WIRE ELECTRIC DIELECTRIC DAMAGE APPARATUS, WIRE ELECTRIC DIELECTRIC DAMAGE METHOD, AND WAFER MANUFACTURING METHOD

Abstract

The wire electric discharge machining apparatus includes a wire electrode that cuts out a plurality of plate-shaped members by electric discharge machining from a workpiece (W) immersed in machining fluid (23), a swing stage (20) 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 monitoring unit that determines the discharge state of the gap based on the pulse current value of a current applied to a gap between the workpiece and the wire electrode, and a control unit (300) that controls the reciprocating movement of the workpiece based on the result of the determination by the gap monitoring unit, and by controlling the swing stage, the control unit controls the position of the workpiece in the wire travel direction relative to the position of the deflected shape in a primary vibration mode of the wire electrode stretched between wire parallel guide rollers (51a, 51b).

Description

[Technical field]

[0001] The present disclosure relates to a wire electric discharge machining apparatus, a wire electric discharge machining method, and a method for manufacturing wafers, which use a wire electrode to collectively cut out multiple wafers from a workpiece. [Background technology]

[0002] In a multi-wire electric discharge machining apparatus, electric discharge is generated between multiple wire electrodes and a workpiece, and multiple plate-shaped members (wafers) are cut out from the workpiece at once. For example, a multi-wire electric discharge machining apparatus is used in a slicing process in a semiconductor manufacturing process, in which multiple wafers are cut out from an ingot of semiconductor material.

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

[0004] The electric discharge machining apparatus 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 one another, and cuts out a wafer using the tensioned thin plate electrode. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2014 / 084277 Summary of the Invention [Problem to be solved by the invention]

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

[0007] The present disclosure has been made in consideration 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. [Means for solving the problem]

[0008] In order to solve the above problems and achieve the object, the wire electric discharge machining apparatus of the present disclosure includes a wire electrode that cuts out a plurality of plate-shaped members from a workpiece immersed in a machining fluid by electric discharge machining, 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 wire electric discharge machining apparatus of the present disclosure also includes a gap monitor that determines a discharge state of the gap based on a pulse current value of a current applied to a gap between the workpiece and the wire electrode, and a controller that controls the reciprocating movement of the workpiece based on the result of the determination by the gap monitor. The controller controls the swing stage to control the position of the workpiece in the wire travel direction with respect to the position of a deflection shape in a primary vibration mode of the wire electrode stretched between guide rollers. Effect of the Invention

[0009] The wire electric discharge machining apparatus according to the present disclosure has the advantage of being able to cut out wafers of uniform thickness even as machining progresses. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram showing a configuration example of a wire electric discharge machining apparatus according to a first embodiment; [Diagram 2] FIG. 1 is a schematic diagram showing a configuration example of a thin plate processing unit and a variable nozzle provided in a wire electric discharge machining apparatus according to a first embodiment; [Diagram 3] FIG. 1 is a schematic diagram showing components of a thin plate machining unit included in a wire electric discharge machining apparatus according to a first embodiment; [Figure 4] FIG. 1 is a schematic diagram showing a configuration example of a cutting wire unit included in a wire electric discharge machining apparatus according to a first embodiment; [Diagram 5] FIG. 1 is a diagram for explaining a machining direction of machining performed by a wire electric discharge machining apparatus according to a first embodiment; [Figure 6] FIG. 1 is a diagram for explaining a shape of a variable nozzle when the wire electric discharge machining apparatus according to the first embodiment oscillates an oscillating stage; [Figure 7] FIG. 1 is a block diagram showing a configuration of a control unit included in a wire electric discharge machining apparatus according to a first embodiment. [Figure 8] 1 is a flowchart showing a processing procedure of wire electric discharge machining executed by a wire electric discharge machining apparatus according to a first embodiment; [Figure 9] FIG. 1 is a diagram for explaining the shape of a workpiece when a wire electric discharge machining device not equipped with a swing stage performs electric discharge cutting; [Figure 10] FIG. 1 is a diagram for explaining the shape of a workpiece when the wire electric discharge machining device according to the first embodiment performs electric discharge cutting; [Figure 11] FIG. 1 is a diagram showing a configuration example of a processing circuit provided in a control unit according to the first to third embodiments, in the case where the processing circuit is realized by a processor and a memory; [Figure 12] FIG. 1 is a diagram showing an example of a processing circuit in a control unit according to the first to third embodiments, in which the processing circuit is configured with dedicated hardware; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[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 drawings.

[0012] Embodiment 1 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] Wire electric discharge machining apparatus 1000 is a multi-wire electric discharge machining apparatus that performs electric discharge cutting using cutting wire portion 1b of wire electrode 1. Hereinafter, electric discharge cutting performed by wire electric discharge machining apparatus 1000 may be referred to as electric discharge machining or machining.

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

[0015] Fig. 3 shows the shapes of components of a thin plate machining unit 70 provided in the wire electric discharge machining apparatus 1000, and there are some parts which differ in shape, size, etc. from the components shown in Fig. 2 etc. In the wire electric discharge machining apparatus 1000, the thin plate machining unit 70 is formed by assembling the components shown in Fig. 3. As shown in Fig. 4, in the cutting wire portion 1b, a plurality of wire electrodes 1 are arranged in parallel to each other at a distance and 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 running direction of the wire electrode 1 on the workpiece W, i.e., the running direction of the wire electrode 1 relative to the workpiece W placed in the wire electric discharge machining apparatus 1000. Thus, in the wire electric discharge machining apparatus 1000, the wire electrode 1 of the cutting wire portion 1b is extended 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 electrode 1 is arranged in parallel on the workpiece W, i.e., the direction in which the wire electrode 1 is arranged in parallel with 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 manner, the workpiece W having an axis parallel to the x-axis direction is placed in the thin plate machining section 70.

[0019] Two axes in a plane parallel to the upper surface of the thin plate processing portion 70 that are perpendicular to each other are the x-axis and y-axis, and an axis perpendicular to the x-axis and y-axis is the z-axis. A plane parallel to the plane on which the wire electrodes 1 of the cutting wire portion 1b are arranged is the xy plane. The xy plane is a plane parallel to the horizontal plane.

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

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

[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 of machining 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 the guide roller holders 55a, 55b outside the thin plate processing unit 70. The wire parallel guide rollers 51a, 51b, the thin plate processing unit 70, and the guide roller holders 55a, 55b will be described in detail later.

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

[0025] The wire electric discharge machining apparatus 1000 cuts out thin plates from the workpiece W by 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 apparatus 1000 fixes the position of the cutting wire 1b in the z-axis direction and cuts out multiple thin plates from the workpiece W by moving the workpiece W in the z-axis direction. The wire electric discharge machining apparatus 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 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 below) that define the distance between the wire electrodes 1. The wire electrodes 1, each disposed in 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 of a desired thickness from which a single piece of metal is cut by electric discharge cutting. The pair of wire parallel guide rollers 51a, 51b allow the wire electrodes 1 of the cutting wire portion 1b to travel in parallel while restraining the wire electrodes 1 so that the distance between the wire electrodes 1 is maintained during electric discharge cutting.

[0028] In electric discharge cutting by the wire electric discharge machining device 1000, the nozzles 7A, 7B spray machining fluid 23 such as deionized water toward a machining groove provided in the tensioning direction (y-axis direction) of the wire electrode 1 of the cutting wire portion 1b. 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 causes vibration of 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 causes vibration of the wire electrode 1 and fluctuations in the tension of the wire electrode 1.

[0030] The wire electrode 1 is bent in a direction perpendicular to a surface of the workpiece W parallel to the yz plane by the impact force of the discharge. The wire electrode 1 cuts out a thin plate by digging a machining groove in the workpiece W, so that the wire electrode 1 is 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 side of one thin plate to the back surface side of the other thin plate by the impact force of the discharge, and is also pushed from the back surface side of the other thin plate to the front surface side 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 that the cutting wire portion 1b is bent 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 51a, 51b vibrates like a chord with the portions contacting the wire guide grooves 56a, 56b 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 51a, 51b on both sides as "nodes" and the central portion of the wire electrode 1 stretched between the wire parallel guide rollers 51a, 51b on both sides as the "antinode" 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 "antinode" of the vibration of the wire electrode 1 is the maximum amplitude portion of the primary vibration.

[0032] The wire electric discharge machining device 1000 melts and removes the workpiece W by continuously generating pulse discharges while maintaining a gap of about 20 to 50 μm between the wire electrode 1 and the machining surface. The above-mentioned bending due to disturbances and changes in the behavior of the wire electrode 1 due to vibration also affect the shape of the machining 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, 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), machining chips tend to accumulate, and the discharge gap expands in addition to the amplitude behavior of the wire electrode 1 due to secondary discharge to the machining chips.

[0034] In addition, machining fluid 23 is supplied into the gaps in 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. Therefore, the wire electrode 1 is subjected to the pressure of the flow of machining fluid 23 and is swayed by the discharge repulsive force proportional to the discharge energy, and the chordal vibration behavior is transferred to the machined surface, which becomes the thin plate. In addition, 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 an ingot made of gallium nitride (GaN) crystals, a large diameter thin plate is often cut out 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, so that the wire electrode 1 becomes more likely to bend, and the concentration of processing waste tends to increase in the center of the workpiece W. Therefore, as the diameter of the thin plate increases, a shape with an increased amplitude is transferred to the processed surface of the thin plate. As a result, the thickness of the cut thin plate may be thin in the center and thicker toward the periphery.

[0036] The wire electric discharge machining apparatus 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 center and the outer periphery of the workpiece W are machined near the "antinodes" of the vibration of the wire electrode 1.

[0037] A semiconductor wafer is processed through many semiconductor manufacturing process steps. If the thickness of the semiconductor wafer is not uniform across the surface, the processing in each semiconductor manufacturing process step will be non-uniform. For this reason, it is desirable that the thickness of the thin plate cut from the ingot crystal be uniform across the surface of the thin plate. In order to uniformize the thickness of the thin plate across the surface of the semiconductor wafer, grinding and polishing are performed. In this case, if there is a large variation in the thickness of the thin plate processed from the ingot across the surface, the processing load increases in the grinding and polishing processes until the plate is finished to a specific thickness, which is a factor that significantly impairs the quality and cost of the thin plate in semiconductor manufacturing.

[0038] The wire electric discharge machining apparatus 1000 uses a wire electrode 1 to perform multi-wire electric discharge machining, in which multiple plate-shaped members, or thin plates, are cut 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] Fig. 2 shows a cross-sectional view of the thin plate processing unit 70 etc. cut along a plane parallel to the yz plane. Fig. 2 shows the positional relationship between the workpiece W, the wire parallel guide rollers 51a, 51b, the guide roller holders 55a, 55b, the nozzles 7A, 7B, the vibration-damping guide rollers 4a, 4b, and the electron supply units 6a, 6b.

[0040] The workpiece W is placed in the thin plate processing section 70, and the bottom part is fixed on the 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, the workpiece W is grooved from the upper side by the cutting wire portion 1b. FIG. 2 shows a state in which the wire electric discharge machining of the cylindrical workpiece W has progressed from the upper side of the workpiece W to a position about halfway up by the electric discharge machining of the cutting wire portion 1b. That is, FIG. 2 shows a state in which the cutting wire portion 1b has formed a groove from the upper side of the workpiece W to a position about halfway up. The wire electric discharge machining apparatus 1000 cuts out a wafer, which is a thin plate, 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, 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 performs power supply, and a control unit 300 that controls wire electric discharge machining apparatus 1000. Wire electric discharge machining apparatus 1000 also includes an electrode gap monitoring unit 400 that monitors the electrode gap, but is not shown in Fig. 1. The electrode gap monitoring unit 400 will be described later.

[0042] Examples of the material of 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 processing mechanism 100 includes a plurality of guide rollers 2 (the reference number "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 in which 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 each other and arranged so that their rotation axes are parallel to each other. Since the rotation axes of the guide rollers 2a to 2d are parallel to each other, the machining mechanism 100 can move the wire electrode 1 with high accuracy. The axial direction of the rotation axis of each of the guide rollers 2a to 2d is parallel to the x-axis.

[0045] One wire electrode 1 is wound multiple times around the guide rollers 2a-2d with intervals in the direction of the rotation axis of each of the guide rollers 2a-2d. These wound wire electrodes 1 form the parallel wire section 1a. Of the parallel wire section 1a, the wire section between the wire parallel guide rollers 51a, 51b forms the cutting wire section 1b. A part of the cutting wire section 1b is disposed at a position facing the workpiece W. The cutting wire section 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. Each of the wire guide grooves 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, so that the guide rollers 2a to 2d keep constant the 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 controller 8a and the traverse controller 9a control the bobbin 3a. The bobbin rotation controller 8b and the traverse controller 9b control the bobbin 3b.

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

[0050] The bobbin rotation controller 8b controls the rotation of the bobbin 3b, and controls the travel of the wire electrode 1. The bobbin rotation controller 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, 3b by the traverse control devices 9a, 9b is called traverse control. The traverse control allows the bobbins 3a, 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 manner, the wire electrode 1 makes multiple revolutions between the guide rollers 2a to 2d, and is then wound onto the bobbin 3b.

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

[0054] The insulating section 26 may be disposed between the workpiece fixing plate 25 and the cutting feed stage 10. The insulating section 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 feed stage 10. For example, the insulating section 26 may be an insulating sheet, and the insulating sheet may be attached to the stage surface of the oscillating stage 20. In addition, the workpiece fixing plate 25 and the two types of drive stages (the oscillating stage 20 and the cutting feed stage 10) may be electrically insulated from each other by applying an insulating coating treatment such as hard anodizing to the cutting 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 disposed 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] Each of the wire parallel guide rollers 51a, 51b has a rotation axis similar to the guide rollers 2a to 2d, and is installed so as to be rotatable around the respective rotation axis. The wire parallel guide rollers 51a, 51b are disposed apart from each other in the y-axis direction, and are disposed 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 made to run with high accuracy. As described above, the axial direction of the rotation axis of each 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, and the wire guide grooves 56a, 56b maintain the arrangement interval 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 the intervals between the wire electrodes 1, i.e., the intervals between the wire electrodes 1 of the cutting wires 1b. By arranging the cutting wires 1b in parallel and at equal intervals, the wire electric discharge machining apparatus 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 manner, the wire parallel guide rollers 51a, 51b guide the running of the wire electrode 1 (cutting wire portion 1b) which is wound multiple times at equal intervals in the axial direction of the rotation shafts of the guide rollers 2a to 2d and runs spaced apart from each other. As a result, the wire parallel guide rollers 51a, 51b suppress vibration of the cutting wire portion 1b in the cutting thickness direction of the workpiece W.

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

[0060] The pair of guide roller holders 55a, 55b are disposed on both sides of the workpiece W in the y-axis direction so as to sandwich the workpiece W therebetween. 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 disposed 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 electronic 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 electronic 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 1b with the cutting wire 1b sandwiched between the nozzle body 7a and the wire parallel guide roller 51a and separated from the cutting wire 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 outlet holes 7c for ejecting the machining fluid 23 filled therein toward the workpiece W in the thin plate machining section 70. The cutting wire section 1b is passed through the machining fluid outlet holes 7c of the variable nozzles 21a and 21b. The variable nozzles 21a and 21b will be described in detail later.

[0068] The machining fluid 23 is stored in a machining fluid tank (not shown), assembled by a machining fluid supply pump (not shown), and sent to the nozzles 7A, 7B along a piping path. 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 in which the machining fluid 23 is stored, 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 limit the movement of the wire electrode 1 in the x-axis direction, and further, the vibration-damping guide rollers 4a, 4b limit 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, it is possible to omit the vibration-damping guide roller 4a and the vibration-damping guide roller 4b.

[0070] The cutting feed stage 10 changes the relative position between the workpiece W and the cutting wire portion 1b. Specifically, the cutting feed stage 10 changes the relative position in the processing direction (z-axis direction) between the cutting wire portion 1b and a workpiece fixing plate 25 to which the workpiece W is fixed and fixedly placed on the oscillating stage 20. As described above, in the first embodiment, the position of the cutting wire portion 1b in the z-axis direction is fixed, and the oscillating 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 away from the cutting wire portion 1b by vertical movement of the cutting feed stage 10. 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 and y-axis directions.

[0072] The oscillating stage 20 changes the relative position between the deflected shape (maximum amplitude part) of the wire electrode 1 stretched between the wire parallel guide rollers 51a, 51b and the workpiece W. 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 portion 1b. In the first embodiment, the stretched position of the cutting wire portion 1b 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 workpiece W in the thin plate processing section 70 in the direction of the wire parallel guide rollers 51a, 51b by moving the thin plate processing section 70 in the left-right direction (direction parallel to the y-axis direction). In the first embodiment, the movement (reciprocating motion) of the oscillating stage 20 in the direction parallel to the y-axis direction is referred to as oscillation.

[0074] By moving the oscillating stage 20 left and right, the wire electric discharge machining apparatus 1000 moves 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 performing intensive electric discharge machining on the thicker parts of the workpiece W to flatten them.

[0075] In electric 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 becomes flat. The oscillating stage 20 may be movable in the x-axis direction and the z-axis direction.

[0076] The machining mechanism 100 may 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 winding speed of the wire electrode 1.

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

[0078] The thin plate processing section 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 section 70 includes a pair of liquid straightening plates 71 (the reference symbol "71" is not shown in Figs. 1 to 3), namely, liquid straightening plate 71a and liquid straightening plate 71b, a workpiece pressing section 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 straightening plates 71a, 71b are fixed to the side surfaces of the workpiece fixing plate 25. The liquid straightening plates 71a, 71b are conductive, are arranged parallel to the traveling direction of the cutting wire 1b, and straighten the flow of the machining liquid 23. The liquid escape prevention plates 22a, 22b, the nozzles 7A, 7B, and the wire parallel guide rollers 51a, 51b may be conductive or insulating.

[0081] The liquid straightening plates 71a and 71b have their front and back surfaces extending in a direction perpendicular to the upper surface of the workpiece fixing plate 25 and the back surfaces of the liquid escape prevention plates 22a and 22b. The liquid straightening plates 71a and 71b are disposed in positions sandwiching the workpiece W in the x-axis direction. That is, the liquid straightening plates 71a and 71b are disposed in positions facing each other with the workpiece W sandwiched between them in the x-axis direction. The liquid straightening plates 71a and 71b are disposed between the liquid escape prevention plates 22a and 22b in the y-axis direction. The liquid straightening plates 71a and 71b have a plate shape (rectangular parallelepiped shape) and are disposed so that the opposing surfaces (surfaces parallel to the yz plane) are parallel to each other.

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

[0083] The liquid rectifying plate 71a is one of a 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 straightening plate 71b is the other of the pair of liquid straightening plates 71, and is disposed parallel to the liquid straightening plate 71a with the workpiece W fixed to the liquid straightening plate 71a sandwiched between the liquid straightening plate 71b and the liquid straightening plate 71a. The liquid straightening plate 71b is in close contact with the workpiece W, and together with the liquid straightening 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 straightening plates 71a and 71b do not change their positions in the x-axis direction, and move in the y-axis direction and z-axis direction while maintaining the distance between them in the x-axis direction.

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

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

[0087] The liquid leakage prevention plates 22a and 22b do not change their positions in the x-axis direction and the z-axis direction, but move in the y-axis direction while maintaining the distance between them in the y-axis direction. When the liquid leakage prevention plate 22a approaches the parallel wire guide roller 51a, the liquid leakage prevention plate 22b moves away from the parallel wire guide roller 51b. When the liquid leakage prevention plate 22b approaches the parallel wire guide roller 51b, the liquid leakage prevention plate 22a moves away from the parallel wire 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 the 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 coincides with the position of the "antinode" of the vibration of the wire electrode 1.

[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 "antinode" 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 "antinode" of the vibration of the wire electrode 1.

[0090] Nozzles 7A and 7B are equipped with variable nozzles 21a and 21b, respectively, which are combinations of multiple tubular (e.g., cylindrical, square, 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 21a and 21b have a variable multi-stage structure in which the lengths of the variable nozzles 21a and 21b in the fluid ejection direction (y-axis direction) are extended and 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 21a and 21b and the wire travel 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. Also, 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. Moreover, the nozzle unit of the variable nozzle 21b closest to the liquid leakage prevention plate 22b is fixed perpendicularly 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 towards 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 the front surface of the fluid escape prevention plate 22b, thereby pressing the thin plate processing section 70 toward the wire parallel guide roller 51a.

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

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

[0100] In this way, 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 when swinging. This pressure generating mechanism is a mechanism that pushes out the variable nozzles 21a, 21b in the direction in which the variable nozzles 21a, 21b extend. The wire electric discharge machining apparatus 1000 pushes out 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] Additionally, 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 manner, 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. As a result, the nozzle unit on the liquid leakage prevention plate 22a side is stored in the nozzle unit on the adjacent wire parallel guide roller 51a side, and the variable nozzle 21a is contracted.

[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, whereby the nozzle unit on the liquid leakage prevention plate 22b side is housed in the nozzle unit on the adjacent wire parallel guide roller 51b side, and the variable nozzle 21b is retracted.

[0104] The variable nozzles 21a and 21b perform extension and contraction movements while being fixed to the liquid leakage prevention plates 22a and 22b, the nozzle bodies 7a and 7b, and the wire parallel guide rollers 51a and 51b. In the variable nozzles 21a and 21b, the tip of the nozzle unit that is assembled on the innermost side among the multiple nozzle units is fixed to the liquid leakage prevention plates 22a and 22b, and expands and contracts due to the swinging movement of the swinging stage 20.

[0105] In this way, during electric discharge cutting, the tips of the nozzle units assembled on the innermost sides of the pair of variable nozzles 21a, 21b arranged on both sides of the workpiece W are pressed against the liquid leakage prevention plates 22a, 22b by the telescopic mechanism. During electric discharge cutting, the machining liquid 23 is supplied between the liquid straightening plates 71a, 71b while the variable nozzles 21a, 21b are maintained fixed to the liquid leakage prevention plates 22a, 22b even while the thin plate machining part 70 is repeatedly swinging toward and away from the nozzle bodies 7a, 7b.

[0106] The variable nozzles 21a, 21b are installed in close contact with the liquid leakage prevention plates 22a, 22b so that the machining fluid ejection holes 7c of the nozzle units arranged at the innermost side of the variable nozzles 21a, 21b and the openings provided in the liquid leakage prevention plates 22a, 22b are coaxial with each other. 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 the liquid straightening plates 71a, 71b and the side surfaces in the y-axis direction.

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

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

[0109] In this manner, in the thin plate processing section 70, a pair of liquid straightening plates 71a, 71b, a workpiece pressing section 72, a workpiece fixing plate 25, and a pair of liquid escape prevention plates 22a, 22b are arranged in close contact with each other to form a chamber. Then, the workpiece W is placed in this chamber, and the workpiece W is subjected to electric discharge cutting processing in 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 machining fluid 23 that fills the chamber has no outlet to the outside except through a notch provided on 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 in a static pressure state, and machining fluid 23 is supplied to the inside of even a narrow machining groove.

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

[0112] When the workpiece W is a material for a semiconductor wafer, the workpiece W is often formed in advance into a cylindrical shape so that the thin plate cut by electric discharge cutting will be a circular thin plate. In this case as well, 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 a thin plate, a wafer, is machined from the workpiece W.

[0113] A specific voltage value is applied to the electrode gap, which is the gap between the cutting wire portion 1b and the workpiece W. When the electrode gap reaches a specific range of values, a discharge occurs between the electrodes, causing the cutting wire portion 1b to heat up and the workpiece W to melt. As a result, multiple plate-shaped members are cut out all at once.

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

[0115] The workpiece holder 72 collectively fixes the 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, and is positioned above the workpiece W. When the cutting of the workpiece W progresses to a specific distance in the Z-axis direction, the workpiece holder 72 descends to the upper part of the workpiece W and contacts the workpiece W to hold down the multiple thin plates. In this way, the workpiece holder 72 suppresses the shaking of the thin plates due to the vibration of the workpiece W generated by the hydraulic pressure of the hydraulic fluid 23 flow that is received by the cut surfaces of the multiple thin plates.

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

[0117] The sliding state of the liquid escape prevention plates 22a, 22b and the liquid straightening plates 71a, 71b is maintained from before the start of processing to the end of processing. Therefore, if the length of the liquid escape prevention plates 22a, 22b in the processing 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 by the liquid straightening plates 71a, 71b will be opened on the liquid escape prevention plates 22a, 22b during processing, and the processing liquid 23 will leak out. To prevent this state, the liquid escape prevention plates 22a, 22b are formed to be sufficiently longer than the length of the side surface of the liquid straightening plates 71a, 71b in the z-axis direction. Specifically, the length of the liquid escape prevention plates 22a, 22b in the z-axis direction is more than twice the length of the workpiece W in the processing direction (z-axis direction). In other words, the length of the liquid escape prevention plates 22a, 22b in the z-axis direction is more than 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 shows a schematic cross-sectional view of the workpiece W cut in the xz plane.

[0119] In the wire electric discharge machining apparatus 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 relative moving direction of the cutting wire 1b with respect to the workpiece W is the machining moving direction (the minus z direction in FIG. 5).

[0120] The cutting wire portion 1b has a cylindrical wire electrode 1, and processes the workpiece W with this cylindrical wire electrode 1. Therefore, the cutting wire portion 1b continues to process the workpiece W while also processing 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 Fig. 5 is the processing surface. In other words, the processing surface of the workpiece W includes the bottom surface SB of the processing 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 out 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 out by the impact force of the discharge is the opposite direction to the direction of the machining surface of the workpiece W (opposite the machining progress direction). In other words, the wire electrode 1 is pushed out 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 repulsive force.

[0122] Of the deflections of the wire electrode 1, the deflection in the x-axis direction has a large 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 locations of the wire electrode 1 with large deflection at various positions in the y-axis direction of the workpiece W.

[0123] 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 oscillates the oscillating stage. Fig. 6 shows a cross-sectional view of the thin plate machining unit 70 and the like cut along a plane parallel to the yz plane. Note that Fig. 6 omits illustration of the liquid straightening plates 71a and 71b, the workpiece holder 72, and the cutting feed stage 10 of the thin plate machining unit 70.

[0124] In Fig. 6, the liquid leakage prevention plates 22a and 22b when the oscillating stage 20 is moving in the plus y direction are illustrated as liquid leakage prevention plates 22A2 and 22B2. Also, in Fig. 6, the liquid leakage prevention plates 22a and 22b when the oscillating stage 20 is moving in the minus y direction are illustrated 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. As a result, the nozzle unit on the liquid leakage prevention plate 22A1 side is stored in the nozzle unit on the adjacent wire parallel guide roller 51a side, and the variable nozzle 21a is retracted.

[0126] For example, a case will be described in which the nozzle unit of the variable nozzle 21a includes a first nozzle unit fixed to the front surface of the liquid escape 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 swing stage 20 moves to the wire parallel guide roller 51a side, the first nozzle unit is pushed back to the wire parallel guide roller 51a side by the liquid escape prevention plate 22a. Also, the second nozzle unit is pushed back to the wire parallel guide roller 51a side by the first nozzle unit, and the third nozzle unit is pushed back to the wire parallel guide roller 51a side by the second nozzle unit. As a result, the variable nozzle 21a is contracted to the wire parallel guide roller 51a side while being fixed to the liquid escape prevention plate 22a.

[0127] Similarly, when the oscillating stage 20 moves in the plus 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 stored in the nozzle unit on the adjacent wire parallel guide roller 51b side, and is contracted toward the wire parallel guide roller 51b.

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

[0129] The electrode gap monitoring unit 400 monitors the pulse current applied by the machining power supply 5 to the electrode gap, which is the gap between the cutting wire portion 1b and the workpiece W, to determine the discharge state (electric discharge machining status). 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 a 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 electrodes 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 electrodes 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 any one of an appropriate discharge state (appropriate discharge state), an open state (tending toward open), and a short state (tending toward short circuit).

[0133] The control unit 300 controls the entire wire electric discharge machining apparatus 1000 based on the gap state information ps transmitted from the discharge state determination device 42 of the 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 oscillation 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 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] Further, based on the 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 processing 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 processing 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 processing 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 in the y-axis direction of the oscillating stage 20. 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 a discharge waveform command wc from the machining control device 31. The discharge waveform control device 32 controls the machining power supply 5 based on the discharge waveform command wc, thereby controlling the voltage waveform applied to the machining gap or the current waveform flowing in the machining gap.

[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 drives and controls the bobbin rotation control devices 8a and 8b based on the wire electrode travel command rc, thereby controlling the travel of the wire electrode 1. The wire travel control device 35 also drives and controls the traverse control devices 9a and 9b based on the wire electrode travel command rc, thereby executing 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 according to 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 according to 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 controller 33 receives an oscillating stage command scS from the processing controller 31. The oscillating stage controller 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 apparatus 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 gap between the wire electrode 1 and the workpiece W, and the current supplied to the 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 discharge state of the gap 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 (movement speed of reciprocating movement in the y-axis direction) to a value faster than the current value. For example, the machining control device 31 transmits a command to the discharge waveform control device 32 to increase the pulse oscillation frequency setting from the current value. In addition, the machining control device 31 transmits 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. In addition, the machining control device 31 transmits 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). The 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 has accumulated 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 to the machining control device 31 electrode state information ps indicating that the discharge state between the electrodes is a short-circuit state.

[0148] When the machining control device 31 receives the gap state information ps indicating that the gap discharge state is 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 transmits 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 transmits 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 gap, since the gap is too close. In addition, the machining control device 31 transmits 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 transmits 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 formation of the machined groove in the width direction (x-axis direction) by the wire electrode 1 progresses sufficiently, 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 transmits 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 becomes the outer peripheral region of the workpiece W. In other words, when the discharge state is an open state, the machining control device 31 transmits a command to the oscillating stage control device 33 to increase the oscillation width.

[0150] The oscillation width is half the moving distance in the reciprocating movement. Therefore, the range of the reciprocating movement by the oscillating stage 20 in 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, when 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 transmits 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 becomes the central region of the workpiece W. In other words, when the discharge state is a short-circuit state, the machining control device 31 transmits 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 discharge state between the electrodes 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 waste is accumulated between the wire electrode 1 and the workpiece W. When the discharge state between the electrodes is an appropriate discharge state, the discharge state determination device 42 transmits to the machining control device 31 electrode state information ps indicating that the discharge state between the electrodes is an appropriate discharge state.

[0153] When the machining control device 31 receives electrode gap state information ps indicating that the electrode gap discharge state is an appropriate discharge state, it does not output any command to any of the discharge waveform control device 32, the cutting stage control device 34, and the oscillation 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 machining fluid 23. The control unit 300 controls the flow rate of machining fluid 23 based on the discharge state between the electrodes, for example. When the discharge state is an open state, the control unit 300 controls the inverter to reduce the flow rate of 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 machining fluid 23.

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

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

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

[0158] Wire electric discharge machining apparatus 1000 manufactures a wafer from 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 device without a swinging stage performs electric discharge cutting. The upper part of Fig. 9 shows a schematic diagram of the shape of the machined groove of the workpiece W when viewed from the z-axis direction (the state of cutting 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 a 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] In the cutting wire section 1b where a plurality of wire electrodes 1 running in parallel are stretched between a pair of wire parallel guide rollers 51a and 51b, the wire electrodes 1 vibrate with the uppermost position in the z-axis direction of the wire guide grooves 56a and 56b provided in the wire parallel guide rollers 51a and 51b as a "node". In FIG. 9, the position of the "node" of the vibration of the wire electrode 1 in the xy plane is shown as node N1.

[0162] In the workpiece W, the machining fluid 23 supplied from nozzles 7A and 7B (not shown in FIG. 9) installed on both end sides in the y-axis direction of the workpiece W collides 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 shown as antinode B1. Thus, in the vicinity of antinode B1, since the machining fluid 23 collides, the wire electrode 1 is more likely to be affected by the machining fluid 23. The antinode B1 of the vibration of the wire electrode 1 is at the central part of the workpiece W in the y-axis direction. At the antinode B1 of the vibration of the wire electrode 1, the wire electrode 1 swings more greatly in the x-axis direction than at node N1.

[0163] FIG. 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 the end portions Le and Re in the y-axis direction of the thin plate Wa is L1 (<L2). Due to these differences in displacement, in the thin plate Wa, a difference in plate thickness occurs between the central region and the outer peripheral region.

[0164] Moreover, in the vicinity of the antinode B1 of the vibration of the wire electrode 1, since the inflow amount of the machining fluid 23 containing machining chips increases, the concentration of the machining chips tends to be high, and secondary discharges to the machining chips are likely to occur. Due to this secondary discharge, the workpiece W is machined more in the x-axis direction at antinode B1 than near 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 position of the workpiece W in the positive y direction moves away from the central axis of the workpiece W, and decreases as the position of the workpiece W in the negative y direction moves away from the central axis of the workpiece W. That is, the width of the machined groove in the workpiece W increases as the position of the workpiece W moves from the outside of the workpiece W in 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 end of the workpiece W in the y-axis direction. For example, at the machining position of the workpiece W that passes through the central axis, the thickness at the central axis is the thinnest, and becomes thicker toward the outer 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 the wire electric discharge machining apparatus according to the first embodiment performs electric discharge cutting. In Fig. 10, a workpiece that is not oscillating is shown as workpiece W, and a workpiece that has been moved in the y-axis direction by oscillation is shown as workpiece WX. Note that in Fig. 10, the workpiece W when the wire electric discharge machining apparatus 1000 moves the workpiece W in the negative y direction is shown as workpiece WX, but when oscillating, the wire electric discharge machining apparatus 1000 also moves the workpiece W in the positive y direction.

[0168] The upper part of Fig. 10 shows a schematic diagram of the shape of the machined grooves of the workpieces W, WX when the workpiece WX is viewed from the z-axis direction (the state of cutting 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 those in Fig. 9 are given the same reference numerals, and duplicated 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 changes the position of the workpiece W facing the wire electrode 1, and moves the workpiece W, for example, to a position indicated by workpiece WX.

[0170] Such movement of the workpiece W changes 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 oscillation, so that various positions of the workpiece W are machined by the antinode B1.

[0171] Figure 10 shows the 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 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 maximum at 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. This results in 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, being 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 the wire electric discharge machining apparatus 1000 performing electric discharge cutting while oscillating the workpiece W in the y-axis direction, the situation in which the machined groove enlarges only near the center of the workpiece W as shown in Fig. 9 is alleviated, and the variation in plate thickness of the machined thin plate Wa is improved. In other words, by the wire electric discharge machining apparatus 1000 oscillating the workpiece W in the y-axis direction, 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] Moreover, the wire electric discharge machining apparatus 1000 continuously supplies machining liquid 23, such as deionized water, to the gap where the discharge pulse is generated. This allows the wire electric discharge machining apparatus 1000 to discharge machining waste generated by the discharge from the gap by the machining liquid 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 by the machining liquid 23, thereby preventing the wire electrode 1 from melting.

[0176] In particular, when machining a thick plate having a long cutting length (machining length in the y-axis direction), the wire electric discharge machining apparatus 1000 can efficiently supply machining fluid 23 to the gap between the electrodes inside the machining groove by bringing the variable nozzles 21a, 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 with a wire electrode stretched in the vertical direction. In the comparative apparatus, an upper nozzle arranged above the workpiece and a lower nozzle arranged below the workpiece spray machining fluid at the machining position on the workpiece by the wire electrode. Also, a cylindrical upper leakage prevention member is arranged on the outside of the upper nozzle to prevent machining fluid from leaking out from the upper surface side of the workpiece, and a cylindrical lower leakage prevention member is arranged on the outside of the lower nozzle to prevent machining fluid from leaking out from the lower surface side of the workpiece.

[0178] The upper leakage prevention member contacts the upper surface of the workpiece due to its own weight, etc., and fills 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 the compression spring, and fills the gap between the lower leakage prevention member and the lower surface of the workpiece. As a result, the comparative example device moves the upper nozzle and the lower nozzle up and down freely to be in constant contact with the workpiece even if the workpiece moves up and down. With this configuration, the comparative example device can prevent liquid leakage, but the vibration of the wire electrode makes it impossible to cut out wafers of uniform thickness.

[0179] The electric discharge machining device described in Patent Document 1 (hereinafter referred to as the thin plate electrode machining device) performs electric discharge machining using a thin plate electrode that is wide in the machining direction. The thin plate electrode machining device uses a thin plate electrode that is not easily melted 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 electric discharge machining while moving the thin plate electrode in the machining direction (downward). In the thin plate electrode machining device, the short side direction of the thin plate electrode is the machining direction. The thin plate electrode machining device performs machining in the short side direction while reciprocating the thin plate electrode in the longitudinal 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, unlike the wire electric discharge machining device 1000 of the first embodiment.

[0182] This thin plate electrode machining device moves the thin plate electrode instead of the wire electrode, but it cannot run the wire electrode 1 as in the wire electric discharge machining device 1000, and cannot continuously supply new thin plate electrodes, so the thin plate electrode is worn out by the electric discharge machining. For this reason, the portion of the thin plate electrode used in the electric discharge machining locally reduces in width in the short direction, and if the portion that holds 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 gradually non-uniform as the processing progresses, causing the thin plate electrode to warp or to develop cracks in the portions where the width is reduced. For this reason, it is particularly difficult for the thin plate electrode processing device to cut and process a columnar ingot with a large diameter.

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

[0185] In addition, the thin plate electrode machining device supplies machining fluid to the machining position from a nozzle installed above the thin plate electrode. Therefore, when cutting a columnar 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 machining fluid to the machining position that is far from the machining start position.

[0186] In order for the thin plate electrode machining device of this configuration to supply the machining fluid to the inside of the machining groove of the workpiece during cutting, it is necessary to increase the machining fluid pressure or the machining fluid flow rate, but such an increase in the machining fluid pressure or the machining fluid flow rate becomes an external force that causes the thin plate electrode to bend. As a result, in the thin plate electrode machining device, the thin plate electrode comes into contact with the wafer surface, which makes it easy for a short circuit to occur, making it difficult to increase the speed of the electric discharge machining and deteriorating the machining accuracy. Therefore, it is difficult for the thin plate electrode machining device to cut multiple wafers, especially wafers with a large diameter, at the same time.

[0187] Here, we will explain the configuration of combining the thin plate electrode machining device with the upper leakage prevention member of the comparative device in order 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 being 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 ejected from the upper and lower nozzles leaks out to the surroundings, and the pressure loss of the machining fluid in the machining groove cannot be prevented. 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, the combined device, which is a combination of the thin plate electrode machining device and the comparative device, cannot force the machining fluid supplied to the machining position in the frame structure into the machining groove formed in the workpiece. In addition, the upper and lower leakage prevention members of the comparative device are not strong enough to prevent leakage of the machining fluid under high hydraulic pressure.

[0190] In this way, when the combined device performs electric 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 an area of ​​the workpiece where the cutting length is short, the hydraulic pressure is insufficient, making it difficult to make the machining fluid flow into the inside of the workpiece. The area of ​​the workpiece where the cutting length is short is near the cutting start position (top of the cylinder) and near the cutting end position (bottom of the cylinder) when cutting out a disk-shaped member from a cylinder.

[0191] For example, when the workpiece W is a cylindrical ingot and a wafer is cut from the cylindrical ingot, there are some areas where the cutting length by the thin plate electrode is long and some areas where it is short. Therefore, the cutting length varies continuously depending on the processing position from the start of processing. In this way, when a wafer is cut from a cylindrical ingot, it is difficult for the combined device to discharge the processing waste and cool the thin plate electrode heated by the discharge energy, and it is difficult to finish the wafer flat. Therefore, the combined device cannot reduce the shape variation such as the thickness and warpage 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 structured to be pressed against the workpiece by using its own weight. Therefore, even if it is installed in a position parallel to the running direction of the wire electrodes 1 that run in parallel horizontally, as in wire electric discharge machining apparatus 1000 of embodiment 1, it cannot press against the workpiece.

[0193] In addition, in a mechanism with one movable nozzle in a nozzle, such as the comparative example device, it is possible to handle a case where the oscillation width of the workpiece is small, 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 against it. In addition, 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 oscillation control of the discharge pulse, feed speed control in the machining direction, and oscillation control 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 21a, 21b, 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 collectively electric discharge cut from the workpiece W.

[0196] Embodiment 2 Next, a description will be given of embodiment 2. In embodiment 2, wire electric discharge machining apparatus 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 for adjusting a set value, based on the gap state information ps received from the gap monitoring unit 400. The setting adjustment command is a command for 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 apparatus 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 traveling direction (y-axis direction) by the oscillating stage control device 33.

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

[0200] When the electrode gap monitoring unit 400 judges that the discharge state of the electrode gap is a short circuit state, the machining control device 31 judges whether the short circuit is in the machining direction or in the oscillation direction. When the short circuit is eliminated by adjusting the oscillation, the machining control device 31 judges that the short circuit is in the oscillation direction, and when the short circuit is not eliminated even after adjusting the oscillation, the machining control device 31 judges that the short circuit is in the machining direction.

[0201] Specifically, when the machining control device 31 receives the gap state information ps indicating that the discharge state of the gap is a short-circuit state, it transmits a setting adjustment command to the oscillating stage control device 33 to determine whether or not there is a short circuit in the oscillation direction. In this case, the setting adjustment command transmitted to the oscillating stage control device 33 includes a command to set the oscillation speed to a 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 of the gap is a short-circuit state even after the oscillation speed or oscillation width is reduced, 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] When the oscillating stage control device 33 receives the setting adjustment command, it changes the oscillation speed or oscillation width to a smaller value in order to eliminate the short-circuit state. While the oscillating stage control device 33 receives the setting adjustment command, it repeats the process of further reducing the oscillation speed or oscillation width. For example, the oscillating stage control device 33 temporarily stops the reciprocating feed operation of the workpiece W by the oscillating stage 20 to wait for the short circuit recovery between the electrodes, or sets the oscillation width to several tens of μm to about half the diameter of the wire electrode 1 and makes the oscillation speed as fast as possible. As a result, the oscillating stage control device 33 oscillates the machining liquid 23 in the machining groove, eliminates the retention of machining chips between the electrodes, and promotes the discharge of machining chips to the outside of the machining groove. In this way, the control unit 300 adjusts the moving speed or moving width of the workpiece W reciprocating according to 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 oscillating 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. In addition, the processing control device 31 transmits a setting adjustment command to the oscillating 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 over 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] The oscillating stage control device 33 may reciprocate the workpiece W by reciprocating the oscillating stage 20 over a width shorter than the cutting length of the workpiece W or over a width longer than the cutting length.

[0207] In this way, when the discharge state of the gap is a short-circuit state, wire electric discharge machining apparatus 1000 inserts a process of discharging machining waste from the gap. The process of discharging machining waste from the gap is any one of the following steps P1 to P4. (P1) Decrease the oscillation speed (P2) Stop the rocking (P3) Decrease the oscillation width and increase the oscillation speed (P4) Pause the processing 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 the presence or absence of a short circuit. In other words, when machining the central portion in the z-axis direction of the workpiece W (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 cut length of the workpiece W is approximately the same length as the diameter may be a region where the ratio of the cut length to the diameter is higher than a specific value, or a region where the difference between the diameter and the cut length is smaller than a specific value.

[0210] Furthermore, if the short circuit condition is not resolved satisfactorily, the wire electric discharge machining apparatus 1000 prevents the wire electrode 1 from breaking 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 condition information ps indicating the short circuit condition 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 the wire electrode 1 from breaking.

[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 travel 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 1 / 2 or less of the machining feed speed.

[0212] The machining control device 31 may also 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 to set the maximum oscillation width to 1 / 2 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 by 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 gap is in an open state, and the machining control device 31 continues to receive 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 oscillation stage control device 33, for example, in which the maximum oscillation width is set to 1 / 2 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 apparatus 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 oscillation control of the traveling direction of the wire electrode 1 based on the discharge state, thereby making it possible to perform electric discharge cutting machining while correcting variations in the thickness of a thin plate.

[0216] Furthermore, when the discharge state is a short circuit state, wire electric discharge machining apparatus 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 state is not resolved for a specific period of time, the wire electric discharge machining apparatus 1000 stops the oscillation of 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 promotes the discharge of machining waste from the gap during a short circuit by controlling the oscillation in response to the discharge state between the electrodes, 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 by controlling the oscillation 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, warping, and other shapes of the cut thin plate.

[0219] Embodiment 3 Next, a description will be given of embodiment 3. In embodiment 3, 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 peripheral end face (end in the z-axis direction) of the workpiece W is taken 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 electric discharge cutting is smallest at the machining start position and machining end position and is 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 passing 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 electric discharge machining device 1000 can improve machining efficiency by changing the oscillation conditions between machining in an area of ​​the workpiece W where the cut length is approximately the same length as the diameter (the center of the workpiece W in the z-axis direction) and machining in an area close to the machining start position or machining end position of the workpiece W (the end of the workpiece W in the z-axis direction).

[0222] For example, 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 larger than that at the start of machining. For example, the wire electric discharge machining apparatus 1000 sets the maximum oscillation width to 1 / 2 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 negative y direction to 1 / 2 the cutting length of the workpiece W and the oscillation width in the positive y direction to 1 / 2 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 apparatus 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. For this reason, if a short circuit occurs, the wire electric discharge machining apparatus 1000 slows down the oscillation speed or reduces the oscillation width.

[0224] Furthermore, the cut length of the workpiece W is smaller in the 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 cut 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] Furthermore, the processing control device 31 may 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). Furthermore, the processing control device 31 may 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 machining control device 31 determines that machining in the direction parallel to the xy plane is sufficient because less current flows in the wire electrode 1 in the direction parallel to the xy plane, and increases the machining speed. On the other hand, in the short-circuit state, the machining control device 31 determines that a lot of machining waste has accumulated in the machined groove because more current flows in the direction parallel to the xy plane of the wire electrode 1, and decreases the machining speed.

[0228] The machining control device 31 calculates the machining speed based on the gap state information ps in order to generate the oscillation stage command scS. The machining control device 31 calculates the ratio of the machining speed to the pulse oscillation frequency, and when this ratio becomes lower than a specific value, it determines that a short-circuit state occurs in which discharge is not effectively generated 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 oscillation control to discharge the machining debris from the gap or to correct the shape of the machined surface due to the 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 oscillation 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 or not a short circuit state exists 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 exists when the ratio of the machining speed to the pulse oscillation frequency becomes lower than a specific value set for each cutting length. The machining control device 31 may adjust the discharge frequency according to the machining speed.

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

[0231] Moreover, since wire electric discharge machining apparatus 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 machine a thin plate while correcting variations in plate thickness.

[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 a memory, or may be dedicated hardware.

[0233] FIG. 11 is a diagram showing a configuration example of a processing circuit in the case where the processing circuit included in the control unit according to the first to third embodiments is realized by a processor and a memory. The processing circuit 90 shown 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 described 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 a memory 92 for storing a control program that results in the processing of the control unit 300 being executed. This control program can also be said to be a program for causing 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 may be provided by other means such as a communication medium.

[0234] The control program can 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 CPU (Central Processing Unit), a processing device, an arithmetic device, a microprocessor, a microcomputer, or a DSP (Digital Signal Processor). The memory 92 is, for example, a non-volatile or volatile semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), a flash memory, an EPROM (Erasable Programmable ROM), or an EEPROM (Electrically EPROM), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD (Digital Versatile Disc).

[0235] Fig. 12 is a diagram showing 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 shown 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 of these. The processing circuit 93 may be partially realized with dedicated hardware and partially realized with software or firmware. In this way, the processing circuit 93 can realize each of the above-mentioned functions by dedicated hardware, software, firmware, or a combination of these.

[0236] The configurations shown in the above embodiments are merely examples, and may be combined with other known technologies, or the embodiments may be combined with each other. Also, parts of the configurations may be omitted or modified without departing from the spirit of the invention. [Explanation of symbols]

[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 source, 6a, 6b power 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 fluid escape 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 section, 71, 71a, 71b fluid straightening plate, 72 workpiece holder, 90, 93 processing circuit, 91 processor, 92 memory, 100 machining mechanism section, 200 power supply section, 300 control section, 400 electrode gap monitoring section, 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 electrode that cuts multiple plate-shaped members from a workpiece immersed in a processing fluid by electrical discharge machining, A rocking stage that reciprocates the workpiece in the wire travel direction, which is the direction in which the wire electrode is unwound and wound up, An electrode monitoring unit that determines the discharge state between electrodes based on the pulse current value of the current applied between the workpiece and the wire electrode, A control unit that controls the reciprocating movement of the workpiece based on the determination result of the determination by the pole-to-pole monitoring unit, Equipped with, The control unit controls the oscillating stage to control the position of the workpiece in the wire travel direction with respect to the position of the deflection shape in the primary vibration mode of the wire electrode stretched between the guide rollers. A wire electrical discharge machining apparatus characterized by the following features.

2. A thin sheet processing section for storing the workpiece and immersing it in the processing liquid, The nozzle through which the wire electrode passes and which is in close contact with the thin sheet processing section perpendicular to the wire travel direction, sprays the processing fluid from outside the thin sheet processing section into the thin sheet processing section, thereby spraying the processing fluid at the processing position of the workpiece. Furthermore, The rocking stage moves the thin plate processing section back and forth in the wire travel direction, thereby moving the workpiece back and forth in the wire travel direction. The nozzle has a variable nozzle that expands and contracts in the wire travel direction as the thin sheet processing section moves, thereby maintaining close contact with the thin sheet processing section while ejecting the processing fluid. The wire electrical discharge machining apparatus according to feature 1.

3. The wire travel direction and the extension / retraction direction of the variable nozzle are horizontal. The aforementioned variable nozzle is When the thin sheet processing section approaches the nozzle, it is shortened while being pressed by the thin sheet processing section. When the thin sheet processing section separates from the nozzle, the variable nozzle is pushed out, causing it to press against the thin sheet processing section and extend. The wire electrical discharge machining apparatus according to feature 2.

4. The aforementioned thin sheet processing section is A workpiece fixing plate on which the workpiece is fixedly placed on the upper surface and which is moved back and forth in the wire travel direction by the rocking stage, A pair of first plate-shaped members, the front and back surfaces of which extend in a direction perpendicular to the wire running direction and sandwich the workpiece, A pair of second plate-shaped members, the front and back surfaces of which extend perpendicularly to the workpiece fixing plate and the first plate-shaped member, and which sandwich the workpiece, It has, The first plate-shaped member has the wire electrode passed through it in the wire travel direction and moves back and forth in the wire travel direction together with the workpiece fixing plate. The second plate-shaped member moves back and forth in the wire travel direction together with the workpiece fixing plate, and moves up and down together with the workpiece fixing plate when the workpiece fixing plate moves up and down. The wire electrical discharge machining apparatus according to feature 2 or 3.

5. The control unit adjusts the distance the oscillating stage moves in the wire travel direction according to the length of the cutting of the workpiece by the wire electrode in the wire travel direction. The wire electrical discharge machining apparatus according to feature 1.

6. The control unit adjusts the reciprocating speed of the workpiece according to the feed rate of the wire electrode in the machining direction. The wire electrical discharge machining apparatus according to feature 1.

7. If the determination result indicates a short circuit between the poles, the control unit reduces the movement speed to a speed slower than the feed speed. The wire electrical discharge machining apparatus according to feature 6.

8. The workpiece is cylindrical in shape. The wire electrode is made by cutting a disc-shaped member from the workpiece. The control unit controls the reciprocating movement of the workpiece by temporarily pausing or slowing down the feed of the wire electrode when the processing position of the workpiece by the wire electrode corresponds to the diameter of the workpiece. The wire electrical discharge machining apparatus according to feature 6.

9. The control unit moves the oscillating stage back and forth within a distance equal to the diameter of the workpiece. The wire electrical discharge machining apparatus according to feature 8.

10. The control unit calculates the ratio of the feed rate to the pulse oscillation frequency in the electrical discharge machining, and when the calculated ratio falls below a specific value, it moves the oscillating stage back and forth. The wire electrical discharge machining apparatus according to feature 6.

11. A wire electrical discharge machining apparatus that cuts out multiple plate-shaped members from a workpiece immersed in a processing fluid by electrical discharge machining using a wire electrode includes a discharge state determination step that determines the discharge state between the electrodes based on the pulse current value of the current applied between the workpiece and the wire electrode, The wire electrical discharge machining apparatus controls a rocking stage that reciprocates the workpiece in the wire travel direction, which is the direction in which the wire electrode is fed out and wound up, based on the determination result of the determination, thereby controlling the workpiece to reciprocate in the wire travel direction, Includes, In the control step, the wire electrical discharge machining apparatus controls the oscillating stage to control the position of the workpiece in the wire travel direction with respect to the position of the deflection shape in the primary vibration mode of the wire electrode stretched between the guide rollers. A wire electrical discharge machining method characterized by the following features.

12. In the control step, the wire electrical discharge machining apparatus adjusts the reciprocating speed of the workpiece according to the feed rate of the wire electrode in the machining direction. The wire electrical discharge machining method according to feature 11.

13. A wire electrical discharge machining method according to claim 11 or 12, wherein multiple wafers are simultaneously cut from the workpiece. A method for manufacturing wafers characterized by the following:

14. The workpiece is a semiconductor ingot, The aforementioned wafer is a semiconductor wafer. The method for manufacturing a wafer according to claim 13, characterized in that it is a wafer manufacturing method.

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