JP2010207988A - Wire electric discharge machining device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent wire from breaking in a wire electric discharge machining device. <P>SOLUTION: In the electric discharge machining device, the workpiece is machined by discharging between the wire and the workpiece simultaneously at a plurality of positions of the wires while feeding the wire. The electric discharge machining device alternately performs an electric discharge machining movement which feeds the wire only by a first length X having wire traveling on at least one circumference of guide roller set while supplying an electric discharge machining power to the wire, and a preliminary feeding movement which lowers a supply power than the electric discharge power and feeds the wire only by a second length Y subtracting the first length from the total length of the length having the wire traveling on the guide roller set by the number of times of winding of the wire and the machining length of a workpiece in the wire feed direction. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a structure of a wire electric discharge machining apparatus.

  Conventionally, a wire saw using abrasive grains is known as a cutting means in the case of cutting a wafer from a cylindrical ingot such as silicon. In this wire saw, a cutting wire wound between a plurality of guide rollers is driven at a high speed in the longitudinal direction, and the workpiece is cut and fed to the wire, thereby simultaneously cutting a large number of thin pieces from the workpiece. is there.

  However, in such a wire saw, it is necessary to simultaneously supply a processing liquid (slurry) mixed with processing abrasive grains to a plurality of cutting wire portions formed between guide rollers, and handling thereof is not easy. . Moreover, in order to suppress the disconnection due to the direct contact of the wire with the workpiece, it is necessary to use a relatively thick wire, and there is a problem that a cutting work cost increases. Furthermore, the conventional wire saw sometimes takes a long time to cut out a wafer from an ingot, and the need for shortening the processing time is increasing.

  On the other hand, in recent years, silicon carbide has attracted attention as a semiconductor material. However, since this silicon carbide is a hard material, the conventional wire saw has a problem that it takes more time than cutting a silicon ingot.

  For this reason, as means for efficiently cutting a hard material workpiece having electrical conductivity, a voltage is intermittently applied between the workpiece and the wire, and the workpiece is cut by each cutting wire portion on the principle of electric discharge machining. The type | formula wire saw is proposed (for example, refer patent document 1).

  The electric discharge type wire saw described in Patent Document 1 forms two to three cutting wire portions for one wire by winding a plurality of wires between guide rollers two to three times, respectively. The workpiece is cut and fed to the cutting wire portion, and a contact is brought into contact with each cutting wire portion to apply a voltage. This discharge type wire saw uses a plurality of wires in order to cut many wafers at once, and there is a problem that the apparatus becomes complicated.

  In view of this, a wire electric discharge machining apparatus has been proposed in which the number of windings of the wire is increased so that a large number of cutting wire portions are formed with a single wire, and the structure is simplified (see, for example, Patent Documents 2 and 3). .

Japanese Patent Laid-Open No. 9-248719 JP 2000-94221 A JP 2006-75952 A

  The wire electric discharge machining apparatus intermittently applies a voltage to the wire and the workpiece, intermittently generates electric discharge between the wire and the workpiece, and processes the workpiece with the heat. For this reason, crater-like depressions and conical hole discharge marks are formed on the wire surface by the discharge, and the periphery of the discharge marks is hardened by the temperature rise due to the discharge. And whenever a wire discharges between workpiece | work, a discharge trace will increase, a thermosetting part will increase, and tensile strength will fall.

  However, in the conventional wire electric discharge machine described in Patent Documents 2 and 3, since one wire is wound around the guide roller many times, the wire supplied to the wire electric discharge machine is wound. It passes between the workpieces for the number of times and discharges with the workpiece. The wire near the supply side has not yet been discharged with the workpiece, and its tensile strength is high, but it is generated on the wire surface as it passes through the workpiece and accumulates discharge with the workpiece. The tensile strength gradually decreases due to discharge marks and heat curing.

  On the other hand, in the wire electric discharge machining apparatus, a predetermined tension is applied to the wire in order to reduce the runout of the wire during the electric discharge machining and to reduce the cutting machining allowance. For this reason, if the tensile strength of the wire decreases due to discharge traces or thermosetting, and the wire cannot withstand a predetermined tension applied to the wire, the wire may break.

  In a wire electric discharge machine, wire breakage during machining is a major problem. The reason is that it is necessary to rewind the wire around a plurality of guide rollers, so that a processing time loss occurs. In particular, in the case of an apparatus as described in Patent Document 2 or 3, there is only one wire. There is a problem that it is necessary to wind the wire many times, and it takes a long time for the recovery, resulting in a large reduction in productivity.

  In addition, when rewinding the wire after the wire breaks, it is necessary to return the workpiece to the original position. Therefore, the position of the workpiece is shifted during reworking, and there is often a step on the cut surface of the workpiece. There was a problem that the quality deteriorated.

  An object of this invention is to suppress the disconnection of a wire in a wire electric discharge machining apparatus.

  A wire electric discharge machining apparatus according to the present invention includes a guide roller set including a plurality of guide rollers arranged at intervals, and a wire wound around the guide roller set a plurality of times at intervals in the longitudinal direction of each guide roller. And a wire feed mechanism for feeding the wire in the winding direction, a power source for supplying power to the wire, and a controller for increasing / decreasing the wire feed speed and power supply power, at a plurality of positions of the wire while feeding the wire A wire electric discharge machining apparatus for machining a workpiece by simultaneously performing electric discharge between the workpiece and the control unit, wherein the control unit supplies an electric discharge machining power to the wire while only the first length that the wire makes at least one round of the guide roller set. The electric discharge machining operation for feeding the wire, the supply power is made lower than the electric discharge machining power, the length that the wire wraps around the guide roller set and the wire feed direction along the wire feed direction. Be carried out with air feeding operation to send the second by a length wires from the total length of the working length of the click minus a first length, it is alternately characterized.

  In the wire electric discharge machining apparatus according to the present invention, the control unit preferably includes a wire feed speed changing unit that makes the wire feed speed during the idle feed operation faster than the wire feed speed during the electric discharge machining operation. And a wire tension changing means that includes a wire tension applying mechanism that applies tension to the wire, and the control unit lowers the tension applied to the wire during the idle feeding operation to be lower than the tension applied to the wire during the electric discharge machining operation. The control unit lowers the tension applied to the wire by the wire tension changing means when starting the idle feeding operation, and then increases the wire feeding speed by the wire feeding speed changing means. A workpiece feeding mechanism that moves the workpiece in a direction crossing the wire feeding direction, and the control unit feeds the workpiece during the idle feeding operation. Providing the work feeding speed changing means slower than the feed rate of the workpiece during the electrical discharge machining operation speed, it is also preferable.

  The present invention has an effect that wire breakage can be suppressed in a wire electric discharge machining apparatus.

It is a systematic diagram which shows the structure of the wire electric discharge machining apparatus in embodiment of this invention. It is a perspective view which shows the cutting | disconnection of the workpiece | work of the wire electric discharge machining apparatus in embodiment of this invention. It is explanatory drawing which expanded and displayed the wire wound around the guide roller group of the wire electrical discharge machining apparatus in embodiment of this invention in linear form. It is a timing chart which shows operation | movement of the wire electric discharge machining apparatus in embodiment of this invention. It is a flowchart which shows operation | movement of the wire electric discharge machining apparatus in embodiment of this invention.

  Hereinafter, a wire electric discharge machining apparatus 100 according to an embodiment of the present invention will be described with reference to the drawings. As shown in FIG. 1, the wire electric discharge machining apparatus 100 includes a feeding bobbin 10 </ b> A for feeding the wire 15, a take-up bobbin 10 </ b> B for winding the wire 15 used for the electric discharge machining, and a wire 15 wound around the wire 15. Pulleys 11A to 11C and 11E to 11G that change directions, a dancer roll 12 that adjusts the total travel length of the wire 15, wire tension sensors 13A and 13B that detect tension applied to the wire 15, and a winding bobbin Electric power is supplied to the wire alignment unit 14 that adjusts the axial position of the winding bobbin 10B of the wire 15 facing 10B, the guide rollers 24A to 24D around which the wire 15 is wound, and the wire 15 and the workpiece 28. Power supply 29, a power supply 41 that supplies power from the power supply 29 to the wire 15, and a machine that moves the work 28. And click feed unit 27, and a control unit 50. The four guide rollers 24 </ b> A to 24 </ b> D constitute one guide roller set 26.

  The feeding bobbin 10A and the take-up bobbin 10B are rotationally driven by motors 25A and 25D, the pulley 11C is rotationally driven by the motor 25B, the guide roller 24D is rotationally driven by the motor 25C, and the work feeding unit 27 is driven by the stepping motor 25E. It is comprised so that. Further, the wire electric discharge machining apparatus 100 includes a position sensor 31 that detects the position of the dancer roll 12 and a break detection sensor 32 that detects a break in the wire. The motor 25B has a built-in rotary encoder and can output the number of rotations.

  The wire 15 fed out from the feeding bobbin 10A in the direction of the arrow shown in FIG. The wire 15 is wound around guide rollers 24A, 24B, 24C, and 24D in this order on the outside of guide rollers 24A to 24D having a large number of guide grooves. The wire 15 exiting the guide roller 24D is again wound around the guide rollers 24A to 24D from a position separated from the portion of the wire 15 wound around the guide roller 24A by a pitch P in the axial direction of the guide roller 24A. Go. The distance in the axial direction between each of the guide rollers 24A to 24D between the portion of the wire 15 wound first and the portion of the wire 15 wound next is the pitch P in any place. Thus, the wire 15 is wound around the guide rollers 24A to 24D a plurality of times.

  As shown in FIG. 1, in this embodiment, the wire 15 is wound five times. Here, the winding number is the number of times the wire 15 is wound around the guide rollers 24A and 24B. Accordingly, even when the wire 15 extends toward the pulley 11G without returning from the guide roller 24D to the guide roller 24A as in the last winding of the wire 15, the wire 15 is wound around the guide rollers 24A and 25B. Count once. That is, the number of times of winding is the number of the wires 15 stretched between the guide roller 24A and the guide roller 24B.

  After the wire 15 is wound around the guide rollers 24A to 24D a plurality of times, the wire 15 passes through the pulley 11G, the wire tension sensor 13B, and the wire alignment unit 14, and is wound around the winding bobbin 10B. The wire 15 is a metal wire such as brass.

  As shown in FIG. 1, the power supply 41 is provided on the guide roller 24A side and the guide roller 24B side of the wire 15 stretched between the guide roller 24A and the guide roller 24B, respectively. Each power supply 41 is in contact with each strip of the wire 15 and includes a plurality of conductive blocks 41A that feed power from the power source 29 to each strip of wire 15 and an insulating block 41B that insulates between each conductive block 41A in the axial direction. The blocks 41A and 41B are integrally fastened by through bolts and nuts (not shown).

  The work feeding unit 27 is arranged so that the work 28 can be moved in the direction orthogonal to the feeding direction of the wire 15 stretched between the guide roller 24A and the guide roller 24B between the electric power supply 41. The motor is driven by a stepping motor 25E. The stepping motor 25E can detect the rotation angle of the internal rotor, and can detect the position of the work 28 from the rotation angle of the rotor.

  In the present embodiment, each power supply 41 is connected to the negative side or ground side of the power source 29 by the conductive wire 30, and the work 28 is connected to the positive side of the power source by the conductive wire 30. The power supply 29 causes a DC pulse current of, for example, several tens of KHz to flow between each of the supply electrons 41 and the work 28, thereby generating intermittent discharge between the work 28 and the wire 15. The work 28 is cut by the heat generated by the electric discharge. The polarities connected to the work 28 and the power supply 41 need only be different from each other. The work 28 may be on the negative side and the wire 15 may be on the positive side.

  In the wire electrical discharge machining apparatus 100 of the present embodiment, the workpiece 28 and the power supply 41 are immersed in pure water or oil-based machining fluid with adjusted electrical conductivity, and the discharge between the wire 15 and the workpiece 28 is underwater. And the temperature rise of the entire workpiece 28 can be suppressed during machining. The machining liquid may be sprayed between the workpiece 28 and the power supply 41.

  The motors 25A and 25D that rotate the bobbins 10A and 10B, the motor 25B that rotates the pulley 11C, the motor 25C that rotates the guide roller 24D, the stepping motor 25E, the wire alignment unit 14, and the power source 29 are control units. 50, and is configured to operate according to a command from the control unit 50. The wire tension sensors 13A and 13B, the position sensor 31 that detects the position of the dancer roll 12, and the disconnection detection sensor 32 that detects the disconnection of the wire 15 are connected to the control unit 50, and each detection signal is controlled. The unit 50 is configured to be input. The control unit 50 stops the operation of the wire electric discharge machining apparatus 100 when the disconnection of the wire 15 is detected by the disconnection detection sensor 32.

The operation of the wire electric discharge machining apparatus 100 configured as described above will be described with reference to FIGS. As shown in step S101 of FIG. 5, when the wire electric discharge machining apparatus 100 is started, the control unit 50 starts the motors 25A to 25D to rotate the bobbins 10A and 10B, the pulley 11C, and the guide roller 24D. As a result, the wire 15 is fed from the feeding bobbin 10A toward the winding bobbin 10B in the direction indicated by the arrow in FIG. Control unit 50 obtains the pulley 11C from the rotary encoder incorporated the rotational speed of the motor 25B for rotating the feed speed of the wire 15 by changing the speed in electrical discharge machining feed speed V ₁ as shown in FIG. 4 Feedback control is performed so that Feed speed of the wire 15 is defined by the rotational speed of the motor 25B, as the motor 25A for rotating the motor 25C for rotating the guide roller 24D, the bobbins 10A, the 10B, 25D is the wire feed speed 15 becomes _{V 1} It is rotating at the driven speed.

When the motor 25C rotates following the rotation of the motor 25B so that the output torque is almost zero, the motor 25C is between the pulley 11C driven by the motor 25B and the guide roller 24D driven by the motor 25C. There is almost no tension applied to a certain wire 15. The control unit 50 outputs a command to increase the output torque of the motor 25C that rotates the guide roller 24D. By this command, the rotation speed of the motor 25C remains the same, the output torque increases, and tension starts to be applied to the wire 15 between the pulley 11C and the guide roller 24D. The control unit 50 is the tension applied to the wire 15 is detected by the wire tension sensor 13A located between the pulleys 11C and the guide roller 24D, tension on the wire 15 in this portion and the discharge machining tension T ₁ shown in FIG. 4 Thus, the output torque command value of the motor 25C is adjusted.

  The motor 25A for rotating the feeding bobbin 10A is controlled in rotational speed and output torque so that the position of the dancer roll 12 detected by the position sensor 31 becomes a predetermined position, and is applied to the wire 15 by the motor 25C driving the guide roller 24D. When the tension starts to be applied, the controller 50 controls the entire length of the wire from the feeding bobbin 10A to the winding bobbin 10B to be kept constant.

  Further, the control unit 50 detects the tension of the wire 15 between the guide roller 24D and the winding bobbin 10B by the wire tension sensor 13B, and the motor prevents the tension of the wire 15 from fluctuating due to the winding operation of the winding bobbin 10B. 25D output torque is controlled.

By the operation as described above, when the wire 15 is fed at the electric discharge machining feed speed V ₁ and the electric discharge machining tension T ₁ is applied, the control unit 50 performs the process at time t ₁ shown in FIG. As shown in step S <b> 102 of FIG. 5, a current for electric discharge machining is applied between each power supply 41 and the work 28. And if the current time t ₂ shown in FIG. 4 reaches the discharge machining current A _1, the control unit 50 starts sending towards the workpiece 28 to the wire 15 by a stepping motor 25E, starts the discharge machining operation.

As shown in FIG. 2, when the cylindrical workpiece 28 is fed toward the wire 15, a discharge is generated between the wire 15 and the workpiece 28, and the cylindrical workpiece 28 is gradually cut by the heat. . As shown in FIG. 2, an electric discharge machining tension T ₁ is applied to the wire 15, and the wire 15 is fed at an electric discharge machining feed speed V ₁ . As shown in FIG. 2, one wire 15 has five strips between the guide roller 24 </ b> A and the guide roller 24 </ b> B, and power is supplied to each strip of the wire 15 from the power supply 41 to guide the guide 28. Discharge is performed between the workpiece 28 and the point a to the point e on the 24A side and the point a ′ to the point e ′ on the guide roller 24B side. Each length L between the point a to the point e and the point a ′ to the point e ′ is the length of the discharge section between the wire 15 and the workpiece 28 and is the machining length of the workpiece 28. As shown in FIG. 2, when the cylindrical workpiece 28 is sliced into a disk shape, the workpiece processing length L of each strip is the same length.

  FIG. 3 shows the wire 15 wound around the guide rollers 24A to 24D or the guide roller set 26 in a linear form, and the arrows in the figure indicate the wire feeding direction. As shown in FIG. 3A, the wire 15 is wound around the guide rollers 24A to 24D five times, and points a and a ', points b and b', points c and points shown in FIG. c ′, point d and point d ′, point e and point e ′ respectively indicate the discharge start position and discharge end position of each strip of the wire 15 and the workpiece 28, and the machining length L of the workpiece 28 is between each point. It is represented as a point that is separated by a distance and arranged in order in the feed direction of the wire 15. Further, the point a and the point b can be expressed as a point in which the wire 15 is separated by a length X that goes around the outer periphery of the guide rollers 24A to 24D shown in FIG. Since the length X that goes around the guide rollers 24A to 24D is constant, the lengths between the points b and c, between the points c and d, and between the points d and e are also X, respectively. . In FIG. 3, point p indicates a point separated from the point a by a length X that goes around the outer periphery of the guide rollers 24 </ b> A to 24 </ b> D in the direction opposite to the feeding direction of the wire 15. A point separated by a machining length L in the feed direction of the wire 15 is shown. 3B indicates a point that is separated from the point e by a length X that goes around the outer circumference of the guide rollers 24A to 24D, and a point q ′ is a processing length in the feed direction of the wire 15 from the point q. A point separated by L is shown.

Wire 15 is applied at the same time discharge machining current A ₁ when fed in the direction of the arrow shown in FIG. 3 (a), when the discharge between the wire 15 and the workpiece 28 is started, first point a And point a ′, point b and point b ′, point c and point c ′, point d and point d ′, point e and point e ′, and discharge between wire 15 and workpiece 28 Will occur. That is, electric discharge is started between the wire 15 and the work 28 at the five machining lengths L. When the wire 15 is sent, the upstream wire 15 sequentially passes through the electric discharge machining section between the points and discharges between the workpiece 28.

  When the wire 15 is fed by the length X that goes around the outer circumference of the guide roller 24A to 24D, as shown in FIG. 3B, the wire 15 at the point p shown in FIG. The portion moves to point a, and the portion of the wire 15 that was at point a moves to point b. Similarly, the portion of the wire 15 at the point b is positioned at the point c, the portion of the wire 15 at the position of the point c is at the point d, and the portion of the wire 15 at the point d is at the point e. The portion of the wire 15 that has been moved to the point q. All the wires 15 positioned between the points a and q shown by hatching in FIG. 3B pass once in the discharge section with the workpiece 28 or the machining length L, and once in the wire 15. Electric discharge marks and thermosetting remain when electric discharge machining is performed.

  As shown in FIG. 3B, before the wire 15 is fed by a length X that goes around the outer circumference of the guide rollers 24A to 24D, the wire 15 that is upstream from the point p shown in FIG. Even after the wire is fed by the length X, the portion is located on the upstream side in the feeding direction of the wire 15 from the point a shown in FIG. No discharge marks or thermosetting occurred.

Control unit 50, as shown in step S103 of FIG. 5, the relationship between the length X of discharge machining feed speed _{V 1} and the wire 15 of the wire 15 around the outer periphery of 24D from the guide rollers 24A, FIG. 4 time Delta] t ₁ for sending a wire 15 shown by a length X to go around the outer periphery of 24D from the guide roller 24A calculates, when the time Delta] t ₁ has elapsed, the length X of the wire 15 to the time t ₃ when 4 It is determined that the electric discharge machining operation is completed. In this case, the length X is the first length.

When the controller 50 determines that the electric discharge machining operation has been completed, the controller 50 starts the idle feed operation. As shown in step S <b> 104 in FIG. 5, the control unit 50 reduces the feed speed of the work 28 from the feed speed at the time of electric discharge machining. This feeding speed is a speed corresponding to a decrease in applied current, which will be described later. Then, it outputs a command to reduce the air-feed current A ₀ shown in FIG. 4 the current applied to the wire 15 as shown in step S105 in FIG. 5 from the discharge machining current A _1. The idle feed current A ₀ is a current that maintains a weak discharge between the wire 15 and the workpiece 28 and does not lower the temperature of the workpiece 28. By this command, the output current from the power source 29 is reduced from A ₁ to A ₀ . When applying current to the time t ₄ when FIG. 4 is empty feed current A _0, the control unit 50, as shown in step S106 of FIG. 5, the air-feed tension T of the wire tension from the discharge machining tension T ₁ Outputs a command to reduce it to _zero . The idle feed tension T ₀ is a tension about half to 1/5 of the electrical discharge machining tension T ₁ . This command is reduced output torque of the motor 25C, tension on the wire 15 is reduced to an empty feed tension T _0. At this time, the tension of the wire 15 is detected by the wire tension sensor 13A, and is fed back to the output torque of the motor 25C so that the tension applied to the wire 15 is smoothly reduced.

Figure 4 control unit 50 if it is reduced the tension of the wire 15 is empty feeding tension T ₀ to time t ₅ shown in, as shown in step S107 of FIG. 5, the wire 15 air-feed speed V ₂ of the feed rate of the The command to increase is output. Check feed speed V ₂ is more than five times the rate of discharge machining feedrate V _1. This command, rotation speed of the motor 25B is increased, increasing the feed rate of the wire 15 to the air feed rate V _2. At this time, the control unit 50 increases the rotational speeds of the other motors 25A, 25C, and 25D to the rotational speed that follows the rotational speed of the motor 25B, so that the feed speed of the wire 15 is increased uniformly. The control unit 50 adjusts the motor 25C, the output torque of 25D as wire tension sensor 13A, the tension of the wire 15 by feeding back the output signal of 13B is held in an empty feed tension _{T 0.}

Control unit 50 reaches the empty feed rate _{V 2} is the feed speed of the wire 15 to the time _{t 6} shown in FIG. 4, as shown in step S108 of FIG. 5, the air feed rate _{V 2} and the wire 15 of the wire 15 guide From the relationship with the length X that goes around the outer circumference of the rollers 24A to 24D, a time Δt ₂ required to send the wire 15 by the length Y shown in FIG. 3B is calculated, and when this time Δt ₂ has elapsed. 4, it is determined that the wire 15 is sent by the length Y at time t ₇ shown in FIG. The length Y is the second length.

  As shown in FIG. 3 (b), the length Y is such that the wire 15 has a length of 5 turns, which is the number of times the wire 15 is wound around the outer periphery of the guide rollers 24A to 24D (guide roller set 26), and the wire The length obtained by subtracting the length X that goes around the outer periphery of 24D from the guide rollers 24A from the total length of the workpiece processing length L along the feed direction = 5X + L, and Y = (5X + L) −X = 4X + L It is. As shown in FIG. 3B, when the wire 15 is sent by the length Y, the portion of the wire 15 that was at the point a before sending the wire 15 comes to the point e ′. For this reason, all the wires 15 in the portion where the processing length L is located are replaced with the wires 15 that have not been discharged once.

Control unit 50, if it is determined that those sent by the length Y of the wire 15 to the time t _7, as shown in step S109 in FIG. 5, return the feed speed of the wire 15 to the original discharge machining feed speed V ₁ Outputs a command. Rotational speed of the motor 25B is reduced by the command feed speed of the wire 15 is reduced from the air feed rate V ₂ to the discharge machining feedrate V _1. At this time, similarly to when the feed speed of the wire 15 is increased, the control unit 50 reduces the rotation speeds of the other motors 25A, 25C, and 25D to the rotation speeds driven by the rotation speed of the motor 25B. The feed rate is reduced uniformly. The control unit 50 adjusts the motor 25C, the output torque of 25D as wire tension sensor 13A, the tension of the wire 15 by feeding back the output signal of 13B is held in an empty feed tension _{T 0.}

When the feed speed of the wire 15 to the time t ₈ as shown in FIG. 4 is lowered to the discharge machining feed speed V _1, the control unit 50, as shown in step S110 of FIG. 5, based on the tension is added to the wire 15 It outputs a command to return to the discharge machining tension T _1. This command, the output torque of the motor 25C is increased, the tension applied to the wire 15 is increased to discharge machining tension T _1. At this time, the tension of the wire 15 is detected by the wire tension sensor 13A, and is fed back to the output torque of the motor 25C so that the tension applied to the wire 15 is smoothly increased.

The tension of the wire 15 to the time t ₉ shown in FIG. 4 reaches the discharge machining tension T _1, the control unit 50, as shown in step S111 in FIG. 5, the air feed current A current applied to the wire 15 ₀ outputs a command to increase the electric discharge machining current a _1. Output current from the power source 29 by the command is increased from A ₀ to A _1. When the applied electric current to the wire 15 reaches the discharge machining current A ₁ to the time t ₁₀ shown in FIG. 4, the control unit 50, as shown in step S112 of FIG. 5, the original discharge machining feed rate of the workpiece 28 The feed speed is returned to the above, the idle feed and the operation are terminated, and the electric discharge machining operation is started. Then, the control unit 50 continues cutting the workpiece 28.

Then, the control unit 50 acquires the position of the work 28 from the position signal of the rotor of the stepping motor 25E of the work feeding unit 27, and determines whether or not the cutting of the work 28 has ended as shown in step S113 of FIG. To do. When the cutting of the workpiece 28 is completed, the operation of the wire electric discharge machining apparatus 100 is stopped, and when it is determined that the workpiece 28 is being cut, the process returns to step S103 in FIG. It is determined whether or not the time Δt ₁ for sending only the length X that goes around the outer circumference of 24A to 24D has elapsed, and the electric discharge machining operation and the idle feeding operation shown in steps S104 to S112 in FIG. 5 are repeated.

In the above description of the operation of the present embodiment, the time of each operation has been described in detail in order to clearly describe the order of each operation. However, the time required for shifting from the electric discharge machining operation to the idle feed operation is described. t between _third time t _6, each time interval is time Delta] t 1 between t ₁₀ from the time t ₇ to shift to the discharge machining operation from the air feeding _operation, but short enough negligible compared to Delta] t ₂ is there.

  As described above, in the wire electric discharge machining apparatus 100 of the present embodiment, the wire 15 passes only once through the discharge section with the workpiece 28 or the section with the machining length L of the workpiece 28 shown in FIGS. It becomes. For this reason, multiple discharge marks and thermosetting do not remain on the wire 15, it is possible to suppress a decrease in the tensile strength of the wire 15, and it is possible to suppress disconnection of the wire 15 during electric discharge machining. Further, in this embodiment, since the wire feed speed during idle feeding of the wire 15 is higher than the speed during the electric discharge machining, the idle feeding time of the wire 15 can be shortened, and the discharge The cutting time of the workpiece 28 by machining can be shortened. Furthermore, in this embodiment, since the tension of the wire 15 is reduced during the idle feeding, the disconnection of the wire 15 can be effectively suppressed even when the feeding speed of the wire 15 is high. Furthermore, in the present embodiment, the workpiece 28 is continuously processed while the workpiece 28 is being fed at a speed corresponding to the applied current during idle feeding, so that a step is generated on the cut surface of the workpiece 28. Can be suppressed. Further, in the present embodiment, since the wire 15 is prevented from being subjected to multiple discharges so as to prevent the wire 15 from being deteriorated, the thin wire 15 can be used, and the processing cost at the time of cutting is reduced. be able to.

  In the embodiment described above, the first length, which is the feed length of the wire 15 during the discharge operation, has been described as the length X that goes around the outer periphery of the guide rollers 24A to 24D. If sufficient, the length may be 2X for two rounds or another length. When the wire feed length during the electric discharge machining operation that is the first length is 2X, the wire feed length Y during the idle feed that is the second length is Y = (5X + L) −2X = 3X + L.

  In the present embodiment, it has been described that the applied current is reduced and the feed speed of the work 28 is reduced during the idle feed operation. However, the applied current may be stopped and the feed of the work 28 may be stopped. . Even in this case, since the work 28 is held at the same position, no step is generated on the cut surface of the work 28.

  As shown in FIG. 2, when the cylindrical workpiece 28 is cut, the length of the discharge section and the machining length L of the workpiece vary depending on the position of the workpiece 28 in the direction perpendicular to the wire 15, that is, the position in the feed direction. The position in the feed direction of the work 28 is obtained from the position of the rotor of the stepping motor 25E that drives the work feed unit 27, the machining length L of the work 28 is calculated from the position in the feed direction of the work 28, and the idle feed operation At this time, the feed length Y of the wire 15 may be changed.

  In the present embodiment, it has been described that the motor 25B that drives the pulley 11C defines the feed speed of the wire 15, and the motor 25C that drives the guide roller 24D defines the tension of the wire 15. The feed speed may be defined, and the motor 25B may regulate the tension of the wire 15.

When the present embodiment has been described as reducing the tension to be added to the wire during the air-feeding operation from the discharge machining tension T ₁ to the air-feed tension T _0, the strength of the wire is sufficient it may be held in the discharge machining tension T ₁ without changing the wire tension during the feeding operation.

  10A feeding bobbin, 10B take-up bobbin, 11A-11C, 11E-11G pulley, 12 dancer roll, 13A, 13B wire tension sensor, 14 wire alignment unit, 15 wire, 24A-24D guide roller, 25A-25D motor, 25E stepping Motor, 26 Guide roller set, 27 Work feed unit, 28 Work, 29 Power supply, 30 Conductive wire, 31 Position sensor, 32 Disconnection detection sensor, 41 Electric supply, 41A Conductive block, 41B Insulation block, 50 Control unit, 100 Wire discharge Processing equipment.

Claims (5)

A guide roller set including a plurality of guide rollers arranged at intervals; and
A wire wound around the guide roller set a plurality of times at intervals in the longitudinal direction of each guide roller;
A wire feed mechanism for feeding the wire in the winding direction;
A power supply for supplying power to the wire;
A controller that increases or decreases the wire feed rate and the power supply power,
A wire electric discharge machining apparatus for machining a workpiece by simultaneously performing electric discharge between the workpiece at a plurality of positions of the wire while feeding the wire,
The control unit
An electric discharge machining operation in which the wire feeds the wire by a first length that makes at least one round of the guide roller set while supplying the electric discharge machining power to the wire, and the supply electric power is made lower than the electric discharge machining power. The idle feeding operation of feeding the wire by a second length obtained by subtracting the first length from the total length of the length of the number of windings and the work length of the workpiece along the wire feeding direction is alternately performed. thing,
A wire electric discharge machining apparatus. The wire electrical discharge machining apparatus according to claim 1,
The control unit includes a wire feed speed changing means for making the wire feed speed during the idle feed operation faster than the wire feed speed during the electric discharge machining operation,
A wire electric discharge machining apparatus. The wire electrical discharge machining apparatus according to claim 1 or 2,
With a wire tensioning mechanism that applies tension to the wire,
The control unit includes wire tension changing means for lowering the tension applied to the wire during the idle feeding operation to be lower than the tension applied to the wire during the electric discharge machining operation;
A wire electric discharge machining apparatus. The wire electrical discharge machining apparatus according to claim 3,
The controller lowers the tension applied to the wire by the wire tension changing means at the start of the idle feed operation, and then increases the wire feed speed by the wire feed speed changing means,
A wire electric discharge machining apparatus. The wire electric discharge machining apparatus according to any one of claims 1 to 4,
Equipped with a workpiece feed mechanism that moves the workpiece in a direction that intersects the wire feed direction,
The control unit includes a workpiece feed rate changing means for making the workpiece feed rate during the idle feed operation slower than the workpiece feed rate during the electric discharge machining operation;
A wire electric discharge machining apparatus.

Images