece W placed in the wire electric discharge machining apparatus 1000. In this way, in the wire electric discharge machining apparatus 1000, the wire electrode 1 of the cutting wire portion 1b extends in the y-axis direction.

[0017] The z-axis direction corresponds to the height direction of the wire electric discharge machining apparatus 1000. The height direction of the wire electric discharge machining apparatus 1000 is the up-down direction, i.e., the vertical direction. The direction in which the cutting wire 1b is moved relative to the workpiece W is the z-axis direction.

[0018] The x-axis direction corresponds to the direction in which the wire electrodes 1 are arranged side by side on the workpiece W, i.e., the direction in which the wire electrodes 1 are arranged side by side with respect to the workpiece W placed in the wire electric discharge machining apparatus 1000. The x-axis direction is a direction parallel to the longitudinal direction of the workpiece W placed in the wire electric discharge machining apparatus 1000. In this way, the workpiece W having an axis parallel to the x-axis direction is placed in the thin plate machining unit 70.

[0019] The x-axis and y-axis are two mutually orthogonal axes in a plane parallel to the top surface of the thin plate processing unit 70, and the z-axis is an axis orthogonal to the x-axis and y-axis. The xy-plane is a plane parallel to the plane on which the wire electrodes 1 of the cutting wire portion 1b are arranged. The xy-plane is a plane parallel to the horizontal plane.

[0020] The wire electric discharge machining apparatus 1000 is used for slicing a plurality of thin plates at once from a workpiece W (e.g., a cylindrical semiconductor ingot), i.e., for electric discharge cutting of a plurality of thin plates at once. Hereinafter, the thin plates may be referred to as wafers. An example of a wafer is a semiconductor wafer. The wire electric discharge machining apparatus 1000 slices semiconductor wafers from the workpiece W, for example, in a semiconductor manufacturing process.

[0021] In the wire electric discharge machining device 1000, thin plates to be machined collectively by electric discharge cutting are machined by electric discharges generated between the cutting wire portion 1b and a plurality of wire electrodes 1 arranged in parallel. For this reason, in the wire electric discharge machining device 1000, the distance between the wire electrodes 1 in the cutting wire portion 1b greatly affects the thickness of the thin plate to be cut out.

[0022] 2, the wire electric discharge machining apparatus 1000 is provided with a pair of wire parallel guide rollers 51a, 51b for preventing the position of the cutting wire 1b from shifting so that the distance between the wire electrodes 1 of the cutting wire 1b does not change from the start to the end of machining. The axial direction of the cylindrical wire parallel guide rollers 51a, 51b is the x-axis direction.

[0023] The wire parallel guide rollers 51a, 51b are provided on both sides of the workpiece W in the y-axis direction so as to sandwich the workpiece W therebetween. The wire parallel guide rollers 51a, 51b are disposed in guide roller holders 55a, 55b outside the thin plate processing unit 70. Details of the wire parallel guide rollers 51a, 51b, the thin plate processing unit 70, and the guide roller holders 55a, 55b will be described later.

[0024] In the wire electric discharge machining apparatus 1000, the wire electrodes 1 wound in parallel constitute the parallel wire portion 1a. Of the parallel wire portion 1a, the portion from above the wire parallel guide roller 51a to above the wire parallel guide roller 51b (the portion between the wire parallel guide rollers 51a and 51b) constitutes the cutting wire portion 1b.

[0025] The wire electric discharge machining device 1000 cuts out thin plates from the workpiece W using the cutting wire 1b by moving the cutting wire 1b relative to the workpiece W. Below, a case will be described in which the wire electric discharge machining device 1000 fixes the position of the cutting wire 1b in the z-axis direction and moves the workpiece W in the z-axis direction to cut out multiple thin plates from the workpiece W. The wire electric discharge machining device 1000 cuts out thin plates by moving the workpiece W in the z-axis direction relative to the cutting wire 1b, so that the front and back surfaces of the thin plates are surfaces parallel to the yz plane.

[0026] The side surfaces of the wire parallel guide rollers 51a, 51b are formed with a plurality of V-shaped wire guide grooves (wire guide grooves 56a, 56b, described later) that define the spacing distance between the wire electrodes 1. The wire electrodes 1, each disposed in a corresponding one of the wire guide grooves 56a, 56b, are stretched between the pair of wire parallel guide rollers 51a, 51b to form the cutting wire portion 1b.

[0027] The wire guide grooves 56a, 56b are formed on the side surfaces of the wire parallel guide rollers 51a, 51b at a distance designed to cut out a thin plate to a desired thickness when it is collectively subjected to electrical discharge cutting. During electrical discharge cutting, the pair of wire parallel guide rollers 51a, 51b restrain the plurality of wire electrodes 1 so that the distance between the plurality of wire electrodes 1 is maintained while allowing the wire electrodes 1 of the cutting wire portion 1b to travel in parallel.

[0028] In electrical discharge cutting using the wire electrical discharge machining device 1000, the nozzles 7A, 7B spray machining fluid 23 such as deionized water toward a machining groove formed in the cutting wire portion 1b in the tensioning direction (y-axis direction) of the wire electrode 1. When the workpiece W is a cylindrical ingot, the flow rate of the machining fluid 23 is adjusted according to the cutting thickness (cutting position).

[0029] However, adjusting the flow rate of the machining fluid 23 can cause vibrations in the wire electrode 1 and fluctuations in the tension of the wire electrode 1. Furthermore, when the discharge energy is increased to speed up the electric discharge machining, the repulsive force caused by the discharge increases. This increase in the repulsive force caused by the discharge can cause vibrations in the wire electrode 1 and fluctuations in the tension of the wire electrode 1.

[0030] The wire electrode 1 is bent by the impact force of the discharge in a direction perpendicular to a surface of the workpiece W that is parallel to the yz plane. The wire electrode 1 cuts out thin plates by drilling a machining groove in the workpiece W, and is therefore sandwiched between the front surface of one thin plate and the back surface of the other thin plate during machining. Therefore, the wire electrode 1 is pushed from the front surface of one thin plate to the back surface of the other thin plate by the impact force of the discharge, and is also pushed from the back surface of the other thin plate to the front surface of the one thin plate. The cutting wire portion 1b is fixed in position in the x-axis direction by the wire parallel guide rollers 51a, 51b, and is pushed between the thin plates by the impact force of the discharge, so it bends significantly near the middle of the wire parallel guide rollers 51a, 51b.

[0031] In the wire electric discharge machining apparatus 1000, the wire electrode 1 stretched between the pair of wire parallel guide rollers 51 a, 51 b vibrates like a chord with the portions of the wire electrode 1 that contact the wire guide grooves 56 a, 56 b as "nodes" due to various disturbances (such as discharge repulsion) during electric discharge cutting. That is, the wire electrode 1 vibrates with the wire parallel guide rollers 51 a, 51 b on both sides as "nodes" and the central portion of the wire electrode 1 stretched between the wire parallel guide rollers 51 a, 51 b on both sides as "antinodes" of the primary vibration. The central portion of the wire electrode 1 is the center of the workpiece W in the y-axis direction. The "antinodes" of the vibration of the wire electrode 1 are the maximum amplitude portions of the primary vibration.

[0032] The wire electric discharge machining device 1000 melts and removes the workpiece W by continuously generating pulsed electric discharges while maintaining a gap of approximately 20 to 50 μm between the wire electrode 1 and the machining surface. The deflection due to the aforementioned disturbances and changes in the behavior of the wire electrode 1 due to vibration also affect the shape of the machined surface. During electric discharge cutting, the machining fluid 23 flows into the machined groove from the inlet and outlet sides of the wire electrode 1 traveling within the machined groove of the workpiece W, collides with each other at the center of the workpiece W, passes through the already machined groove, and escapes to the outside of the workpiece W.

[0033] In this way, in the wire electric discharge machining apparatus 1000, the wire electrode 1 is vibrated by the liquid flow of the machining fluid 23, the repulsive force of the discharge, etc. Furthermore, chips tend to accumulate near the antinodes of the vibration of the wire electrode 1 in the direction perpendicular to the traveling direction of the wire electrode 1 (the in-plane direction of the thin plate), and secondary discharges to the chips cause the amplitude behavior of the wire electrode 1 to increase and the discharge gap to expand.

[0034] In addition, machining fluid 23 is supplied into the gap between the thin plate being formed to improve the discharge of machining chips generated by the discharge and the cooling of the wire electrode 1 heated by the discharge energy. As a result, the wire electrode 1 is subjected to the pressure of the flow of the machining fluid 23 and is shaken by the discharge repulsive force proportional to the discharge energy, and the chordal vibration behavior is transferred to the machined surface of the thin plate. Furthermore, a shape with an even larger amplitude is transferred to the machined surface of the thin plate by secondary discharge to the machining chips inside the machined groove.

[0035] When the workpiece W is, for example, an ingot made of silicon carbide (SiC) crystals or gallium nitride (GaN) crystals, a large-diameter thin plate is often cut from the large-diameter ingot. As the diameter of the cut thin plate increases, the distance between the pair of wire parallel guide rollers 51a, 51b increases, making the wire electrode 1 more likely to bend and increasing the concentration of machining debris in the center of the workpiece W. Therefore, as the diameter of the thin plate increases, a shape with increased amplitude is transferred to the cut surface of the thin plate. As a result, the thickness of the cut thin plate may be thinner in the center and thicker toward the periphery.

[0036] The wire electric discharge machining device 1000 of the first embodiment varies the position of the workpiece W in the y-axis direction relative to the wire electrode 1 extending in the y-axis direction of the cutting wire portion 1b. As a result, both the central portion and the outer periphery of the workpiece W are machined near the "antinodes" of the vibration of the wire electrode 1.

[0037] Semiconductor wafers are processed through many semiconductor manufacturing process steps. If the thickness of a semiconductor wafer is non-uniform across its surface, the processing at each semiconductor manufacturing process step will be non-uniform. For this reason, it is desirable that the thickness of the thin plates cut from an ingot crystal be uniform across its surface. In order to uniformize the thickness of the thin plates across the semiconductor wafer surface, grinding and polishing processes are performed. In this case, if there is a large variation in the thickness of the thin plates processed from the ingot across its surface, the processing load in the grinding and polishing processes until the plate is finished to a specific thickness increases, which becomes a factor that significantly impairs the quality and cost of the thin plates used in semiconductor manufacturing.

[0038] The wire electric discharge machining device 1000 uses a wire electrode 1 to perform multi-wire electric discharge machining, which cuts multiple thin plates, which are plate-shaped members, from a workpiece W at once, thereby making the thickness of the thin plates uniform across the wafer surface, thereby reducing the processing load of grinding and polishing the thin plates.

[0039] 2 shows a cross-sectional view of the thin plate processing portion 70, etc., cut along a plane parallel to the yz plane. Fig. 2 shows the positional relationship between the workpiece W, wire parallel guide rollers 51a and 51b, guide roller holders 55a and 55b, nozzles 7A and 7B, vibration-damping guide rollers 4a and 4b, and electron feed units 6a and 6b.

[0040] The workpiece W is placed in the thin plate machining unit 70, and its bottom is fixed on a workpiece fixing plate 25 by a jig (not shown) for fixing the workpiece W. The workpiece fixing plate 25 is conductive. The wire electric discharge machining apparatus 1000 moves the workpiece W in the z-axis direction by moving the workpiece fixing plate 25 in the positive z direction. As a result, grooves are machined into the workpiece W from above by the cutting wire 1b. FIG. 2 shows a state in which wire electric discharge machining of the cylindrical workpiece W by the cutting wire 1b has progressed to a position approximately halfway from the top of the workpiece W. In other words, FIG. 2 shows a state in which the cutting wire 1b has formed grooves approximately halfway from the top of the workpiece W. The wire electric discharge machining apparatus 1000 cuts out a thin wafer from the workpiece W by further moving the workpiece W in the positive z direction from the state shown in FIG. 2.

[0041] As shown in Fig. 1, the wire electric discharge machining apparatus 1000 includes a machining mechanism unit 100 that performs electric discharge machining on a workpiece W using a wire electrode 1, a power supply unit 200 that supplies power, and a control unit 300 that controls the wire electric discharge machining apparatus 1000. The wire electric discharge machining apparatus 1000 also includes a machining gap monitoring unit 400 that monitors the machining gap, but this is not shown in Fig. 1. The machining gap monitoring unit 400 will be described later.

[0042] Examples of materials for the workpiece W include tungsten, molybdenum, silicon carbide, single crystal silicon, single crystal silicon carbide, gallium nitride, polycrystalline silicon, etc. Silicon carbide is also called silicon carbide.

[0043] The machining mechanism 100 includes a plurality of guide rollers 2 (the reference numeral "2" is not shown in FIG. 1), bobbins 3a, 3b, vibration-damping guide rollers 4a, 4b, nozzles 7A, 7B, bobbin rotation control devices 8a, 8b, traverse control devices 9a, 9b, and a cutting and feeding stage 10. FIG. 1 shows a case where the plurality of guide rollers 2 are guide roller 2a, guide roller 2b, guide roller 2c, and guide roller 2d. The guide rollers 2a to 2d guide the travel of the wire electrode 1. Each of the guide rollers 2a to 2d is installed rotatably around its own rotation axis.

[0044] The guide rollers 2a to 2d are spaced apart from one another and arranged so that their rotation axes are parallel to one another. Because the rotation axes of the guide rollers 2a to 2d are parallel to one another, the machining mechanism 100 can move the wire electrode 1 with high precision. The axial direction of the rotation axis of each of the guide rollers 2a to 2d is parallel to the x-axis.

[0045] A single wire electrode 1 is wound multiple times around the guide rollers 2a to 2d at intervals in the direction of the rotation axis of each of the guide rollers 2a to 2d. These wound wire electrodes 1 form the parallel wire portion 1a. Of the parallel wire portion 1a, the wire portion between the wire parallel guide rollers 51a and 51b forms the cutting wire portion 1b. A portion of the cutting wire portion 1b is positioned opposite the workpiece W. The cutting wire portion 1b is composed of multiple wire electrodes 1 arranged in parallel.

[0046] A plurality of wire guide grooves 2e are formed at equal intervals on the front surfaces of the guide rollers 2a to 2d, and each wire guide groove 2e is formed so as to describe a circle on the side surface of the guide rollers 2a to 2d.

[0047] The wire electrode 1 is wound around the front surfaces of the guide rollers 2a to 2d along the multiple wire guide grooves 2e, and the guide rollers 2a to 2d maintain constant spacing between the wire electrodes 1, i.e., the spacing between the wire electrodes 1 in the parallel wire portion 1a. The number of guide rollers 2 does not necessarily have to be four, and may be three or less, or five or more.

[0048] The bobbins 3a and 3b run the wire electrode 1 by unwinding and winding the wire electrode 1. The bobbin 3a unwinds the wire electrode 1. The bobbin 3b winds the wire electrode 1. The axial direction of the bobbins 3a and 3b is the x-axis direction. The bobbin rotation control device 8a and the traverse control device 9a control the bobbin 3a. The bobbin rotation control device 8b and the traverse control device 9b control the bobbin 3b.

[0049] The bobbin rotation control device 8a controls the rotation of the bobbin 3a and the travel of the wire electrode 1. The bobbin rotation control device 8a controls, for example, the travel direction and travel speed of the wire electrode 1.

[0050] The bobbin rotation control device 8b controls the rotation of the bobbin 3b and the travel of the wire electrode 1. The bobbin rotation control device 8b controls, for example, the travel direction and travel speed of the wire electrode 1.

[0051] The traverse control device 9a controls the position of the bobbin 3a in the x-axis direction to control the payout position of the wire electrode 1. The traverse control device 9b controls the position of the bobbin 3b in the x-axis direction to control the winding position of the wire electrode 1. The position control of the bobbins 3a and 3b by the traverse control devices 9a and 9b is called traverse control. The traverse control allows the bobbins 3a and 3b to run the wire electrode 1 stably and with high precision.

[0052] The wire electrode 1 unwound from the bobbin 3a is wound around the guide roller 2b, the guide roller 2a, the guide roller 2d, and the guide roller 2c in this order, and then continues to be wound around the guide roller 2b again. In this way, the wire electrode 1 makes multiple revolutions between the guide rollers 2a to 2d before being wound onto the bobbin 3b.

[0053] As shown in Fig. 2, the workpiece W is fixedly placed on a workpiece fixing plate 25, which is fixed to the oscillating stage 20 via an insulating portion 26. The oscillating stage 20 is also fixedly placed on the cutting and feed stage 10. In this way, the workpiece fixing plate 25 and the oscillating stage 20 are fixed via the insulating portion 26, so that the workpiece fixing plate 25 is insulated from the oscillating stage 20 and the cutting and feed stage 10. The insulating portion 26 is made of an insulating material such as a resin plate. Examples of the insulating portion 26 include an insulating plate, an insulating sheet, and an insulating coating.

[0054] The insulating portion 26 may be disposed between the workpiece fixing plate 25 and the cutting and feed stage 10. The insulating portion 26 may be disposed, for example, on the stage surface of the oscillating stage 20 with which the workpiece fixing plate 25 comes into contact, or may be disposed at the boundary between the oscillating stage 20 and the cutting and feed stage 10. For example, the insulating portion 26 may be an insulating sheet that is attached to the stage surface of the oscillating stage 20. Furthermore, the workpiece fixing plate 25 and the two drive stages (the oscillating stage 20 and the cutting and feed stage 10) may be electrically insulated from each other by applying an insulating coating treatment such as hard anodizing to the cutting and feed stage 10. The workpiece fixing plate 25, on which the workpiece W is fixed and placed, is disposed between the wire parallel guide roller 51a and the wire parallel guide roller 51b in the y-axis direction.

[0055] The wire parallel guide rollers 51a, 51b are arranged on both sides of the workpiece W in the y-axis direction so as to sandwich the workpiece W therebetween. The wire parallel guide rollers 51a, 51b are also installed between the vibration-damping guide roller 4a and the vibration-damping guide roller 4b in the y-axis direction. The wire parallel guide rollers 51a, 51b limit the movement of the wire electrode 1 in the x-axis direction. Specifically, the wire parallel guide rollers 51a, 51b limit the movement of the cutting wire portion 1b in the x-axis direction.

[0056] Like the guide rollers 2a to 2d, the wire parallel guide rollers 51a, 51b each have a rotation axis and are installed to be rotatable around their respective rotation axes. The wire parallel guide rollers 51a, 51b are spaced apart from each other in the y-axis direction and are arranged so that their rotation axes are parallel to each other. Since the rotation axes of the wire parallel guide rollers 51a, 51b are parallel to each other, the wire electrode 1 can be run with high precision. As described above, the axial direction of the rotation axes of the wire parallel guide rollers 51a, 51b is parallel to the x-axis.

[0057] As described above, the wire parallel guide rollers 51a, 51b have a plurality of wire guide grooves 56a, 56b formed at equal intervals on their side surfaces, which maintain the arrangement spacing of the cutting wires 1b with high precision. The wire parallel guide rollers 51a, 51b run the wire electrodes 1 along the plurality of wire guide grooves 56a, 56b, thereby maintaining constant spacing between the wire electrodes 1, i.e., the spacing between the wire electrodes 1 of the cutting wires 1b. By arranging the cutting wires 1b parallel to one another and at equal intervals, the wire electric discharge machining device 1000 can equalize the thicknesses of the plurality of thin plates cut out from the workpiece W and make the cross sections of the plurality of thin plates nearly parallel.

[0058] In this way, the wire parallel guide rollers 51 a, 51 b guide the running of the wire electrode 1 (cutting wire portion 1 b), which is wound multiple times at equal intervals in the axial direction of the rotation shaft of each of the guide rollers 2 a to 2 d and runs spaced apart from each other, thereby suppressing vibration of the cutting wire portion 1 b in the cutting thickness direction of the workpiece W.

[0059] 2, the wire parallel guide rollers 51a and 51b are supported by a pair of guide roller holders 55a and 55b. The pair of guide roller holders 55a and 55b are provided with bearings (not shown) that support the wire parallel guide rollers 51a and 51b so that the wire parallel guide rollers 51a and 51b can rotate around their respective rotation axes.

[0060] The pair of guide roller holders 55a, 55b are arranged on both sides of the workpiece W in the y-axis direction so as to sandwich the workpiece W. The pair of guide roller holders 55a, 55b are fixed to both sides of the workpiece W so that the rotation axes of the wire parallel guide rollers 51a, 51b are arranged parallel to the x-axis direction.

[0061] The guide roller holder 55a supports the rotation shaft of the wire parallel guide roller 51a with the upper end portion of the wire parallel guide roller 51a protruding upward from the upper surface of the guide roller holder 55a, thereby supporting the wire parallel guide roller 51a.

[0062] Similarly, the guide roller holder 55b supports the rotation shaft of the wire parallel guide roller 51b with the upper end portion of the wire parallel guide roller 51b protruding upward from the upper surface of the guide roller holder 55b, thereby supporting the wire parallel guide roller 51b.

[0063] The vibration-damping guide roller 4a is disposed between the wire parallel guide roller 51a and the electron supply unit 6a in the y-axis direction. The vibration-damping guide roller 4b is disposed between the wire parallel guide roller 51b and the electron supply unit 6b in the y-axis direction. The vibration-damping guide rollers 4a and 4b have rotation axes that extend in the x-axis direction. The vibration-damping guide rollers 4a and 4b limit the movement of the wire electrode 1 in the z-axis direction.

[0064] Nozzle 7A is disposed between vibration-damping guide roller 4a and workpiece W in the y-axis direction. Nozzle 7A has a nozzle body 7a and a variable nozzle 21a. Nozzle 7B is disposed between vibration-damping guide roller 4b and workpiece W in the y-axis direction. Nozzle 7B has a nozzle body 7b and a variable nozzle 21b.

[0065] The nozzle body 7a is disposed above the cutting wire portion 1b with the cutting wire portion 1b sandwiched between the nozzle body 7a and the wire parallel guide roller 51a and spaced apart from the cutting wire portion 1b in the z-axis direction.

[0066] Similarly, the nozzle body 7b is positioned above the cutting wire portion 1b, with the cutting wire portion 1b sandwiched between the nozzle body 7b and the wire parallel guide roller 51b and spaced apart from the cutting wire portion 1b in the z-axis direction.

[0067] The nozzles 7A and 7B are filled with machining fluid 23 supplied from a machining fluid supply pipe 62. The variable nozzles 21a and 21b have machining fluid ejection holes 7c that eject the machining fluid 23 filled therein toward the workpiece W in the thin plate machining section 70. The cutting wire 1b is passed through the machining fluid ejection holes 7c of the variable nozzles 21a and 21b. Details of the variable nozzles 21a and 21b will be described later.

[0068] The machining fluid 23 is stored in a machining fluid tank (not shown), pumped up by a machining fluid supply pump (not shown), and sent to the nozzles 7A and 7B along the piping. The machining fluid 23 is stored in the thin plate machining unit 70, and electric discharge machining is performed with the workpiece W immersed in the machining fluid 23. Note that the thin plate machining unit 70, to which the workpiece W is fixed, may be placed inside a machining tank that stores the machining fluid 23, so that electric discharge machining is performed with the workpiece W immersed in the machining fluid 23.

[0069] In the wire electric discharge machining apparatus 1000, the wire parallel guide rollers 51a, 51b restrict the movement of the wire electrode 1 in the x-axis direction, and further, the vibration-damping guide rollers 4a, 4b restrict the movement of the wire electrode 1 in the z-axis direction, thereby suppressing vibration of the wire electrode 1 in the cutting wire portion 1b. Note that in the wire electric discharge machining apparatus 1000, the vibration-damping guide rollers 4a and 4b can be omitted.

[0070] The cutting feed stage 10 changes the relative position between the workpiece W and the cutting wire 1b. Specifically, the cutting feed stage 10 changes the relative position in the processing direction (z-axis direction) between the cutting wire 1b and the workpiece fixing plate 25, to which the workpiece W is fixed and which is fixedly placed on the swing stage 20. As described above, in the first embodiment, the position of the cutting wire 1b in the z-axis direction is fixed, and the swing stage 20, the cutting feed stage 10, and the workpiece fixing plate 25 are movable in the z-axis direction.

[0071] The cutting feed stage 10 moves the workpiece W in the vertical direction (z-axis direction). The wire electric discharge machining device 1000 moves the workpiece W relatively closer to or farther away from the cutting wire portion 1b by moving the cutting feed stage 10 in the vertical direction. The cutting feed stage 10 moves the workpiece W upward during electric discharge machining, and moves it downward when a short circuit occurs. As a result, a machining groove is formed in the workpiece W along the cutting wire portion 1b, and the workpiece W is cut. The cutting feed stage 10 may be movable in the x-axis direction and the y-axis direction.

[0072] The oscillating stage 20 changes the relative position of the workpiece W and the deflected shape (maximum amplitude portion) of the wire electrode 1 stretched between the wire parallel guide rollers 51 a, 51 b. That is, the oscillating stage 20 changes the relative position in the wire running direction (y-axis direction) between the workpiece fixing plate 25 to which the workpiece W is fixed and the cutting wire 1 b. In the first embodiment, the stretched position of the cutting wire 1 b in the y-axis direction is fixed, and the oscillating stage 20 is movable in the y-axis direction.

[0073] The oscillating stage 20 moves the thin plate processing unit 70 in the left-right direction (direction parallel to the y-axis direction), thereby moving the workpiece W in the thin plate processing unit 70 toward the wire parallel guide rollers 51 a, 51 b. In the first embodiment, the movement (reciprocating movement) of the oscillating stage 20 in the direction parallel to the y-axis direction is referred to as oscillating.

[0074] The wire electric discharge machining device 1000 moves the oscillating stage 20 left and right to move the center position of the workpiece W in the y-axis direction relatively closer to or farther away from the maximum amplitude part of the cutting wire part 1b, thereby concentrating electric discharge machining on the thick parts of the workpiece W to flatten them.

[0075] During electrical discharge machining of the workpiece W, a machined groove is formed in the workpiece W along the deflected shape of the cutting wire portion 1b. In this case, in the first embodiment, the oscillating stage 20 changes the relative position between the maximum amplitude portion of the wire electrode 1 and the workpiece W, so that the thin plate cut out from the workpiece W is flat. The oscillating stage 20 may be movable in the x-axis direction and the z-axis direction.

[0076] The machining mechanism 100 may also include components such as a guide pulley for suppressing vibration of the wire electrode 1, a load cell for measuring the tension of the wire electrode 1, and a dancer roller for controlling the tension of the wire electrode 1. In the machining mechanism 100, for example, the dancer roller may control the tension of the wire electrode 1 by changing the payout speed and take-up speed of the wire electrode 1.

[0077] The power supply unit 200 includes a machining power supply 5 and power supply units 6a and 6b. The machining power supply 5 is connected to the power supply units 6a and 6b. The machining power supply 5 supplies power to the wire electrode 1 via the power supply units 6a and 6b connected to the wire electrode 1. The machining power supply 5 also supplies power to the workpiece W via a liquid rectifying plate (workpiece jig) 71a included in the thin plate processing unit 70. Details of the liquid rectifying plate 71a will be described later.

[0078] The thin plate processing unit 70 is disposed between the vibration-damping guide roller 4a and the vibration-damping guide roller 4b, and between the variable nozzle 21a of the nozzle 7A and the variable nozzle 21b of the nozzle 7B. The thin plate processing unit 70 includes a pair of liquid rectifying plates 71a and 71b (the reference numeral "71" is not shown in FIGS. 1 to 3), a workpiece holder 72, liquid escape prevention plates 22a and 22b, and a workpiece fixing plate 25.

[0079] As shown in Figure 3, the liquid straightening plates 71a, 71b and the liquid leakage prevention plates 22a, 22b correspond to the side surfaces of the thin plate processing section 70, the workpiece holding section 72 corresponds to the upper surface of the thin plate processing section 70, and the workpiece fixing plate 25 corresponds to the lower surface of the thin plate processing section 70.

[0080] The liquid rectifying plates 71a, 71b are fixed to the side surfaces of the workpiece fixing plate 25. The liquid rectifying plates 71a, 71b are electrically conductive, are arranged parallel to the traveling direction of the cutting wire 1b, and rectify the flow of the machining liquid 23. The liquid leakage prevention plates 22a, 22b, the nozzles 7A, 7B, and the wire parallel guide rollers 51a, 51b may be either electrically conductive or insulating.

[0081] The front and back surfaces of the liquid rectifying plates 71a, 71b extend in a direction perpendicular to the upper surface of the workpiece fixing plate 25 and the back surfaces of the liquid leakage prevention plates 22a, 22b. The liquid rectifying plates 71a, 71b are arranged in positions that sandwich the workpiece W in the x-axis direction. In other words, the liquid rectifying plates 71a, 71b are arranged in positions that face each other with the workpiece W sandwiched between them in the x-axis direction. The liquid rectifying plates 71a, 71b are arranged between the liquid leakage prevention plates 22a, 22b in the y-axis direction. The liquid rectifying plates 71a and 71b have a plate shape (a rectangular parallelepiped shape) and are arranged so that their opposing surfaces (surfaces parallel to the yz plane) are parallel to each other.

[0082] The workpiece W is sandwiched between the back surfaces of the liquid rectifying plates 71a and 71b and fixed to the liquid rectifying plates 71a and 71B. That is, one end surface (top surface) of the columnar workpiece W contacts the back surface of the liquid rectifying plate 71a, and the other end surface (bottom surface) contacts the back surface of the liquid rectifying plate 71b. The top and bottom surfaces of the columnar workpiece W are parallel to the yz plane, and are sandwiched between the back surfaces of the liquid rectifying plates 71a and 71b, which are also parallel to the yz plane. The back surfaces of the liquid rectifying plates 71a and 71b are the inner surfaces (inner wall surfaces) of the thin plate processing section 70.

[0083] The liquid rectifying plate 71a is one of the pair of liquid rectifying plates 71, and is connected to the machining power source 5. As a result, power is supplied from the electric discharge machining power source to the workpiece W from the liquid rectifying plate 71a, which is in contact with the end face of the workpiece W.

[0084] The liquid rectifying plate 71b is the other of the pair of liquid rectifying plates 71, and is arranged parallel to the liquid rectifying plate 71a with the workpiece W fixed to the liquid rectifying plate 71a sandwiched between the liquid rectifying plate 71b and the liquid rectifying plate 71a. The liquid rectifying plate 71b is in close contact with the workpiece W and, together with the liquid rectifying plate 71a, forms a flow path that guides the machining liquid 23 supplied from the nozzles 7A and 7B to the workpiece W. The liquid rectifying plates 71a and 71b move in the y-axis and z-axis directions while maintaining the distance between them in the x-axis direction, without changing their positions in the x-axis direction.

[0085] The front and back surfaces of the liquid leakage prevention plates 22a, 22b extend in a direction perpendicular to the wire traveling direction. The liquid leakage prevention plates 22a, 22b are arranged in positions sandwiching the workpiece W in the y-axis direction. That is, the liquid leakage prevention plates 22a, 22b are arranged in positions facing each other in the y-axis direction with the workpiece W sandwiched between them. The liquid leakage prevention plates 22a and 22b have a plate shape (a rectangular parallelepiped shape) and are arranged so that their opposing surfaces (surfaces parallel to the xz plane) are parallel to each other. The liquid leakage prevention plates 22a, 22b are a pair of first plate-like members, and the liquid straightening plates 71a, 71b are a pair of second plate-like members.

[0086] The workpiece W is sandwiched between the back surfaces of the liquid leakage prevention plates 22 a and 22 b. The back surfaces of the liquid leakage prevention plates 22 a and 22 b are the inner surfaces (inner wall surfaces) of the thin plate processing section 70.

[0087] The liquid leakage prevention plates 22a and 22b move in the y-axis direction while maintaining the distance between them in the y-axis direction, without changing their positions in the x-axis direction and the z-axis direction. When the liquid leakage prevention plate 22a approaches the wire parallel guide roller 51a, the liquid leakage prevention plate 22b moves away from the wire parallel guide roller 51b. When the liquid leakage prevention plate 22b approaches the wire parallel guide roller 51b, the liquid leakage prevention plate 22a moves away from the wire parallel guide roller 51a.

[0088] The midpoint in the y-axis direction between the liquid leakage prevention plates 22a and 22b is the position of the central axis of the workpiece W. When the position of the central axis of the workpiece W is midpoint between the wire parallel guide rollers 51a and 51b, the position of the central axis of the workpiece W in the y-axis direction and the position of the "antinode" of the vibration of the wire electrode 1 overlap.

[0089] When the liquid leakage prevention plate 22a approaches the wire parallel guide roller 51a, the central axis of the workpiece W approaches the wire parallel guide roller 51a and moves away from the anti-node of the vibration of the wire electrode 1. When the liquid leakage prevention plate 22b approaches the wire parallel guide roller 51b, the central axis of the workpiece W approaches the wire parallel guide roller 51b and moves away from the anti-node of the vibration of the wire electrode 1.

[0090] Nozzles 7A and 7B each include variable nozzles 21a and 21b, which are made up of a combination of multiple tubular (e.g., cylindrical, rectangular, etc.) nozzle units of different sizes. The nozzle units of variable nozzle 21a have different diameters but the same axial direction. Similarly, the nozzle units of variable nozzle 21b have different diameters but the same axial direction.

[0091] In the variable nozzle 21a, the nozzle units closer to the liquid leakage prevention plate 22a have smaller diameters and are located further inward. Similarly, in the variable nozzle 21b, the nozzle units closer to the liquid leakage prevention plate 22b have smaller diameters and are located further inward.

[0092] The variable nozzles 21 a, 21 b have a variable multi-stage structure in which the lengths of the variable nozzles 21 a, 21 b in the fluid ejection direction (y-axis direction) are extended or retracted by sliding each of these nozzle units along the axial direction. In the first embodiment, the extension and retraction directions of the variable nozzles 21 a, 21 b and the wire running direction are horizontal.

[0093] The nozzle unit of the variable nozzle 21a closest to the wire parallel guide roller 51a is fixed to the guide roller holder 55a and the nozzle body 7a, and the nozzle unit of the variable nozzle 21a closest to the liquid leakage prevention plate 22a is fixed perpendicularly to and in close contact with the front surface of the liquid leakage prevention plate 22a.

[0094] Similarly, the nozzle unit of the variable nozzle 21b closest to the wire parallel guide roller 51b is fixed to the guide roller holder 55b and the nozzle body 7b. Furthermore, the nozzle unit of the variable nozzle 21b closest to the liquid leakage prevention plate 22b is fixed perpendicularly to and in close contact with the front surface of the liquid leakage prevention plate 22b.

[0095] The variable nozzles 21a, 21b are extended by being pushed out in the ejection direction of the machining fluid 23 by a repulsive mechanism such as a spring installed between the nozzle units of each stage, or by the pressure of the flow of the machining fluid 23 ejected from the nozzle bodies 7a, 7b. The repulsive mechanism such as a spring pushes out each nozzle unit in the ejection direction of the machining fluid 23 by using the restoring force of an elastic body such as a spring.

[0096] When the variable nozzle 21a extends, the nozzle unit at the tip end closest to the machining fluid ejection hole 7c presses the front surface of the fluid escape prevention plate 22a, thereby pressing the thin plate processing section 70 toward the wire parallel guide roller 51b.

[0097] Similarly, when the variable nozzle 21b extends, the nozzle unit at the tip end closest to the machining fluid ejection hole 7c presses against the front surface of the fluid escape prevention plate 22b, thereby pushing the thin plate machining section 70 toward the wire parallel guide roller 51a.

[0098] In the wire electric discharge machining apparatus 1000, when the oscillating stage 20 oscillates in the positive y direction, the variable nozzle 21a extends in the positive y direction, and the variable nozzle 21b contracts in the positive y direction.

[0099] Similarly, in the wire electric discharge machining apparatus 1000, when the oscillating stage 20 oscillates in the minus y direction, the variable nozzle 21b extends in the minus y direction, and the variable nozzle 21a contracts in the minus y direction.

[0100] As described above, the wire electric discharge machining apparatus 1000 has a mechanism (pressure generating mechanism) that generates pressure between the variable nozzles 21a, 21b and the liquid leakage prevention plates 22a, 22b during oscillation. This pressure generating mechanism pushes the variable nozzles 21a, 21b in the direction in which the variable nozzles 21a, 21b extend. The wire electric discharge machining apparatus 1000 pushes the variable nozzles 21a, 21b using the pressure generating mechanism, thereby pressing the variable nozzles 21a, 21b against the liquid leakage prevention plates 22a, 22b. As a result, the wire electric discharge machining apparatus 1000 extends while the variable nozzles 21a, 21b are pressed against the liquid leakage prevention plates 22a, 22b.

[0101] Furthermore, variable nozzle 21a contracts in a direction parallel to the y-axis direction as the nozzle unit at the tip closest to machining fluid ejection hole 7c is pressed against the front surface of liquid escape prevention plate 22a. Similarly, variable nozzle 21b contracts in a direction parallel to the y-axis direction as the nozzle unit at the tip closest to machining fluid ejection hole 7c is pressed against the front surface of liquid escape prevention plate 22b. In this way, variable nozzles 21a and 21b contract while being pressed by liquid escape prevention plates 22a and 22b.

[0102] For example, when the oscillating stage 20, which moves parallel to the sliding direction of the nozzle unit, moves toward the wire parallel guide roller 51a, the nozzle unit of the variable nozzle 21a is pushed back toward the wire parallel guide roller 51a, causing the nozzle unit on the liquid leakage prevention plate 22a side to be housed in the nozzle unit on the adjacent wire parallel guide roller 51a side, and the variable nozzle 21a to retract.

[0103] Similarly, when the oscillating stage 20 moves toward the wire parallel guide roller 51b, the nozzle unit of the variable nozzle 21b is pushed back toward the wire parallel guide roller 51b, causing the nozzle unit on the liquid leakage prevention plate 22b side to be housed in the nozzle unit on the adjacent wire parallel guide roller 51b side, and the variable nozzle 21b retracts.

[0104] The variable nozzles 21 a and 21 b extend and contract while being fixed to the liquid leakage prevention plates 22 a and 22 b, the nozzle bodies 7 a and 7 b, and the wire parallel guide rollers 51 a and 51 b. In the variable nozzles 21 a and 21 b, the tip of the nozzle unit that is incorporated innermost among the multiple nozzle units extends and contracts in response to the swinging motion of the swinging stage 20 while being fixed to the liquid leakage prevention plates 22 a and 22 b.

[0105] In this way, during electrical discharge cutting, the tips of the nozzle units incorporated into the innermost portions of the pair of variable nozzles 21a, 21b disposed on both sides of the workpiece W are pressed against the liquid leakage prevention plates 22a, 22b by the extension / retraction mechanism. During electrical discharge cutting, even while the thin plate processing section 70 is repeatedly swinging toward and away from the nozzle bodies 7a, 7b, the variable nozzles 21a, 21b remain fixed to the liquid leakage prevention plates 22a, 22b, and the machining liquid 23 is supplied between the liquid rectifying plates 71a, 71b.

[0106] The variable nozzles 21a, 21b are installed in close contact with the liquid leakage prevention plates 22a, 22b so that the machining liquid ejection holes 7c of the nozzle units arranged innermost in the variable nozzles 21a, 21b and the openings provided in the liquid leakage prevention plates 22a, 22b are coaxial. The liquid leakage prevention plates 22a, 22b on which the variable nozzles 21a, 21b are installed are pressed against the liquid straightening plates 71a, 71b so that there is no gap between them and the side surfaces of the liquid straightening plates 71a, 71b in the y-axis direction.

[0107] During electrical discharge cutting, even when the workpiece W is moved up and down by the cutting feed stage 10, the liquid rectifying plates 71a, 71b slide together with the workpiece fixing plate 25 while remaining in close contact with the rear surfaces of the liquid leakage prevention plates 22a, 22b. As a result, during electrical discharge cutting, the guide roller holder 55a and the nozzle main body 7a are maintained in close contact with the variable nozzle 21a, and the front surface of the liquid leakage prevention plate 22a is maintained in close contact with the variable nozzle 21a. Similarly, during electrical discharge cutting, the guide roller holder 55b and the nozzle main body 7b are maintained in close contact with the variable nozzle 21b, and the front surface of the liquid leakage prevention plate 22b is maintained in close contact with the variable nozzle 21b.

[0108] During electrical discharge cutting, machining fluid 23 is supplied from nozzles 7A, 7B through the openings in fluid escape prevention plates 22a, 22b to the gap between the fluid rectifying plates 71a, 71b toward the workpiece W. This prevents the machining fluid 23 from diffusing in the thickness direction (x-axis direction) of the thin plate while the machining groove is being formed.

[0109] In this way, the pair of liquid rectifying plates 71 a, 71 b, the workpiece holder 72, the workpiece fixing plate 25, and the pair of liquid leakage prevention plates 22 a, 22 b are arranged in close proximity to each other to form a chamber in the thin plate processing section 70. The workpiece W is placed in this chamber, and is subjected to electrical discharge cutting within the chamber.

[0110] Machining fluid 23 supplied from nozzles 7A and 7B is injected into the chamber, and even after the chamber is filled with machining fluid 23, machining fluid 23 is pressurized into the chamber by a machining fluid supply pump or the like. The only outlet for machining fluid 23 filling the chamber is a notch provided in the upper surface of workpiece holder 72. The only flow path for machining fluid 23 to reach this notch is through a machining groove formed in workpiece W. Therefore, machining fluid 23 inside the chamber is at a static pressure, and machining fluid 23 is supplied to the interior of even narrow machining grooves.

[0111] In the wire electric discharge machining device 1000, the machining fluid 23 supplied from the nozzles 7A, 7B is rectified in the machining groove, thereby suppressing the diffusion of the machining fluid 23, reducing the possibility of the thin plate being shaken and cracked by the machining fluid 23 during formation, and the machining fluid 23 is supplied uniformly to multiple machining grooves.

[0112] When the workpiece W is a material for a semiconductor wafer, the workpiece W is often formed into a cylindrical shape in advance so that the thin plate processed by electrical discharge cutting will be a circular thin plate. In this case, too, the workpiece W is fixed and placed on the upper surface of the workpiece fixing plate 25 inside the thin plate processing unit 70 so that the outer peripheral side surface (curved surface) of the cylindrical workpiece W faces the cutting wire portion 1b. The workpiece W is sliced ​​into rings by the cutting wire portion 1b, and thin plates, called wafers, are processed from the workpiece W.

[0113] A specific voltage value is applied to the inter-electrode gap, which is the gap between the cutting wire portion 1b and the workpiece W, and when the inter-electrode distance reaches a specific range of values, an electric discharge occurs between the electrodes, causing the cutting wire portion 1b to heat up and melt the workpiece W, resulting in multiple plate-shaped members being cut out all at once.

[0114] When the machining fluid 23 is supplied to the gap between the workpiece W and the cutting wire 1b during electrical discharge cutting, machining debris generated between the workpiece W and the cutting wire 1b is discharged to the outside of the gap. This machining debris can cause a short circuit between the workpiece W and the cutting wire 1b. The wire electrical discharge machining device 1000 discharges machining debris by supplying the machining fluid 23 to the gap, thereby reducing the frequency of short circuits.

[0115] The workpiece holder 72 collectively secures multiple thin plates in the process of being formed from the upper side of the thin plate processing unit 70. The workpiece holder 72 is not in contact with the workpiece W at the start of processing, but is positioned above the workpiece W. When cutting into the workpiece W progresses to a specific distance in the Z-axis direction, the workpiece holder 72 descends to the top of the workpiece W, contacts the workpiece W, and holds down the multiple thin plates. In this way, the workpiece holder 72 suppresses shaking of the multiple thin plates due to vibrations of the workpiece W generated by the hydraulic pressure of the flow of machining fluid 23 that is applied to the cut surfaces of the multiple thin plates.

[0116] As the machining progresses, the workpiece W, liquid rectifying plates 71a, 71b, workpiece fixing plate 25, and workpiece holder 72 move upward (in the z-axis direction) by the cutting feed stage 10. In this case, since the liquid leakage prevention plates 22a, 22b are fixed in the z-axis direction by the variable nozzles 21a, 21b, the liquid rectifying plates 71a, 71b slide relatively in close contact with the rear surfaces of the liquid leakage prevention plates 22a, 22b.

[0117] The sliding state of the liquid leakage prevention plates 22a, 22b and the liquid rectifying plates 71a, 71b is maintained from before machining begins until machining ends. Therefore, if the length of the liquid leakage prevention plates 22a, 22b in the machining direction (z-axis direction) is shorter than the sliding distance (the movement distance of the workpiece W in the z-axis direction), the area sandwiched between the liquid rectifying plates 71a, 71b will be opened on the liquid leakage prevention plates 22a, 22b during machining, causing the machining liquid 23 to leak. To prevent this condition, the liquid leakage prevention plates 22a, 22b are formed sufficiently longer than the length of the side surfaces of the liquid rectifying plates 71a, 71b in the z-axis direction. Specifically, the length of the liquid leakage prevention plates 22a, 22b in the z-axis direction is at least twice the length of the workpiece W in the machining direction (z-axis direction). In other words, the length of the liquid leakage prevention plates 22a, 22b in the z-axis direction is at least twice the movement distance of the workpiece W.

[0118] Fig. 5 is a diagram for explaining the machining direction of the machining performed by the wire electric discharge machining apparatus according to the first embodiment. Fig. 5 schematically shows a cross-sectional view of the workpiece W cut in the xz plane.

[0119] In the wire electric discharge machining device 1000, the workpiece W is machined by the cutting wire 1b as the thin plate machining unit 70 moves in the plus z direction. The direction of movement of the cutting wire 1b relative to the workpiece W is the machining advance direction (the minus z direction in FIG. 5 ).

[0120] The cutting wire portion 1b has a cylindrical wire electrode 1, and this cylindrical wire electrode 1 is used to machine the workpiece W. Therefore, the cutting wire portion 1b continues to machine the workpiece W while also machining the workpiece W in the thickness direction of the wire electrode 1. The surface of the workpiece W facing the lower half (hemispherical portion) of the wire electrode 1 shown in Figure 5 is the machined surface. In other words, the machined surface of the workpiece W includes the bottom surface SB of the machined groove Gr formed in the workpiece W by the wire electrode 1 and the side surface adjacent to this bottom surface SB.

[0121] The wire electrode 1 is pushed and bent in the opposite direction to the machining surface of the workpiece W by the impact force of the discharge. The direction in which the wire electrode 1 is pushed by the impact force of the discharge is the opposite direction to the machining surface of the workpiece W (opposite to the machining progress direction). In other words, the wire electrode 1 is pushed and bent in the opposite direction to the machining progress direction by the impact force of the discharge. The impact force of the discharge that pushes the wire electrode 1 in the opposite direction to the machining progress direction is the discharge repulsion force.

[0122] Of the deflections of the wire electrode 1, the deflection in the x-axis direction has a significant effect on the shape of the machined groove Gr in the workpiece W. In the first embodiment, the wire electric discharge machining device 1000 reciprocates the workpiece W in the y-axis direction, thereby performing machining at the locations of the wire electrode 1 where the deflection is large at various positions in the y-axis direction of the workpiece W.

[0123] Fig. 6 is a diagram illustrating the shape of the variable nozzle when the swing stage of the wire electric discharge machining apparatus according to the first embodiment is swung. Fig. 6 shows a cross-sectional view of the thin plate processing unit 70 and the like cut along a plane parallel to the yz plane. Note that Fig. 6 does not illustrate the liquid rectifying plates 71a and 71b, the workpiece holder 72, and the cutting feed stage 10 of the thin plate processing unit 70.

[0124] 6, the liquid leakage prevention plates 22a and 22b when the oscillating stage 20 is moving in the positive y direction are shown as liquid leakage prevention plates 22A2 and 22B2, and the liquid leakage prevention plates 22a and 22b when the oscillating stage 20 is moving in the negative y direction are shown as liquid leakage prevention plates 22A1 and 22B1.

[0125] For example, when the oscillating stage 20 moves in the negative y direction by the oscillating operation, that is, when the oscillating stage 20 moves toward the wire parallel guide roller 51a, the nozzle unit of the variable nozzle 21a is pushed back toward the wire parallel guide roller 51a, whereby the nozzle unit on the liquid leakage prevention plate 22A1 side is accommodated in the nozzle unit on the adjacent wire parallel guide roller 51a side, and the variable nozzle 21a is retracted.

[0126] For example, consider a case where the nozzle unit of the variable nozzle 21a includes a first nozzle unit fixed to the front surface of the liquid leakage prevention plate 22a, a second nozzle unit connected to the first nozzle unit on the wire parallel guide roller 51a side of the first nozzle unit, and a third nozzle unit connected to the second nozzle unit on the wire parallel guide roller 51a side of the second nozzle unit. In this case, when the oscillation stage 20 moves toward the wire parallel guide roller 51a, the first nozzle unit is pushed back toward the wire parallel guide roller 51a by the liquid leakage prevention plate 22a. The second nozzle unit is also pushed back toward the wire parallel guide roller 51a by the first nozzle unit, and the third nozzle unit is pushed back toward the wire parallel guide roller 51a by the second nozzle unit. As a result, the variable nozzle 21a is retracted toward the wire parallel guide roller 51a while being fixed to the liquid leakage prevention plate 22a.

[0127] Similarly, when the oscillating stage 20 moves in the positive y direction by the oscillating operation, that is, when the oscillating stage 20 moves toward the wire parallel guide roller 51b, the nozzle unit of the variable nozzle 21b is pushed back toward the wire parallel guide roller 51b. As a result, the nozzle unit on the liquid leakage prevention plate 22B2 side is housed in the nozzle unit on the adjacent wire parallel guide roller 51b side, and is retracted toward the wire parallel guide roller 51b.

[0128] 7 is a block diagram showing the configuration of a control unit provided in the wire electric discharge machining apparatus according to embodiment 1. The control unit 300 provided in the wire electric discharge machining apparatus 1000 is connected to the machining gap monitoring unit 400 and the machining power supply 5. The control unit 300 is also connected to the bobbin rotation control units 8a and 8b, the traverse control units 9a and 9b, the cutting feed stage 10, and the swing stage 20.

[0129] The electrode gap monitoring unit 400 determines the discharge state (electric discharge machining status) by monitoring the pulse current applied by the machining power supply 5 to the electrode gap, which is the gap between the cutting wire 1b and the workpiece W. The electrode gap monitoring unit 400 includes a pulse current detection device 41 and a discharge state determination device 42.

[0130] The pulse current detection device 41 detects the pulse current value of the pulse current applied by the machining power supply 5 to the inter-electrode gap, which is the gap between the cutting wire 1b and the workpiece W. The pulse current detection device 41 sends the detected pulse current value to the discharge state determination device 42.

[0131] The discharge state determination device 42 determines the discharge state between the poles based on the pulse current value detected by the pulse current detection device 41. The discharge state determination device 42 determines the discharge state between the poles based on, for example, the magnitude of the pulse current value per unit time.

[0132] The discharge state determination device 42 transmits state monitoring information indicating the determination result of the discharge state as gap state information (machining state information) ps to the control unit 300. The gap state information ps includes the determination result of the discharge state of each wire electrode 1 included in the cutting wire portion 1b. The discharge state is one of an appropriate discharge state (appropriate discharge state), an open state (tending to open), and a short state (tending to short circuit).

[0133] The control unit 300 controls the entire wire electric discharge machining apparatus 1000 based on the machining gap state information ps transmitted from the discharge state determination device 42 of the machining gap monitoring unit 400. The control unit 300 includes a machining control device 31, a discharge waveform control device 32, a cutting stage control device 34, a swing stage control device 33, and a wire travel control device 35.

[0134] The machining control device 31 receives the gap state information ps sent from the discharge state determination device 42. The machining control device 31 controls the discharge waveform control device 32, the cutting stage control device 34, the swing stage control device 33, and the wire travel control device 35 based on the gap state information ps.

[0135] The machining control device 31 generates a discharge waveform command (pulse oscillation command) wc, which is a command for controlling the waveform of the discharge, based on the machining gap state information ps. The machining control device 31 transmits the generated discharge waveform command wc to the discharge waveform control device 32.

[0136] Furthermore, based on the electrode gap state information ps, the machining control device 31 generates a wire electrode travel command rc, which is a command for controlling the travel of the wire electrode 1. The machining control device 31 transmits the generated wire electrode travel command rc to the wire travel control device 35.

[0137] Furthermore, the machining control device 31 generates a cutting stage command scC, which is a command for controlling the relative position in the z-axis direction between the workpiece W and the cutting wire portion 1b, based on the gap state information ps. The machining control device 31 generates a cutting stage command scC, which is a command for controlling the position in the z-axis direction of the cutting feed stage 10, based on, for example, the gap state information ps. The machining control device 31 transmits the generated cutting stage command scC to the cutting stage control device 34.

[0138] Furthermore, based on the gap state information ps, the processing control device 31 generates an oscillating stage command scS, which is a command for controlling the position of the oscillating stage 20 in the y-axis direction. The processing control device 31 transmits the generated oscillating stage command scS to the oscillating stage control device 33.

[0139] The discharge waveform control device 32 receives the discharge waveform command wc from the machining control device 31. The discharge waveform control device 32 controls the voltage waveform applied between the machining gap or the current waveform flowing between the machining gap by controlling the machining power supply 5 based on the discharge waveform command wc.

[0140] The wire travel control device 35 receives a wire electrode travel command rc from the machining control device 31. The wire travel control device 35 controls the driving of the bobbin rotation control devices 8a and 8b based on the wire electrode travel command rc, thereby controlling the traveling of the wire electrode 1. The wire travel control device 35 also controls the driving of the traverse control devices 9a and 9b based on the wire electrode travel command rc, thereby performing traverse control, which is position control of the bobbins 3a and 3b.

[0141] The bobbin rotation control devices 8a and 8b control the rotational positions of the bobbins 3a and 3b in accordance with instructions from the wire travel control device 35. The traverse control devices 9a and 9b control the positions of the bobbins 3a and 3b in the x-axis direction in accordance with instructions from the wire travel control device 35.

[0142] The cutting stage control device 34 receives a cutting stage command scC from the processing control device 31. The cutting stage control device 34 drives the cutting feed stage 10 based on the cutting stage command scC, and controls the relative position in the z-axis direction between the workpiece W and the cutting wire portion 1b.

[0143] The oscillating stage control device 33 receives the oscillating stage command scS from the processing control device 31. The oscillating stage control device 33 drives the oscillating stage 20 based on the oscillating stage command scS, and controls the relative position in the y-axis direction between the workpiece W and the cutting wire portion 1b.

[0144] When the wire electric discharge machining device 1000 starts electric discharge cutting, the electric discharge waveform control device 32 controls the machining power supply 5 based on the electric discharge waveform command wc. As a result, the machining power supply 5 applies a voltage to the inter-electrode gap between the wire electrode 1 and the workpiece W, and the current supplied to the inter-electrode gap is detected by the pulse current detection device 41.

[0145] The discharge state determination device 42 determines that the discharge state between the electrodes is an open state when the pulse current value per unit time is equal to or less than a specific value (first current value). The open state is a state in which the distance between the wire electrode 1 and the workpiece W is long and the number of discharges is small. When the discharge state between the electrodes is an open state, the discharge state determination device 42 transmits electrode state information ps indicating that the discharge state between the electrodes is an open state to the machining control device 31.

[0146] When the machining control device 31 receives the gap state information ps indicating that the gap discharge state is an open state, it outputs a command to increase the pulse oscillation frequency setting from the current value, a command to set the machining feed rate to a value faster than the current value, and a command to set the oscillation speed (the speed of reciprocating movement in the y-axis direction) to a value faster than the current value. For example, the machining control device 31 sends a command to the discharge waveform control device 32 to increase the pulse oscillation frequency setting from the current value. The machining control device 31 also sends a command to the cutting stage control device 34 to set the machining feed rate to a value faster than the current value in order to narrow the gap and promote the generation of discharge. The machining control device 31 also sends a command to the oscillation stage control device 33 to set the oscillation speed to a value faster than the current value.

[0147] On the other hand, the discharge state determination device 42 determines that the discharge state between the electrodes is a short-circuit state when the pulse current value per unit time is equal to or greater than a specific value (second current value). A short-circuit state is a state in which the distance between the wire electrode 1 and the workpiece W is short or a state in which machining waste accumulates between the wire electrode 1 and the workpiece W. When the discharge state between the electrodes is a short-circuit state, the discharge state determination device 42 transmits electrode state information ps indicating that the discharge state between the electrodes is a short-circuit state to the machining control device 31.

[0148] When the machining control device 31 receives machining gap state information ps indicating that the machining gap is in a short-circuit state, it outputs a command to reduce the pulse oscillation frequency setting from the current value, a command to set the machining feed rate to a value slower than the current value, and a command to set the oscillation speed to a value slower than the current value. For example, the machining control device 31 sends a command to the discharge waveform control device 32 to reduce the pulse oscillation frequency setting from the current value. In addition, the machining control device 31 sends a command to the cutting stage control device 34 to set the machining feed rate to a value slower than the current value in order to widen the machining gap, since the machining gap is too close. In addition, the machining control device 31 sends a command to the oscillation stage control device 33 to set the oscillation speed to a value slower than the current value.

[0149] The machining control device 31 sends a command to the oscillating stage control device 33 to change the oscillation width (movement distance in the y-axis direction) depending on the discharge state described above. For example, when the wire electrode 1 has sufficiently formed a machined groove in the width direction (x-axis direction), the distance between the wire electrode 1 and the workpiece W increases, and the discharge state becomes an open state. In this case, the machining control device 31 sends a command to the oscillating stage control device 33 to increase the oscillation width so that the position of the "antinode" of the vibration of the wire electrode 1 is located in the outer periphery of the workpiece W. That is, when the discharge state is an open state, the machining control device 31 sends a command to the oscillating stage control device 33 to increase the oscillation width.

[0150] The oscillation width is half the moving distance of the reciprocating movement. Therefore, the range of reciprocating movement by the oscillating stage 20 of the first embodiment is the sum of the oscillation width in the positive y direction and the oscillation width in the negative y direction.

[0151] Furthermore, if the formation of the machined groove in the width direction by the wire electrode 1 is insufficient, the distance between the wire electrode 1 and the workpiece W is small, and the discharge state becomes a short-circuit state. In this case, the machining control device 31 sends a command to the oscillating stage control device 33 to reduce the oscillation width so that the position of the "antinode" of the vibration of the wire electrode 1 is in the central region of the workpiece W. In other words, if the discharge state is a short-circuit state, the machining control device 31 sends a command to the oscillating stage control device 33 to reduce the oscillation width.

[0152] Furthermore, the discharge state determination device 42 determines that the inter-pole discharge state is an appropriate discharge state when the pulse current value per unit time is greater than the first current value and less than the second current value. The appropriate discharge state is a state in which the distance between the wire electrode 1 and the workpiece W is appropriate and no machining debris accumulates between the wire electrode 1 and the workpiece W. When the inter-pole discharge state is an appropriate discharge state, the discharge state determination device 42 transmits inter-pole state information ps indicating that the inter-pole discharge state is an appropriate discharge state to the machining control device 31.

[0153] When the machining control device 31 receives inter-pole state information ps indicating that the discharge state between the poles is an appropriate discharge state, it does not output a command to any of the discharge waveform control device 32, the cutting stage control device 34, and the swing stage control device 33.

[0154] When the rotation speed of the pump for supplying machining fluid is controlled by an inverter, the control unit 300 may control the pump frequency to control the flow rate of the machining fluid 23. The control unit 300 controls the flow rate of the machining fluid 23, for example, based on the discharge state between the electrodes. When the discharge state is an open state, the control unit 300 controls the inverter to reduce the flow rate of the machining fluid 23, and when the discharge state is a short-circuit state, the control unit 300 controls the inverter to increase the flow rate of the machining fluid 23.

[0155] FIG. 8 is a flowchart showing a processing procedure for wire electric discharge machining executed by the wire electric discharge machining apparatus according to the first embodiment.

[0156] When the wire electric discharge machining device 1000 starts electric discharge machining, the electrode gap monitoring unit 400 determines the electrode gap discharge state based on the pulse current value of the current applied to the electrode gap between the workpiece W and the wire electrode 1 (step S10).

[0157] The control unit 300 of the wire electric discharge machining apparatus 1000 controls the swing stage 20 based on the determination result by the electrode gap monitoring unit 400, thereby reciprocating the workpiece W in the wire running direction (step S20). As a result, the control unit 300 controls the position of the workpiece W in the wire running direction relative to the position of the deflection shape in the primary vibration mode (primary vibration mode) of the wire electrode 1 stretched between the wire parallel guide rollers 51 a, 51 b.

[0158] The wire electric discharge machining apparatus 1000 manufactures a wafer from the workpiece W by executing the processes of steps S10 and S20 described above.

[0159] Fig. 9 is a diagram for explaining the shape of a workpiece when a wire electric discharge machining apparatus without a swing stage performs electric discharge cutting. The upper part of Fig. 9 schematically shows the shape of the machined groove in the workpiece W when viewed from the z-axis direction (the cutting state of the workpiece W by electric discharge cutting) and the vibration range of the wire electrode 1. The lower part of Fig. 9 shows the workpiece W when viewed from the x-axis direction.

[0160] The behavior of the wire electrode in a wire electric discharge machining apparatus that does not have an oscillating stage is similar to the behavior of the wire electrode 1 when the wire electric discharge machining apparatus 1000 does not operate the oscillating stage 20, so here we will explain the behavior of the wire electrode 1 when the wire electric discharge machining apparatus 1000 does not operate the oscillating stage 20.

[0161] The cutting wire 1b, which has multiple wire electrodes 1 running parallel to each other and suspended between a pair of wire parallel guide rollers 51a, 51b, vibrates with a "node" at the top position in the z-axis direction of the wire guide grooves 56a, 56b provided in the wire parallel guide rollers 51a, 51b. In Figure 9, the position of the "node" of the vibration of the wire electrode 1 in the xy plane is illustrated as node N1.

[0162] Machining fluid 23 supplied from nozzles 7A, 7B (not shown in FIG. 9 ) installed on both ends of the workpiece W in the y-axis direction collides with the workpiece W near the "antinode" of the vibration of the wire electrode 1. In FIG. 9 , the position of the "antinode" of the vibration of the wire electrode 1 in the xy plane is illustrated as antinode B1. As such, the machining fluid 23 collides in the region near antinode B1, making the wire electrode 1 more susceptible to the influence of the machining fluid 23. Antinode B1 of the vibration of the wire electrode 1 is located at the center of the workpiece W in the y-axis direction. At antinode B1 of the vibration of the wire electrode 1, the wire electrode 1 vibrates more in the x-axis direction than at node N1.

[0163] 9 shows a case where the displacement of the wire electrode 1 in the x-axis direction at antinode B1 is L2. Also, FIG. 9 shows a case where the displacement of the wire electrode 1 in the x-axis direction at ends Le and Re of the thin plate Wa in the y-axis direction is L1 (<L2). Due to the difference in these displacements, a difference in plate thickness occurs between the central region and the peripheral region of the thin plate Wa.

[0164] Furthermore, in the region near the antinode B1 of the vibration of the wire electrode 1, the amount of machining fluid 23 containing machining chips increases, which tends to increase the concentration of the machining chips and makes it easier for secondary discharges to occur in the machining chips. Due to this secondary discharge, the workpiece W is machined more in the x-axis direction at the antinode B1 than at the region near the node N1.

[0165] As a result, the width of the machined groove in the workpiece W increases as the position of the workpiece W in the y-axis direction approaches the central axis. In other words, the width of the machined groove in the workpiece W decreases as the workpiece W moves away from the central axis of the workpiece W in the positive y-axis direction, and decreases as the workpiece moves away from the central axis of the workpiece W in the negative y-axis direction. That is, the width of the machined groove in the workpiece W increases as the workpiece W moves from the outside of the y-axis direction toward the center of the workpiece W in the y-axis direction. Therefore, the thickness (width in the x-axis direction) of the thin plate Wa formed by machining is thin near the center of the workpiece W (thin plate Wa) in the y-axis direction and thick at the ends in the y-axis direction. For example, at a machining position of the workpiece W that passes through the central axis, the thickness is thinnest at the central axis and thickens toward the periphery.

[0166] In this way, when the wire electric discharge machining apparatus 1000 does not operate the oscillating stage 20, the thin plate Wa formed by the wire electric discharge machining apparatus 1000 has poor flatness.

[0167] Fig. 10 is a diagram for explaining the shape of a workpiece when electric discharge cutting is performed by the wire electric discharge machining apparatus according to the first embodiment. In Fig. 10, a workpiece that is not oscillating is indicated as workpiece W, and a workpiece that has been moved in the y-axis direction by oscillation is indicated as workpiece WX. Note that Fig. 10 illustrates the workpiece W when the wire electric discharge machining apparatus 1000 moves the workpiece W in the minus y direction as workpiece WX, but when oscillating, the wire electric discharge machining apparatus 1000 also moves the workpiece W in the plus y direction.

[0168] The upper part of Fig. 10 schematically shows the shape of the machined grooves in the workpieces W, WX when the workpiece WX is viewed from the z-axis direction (the cutting state of the workpiece WX by electric discharge cutting), and the vibration range of the wire electrode 1. The lower part of Fig. 10 shows the workpieces W, WX when viewed from the x-axis direction. Note that, among the components in Fig. 10, components that achieve the same functions as the components shown in Fig. 9 are given the same reference numerals, and redundant explanations will be omitted.

[0169] The wire electric discharge machining apparatus 1000 of the first embodiment is equipped with a swing stage 20 (swing mechanism) that moves the workpiece W back and forth horizontally relative to the wire travel direction (y-axis direction). The wire electric discharge machining apparatus 1000 moves the workpiece W left and right (positive y direction and negative y direction) using the swing stage 20. In this way, the wire electric discharge machining apparatus 1000 varies the position of the workpiece W facing the wire electrode 1, and moves the workpiece W to, for example, the position indicated by workpiece WX.

[0170] This movement of the workpiece W fluctuates the gap between the wire electrode 1 and the machining surface of the workpiece WX, resulting in various different discharge frequencies depending on the machining position. That is, the position of the workpiece W in the y-axis direction relative to the antinode B1 changes due to the swinging motion, and as a result, various positions of the workpiece W are machined by the antinode B1.

[0171] Figure 10 shows a case where the thin plate Wa has moved in the negative y direction from the position in Figure 9, so that the right end Re of the thin plate Wa in the y-axis direction is at the position of the antinode B1, and the center of the thin plate Wa in the y-axis direction is at the position of the left end Le of the thin plate Wa in the y-axis direction shown in Figure 9.

[0172] 10, as in the case of FIG. 9, the displacement of the wire electrode 1 in the x-axis direction is greatest at the antinode B1. That is, the displacement of the wire electrode 1 in the x-axis direction is greater toward the right end Re of the workpiece WX, and is smaller toward the left end Le. As a result, in the case of FIG. 10, the right end Re of the thin plate Wa in the y-axis direction is machined more than the central portion of the thin plate Wa in the y-axis direction. As a result, the end region Rw near the right end Re of the thin plate Wa in the y-axis direction, which was not machined in FIG. 9, is machined.

[0173] Similarly, when the thin plate Wa moves in the positive y direction from the position in FIG. 9, the end region near the left end Le in the y-axis direction of the thin plate Wa that was not machined in FIG. 9 will be machined.

[0174] In this way, by performing electric discharge cutting while oscillating the workpiece W in the y-axis direction with the wire electric discharge machining device 1000, the situation in which the machined groove enlarges only near the center of the workpiece W as shown in Figure 9 is alleviated, and the variation in plate thickness of the machined thin plate Wa is improved. In other words, by oscillating the workpiece W in the y-axis direction with the wire electric discharge machining device 1000, various positions in the y-axis direction of the thin plate Wa are machined by the antinode B1 of the wire electrode 1, and the flatness of the thin plate Wa is improved.

[0175] Furthermore, the wire electric discharge machining apparatus 1000 continuously supplies machining fluid 23, such as deionized water, to the gap where the discharge pulse is generated. This allows the wire electric discharge machining apparatus 1000 to remove machining waste generated by the discharge from the gap using the machining fluid 23, thereby stabilizing the electric discharge machining. Furthermore, the wire electric discharge machining apparatus 1000 can cool the wire electrode 1 heated by the discharge using the machining fluid 23, preventing the wire electrode 1 from melting.

[0176] When machining thick plates with a long cutting length (machining length in the y-axis direction), the wire electric discharge machining device 1000 can efficiently supply machining fluid 23 to the gap between the electrodes inside the machining groove by bringing the variable nozzles 21a and 21b close to the workpiece W, thereby enabling stable and high-speed wire electric discharge machining.

[0177] Here, a comparative wire electric discharge machining apparatus (hereinafter referred to as the comparative apparatus) will be described. The comparative apparatus cuts a workpiece using a wire electrode suspended in the vertical direction. In the comparative apparatus, an upper nozzle located above the workpiece and a lower nozzle located below the workpiece spray machining fluid onto the machining position of the workpiece using the wire electrode. A cylindrical upper leakage prevention member is located outside the upper nozzle to prevent machining fluid from leaking from the upper surface of the workpiece, and a cylindrical lower leakage prevention member is located outside the lower nozzle to prevent machining fluid from leaking from the lower surface of the workpiece.

[0178] The upper leakage prevention member contacts the upper surface of the workpiece due to its own weight, filling the gap between the upper leakage prevention member and the upper surface of the workpiece. The lower leakage prevention member presses against the lower surface of the workpiece due to the force of a compression spring, filling the gap between the lower leakage prevention member and the lower surface of the workpiece. As a result, the comparative example device allows the upper and lower nozzles to move up and down freely, ensuring constant contact with the workpiece, even when the workpiece moves up and down. While this configuration prevents liquid leakage, the comparative example device is unable to cut out wafers with a uniform thickness due to vibration of the wire electrode.

[0179] The electric discharge machining apparatus (hereinafter referred to as the thin plate electrode machining apparatus) described in Patent Document 1 performs electric discharge machining using a thin plate electrode that is wide in the machining direction. The thin plate electrode machining apparatus uses a thin plate electrode that is resistant to melting even when a high voltage is applied, thereby increasing the applied voltage and realizing high-speed machining.

[0180] The thin plate electrode machining device cuts the workpiece into plates by electrical discharge machining while moving the thin plate electrode in the machining direction (downward). In the thin plate electrode machining device, the machining direction is the short side direction of the thin plate electrode. The thin plate electrode machining device performs machining in the short side direction while moving the thin plate electrode back and forth in the long side direction of the thin plate electrode to discharge the generated machining waste.

[0181] In the thin plate electrode machining device, the stroke and period for reciprocating the thin plate electrode are set according to the machining conditions. That is, the thin plate electrode machining device does not move the position of the electrode relative to the workpiece according to the discharge state, as in the wire electric discharge machining device 1000 of the first embodiment.

[0182] This thin plate electrode machining device moves a thin plate electrode instead of a wire electrode, but it cannot run the wire electrode 1 as in the wire electric discharge machining device 1000, and new thin plate electrodes cannot be continuously supplied, so the thin plate electrode is worn out by electric discharge machining. As a result, the width of the lateral direction of the portion of the thin plate electrode used in electric discharge machining is locally reduced, and if the portion that grips the thin plate electrode to apply tension to the thin plate electrode remains in its initial state, it is difficult to continue applying the tension to the thin plate electrode at the start of machining.

[0183] As a result, the tension acting on the surface of the thin plate electrode becomes increasingly uneven as the machining progresses, causing the thin plate electrode to warp or cracks to appear in the areas where the width decreases. For this reason, it is particularly difficult for the thin plate electrode machining device to cut and process cylindrical ingots with large diameters.

[0184] In order to cut out large-diameter wafers with large diameters and long cutting distances, thin plate electrode machining devices must use thin plate electrodes that are wide in the machining direction. To maintain the straightness of such thin plate electrodes with a wide width in the machining direction, thin plate electrode machining devices must apply high tension to the thin plate electrodes. However, it is difficult to perform electrical discharge machining while continuously applying high tension to the thin plate electrodes. As a result, the width of the machining groove in thin plate electrode machining devices increases, resulting in a deterioration in wafer machining accuracy.

[0185] In addition, the thin plate electrode machining device supplies the machining fluid to the machining position from a nozzle installed above the thin plate electrode. Therefore, when cutting a cylindrical ingot with a large diameter, the distance from the nozzle to the machining position gradually increases as the machining progresses, making it difficult to supply the machining fluid to the machining position that is far from the machining start position.

[0186] In order for a thin plate electrode machining device with this configuration to supply machining fluid to the inside of the machining groove in the workpiece during cutting, it is necessary to increase the machining fluid pressure or machining fluid flow rate. However, such an increase in machining fluid pressure or machining fluid flow rate acts as an external force, which deflects the thin plate electrode. As a result, in the thin plate electrode machining device, the thin plate electrode is likely to come into contact with the wafer surface, causing a short circuit, making it difficult to increase the electric discharge machining speed and reducing machining accuracy. Therefore, it is difficult for a thin plate electrode machining device to cut multiple wafers, especially large-diameter wafers, simultaneously.

[0187] Here, we will explain a configuration in which a thin plate electrode machining device is combined with an upper leakage prevention member of a comparative device to improve the supply of machining fluid in the thin plate electrode machining device. In the comparative device, the upper leakage prevention member supplies machining fluid while in close contact with the workpiece to prevent the machining fluid sprayed from the upper nozzle toward the machining position of the workpiece from leaking out. In addition, the thin plate electrode machining device machines the workpiece using a frame structure configured to apply a tensile force to the thin plate electrode.

[0188] In this case, even if the upper leakage prevention member presses against the frame structure of the thin plate electrode machining device, the frame structure has slits through which the thin plate electrode passes as machining progresses, so the machining fluid sprayed from the upper and lower nozzles leaks out to the surrounding area, and it is not possible to prevent pressure loss of the machining fluid in the machining groove. Thus, even if the machining fluid supply mechanism of the comparative example device is applied to the machining fluid supply mechanism of the thin plate electrode machining device, the supplied machining fluid leaks out from the slits provided in the frame structure, and the hydraulic pressure of the machining fluid supplied inside the frame structure does not increase.

[0189] Therefore, in the combined device that combines the thin plate electrode machining device and the comparative device, the machining fluid supplied to the machining position in the frame structure cannot be forced into the machining groove formed in the workpiece. Furthermore, the upper and lower leakage prevention members provided in the comparative device are not strong enough to prevent leakage of the machining fluid under high hydraulic pressure.

[0190] As described above, when the combined device performs electrical discharge cutting on a cylindrical workpiece, if the cutting length of the workpiece is short, the tips of the upper and lower nozzles are separated from the workpiece, making it difficult to efficiently supply the machining fluid into the machining groove. Therefore, when the combined device processes the short-cut region of the workpiece, the hydraulic pressure is insufficient, making it difficult to inject the machining fluid into the workpiece. The short-cut region of the workpiece is near the cutting start position (top of the cylinder) and the cutting end position (bottom of the cylinder) when cutting a disc-shaped member from a cylinder.

[0191] For example, when the workpiece W is a cylindrical ingot and wafers are cut from the cylindrical ingot, there will be a mixture of long and short cut lengths by the thin plate electrodes. Therefore, the cut length will vary continuously depending on the machining position from the start of machining. When cutting wafers from a cylindrical ingot, the combined device has difficulty discharging the machining waste and cooling the thin plate electrodes heated by the discharge energy, making it difficult to finish the wafers flat. Therefore, the combined device cannot reduce the variations in the thickness, warpage, and other shapes of the thin plate machined from the workpiece.

[0192] Furthermore, the pair of upper and lower nozzles in the comparative example device are installed facing each other in the vertical direction, and the upper nozzle is configured to be pressed against the workpiece using its own weight. Therefore, even if the upper nozzle is installed in a position parallel to the running direction of the wire electrodes 1 running in parallel in the horizontal direction, as in the wire electric discharge machining device 1000 of embodiment 1, it cannot press against the workpiece.

[0193] Furthermore, in a mechanism with one movable nozzle in a nozzle, such as the comparative example device, it can accommodate a small oscillation width of the workpiece, but due to the constraints of the nozzle length that can be stored in the nozzle holder, when the oscillation width is large, the extension range of the movable nozzle is insufficient and it is not possible to press the workpiece into contact. Also, in the case of the comparative example device, in order to expand the extension range of the nozzle, it is necessary to make both the nozzle holder and the movable nozzle longer, which makes the nozzle body larger and makes it difficult to incorporate into the comparative example device.

[0194] In this way, the wire electric discharge machining apparatus 1000 according to the first embodiment determines the discharge state between the electrodes based on changes in the discharge current supplied to the parallel wire portion 1a, and executes control of the oscillation of the discharge pulse, control of the feed speed in the machining direction, and control of the oscillation of the workpiece W. In this way, the wire electric discharge machining apparatus 1000 can change the positional relationship between the workpiece W and the wire electrode 1 to reduce variations in the thickness and shape, such as warpage, of the thin plate machined from the workpiece W.

[0195] Furthermore, since the wire electric discharge machining apparatus 1000 is equipped with variable nozzles 21 a, 21 b, the flow of machining fluid 23 passing through the machining groove of the workpiece W through which the wire electrode 1 is inserted is stable regardless of the swing position of the workpiece W, and machining chips can be efficiently discharged from the machining groove. As a result, the wire electric discharge machining apparatus 1000 reduces secondary discharges on the machining chips, stabilizing wire electric discharge machining and making it possible to uniform the thickness of thin plates that are machined collectively from the workpiece W by electric discharge cutting.

[0196] Second Embodiment Next, a second embodiment will be described. In the second embodiment, the wire electric discharge machining device 1000 executes various swing controls according to the discharge state between the electrodes.

[0197] In the second embodiment, the machining control device 31 generates a setting adjustment command, which is a command to adjust a set value, based on the gap state information ps received from the gap monitoring unit 400. The setting adjustment command is a command to the oscillating stage control device 33 to adjust the set value. The machining control device 31 transmits the generated setting adjustment command to the oscillating stage control device 33. As a result, the wire electric discharge machining device 1000 controls the discharge state of the gap by driving and controlling the oscillating stage 20.

[0198] The setting adjustment command may include a command for adjusting the setting value for the cutting stage control device 34. In this case, the machining control device 31 transmits the generated setting adjustment command to the cutting stage control device 34 and the oscillating stage control device 33. In this case, the drive control by the wire electric discharge machining device 1000 includes feed control in the machining direction (z-axis direction) by the cutting stage control device 34 and feed control (reciprocating movement control) in the wire running direction (y-axis direction) by the oscillating stage control device 33.

[0199] The setting adjustment command may also include a command to adjust the setting value for the discharge waveform control device 32. In this case, the machining control device 31 transmits the generated setting adjustment command to the discharge waveform control device 32 and the oscillation stage control device 33.

[0200] If the electrode gap monitoring unit 400 determines that the discharge state between the electrodes is a short circuit state, the machining control device 31 determines whether the short circuit is in the machining direction or the swing direction. If the short circuit is resolved by adjusting the swing, the machining control device 31 determines that the short circuit is in the swing direction, and if the short circuit is not resolved even after adjusting the swing, the machining control device 31 determines that the short circuit is in the machining direction.

[0201] Specifically, when the machining control device 31 receives inter-electrode state information ps indicating that the discharge state between the electrodes is a short-circuit state, it transmits a setting adjustment command to the oscillation stage control device 33 to determine whether or not the short circuit is in the oscillation direction. The setting adjustment command transmitted to the oscillation stage control device 33 in this case includes a command to make the oscillation speed sufficiently slower than the machining feed speed, or a command to reduce the oscillation width. In other words, the setting adjustment command specifies the oscillation speed or oscillation width to be adjusted according to the machining feed speed.

[0202] The machining control device 31 adjusts the oscillation speed or oscillation width based on the gap state information ps from the gap monitoring unit 400. That is, if the machining control device 31 continues to receive gap state information ps indicating that the discharge state between the electrodes is a short-circuit state even after reducing the oscillation speed or oscillation width, the machining control device 31 transmits a setting adjustment command to the oscillation stage control device 33 to further reduce the oscillation speed or oscillation width. The machining control device 31 continues to transmit a setting adjustment command to the oscillation stage control device 33 to reduce the oscillation speed or oscillation width until the short-circuit state is resolved.

[0203] Upon receiving the setting adjustment command, the oscillating stage control device 33 reduces the oscillation speed or oscillation width to eliminate the short-circuit state. While receiving the setting adjustment command, the oscillating stage control device 33 repeatedly reduces the oscillation speed or oscillation width. For example, the oscillating stage control device 33 temporarily stops the reciprocating movement of the workpiece W by the oscillating stage 20 and waits for the short circuit between the electrodes to be resolved, or sets the oscillation width to a value ranging from several tens of micrometers to approximately half the diameter of the wire electrode 1 and increases the oscillation speed as fast as possible. This causes the oscillating stage control device 33 to oscillate the machining fluid 23 in the machining groove, eliminating the accumulation of machining debris between the electrodes and promoting the discharge of machining debris out of the machining groove. In this way, the control unit 300 adjusts the moving speed or moving width of the reciprocating movement of the workpiece W depending on the feed speed of the wire electrode 1 in the machining direction.

[0204] If the short circuit state is not resolved even by adjusting the oscillation speed or oscillation width by the oscillation stage control device 33, the processing control device 31 determines that the short circuit is in the processing direction. In this case, the processing control device 31 transmits a setting adjustment command to the cutting stage control device 34 to temporarily suspend the processing feed in the processing direction. The processing control device 31 also transmits a setting adjustment command to the oscillation stage control device 33 to increase the oscillation width.

[0205] In this case, when the cutting stage control device 34 receives the setting adjustment command, it temporarily suspends the processing feed. Also, when the oscillating stage control device 33 receives the setting adjustment command, it moves the oscillating stage 20 back and forth by the width of the cutting length of the workpiece W (the processing length in the y-axis direction during cutting), thereby moving the workpiece W back and forth and discharging processing waste from the gap. Note that the processing control device 31 can calculate the cutting length of the workpiece W based on the position of the workpiece W in the z-axis direction and the dimension of the workpiece W in the z-axis direction.

[0206] In addition, the oscillating stage control device 33 may move the workpiece W back and forth by moving the oscillating stage 20 back and forth at a width shorter than the cutting length of the workpiece W or a width longer than the cutting length.

[0207] In this way, when the discharge state between the electrodes is a short-circuit state, the wire electric discharge machining device 1000 inserts a process for discharging machining waste from the electrode gap. The process for discharging machining waste from the electrode gap is one of the following processes P1 to P4: (P1) Decrease the oscillation speed (P2) Stop oscillation (P3) Decrease the oscillation width and increase the oscillation speed (P4) Pause the machining feed and increase the oscillation width

[0208] Note that the wire electric discharge machining apparatus 1000 may stop or slow down the machining feed and perform only the oscillation control in a region where the cutting length of the workpiece W is approximately the same as the diameter, regardless of whether a short circuit occurs. That is, when machining the central portion of the workpiece W in the z-axis direction (e.g., a position corresponding to the diameter of the workpiece W), the wire electric discharge machining apparatus 1000 may cyclically repeat oscillation control while performing the machining feed and oscillation control with the machining feed stopped or slowed down.

[0209] The region where the cutting length of the workpiece W is approximately the same length as the diameter may be a region where the ratio of the cutting length to the diameter is higher than a specific value, or a region where the difference between the diameter and the cutting length is smaller than a specific value.

[0210] Furthermore, if the short-circuit state is not resolved satisfactorily, the wire electric discharge machining apparatus 1000 prevents breakage of the wire electrode 1 by stopping the oscillation of the discharge pulse or setting the oscillation frequency lower than a specific value. Specifically, when the machining control device 31 continues to receive inter-electrode state information ps indicating a short-circuit state for a specific period of time, it transmits a setting adjustment command to the discharge waveform control device 32 to change the discharge operation. Upon receiving the setting adjustment command, the discharge waveform control device 32 stops the oscillation of the discharge pulse or sets the oscillation frequency lower than a specific value. In this way, the wire electric discharge machining apparatus 1000 prevents breakage of the wire electrode 1.

[0211] On the other hand, when the electrode gap monitoring unit 400 determines that the discharge state of the electrode gap is an open state, the machining control device 31 transmits a setting adjustment command, which is a command to increase the oscillation speed, to the oscillation stage control device 33. In this case, in order to prevent the occurrence of a short circuit in the wire traveling direction due to the oscillation operation, the machining control device 31 may transmit a setting adjustment command to the oscillation stage control device 33 to increase the oscillation speed while limiting the oscillation speed to ½ or less of the machining feed speed.

[0212] Furthermore, the machining control device 31 may monitor the gap state information ps received from the gap monitoring unit 400 and transmit a setting adjustment command to the oscillating stage control device 33 to set the oscillation width based on the monitoring results. The setting adjustment command in this case is, for example, a command that sets the maximum oscillation width to 1 / 2 of the maximum cutting length of the workpiece W. The machining control device 31 reciprocates the oscillating stage 20 within a distance equal to the diameter of the workpiece W.

[0213] For example, if machining of the workpiece W with the wire electrode 1 continues without oscillating the workpiece W, a machining groove is formed and the distance between the wire electrode 1 and the workpiece W increases. In this case, the machining gap is in an open state, and the machining control device 31 continues to receive the machining gap state information ps indicating the open state for a specific period of time. In such a case, the machining control device 31 transmits a setting adjustment command to the oscillating stage control device 33, for example, setting the maximum oscillation width to half the maximum cutting length of the workpiece W. This allows the wire electric discharge machining device 1000 to perform electric discharge cutting while oscillating the workpiece W.

[0214] It should be noted that the wire electric discharge machining device 1000 may increase the machining feed speed if the discharge state between the electrodes is in an open state regardless of the position to which the workpiece W is moved.

[0215] In this way, the wire electric discharge machining apparatus 1000 according to the second embodiment determines the discharge state between the electrodes based on the change in the discharge current supplied to the parallel wire portion 1a (electrode state information ps), and performs swing control of the traveling direction of the wire electrode 1 based on the discharge state, thereby enabling electric discharge cutting machining to be performed while correcting variations in the thickness of thin plates.

[0216] Furthermore, when the discharge state is a short circuit state, the wire electric discharge machining device 1000 temporarily stops the machining feed, so that machining waste can be discharged from the machining gap in a short time.

[0217] Furthermore, if the short circuit condition is not resolved for a specific period of time, the wire electric discharge machining device 1000 stops oscillating the discharge pulse or reduces the oscillation frequency below a specific value, thereby preventing breakage of the wire electrode 1.

[0218] Furthermore, the wire electric discharge machining apparatus 1000 uses swing control in response to the discharge state between the electrodes to promote the discharge of machining debris from the gap during a short circuit, thereby suppressing secondary discharge. Furthermore, the wire electric discharge machining apparatus 1000 changes the relative position between the workpiece W and the vibration-damping guide rollers 4a, 4b through swing control in response to the discharge state between the electrodes, thereby changing the positional relationship between the workpiece W and the deflection position of the wire electrode 1. This allows the wire electric discharge machining apparatus 1000 to reduce variations in the thickness, warpage, and other shapes of the thin plate being cut out.

[0219] Third Embodiment Next, a third embodiment will be described. In the third embodiment, at least one of the oscillation width and the oscillation speed is controlled in accordance with the cutting length of the workpiece W.

[0220] When the workpiece W is cylindrical, if the outer end surface (end in the z-axis direction) of the workpiece W is set as the starting position for machining, the cutting length (length in the y-axis direction) of the workpiece W by the wire electrode 1 changes depending on the distance in the machining direction from the starting position for machining (position in the z-axis direction).

[0221] The length in the y-axis direction (cut length) of a disk-shaped thin plate machined by electrical discharge cutting is smallest at the machining start position and machining end position and largest at the diameter portion. That is, the cut length in the y-axis direction of the thin plate is largest when machined at a machining position that passes through the central axis of the workpiece W, and the cut length in the y-axis direction decreases as the distance from the central axis increases. For this reason, the wire electrical discharge machining device 1000 can improve machining efficiency by changing the oscillation conditions between machining in a region of the workpiece W where the cut length is approximately the same as the diameter (the center of the workpiece W in the z-axis direction) and machining in a region close to the machining start position or machining end position of the workpiece W (the end portion of the workpiece W in the z-axis direction).

[0222] For example, the wire electric discharge machining apparatus 1000 sets the oscillation width larger than that at the start of machining in a region where the cutting length of the workpiece W is close to the diameter of the workpiece W. For example, the wire electric discharge machining apparatus 1000 sets the maximum oscillation width to ½ of the cutting length of the workpiece W. That is, in a region where the cutting length of the workpiece W is close to the diameter of the workpiece W, the wire electric discharge machining apparatus 1000 sets the oscillation width in the minus y direction to ½ of the cutting length of the workpiece W and the oscillation width in the plus y direction to ½ of the cutting length of the workpiece W.

[0223] If the oscillation speed is too fast or the oscillation width is too large, a short circuit will occur, so the wire electric discharge machining device 1000 should adjust the oscillation speed while monitoring to ensure that no short circuit occurs between the wire electrode 1 and the workpiece W. For example, if the oscillation speed is too fast or the oscillation width is too large, a short circuit is likely to occur at the outer periphery of the workpiece W in a region where the cutting length of the workpiece W is approximately the same as the diameter. Therefore, if a short circuit occurs, the wire electric discharge machining device 1000 slows down the oscillation speed or reduces the oscillation width.

[0224] Furthermore, the cutting length of the workpiece W is smaller in regions close to the machining start position and the machining end position. For this reason, the wire electric discharge machining device 1000 may make the oscillation width smaller in the regions close to the machining start position and the machining end position than in other machining positions (for example, regions where the cutting length is approximately the same length as the diameter), or may not oscillate at all.

[0225] The processing control device 31 can geometrically calculate the cutting length from the processing position (position in the z-axis direction) from the processing start position and information on the diameter of the workpiece W. For this reason, the processing control device 31 performs swing control to adjust at least one of the swing width and the swing speed according to the cutting length, for example.

[0226] The processing control device 31 may also execute swing control to adjust at least one of the swing width and the swing speed when the cutting length becomes equal to or greater than a specific value (first reference value).The processing control device 31 may also execute swing control to stop at least one of the swing width and the swing speed when the cutting length becomes equal to or less than a specific value (second reference value).

[0227] The machining control device 31 may also control the oscillation speed according to the pulse oscillation frequency (discharge frequency) and the machining speed (machining feed speed in the z-axis direction). In the open state, the current flowing in the direction parallel to the xy plane of the wire electrode 1 is small, so the machining control device 31 determines that machining in the direction parallel to the xy plane is sufficient and increases the machining speed. On the other hand, in the short-circuited state, the current flowing in the direction parallel to the xy plane of the wire electrode 1 is large, so the machining control device 31 determines that a lot of machining debris has accumulated in the machined groove and decreases the machining speed.

[0228] The machining control device 31 calculates the machining speed based on the machining gap state information ps to generate the swing stage command scS. The machining control device 31 calculates the ratio of the machining speed to the pulse oscillation frequency, and if this ratio falls below a specific value, it determines that a short-circuit state has occurred in which discharge is not effectively occurring in the machining direction due to bending of the wire electrode 1 or an increase in the concentration of machining debris. In this case, the machining control device 31 performs swing control to remove machining debris from the machining gap or to correct the shape of the machined surface caused by bending of the wire electrode 1. The pulse oscillation frequency here corresponds to the discharge waveform command wc, and the machining speed corresponds to the swing stage command scS.

[0229] In the wire electric discharge machining device 1000, the longer the cutting length, the longer the machining time required, and therefore the slower the machining speed. Therefore, the machining control device 31 may determine whether a short circuit state has occurred based on the ratio of the machining speed to the pulse oscillation frequency and the cutting length. The machining control device 31 determines that a short circuit state has occurred when the ratio of the machining speed to the pulse oscillation frequency is lower than a specific value set for each cutting length. Note that the machining control device 31 may adjust the discharge frequency according to the machining speed.

[0230] In this way, in electric discharge cutting, in which the cutting length of the workpiece W changes as the cutting progresses, the wire electric discharge machining apparatus 1000 of embodiment 3 controls at least one of the oscillation width and the oscillation speed according to the cutting length of the workpiece W calculated from the cutting position, so that it is possible to process thin plates while correcting variations in plate thickness.

[0231] Furthermore, since the wire electric discharge machining device 1000 controls at least one of the oscillation width and the oscillation speed based on the machining gap state information ps, it is possible to correct variations in the thickness of a thin plate while machining.

[0232] Next, a description will be given of the hardware configuration of the control unit 300. The control unit 300 is realized by a processing circuit. The processing circuit may be a processor and memory that executes a program stored in memory, or may be dedicated hardware.

[0233] FIG. 11 is a diagram illustrating an example of the configuration of a processing circuit provided in the control unit according to the first to third embodiments, when the processing circuit is realized by a processor and a memory. The processing circuit 90 illustrated in FIG. 11 includes a processor 91 and a memory 92. When the processing circuit 90 is configured with the processor 91 and the memory 92, each function of the processing circuit 90 is realized by software, firmware, or a combination of software and firmware. The software or firmware is written as a control program and stored in the memory 92. In the processing circuit 90, each function is realized by the processor 91 reading and executing the control program stored in the memory 92. That is, the processing circuit 90 includes the memory 92 for storing a control program that results in the processing of the control unit 300. This control program can also be said to be a program that causes the control unit 300 to execute each function realized by the processing circuit 90. This control program may be provided by a computer-readable recording medium on which the control program is recorded, or by other means such as a communication medium.

[0234] The control program can also be said to be a program that causes the control unit 300 to execute the process of step S20 in Fig. 8. Here, the processor 91 is, for example, a central processing unit (CPU), a processing device, an arithmetic unit, a microprocessor, a microcomputer, or a digital signal processor (DSP). The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as a random access memory (RAM), a read-only memory (ROM), a flash memory, an erasable programmable read-only memory (EPROM), or an electrically programmable programmable read-only memory (EEPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a minidisk, or a digital versatile disk (DVD).

[0235] FIG. 12 is a diagram illustrating an example of a processing circuit provided in the control unit according to the first to third embodiments, configured with dedicated hardware. The processing circuit 93 illustrated in FIG. 12 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The processing circuit 93 may be partially implemented with dedicated hardware and partially implemented with software or firmware. In this way, the processing circuit 93 can realize each of the above-described functions by dedicated hardware, software, firmware, or a combination thereof.

[0236] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or different embodiments may be combined with each other. It is also possible to omit or modify parts of the configurations as long as they do not deviate from the gist of the invention.

[0237] 1 Wire electrode, 1a Parallel wire portion, 1b Cutting wire portion, 2, 2a to 2d Guide roller, 2e Wire guide groove, 3a, 3b Bobbin, 4a, 4b Vibration-damping guide roller, 5 Machining power supply, 6a, 6b Electronic supply unit, 7A, 7B Nozzle, 7a, 7b Nozzle body, 7c Machining fluid ejection hole, 8a, 8b Bobbin rotation control device, 9a, 9b Traverse control device, 10 Cutting feed stage, 20 Oscillating stage, 21a, 21b Variable nozzle, 22a, 22b, 22A1, 22A2, 22B1, 22B2 Liquid leakage prevention plate, 23 Machining fluid, 25 Workpiece fixing plate, 26 Insulating part, 31 Machining control device, 32 Discharge waveform control device, 33 Oscillating stage control device, 34 Cutting stage control device, 35 Wire travel control device, 41 Pulse current detection device, 42 Discharge state determination device, 51a, 51b wire parallel guide rollers, 55a, 55b guide roller holder, 56a, 56b wire guide groove, 62 machining fluid supply pipe, 70 thin plate machining unit, 71, 71a, 71b fluid rectifying plate, 72 workpiece holder, 90, 93 processing circuit, 91 processor, 92 memory, 100 machining mechanism unit, 200 power supply unit, 300 control unit, 400 electrode gap monitoring unit, 1000 wire electric discharge machining device, B1 antinode, Gr machining groove, Le, Re end, N1 node, ps electrode gap state information, rc wire electrode travel command, Rw end area, SB bottom surface, scC cutting stage command, scS swing stage command, W, WX workpiece, Wa thin plate, wc discharge waveform command.

Claims

1. A wire electric discharge machining apparatus comprising: a wire electrode that cuts out a plurality of plate-shaped members by electric discharge machining from a workpiece immersed in a machining fluid; an oscillation stage that moves the workpiece back and forth in the wire travel direction, which is the direction in which the wire electrode is paid out and wound up; a gap monitor that determines the discharge state between the electrodes based on the pulse current value of the current applied to the gap between the workpiece and the wire electrode; and a control unit that controls the reciprocating movement of the workpiece based on the determination result by the gap monitor, wherein the control unit controls the oscillation stage to control the position of the workpiece in the wire travel direction relative to the position of the deflected shape of the wire electrode in a primary vibration mode when the wire electrode is stretched between guide rollers.

2. The wire electric discharge machining device according to claim 1, further comprising: a thin plate machining unit that stores the workpiece and immerses it in the machining fluid; and a nozzle through which the wire electrode is passed and that is in close contact with the thin plate machining unit perpendicular to the wire running direction and thereby sprays the machining fluid from outside the thin plate machining unit into the thin plate machining unit to the machining position of the workpiece; wherein the oscillating stage moves the thin plate machining unit back and forth in the wire running direction, thereby moving the workpiece back and forth in the wire running direction; and the nozzle has a variable nozzle that expands and contracts in the wire running direction as the thin plate machining unit moves, thereby spraying the machining fluid while maintaining close contact with the thin plate machining unit.

3. The wire electric discharge machining device according to claim 2, characterized in that the wire travel direction and the extension / retraction direction of the variable nozzle are horizontal, and when the thin plate processing section approaches the nozzle, the variable nozzle is pushed by the thin plate processing section and shortens, and when the thin plate processing section moves away from the nozzle, the variable nozzle is pushed out, thereby extending while pressing the variable nozzle against the thin plate processing section.

4. The wire electric discharge machining device according to claim 2 or 3, characterized in that the thin plate processing section comprises: a workpiece fixing plate on whose upper surface the workpiece is fixedly placed and which is moved back and forth in the wire running direction by the oscillating stage, thereby moving the workpiece back and forth; a pair of first plate-shaped members whose front and back surfaces extend in a direction perpendicular to the wire running direction and sandwich the workpiece; and a pair of second plate-shaped members whose front and back surfaces extend in a direction perpendicular to the workpiece fixing plate and the first plate-shaped members and sandwich the workpiece; wherein the wire electrode is passed through the first plate-shaped members in the wire running direction and the first plate-shaped members move back and forth in the wire running direction together with the workpiece fixing plate; and the second plate-shaped members move back and forth in the wire running direction together with the workpiece fixing plate, and also move up and down together with the workpiece fixing plate when the workpiece fixing plate moves up and down.

5. A wire electric discharge machining device as described in any one of claims 1 to 4, characterized in that the control unit adjusts the movement distance of the oscillating stage in the wire running direction depending on the cutting length of the workpiece in the wire running direction by the wire electrode.

6. The wire electric discharge machining device according to any one of claims 1 to 5, characterized in that the control unit adjusts the speed at which the workpiece is reciprocated in accordance with the feed speed of the wire electrode in the machining direction.

7. The wire electric discharge machining device according to claim 6, wherein the control unit makes the moving speed slower than the feed speed when the determination result indicates a short circuit between the electrodes.

8. The wire electric discharge machining device according to claim 6, characterized in that: the workpiece is cylindrical; the wire electrode cuts out a disk-shaped member from the workpiece; and the control unit temporarily suspends or slows down the feeding of the wire electrode to control the reciprocating movement of the workpiece when the machining position of the workpiece by the wire electrode corresponds to the diameter of the workpiece.

9. The wire electric discharge machining device according to claim 8, wherein the control unit reciprocates the oscillating stage within a distance equal to the diameter of the workpiece.

10. The wire electric discharge machining device according to claim 6, characterized in that the control unit calculates the ratio of the feed speed to the pulse oscillation frequency in the electric discharge machining, and when the calculated ratio becomes lower than a specific value, moves the oscillating stage back and forth.

11. A wire electric discharge machining method comprising: a discharge state determination step in which a wire electric discharge machining device that cuts out a plurality of plate-shaped members from a workpiece immersed in a machining fluid by electric discharge machining using a wire electrode determines the discharge state between the workpiece and the wire electrode based on the pulse current value of the current applied between the electrodes; and a control step in which the wire electric discharge machining device controls a swing stage that moves the workpiece back and forth in the wire traveling direction, which is the direction in which the wire electrode is paid out and wound up, based on the determination result of the determination, thereby moving the workpiece back and forth in the wire traveling direction, wherein in the control step, the wire electric discharge machining device controls the swing stage to control the position of the workpiece in the wire traveling direction relative to the position of the deflected shape in the primary vibration mode of the wire electrode stretched between guide rollers.

12. The wire electric discharge machining method according to claim 11, wherein in the control step, the wire electric discharge machining device adjusts the speed at which the workpiece is reciprocated in accordance with the feed speed of the wire electrode in the machining direction.

13. A method for manufacturing wafers, comprising simultaneously cutting a plurality of wafers from the workpiece by the wire electric discharge machining method according to claim 11 or 12.

14. The method for manufacturing a wafer according to claim 13, wherein the workpiece is a semiconductor ingot, and the wafer is a semiconductor wafer.

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