HK1168327A - Method of cutting out part with making partially welded spots in wire-cut electrical discharge machining - Google Patents

Description

Method for cutting off portion in wire electric discharge machining

Technical Field

The present invention relates to a cut-out portion machining method for performing electric discharge machining on a workpiece by electric discharge energy generated by applying an inter-electrode voltage between a wire electrode and the workpiece, and capable of holding a cut-out portion cut out from the workpiece by the electric discharge machining in the wire electric discharge machining on the workpiece.

Background

In general, a wire electric discharge machine is a machine tool that cuts a workpiece by causing an electric discharge phenomenon between a wire electrode and the workpiece such as cemented carbide or hardened steel, and when starting electric discharge machining, the wire electrode is inserted into a hole such as a threading hole penetrating the workpiece in advance, and during the electric discharge machining, the wire electrode is always supplied to an electric discharge machining portion of the workpiece having a predetermined machining shape. In an immersion type wire electric discharge machine, for example, a workpiece is fixed to a table by a holder while being immersed in a working fluid in a working tank. In electric discharge machining in which a wire electrode is passed through an electric discharge machining portion of a workpiece, a workpiece is separated or a portion is cut out when an electric discharge machining path is closed.

Conventionally, as a wire electric discharge machining method, a method is known in which the 1 st machining and the 2 nd cutting are performed in 1 machining program. In this wire electric discharge machining method, a program for inputting a machining path for cutting out each punch (male pattern), a cutting residual amount, and a return amount are set in advance, and when the set cutting residual amount is left in the 1 st machining, electric discharge machining is stopped, and the position is stored. In the 2 nd pass of the residual machining, the wire is automatically connected at a position where the machining is returned from the machining stop position of the 1 st pass along the machining groove by a set return amount, and the electric discharge machining is started from the position to cut each punch (for example, see JP 3366509 a).

Further, the wire electric discharge machining method developed by the present applicant can simplify and quicken the manufacturing of the machining program by cutting out the workpiece based on the preset machining program and determining the machining allowance distance immediately before the end of machining based on the shape of the cutting out determined by the preset machining program, and can reliably prevent the scrap from falling down by forming the machining allowance distance suitable for the machining shape (for example, refer to JP 2000-280124 a).

Further, the wire electric discharge machining apparatus developed by the present applicant is configured to continuously and automatically perform an operation of discharging scraps having a small shape and an operation of cutting off machining, and to move a wire electrode along a predetermined machining path by an electrode movement control unit, and an electrode spacing control unit controls an electric discharge gap of the wire electrode during machining movement and outputs a retreat end alarm for ending the machining operation, and when the movement on the machining path is ended, the retreat end alarm is disabled, and after the movement on the machining path is ended, a scrap discharge control unit discharges scraps from a workpiece, and by such an apparatus, the operation of discharging scraps can be continuously performed after a machining operation (for example, see JP 3521283 a).

In addition, the immersion type electric discharge machine developed by the present applicant is capable of supporting a cut-off piece generated by cutting off a workpiece by a floating body to prevent a short circuit between the cut-off piece and a wire electrode and safely supporting a heavy cut-off piece, and the floating body having a specific gravity smaller than that of a machining liquid is disposed on a lower surface of the workpiece to support the cut-off piece generated by cutting off the workpiece by the wire electrode by buoyancy of the machining liquid to the floating body without sinking the cut-off piece into the machining liquid (see, for example, JP 4480822 a).

However, in the wire electric discharge machining method, when the first machining is performed, such as the die pad machining, the next shape machining is performed by changing the cutting process without performing the electric discharge machining for only a distance of about several mm, and thereafter, the operation of cutting off the scrap from the workpiece is performed and the process is shifted to the machining process of finishing the workpiece. In addition, when the workpiece is to be electric discharge machined into a predetermined machined shape, the workpiece is cut into a machined shape with a margin so as not to drop scraps from the workpiece, and then scraps are cut out from the workpiece, or a scrap collecting device is required. Further, in the case where the last portion to be formed into the machined shape is left without cutting, immediately before the end of machining of the workpiece, the cut-off piece to be cut off from the workpiece is inclined with respect to the clamped workpiece, and short-circuiting between the wire electrode and the scrap as the cut-off piece interrupts electric discharge machining or generates abnormal electric discharge, and the machined surface of the machined workpiece is damaged when the cut-off piece is a machined workpiece. When the cut-off piece is completely cut out by cutting to the last portion of the machined shape, the workpiece may not be attracted to the magnet, and even if the workpiece may be attracted to the magnet, the scrap may not be supported completely by the magnetic force due to the difference in weight of the scrap as the cut-off piece.

The present inventors paid attention to the fact that, in the case where insulation breakdown occurs when a metal electrode is disposed in an insulator (gas), the long-gap discharge phenomenon is qualitatively described as a phenomenon in which a spark (spark) discharge is performed after a corona discharge, and then the insulation breakdown is terminated by an arc discharge phenomenon, and developed the following technique: by controlling the "voltage-current characteristics" of these phenomena, it is possible to perform electric discharge machining by spark discharge and arc welding, that is, plasma arc welding, by arc discharge. The present inventors conceived the technical idea of forming a cut-out portion by performing electric discharge machining on a workpiece using a wire electrode by utilizing the above phenomenon, and welding the cut-out portion to the workpiece by arc welding.

Disclosure of Invention

An object of the present invention is to solve the above-described problems and to provide a method of machining a cut-out portion in wire electric discharge machining, characterized in that at least one portion of a workpiece to be machined having a predetermined shape is subjected to electric discharge machining, electric machining conditions are changed to melt a portion of the outer periphery of a wire electrode, and the workpiece and the cut-out portion that has been cut out are welded in a machining shape region, thereby preventing the cut-out portion from falling off from the workpiece.

A method of cutting off a portion in wire electric discharge machining according to the present invention is characterized in that a wire electrode fed from a source wire bobbin provided in an apparatus main body is supplied to a workpiece mounted below an upper head and a lower head arranged below the workpiece and facing the upper head, the wire electrode is discarded via a guide member arranged below the lower head, an electric machining condition applied between the wire electrode and the workpiece is changed from a machining cycle to a welding cycle at least one position of a predetermined machining shape of the workpiece, a portion of the wire electrode is melted, the workpiece and a cut-off portion cut off from the workpiece are welded by a wire electrode melt at a welding portion located at a predetermined position, and the cut-off portion is held by the welding portion on the workpiece, the cut-out portion is prevented from falling off from the workpiece.

Further, in order to weld the workpiece and the cut-off portion by the welding portion and to pass the current of the wire electrode, a current peak value is smaller and longer than a current for wire electric discharge machining of the workpiece, a current peak value is changed from machining electric discharge to arc electric discharge, and the cut-off portion is welded to the workpiece at the welding portion by welding using the wire electrode melt.

The welding cycle has the following processing conditions: and welding the workpiece and the cut-out portion by using a part of the workpiece and a part of the cut-out portion facing each other as the welded portion while cutting the workpiece. In addition, the welded portion of the work and the cut-out portion is separated from the work by breaking the welded portion by an external force after the electric discharge machining of the work.

The present cut-away portion processing method is basically realized by the following circuit. That is, in the present method of partially cutting machining, the change of the machining condition is realized by connecting a 1 st circuit, a 2 nd circuit and a 3 rd circuit in parallel between both electrodes of the wire electrode and the workpiece (corresponding to the other electrode in the present invention), and controlling on/off of the 1 st switch, the 2 nd switch and the 3 rd switch, wherein the 1 st circuit is a circuit in which a low voltage load with a resistance for checking an inter-electrode condition and the 1 st switch are connected in series, the 2 nd circuit is a circuit in which a high voltage load for electric discharge machining and the 2 nd switch are connected in series, and the 3 rd circuit is a circuit in which a 1 st diode and the 3 rd switch are connected in series. Further, the machining cycle of the workpiece is executed by 1 st specific control, the 1 st specific control being: the 1 st switch is turned on to apply the low voltage load between the wire electrode and the workpiece, and the 1 st switch is turned off to turn on the 2 nd switch to apply the high voltage load between the wire electrode and the workpiece, thereby performing electric discharge machining on the workpiece by the wire electrode. Further, the welding cycle of the workpiece is executed by 2 nd specific control, the 2 nd specific control being: turning on the 1 st switch and the 3 rd switch to apply the low voltage load between the wire electrode and the workpiece, continuing the on state of the 3 rd switch, turning off the 1 st switch and turning on the 2 nd switch to apply the high voltage load between the wire electrode and the workpiece, and finally turning off the 2 nd switch to continue the on state of the 3 rd switch to release the high voltage load from the applied state, and passing a circulating current between the wire electrode and the workpiece to generate a current having a large pulse width, thereby welding the cut-off portion to the workpiece.

Alternatively, the present cut-away portion processing method is specifically realized by the following circuit. That is, in the present partial cutting machining method, the electric machining condition is changed by controlling on/off of a 1 st switch, a 4 th switch, and a 5 th switch in an electric circuit in which the 1 st circuit, the 2 nd circuit, the 3 rd circuit, and the 4 th switch are connected in series, and the 4 th circuit, the 3 rd diode, and the 5 th switch are connected in series, in which the 1 st circuit, the 2 nd circuit, the 4 th circuit, and the 5 th switch are connected in parallel between the wire electrode and the workpiece, respectively. Further, the machining cycle of the workpiece is executed by 3 rd specific control, the 3 rd specific control being: the 1 st switch is turned on to apply the low voltage load between the wire electrode and the workpiece, and the 4 th switch and the 5 th switch are turned off to apply the high voltage load between the wire electrode and the workpiece, thereby performing electric discharge machining on the workpiece by the wire electrode. Further, the welding cycle of the workpiece is executed by a 4 th specific control, the 4 th specific control being: the method includes turning on the 1 st switch to apply the low voltage load between the wire electrode and the workpiece, turning off the 1 st switch and turning on the 4 th switch and the 5 th switch to apply the high voltage load between the wire electrode and the workpiece, maintaining the on states of the 4 th switch and the 5 th switch to continue the high voltage load application, and turning off the fourth switch to continue the on state of the 5 th switch to release the high voltage load application, and passing a circulating current between the wire electrode and the workpiece to generate a current having a large pulse width to cut off the welded portion.

In the cut-off portion machining method, the portion of the wire electrode melted to weld the workpiece and the cut-off portion is a wire peripheral portion of the wire electrode, and when the cut-off portion and the workpiece are welded by melting the portion of the wire electrode, the wire electrode is not broken, and the feeding state of the wire electrode can be maintained. In the cut-off portion machining method, in the step of welding the cut-off portion and the workpiece by melting the part of the wire electrode, when the wire electrode is broken, the wire electrode can be supplied to a machining seam at the wire breakage point, and the welding step or the machining step can be continued.

Since the method of machining a cut-out portion by wire electric discharge machining according to the present invention is configured as described above, it is not necessary to perform electric discharge machining again on a workpiece to remove the cut-out portion of the workpiece as in the conventional art, and machining can be performed in a state where the cut-out portion is easily separated from the workpiece by one electric discharge machining. That is, since the welded portion that holds the cut-out portion on the workpiece is not as strong as the material of the workpiece and can be easily broken by a small external force, the cut-out portion can be separated from the workpiece by a small external force breakage in order to separate the cut-out portion from the workpiece, the workpiece does not need to be subjected to electric discharge machining again, the machining time can be shortened, the machining efficiency can be greatly improved, and the workpiece or the cut-out portion is not damaged by the cut-out portion being inclined or falling, and thus the workpiece can be subjected to favorable electric discharge machining.

However, in terms of properties, when a long-gap discharge phenomenon occurs between metal electrodes in an insulator, qualitatively, the insulation breakdown is terminated by a phenomenon in which a spark discharge is performed after a corona discharge, and then an arc discharge is performed. In addition, in the electric discharge machining of a workpiece, the current supply is stopped during the spark discharge to machine the workpiece. In the welding cycle in the cut-away portion machining method of the present invention, by controlling so that the electric discharge machining is performed on the workpiece in the spark discharge stage, then in the arc discharge stage, the cut-away portion is arc-welded to the workpiece, and at the time of the arc discharge, a part of the outer periphery of the wire electrode is melted into the welding filler. As a result, the workpiece is electric discharge machined in parallel with the wire electrode conveyance direction according to the trajectory of the wire electrode, and the portion that has been electric discharge machined immediately before is welded, that is, the cut-out portion is welded to the workpiece by the welding filler by the subsequent arc discharge.

Drawings

Fig. 1 is an explanatory view showing a wire electric discharge machine for explaining a method of cutting out a portion in wire electric discharge machining according to the present invention.

Fig. 2 is a circuit diagram showing a basic circuit for realizing the cut-away portion processing method in the wire electric discharge processing of the present invention.

Fig. 3(a) and 3(B) are waveform diagrams showing voltage waveforms and current waveforms for on/off control of the switch S1 and the switch S2 in the circuit of fig. 2, the upper side showing the voltage waveforms and the lower side showing the current waveforms, wherein fig. 3(a) is a waveform diagram showing the voltage waveforms and the current waveforms in a machining cycle in which normal machining is performed by the basic circuit of fig. 2, and fig. 3(B) is a waveform diagram showing the voltage waveforms and the current waveforms in a welding cycle in which a workpiece is welded and a cut-off portion is welded by the basic circuit of fig. 2.

Fig. 4 is a circuit diagram showing a circuit embodying a basic technical idea for realizing a cut-out portion processing method in the wire electric discharge machining of the present invention.

Fig. 5 is a waveform diagram showing voltage and current waveforms of the circuit of fig. 4, in which the on/off control of the switch S1, the switch S2, and the switch S3 is performed, the upper side shows the voltage waveform, and the lower side shows the current waveform, wherein (a) is a waveform diagram showing the voltage and current waveforms in a machining cycle in which normal machining is performed by the circuit of fig. 4, and (B) is a waveform diagram showing the voltage and current waveforms in a welding cycle in which a workpiece and a cut-out portion are welded by the circuit of fig. 4.

Fig. 6 is a circuit diagram showing an example of a specific circuit for realizing the cut-away portion processing method in the wire electric discharge processing of the present invention.

Fig. 7(a) and 7(B) show the relation between the workpiece and the cut-out portion in the cut-out portion processing method in the wire electric discharge machining, in which fig. 7(a) is a perspective enlarged view showing a state where the workpiece is processed into a quadrangular processing shape from a wire feed hole and the cut-out portion is welded at two places, and fig. 7(B) is a perspective enlarged view showing a processing locus of the workpiece in (a) in which electric discharge processing is performed with a broken line exaggeratedly.

Fig. 8 is a graph showing the result of breaking the load resistance of the welded portion between the workpiece and the cut-out portion in the method of machining the cut-out portion by wire electric discharge machining according to the present invention.

Fig. 9(a) and 9(B) are process flow charts for realizing the present invention and the conventional method for machining a cut-out portion, in which fig. 9(a) is a process flow chart showing a process step of the method for machining a cut-out portion in the present wire electric discharge machining, and fig. 9(B) is a process flow chart showing a process step of the method for machining a cut-out portion in the conventional wire electric discharge machining.

Detailed Description

The method of machining a cut-out portion in the wire electric discharge machining is preferably applied to a wire electric discharge machine that performs electric discharge machining on a workpiece by electric discharge energy generated by applying a machining voltage between a wire electrode and the workpiece, for example, and holds the cut-out portion of the workpiece so as not to fall off the workpiece. A wire electric discharge machine for realizing the method of machining a cut-out portion in wire electric discharge machining according to the present invention will be described below with reference to fig. 1. The wire electric discharge machine mainly comprises: a source bobbin 7 mounted on the apparatus main body 15 and around which the wire electrode 5 is wound; a plurality of direction switching rollers 8 that switch the direction of the wire electrode 5 in the on-line conveying system sent out from the source bobbin 7; a brake roller 9 for braking the wire electrode 5 to satisfactorily feed the wire electrode 5; a tension roller 12 that applies tension to the fed wire electrode 5; the guide roller 32 guides the wire electrode 5 to the supply pipe 13. The wire electrode 5 passes through the direction switching roller 8 and the guide roller 32 of the wire feeding system, passes through a pair of annealing rollers, i.e., a wire feeding roller 10, a feeding pipe 13 supported by the wire electrode conveying unit 24, and a pair of common rollers 11 provided on the body head 1, is sandwiched between the pair of wire feeding rollers 10 and the pair of common rollers 11, supplies a current from the machining power source to the wire feeding roller 10, the wire electrode 5, and the common rollers 11 through a power supply 18 (fig. 2 and 4) between the wire feeding roller 10 and the common rollers 11, and anneals the wire electrode 5 between the wire feeding roller 10 and the common rollers 11 to eliminate defects such as bending, and then cuts off and discharges an unannealed tip portion of the wire electrode 5 by the cutting blade 14. After that, the annealed wire electrode 5 is guided by the supply pipe 13 in accordance with the feeding operation of the wire supply roller 10 and the lowering operation of the supply pipe 13 supported by the supply pipe holder serving as the wire electrode transport unit 24, and reaches and passes through the upper head 2.

Further, between the annealing roller 10 and the common roller 11, there are provided a cutting blade 14 for cutting the leading end portion of the wire electrode 5 when the leading end of the wire electrode 5 is made good, the wire electrode 5 is cut, annealing treatment is performed, and a waste wire holder (not shown) for discarding the wire electrode 5 cut by the cutting blade 14. The cutting blade 14 is configured to cut the wire electrode 5 by operating a cutting blade unit. When the wire electrode 5 is connected, the wire electrode 5 passed through the supply tube 13 is first supplied to the upper head portion 2 by the low-speed rotation of the wire supply roller 10, passes through the upper head portion 2, passes through the wire feed hole of the workpiece 6 and the hole 19 of the machining trajectory, is then received by the lower head portion 4 facing the lower side of the upper head portion 2, the wire supply roller 10 is switched to the high-speed rotation state after the wire electrode 5 passes through the lower head portion 4, and the wire electrode 5 fed out from the lower head portion 4 is sequentially passed through the wire guide tube 37 from the direction change roller provided in the lower arm 3, the water separation portion provided at the outlet of the wire guide tube 37, and the take-up roller 35 provided downstream of the water separation portion, is drawn out by the take-up roller 35, is further sucked by a suction device or the like provided downstream of the take-up roller 35, and. In addition, an encoder 16 for detecting the rotation speed is provided on the brake roller 9. A sensor 17 is attached to a support (not shown) at the lower portion of the body head 1, and the sensor 17 is used to detect the state of flexure, bending, or passing of the wire electrode 5.

In the wire electric discharge machine, the material of the workpiece 6 is, for example, an iron-based material or a hard material. The wire electrode 5 is made of a metal material such as tungsten, copper alloy (brass), or brass wire, and the surface of the wire electrode is covered with the metal material as a core material, and for example, the wire electrode is made of a material in which the core material is a material other than copper alloy and the covering layer is a copper alloy, or a material in which the core material is a copper alloy and the covering layer is zinc. In the present embodiment, the workpiece 6 is, as shown in fig. 7(a) and 7(B), in particular, in a flat plate shape, and when a current is supplied to the wire electrode 5 by the power feeding unit 18 after the wire electrode 5 passes through the plurality of holes 19 such as the threading holes and the machining trajectory, and a voltage is applied between the wire electrode 5 and the workpiece 6 to perform electric discharge machining on the workpiece 6, a cut-out portion 26 of the plate or the like is generated. Further, the state of the tip of the wire electrode 5 can be detected by the sensor 17 when the tip of the wire electrode 5 abuts against any obstacle such as the upper head 2, the workpiece 6, and the lower head 4 and the wire electrode 5 is bent or curved while the tip of the wire electrode 5 passes through the workpiece 6 in order from the upper head 2 and passes through the lower head 4. Since a voltage is applied between the wire feeding roller 10 and the sensor 17, which is the upper part of the holder of the feeding tube holder, the deflection of the wire electrode 5 is detected when the deflection part of the wire electrode 5 comes into contact with the sensor 17. Since the wire supply roller 10 is supplied with power by the power supply means and the wire electrode 5 is applied with voltage in a state where the wire supply roller 10 is disconnected and the wire electrode 5 is pinched, the contact state of the wire electrode 5 can be detected by the sensor 17.

The method of machining a cut-out portion by wire electric discharge machining according to the present invention is characterized in that the cut-out portion 26 of the predetermined machining shape 21 is separated from the workpiece 6, but a part of the wire electrode 5 is melted, and the cut-out portion 26 is welded to the workpiece 6 by the welding portion 20 on the machining trajectory and is temporarily held. Here, a part of the wire electrode 5 to be melted is a wire peripheral portion of a predetermined length of the wire electrode 5, and when the cut-out portion 26 is welded to the workpiece 6 by the wire electrode melt, the wire electrode 5 is not disconnected and the feeding state of the wire electrode 5 is maintained. By the cut-out portion processing method, the workpiece 6 and the cut-out portion 26 can be welded well by including the copper alloy material in the wire electrode 5 in particular. In the method for cutting off a portion of a workpiece, a wire electrode 5 fed from a source wire bobbin 7 provided in an apparatus body 15 is nipped by a wire supply roller 10 provided in a body head 1, the wire supply roller 10 is driven, the wire electrode 5 is supplied to an upper head 2, a workpiece 6 mounted below the upper head 2, and a lower head 4 disposed below the workpiece 6 so as to face the upper head Z through a supply pipe 13, the wire electrode 5 is drawn out by a take-up roller 35 via a guide member disposed below the lower head 4 and discarded, the method for cutting off a portion of a workpiece is characterized in that an electrical machining condition applied between the wire electrode 5 and the workpiece 6 is changed from a machining cycle to a welding cycle at least at one place (two places in the embodiment) of a predetermined machining shape 21 of the workpiece 6, and a part of the wire electrode 5 is melted, the work 6 and the cut-out portion 26 are welded to each other at the welding portion 20 at a predetermined position determined in advance, and the cut-out portion 26 is held on the work 6 by the welding portion 20, thereby preventing the cut-out portion 26 from falling off from the work 6. As shown in fig. 7(a) and 7(B), since the workpiece 6 and the welded portion 20 of the cut-out portion 26 have two positions at opposite positions, the cut-out portion 26 can be held in a balanced manner on the workpiece 6. In the present cutaway portion machining method, in the step of welding the cutaway portion 26 and the workpiece 6 by melting a part of the wire electrode 5, when the wire electrode 5 is broken, the wire electrode 5 is supplied to the machining gap 22 at the wire breakage point, and then the workpiece 5 and the cutaway portion 26 can be welded, or the machining step of performing the electric discharge machining on the workpiece 6 by the wire electrode 5 can be continued. In addition, the cut-out 26 is sometimes an article and sometimes an unwanted scrap (scrap).

In the present method of cutting out a portion, in order to change the electric machining conditions from the machining cycle to the welding cycle, as shown in fig. 3(a), 3(B) and 5, the current (a) flowing through the wire electrode 5 is reduced to about 1/4, for example, in the peak value of the current flowing from the high voltage load HV to the wire electrode 5, to about 1/4, for example, as compared with the current for wire electric discharge machining of the workpiece 6, the voltage (V) applied between the wire electrode 5 and the workpiece 6 is reduced to about 1/4, and the pulse of the current flowing through the wire electrode 5 is increased to about 2 times, for example, so that the machining discharge is changed to arc discharge, and the cut-out portion 26 is welded to the workpiece 6 by the arc welding portion 20 by the wire electrode 5. In the welding cycle, the workpiece 6 is cut and the workpiece 6 and the cut-out portion 26 are welded together by using a part of the facing portions of the workpiece 6 and the cut-out portion 26 as the welded portion 20. Here, the part of the facing portion refers to a part of the portion where the workpiece 6 and the cut-out portion 26 face each other. For example, the welded portion of the wire electrode 5 may be a portion of the workpiece 6 on the upper head 2 side in the machining shape, or may be a portion of the workpiece 6 on the lower head 4 side. Further, since the welded portion 20 between the workpiece 6 and the cut-out portion 26 is located at the edge portion (only the upper portion in fig. 7 a and 7B), it can be broken by a small external force, and after the electric discharge machining of the workpiece 6 is completed, the welded portion 20 is broken by the external force, and for example, an impact force due to the external force is applied to the cut-out portion 26 from the workpiece 6, and the cut-out portion 26 can be easily separated from the workpiece 6.

In the present cut-away portion processing method, the welded portion 20 between the work 6 and the cut-away portion 26 can be broken by a small external force, but the fracture-resistant load of the welded portion 20 between the work 6 and the cut-away portion 26 is as shown in fig. 8. Fig. 8 shows a case where a square column of 8mm is machined on the workpiece 6, the cut-away portion 26 to be separated is a square column of 8mm, the length of the welded portion 20 is 2mm on 2 sides of the cut-away portion 26 facing each other, and a relationship between the static load kgf (vertical axis) of the welded portion 20 and the predetermined distance mm (horizontal axis) is shown.

Next, the basic principle of the method for machining the cut-out portion in the wire electric discharge machining will be described with reference to fig. 2, 3(a) and 3(B), and a specific example of the method for machining the cut-out portion in the wire electric discharge machining will be described with reference to fig. 4 and 5.

In fig. 5, specific numerical values of the 1 st switch S1, the 2 nd switch S2, the 3 rd switch S3, the voltage waveform (V), and the current waveform (a) are described, but these numerical values are examples for easy understanding, and the voltage waveform (V) and the current waveform (a) are also exemplified waveforms. That is, the time for turning ON (ON) the 1 st switch S1 is determined by the inter-electrode state between the wire electrode 5 and the workpiece 6 (for example, parameters that vary depending ON conditions such as the machining power supply, the material and wire diameter of the wire electrode 5, and the material and thickness of the workpiece 6), and may be about several μ sec (microseconds) or several tens μ sec when the time cannot be determined by the machining conditions or the like, and 2 μ sec is described as an example in the following description of the machining cycle and the welding cycle. The ON time of the 2 nd switch S2 is set to the ON time determined by the machining conditions (input parameters), but is described as 0.8 μ sec as an example in the following description of the machining cycle and the welding cycle. The time of current flow of the current waveform and the time of application of the voltage waveform in fig. 5(B) are not determined by machining conditions and the like, and are not constant, and are described as 3 μ sec as an example in the following description of the machining cycle and the welding cycle.

The circuit shown in fig. 2 is a circuit in which a 1 st circuit and a 2 nd circuit are connected in parallel between the wire electrode 5 and the workpiece 6, wherein the 1 st circuit is a circuit in which a 1 st switch S1 and a low-voltage load LV with a resistance for checking the inter-electrode state are connected in series, and the 2 nd circuit is a circuit in which a 2 nd switch S2 and a high-voltage load HV for electric discharge machining are connected in series. The 1 st circuit is a circuit for checking a state between the wire electrode 5 and the workpiece 6, and detects whether the workpiece 6 and the wire electrode 5 are in an appropriate positional relationship when the workpiece 6 is subjected to electric discharge machining, and the resistor R has a function of adjusting a current flowing through the 1 st circuit. The switch S1 is a switch that is turned ON/OFF (ON/OFF) temporally before the electric discharge machining is performed ON the workpiece 6. The 2 nd circuit is used for performing electric discharge machining, and when the workpiece 6 is subjected to electric discharge machining, a large current needs to be passed in a short time, and a circuit having no resistance or the like is required.

Next, a machining cycle and a welding cycle of the method for machining a cut-out portion in the wire electric discharge machining will be described.

In a machining cycle as normal machining shown in fig. 3(a), the 1 st switch S1 is turned ON to generate a pulse, a low voltage load LV of about 80V, for example, about 2 μ sec is applied between the wire electrode 5 and the workpiece 6 to check whether or not the condition of the electrode gap between the wire electrode 5 and the workpiece 6 is an appropriate position, and if the condition of the electrode gap is appropriate, discharge between the electrode gap is started. Next, when the 1 st switch S1 is turned OFF (OFF) and the 2 nd switch S2 is turned ON (ON) to generate a pulse, a current of about 400A flows through the wire electrode 5 for a flow time of, for example, about 0.8 μ sec, and a voltage of about 240V is applied between the wire electrode 5 and the workpiece 6 from the high voltage load HV, whereby the workpiece 6 is discharge-machined by the wire electrode 5.

In the welding cycle of the workpiece 6 and the cut-out portion 26 shown in fig. 3B, when the 1 st switch S1 is turned ON (ON) to generate a pulse, a low voltage load LV of about 80V, for example, about 2 μ sec is applied between the wire electrode 5 and the workpiece 6 to check whether or not the inter-electrode condition between the wire electrode 5 and the workpiece 6 is an appropriate position, and if the inter-electrode condition is appropriate, discharge is started. Next, when the 1 st switch S1 is turned OFF (OFF) and the 2 nd switch S2 is turned ON (ON) to generate a pulse, a current of about 110A flows through the wire electrode 5 for a period of, for example, about 3 μ sec, and a voltage of about 70V, which is a voltage of about 1/4 during machining, is applied between the wire electrode 5 and the workpiece 6 from the high-voltage load HV to cause arc discharge, so that the wire electrode 5 is melted, and the cut-out portion 26 is welded to the workpiece 6 by the wire electrode melt.

Next, a basic configuration of the technical idea of the method for machining a cut-out portion in the wire electric discharge machining will be described with reference to fig. 4 and 5. In a basic circuit for realizing the method of the wire electric discharge machining for cutting off the cut-off portion, a 1 st circuit, a 2 nd circuit and a 3 rd circuit are connected in parallel between the wire electrode 5 and the workpiece 6, wherein the 1 st circuit is a circuit in which a low-voltage load LV having a resistance R for checking the inter-electrode state and a 1 st switch S1 are connected in series, the 2 nd circuit is a circuit in which a high-voltage load for electric discharge machining and a 2 nd switch SZ are connected in series, and the 3 rd circuit is a circuit in which a 1 st diode D1 and a 3 rd switch S3 are connected in series. In this circuit, the electric machining conditions are changed from the machining cycle to the welding cycle by ON (ON)/OFF (OFF) controlling the 1 st switch S1, the 2 nd switch S2, and the 3 rd switch S3.

The basic configuration of the wire electric discharge machine is such that a machining cycle for machining a workpiece 6 by a wire electrode 5 is realized by performing control of: the 1 st switch S1 is turned ON (ON) to apply a low voltage load LV between the wire 5 and the workpiece 6, and the 1 st switch S1 is turned OFF (OFF) to turn ON the 2 nd switch S2 to apply a high voltage load HV between the wire 5 and the workpiece 6. Further, the welding cycle of the workpiece 6 and the cut-out portion 26 is realized by performing control of: the 3 rd switch S3 is continuously turned ON (ON), the 1 st switch S1 is turned ON (ON), a low voltage load LV is applied between the wire 5 and the workpiece 6, the 1 st switch S1 is then turned OFF (OFF), the 2 nd switch S2 is turned ON (ON), a high voltage load HV is applied between the wire 5 and the workpiece 6, and finally the 2 nd switch S2 is turned OFF (OFF). Here, although the 2 nd switch S2 is turned OFF (OFF) after a predetermined time by switching the electrical machining conditions from the voltage current waveform of the machining cycle in which the wire electrode 5 machines the workpiece 6 to the voltage current waveform of the welding cycle in which the workpiece 6 and the cut-OFF portion 26 are welded, since the 3 rd switch S3 is always turned ON (ON), the circulating current passing through the 1 st diode D1 and the 3 rd switch S3 flows between the both electrodes of the workpiece 6 and the wire electrode 5, a current having a large pulse width can be generated, the discharge state becomes arc discharge, and a part of the wire electrode 5 is welded between the workpiece 6 and the cut-OFF portion 26, and as a result, the workpiece 6 and the cut-OFF portion 26 are welded.

A machining cycle of the method of machining the cut-out portion in the wire electric discharge machining will be described below with reference to table 1, fig. 4, and fig. 5 (a).

[ Table 1 ]

	S1	S2	S3	LV	HV
						Step 1 of	Is connected to	Disconnect	Disconnect	Under load	Without load
Step 2	Disconnect	Is connected to	Disconnect	Without load	Under load
						Step 3 of	Disconnect	Is connected to	Disconnect	Without load	Under load
Step 4	Disconnect	Disconnect	Disconnect	Without load	Without load

In the 1 st step, when the 1 st switch S1 is turned ON (ON) and the low voltage load LV is applied for a certain period of time, for example, about 2 μ sec, electric discharge starts between the wire electrode 5 and the workpiece 6.

In the 2 nd step, the 2 nd switch S2 is turned ON (ON), and a high voltage load HV is applied to trigger the voltage drop, and the current is increased, whereby the workpiece 6 is subjected to the electric discharge machining by the wire electrode 5.

In the 3 rd step, the discharge time between the wire electrode 5 and the workpiece 6 is determined by the machining conditions of the workpiece 6, and is, for example, a discharge time of about 0.8 μ sec.

In the 4 th step, the 1 st switch S1, the 2 nd switch S2, and the 3 rd switch S3 are temporarily turned OFF (OFF) to set the voltage applied between the electrodes of the wire electrode 5 and the workpiece 6 to a no-load state, thereby setting the time to a stop. When the workpiece 6 is to be machined into the machined shape 21 by the wire electrode 5, the above-described cycle is repeated at a cycle of 125k to 2000kHz to machine the workpiece 6 into the machined shape 21.

The welding cycle in the cut-out portion processing method in the present wire electric discharge machining will be described below with reference to table 2, fig. 4, and fig. 5 (B).

[ Table 2 ]

	S 1	S2	S3	LV	HV
						Step 1 of	Is connected to	Disconnect	Is connected to	Under load	Without load
Step 2	Disconnect	Is connected to	Is connected to	Without load	Under load
						Step 3 of	Disconnect	Disconnect	Is connected to	Without load	Without load
Step 4	Disconnect	Disconnect	Disconnect	Without load	Without load

In the 1 st step, when the 1 st switch SI is turned ON (ON) and the supply of the low-voltage load LV continues for a predetermined time, for example, about 2 μ sec, the discharge starts between the wire electrode 5 and the workpiece 6.

In the 2 nd step, the 2 nd switch S2 is turned ON (ON), and a high voltage load HV is applied to trigger the voltage drop, so that the current is increased, and the workpiece 6 is electric discharge machined by the wire electrode 5.

In the 3 rd step, when switching from the normal cycle, which is a machining cycle, to the welding cycle, the 2 nd switch S2 is turned OFF (OFF) after being turned ON (ON) for a predetermined time, but since the 3 rd switch S3 is always turned ON (ON), a circulating current flows between the workpiece 6 and the wire electrode 5, a current having a large pulse width can be generated, and at this time, the wire electrode 5 melts and is welded to the workpiece 6 and the cut-out portion 26, and as a result, the cut-out portion 26 is welded to the workpiece 6.

In the 4 th step, after no circulation current flows, the 3 rd switch S3 is turned OFF (OFF) and is in the OFF time.

Next, a specific circuit diagram of the method for machining a cut-out portion in the wire electric discharge machining will be described with reference to fig. 6. Here, in the circuit diagram of fig. 6, the voltage waveform and the current waveform generated by ON (ON)/OFF (OFF) control of the 1 st switch S1, the 4 th switch S4, and the 5 th switch S5 are omitted.

A specific circuit for realizing the method for machining a residual workpiece by wire electric discharge machining is a circuit in which a 1 st circuit, a 2 nd circuit, a 3 rd circuit, and a 4 th circuit are connected in parallel between the wire electrode 5 and the workpiece 6, wherein the 1 st circuit is a circuit in which a low-voltage load with a resistance for checking the condition of the machining gap and a 1 st switch S1 are connected in series, the 2 nd circuit is a circuit in which a high-voltage load for electric discharge machining, a 4 th switch S4, and a 5 th switch S5 are connected in series, the 3 rd circuit is a circuit in which a 2 nd diode D2 and a 5 th switch S5 are connected in series, and the 4 th circuit is a circuit in which a 3 rd diode D3 and a 4 th switch S4 are connected in series. In this circuit, if the 4 th switch S4 and the 5 th switch S5 are turned ON (ON), a high voltage load HV can be applied between the wire electrode 5 and the workpiece 6.

In this circuit, the electric machining conditions are changed from the machining cycle to the welding cycle by ON (ON)/OFF (OFF) controlling the 1 st switch S1, the 4 th switch S4, and the 5 th switch S5. When the 5 th switch S5 is turned ON (ON), the 4 th switch S4 is turned OFF (OFF), and then the 1 st circulating current that passes through the 2 nd diode D2 and the 5 th switch S5 flows between the wire electrode 5 and the workpiece 6. When the 4 th switch S4 is turned ON (ON), the 5 th switch S5 is turned OFF (OFF), and then the 2 nd circulating current passing through the 3 rd diode D3 and the 4 th switch S4 flows between the wire 5 and the workpiece 6. That is, in this circuit, the 1 st cycle current and the 2 nd cycle current alternately flow by ON (ON)/OFF (OFF) controlling the 1 st switch S1, the 4 th switch S4, and the 5 th switch S5. In the method of machining a cut-out portion in wire electric discharge machining according to the present invention, since 2 circulation currents are generated using a specific circuit incorporating the diode D2 and the diode D3, the current waveform of electric discharge machining can be made close to a trapezoidal shape, and the problem of heat generation due to switching can be alleviated by alternately generating circulation currents. That is, in the method of machining a cut-out portion in the present wire electric discharge machining, since the workpiece 6 and the cut-out portion 26 are welded by the circulating current, the current waveform can be made to decrease slowly compared to the case where the workpiece 6 is subjected to the electric discharge machining. Further, the timings of turning ON (ON) and OFF (OFF) of the 4 th switch S4 and the 5 th switch S5 may be reversed from those described below.

A machining cycle of the cut-out portion machining method in the present wire electric discharge machining will be described below with reference to table 3 and fig. 6.

[ Table 3 ]

	S 1	S4	S5	LV	HV
						Step 1 of	Is connected to	Disconnect	Disconnect	Under load	Without load
Step 2	Disconnect	Is connected to	Is connected to	Without load	Under load
						Step 3 of	Disconnect	Is connected to	Is connected to	Without load	Under load
Step 4	Disconnect	Disconnect	Is connected to	Without load	Without load
						Step 5	Disconnect	Disconnect	Disconnect	Without load	Without load

In the 1 st step, when the 1 st switch S1 is turned ON (ON) and the supply of the low voltage load LV continues for a predetermined time, for example, about 2 μ sec, the discharge starts between the wire electrode 5 and the workpiece 6.

In the 2 nd step, the 1 st switch S1 is turned OFF (OFF), the 4 th switch S4 and the 5 th switch S5 are turned ON (ON), a high voltage load HV is applied with a voltage drop as a trigger, and the current is increased, so that the workpiece 6 is discharge-machined by the wire electrode 5.

In the 3 rd step, the ON (ON) states of the 4 th switch S4 and the 5 th switch S5 are continued, and the discharge time between the wire electrode 5 and the workpiece 6 is determined by the machining conditions of the workpiece 6, for example, a discharge time of about 0.8 μ sec.

In the 4 th step, the 5 th switch S5 is kept in the ON state, and after the 4 th switch S4 is turned OFF (OFF), the 5 th switch 5 is turned ON for sub-microsecond only to release the state of application of the high-voltage load HV, thereby making the current waveform close to a trapezoidal shape.

In the 5 th step, the 1 st switch S1, the 4 th switch S4, and the 5 th switch S5 are temporarily turned OFF (OFF) to set the voltage applied between the wire 5 and the workpiece 6 in a no-load state for a stop time. When the workpiece 6 is to be machined into the machined shape 21 by the wire electrode 5, the above-described cycle is repeated at a cycle of 125k to 2000 kHz.

A welding cycle of the cut-out portion processing method in the present wire electric discharge machining will be described below with reference to table 4 and fig. 6.

[ Table 4 ]

	S 1	S4	S5	LV	HV
						Step 1 of	Is connected to	Disconnect	Disconnect	Under load	Without load
Step 2	Disconnect	Is connected to	Is connected to	Without load	Under load
						Step 3 of	Disconnect	Is connected to	Is connected to	Without load	Under load
Step 4	Disconnect	Disconnect	Is connected to	Without load	Without load
						Step 5	Disconnect	Disconnect	Disconnect	Without load	Without load

In the 1 st step, when the 1 st switch S1 is turned ON (ON) and the supply of the low voltage load LV continues for a predetermined time, for example, about 2 μ sec, the discharge starts between the wire electrode 5 and the workpiece 6.

In the 2 nd step, the 4 th switch S4 and the 5 th switch S5 are turned ON (ON), a high voltage load HV is applied with a voltage drop as a trigger, and a current is increased to perform electric discharge machining ON the workpiece 6 via the wire electrode 5.

In the 3 rd step, the ON (ON) states of the 4 th switch S4 and the 5 th switch S5 are continued, and the discharge time is determined by the machining conditions, for example, a discharge time of about 0.8 μ sec.

In the 4 th step, the 4 th switch S4 is turned OFF (OFF) after a predetermined time, but since the 5 th switch S5 is always turned ON (ON), a circulating current flows between the wire electrode 5 and the workpiece 6, the state of application of the high voltage load HV is released, and a current having a large pulse width can be generated, so that arc welding is performed between the workpiece 6 and the cut-out portion 26 at this time, and both are welded.

In the 5 th step, after no circulation current flows, the 5 th switch S5 is turned OFF (OFF) to be a stop time.

In the method of machining a cut-out portion in the wire electric discharge machining, in the welding step of welding the cut-out portion 26 to the workpiece 6, one or more welded portions 20 may be formed according to the size of the cut-out portion 26, and the slight inclination of the cut-out portion 26 may be ignored as long as the cut-out portion 26 is not separated from the workpiece 6. For example, if the cut-out portion 26 is small and light, the cut-out portion 26 can be held on the workpiece 6 by making the workpiece 6 and the welded portion 20 of the cut-out portion 26 to be one. In addition, if the cut-out portion 26 is large or heavy, the work 6 and the welded portion 20 of the cut-out portion 26 can be formed in a plurality of places to maintain the cut-out portion 26 on the work 6 in a balanced manner.

The method of machining a cut-out portion in the wire electric discharge machining can be applied to die-side machining for machining a workpiece 6 as a product with the cut-out portion 26 as a waste, or punch-side machining for machining a workpiece 6 as a waste with the cut-out portion 26 as a product. In fig. 7(a) and 7(B), since the hole 19 such as a threading hole is formed on the cut-out portion 26 side, the cut-out portion 26 is scrap and is discarded, and the processing is die side processing. Although not shown, when the workpiece 6 is subjected to the punch side processing, the cut-out portion 26 is to be a product, and therefore, the hole 19 such as a threading hole is formed not on the side where the cut-out portion 26 is to be formed but on the side of the workpiece 6 which is a waste product.

Next, a difference in the cumulative machining time taken to perform the electric discharge machining on the workpiece 6 by the cut-out portion machining method of the present invention and the conventional cut-out portion machining method will be described with reference to fig. 9(a) and 9 (a). In the present embodiment, as shown in fig. 7(a) and 7(a), in the cut-out portion processing method, since the hole 19 such as a threading hole is formed on the cut-out portion 26 side, the die side processing is performed to form the workpiece 6 into a product by using the cut-out portion 26 as a waste.

First, a wire electric discharge machining method according to the present invention will be described with reference to fig. 9 (a). In the present cut-out portion processing method, in the step of roughly processing the workpiece 6, rough processing is performed while welding a predetermined distance at an arbitrary position. In order to weld the cut-out portion 26 to the workpiece 6 by melting the wire electrode 5 at one or more (two in the drawing) positions during the rough machining, the electric discharge machining is continued for the workpiece 6, the welding portion 20 is formed by arc welding in the region where the cut-out portion 26 is left on the workpiece 6 in the related art, and the region other than the welding portion 20 is machined until the cut-out portion 26 is separated from the workpiece 6. At this time, since the cut-out portion 26 is in a state of being spot-welded to the workpiece 6 at the welded portion 20 by a part of the melted wire electrode 5, the cut-out portion 26 is not cut off from the workpiece 6, and is held on the workpiece 6 (step S1). It is determined whether or not the next machined shape 21 to be subjected to electric discharge machining is present on the same workpiece 6, and when the next machined shape 21 is present, the processing step S1 is repeated to perform electric discharge machining on all the remaining machined shapes 21 to be subjected to electric discharge machining. If there is no next machined shape 21 to be subjected to electric discharge machining, the process proceeds to the subsequent processing step (step S2). Next, when all rough machining is performed on the workpiece 6, the workpiece is moved to the first machined shape 21, automatic electric discharge machining of the workpiece 6 by the wire electric discharge machine is temporarily stopped (step S3), the operator moves the table (performs axial movement) to move the workpiece 6 to the position where the cut-out portions 26 are separated, and all the cut-out portions 26 are separated from the workpiece 6 by an external force such as tapping (step S4). Subsequently, the workpiece 6 to be processed for forming the product is finished, and the processing is terminated (step S5). In the wire electric discharge machining, the operation performed by the operator in the wire electric discharge machine is only a step of separating the cut-out portion 26 from the workpiece 6, and the time required for this step is several seconds, and most of the steps are automatically processed.

Next, a conventional wire electric discharge machining method will be described with reference to fig. 9 (B). In the conventional cut-out portion machining method, in the step of rough machining the workpiece 6, the electric discharge machining is performed in a state of cutting residue, instead of rough machining at an arbitrary position by a predetermined distance. At this time, the cut-out portion 26 is held by the workpiece 6 by the residual cutting portion, and the cut-out portion 26 remains on the workpiece 6 without being cut off from the workpiece 6 (step S11). It is determined whether or not the next machined shape 21 to be subjected to electric discharge machining is present on the same workpiece 6, and if the next machined shape 21 is present, the processing step S11 is repeated to machine all the remaining machined shapes 21 to be subjected to electric discharge machining. If there is no next machined shape 21 to be subjected to electric discharge machining, the process proceeds to the subsequent processing step (step S12). Next, when all the machining shapes 21 are roughly machined, the wire electric discharge machine moves to the first machining shape 21 and stops the automatic electric discharge machining of the workpiece 6 by the wire electric discharge machine (step S13). Next, the operator restarts the program to perform the electric discharge machining on the portion remaining after the cutting. When the cut-out portion 26 is cut out from the workpiece 6, the program is stopped. Here, the wire electric discharge machine is changed to the manual mode, the Z axis and the table are moved, the cut-out portion 26 is removed from the workpiece 6, the axes are returned to the original positions manually or automatically, and the program is started (step S14). It is determined whether or not the next machined shape 21 to be separated is present on the same workpiece 6, and if there are any machined shapes 21, the process S14 is repeated the number of times these operations are repeated by the number of machined shapes 21, and all the processes of separating the cut-out portion 26 from the workpiece 6 by electric discharge machining are performed (step S15). Subsequently, the workpiece 6 to be processed is finished to finish the processing (step S16).

The cut-out portion processing method of the present invention and the conventional cut-out portion processing method are subjected to the above-described treatment steps, but when comparing the two, the cut-out portion processing method of the present invention can significantly shorten the time required for the electric discharge machining of the workpiece 6 as compared with the conventional cut-out portion processing method.

For example, when 1 workpiece 6 is processed into square holes of 100 predetermined processing shapes 21, the following results can be obtained. In the conventional machining method, when machining a square hole at one location, the rough machining time takes about 10 minutes, the machining time (including the shaft movement time) for separating the cutout portion 26 from the workpiece 6 takes about 3 minutes, and the finish machining time takes about 14 minutes. Therefore, all the rough processing required 16.7 hours, the separation processing required 5 hours, and the finishing required 23.3 hours. The separation process required 3 minutes, and 5 hours since there were 100 spots, during which the operator was unable to leave the wire electric discharge machine and had to perform the work. Within 3 minutes of the separation processing, 2 minutes is a time for the wire electric discharge machine to perform the processing of separating the cut-out portion 26, and is a time for the operator to monitor until the cut-out portion 26 falls, and the operator needs a standby time of 3.3 hours and cannot leave the wire electric discharge machine. In contrast, in the cut-out portion processing method of the present invention, when the same processed shape 21 rectangular hole is processed at one location, the rough processing time takes about 11 minutes, the separating time (including the shaft moving time) for knocking out the cut-out portion 26 from the workpiece 6 takes about 5 seconds, and the finish processing time takes about 14 minutes. Therefore, the entire rough machining takes 18.3 hours, the cutting-out machining takes 8.3 minutes, and the finishing machining takes 23.3 hours, and the entire process can be shortened by 3.2 hours. Therefore, in terms of improving productivity of the wire electric discharge machine for performing electric discharge machining on the workpiece, not only the time of 3.2. hours can be shortened, but the time for an operator to perform work near the wire electric discharge machine accounts for about 11% of the total machining time in the conventional cutting-off portion machining method, and when this function is used, the time is reduced to 0.3% or less, and 99.7% of the time in the entire working process can be operated without a person. In addition, although a command for enabling the original function in rough machining is added to the machining program for making the cut-out portion machining method of the present invention, a separate machining program is not required, and the program can be simplified as compared with the conventional cut-out portion machining method. Further, even in the punching process, the present invention can be used even when the separating process is performed after the finish process is completed, and the completely unmanned process can be realized until the separating process, and the cut-out portion can be removed from the workpiece by lightly tapping after the completion of the process, as in the case of the cut-out portion process in the die pad process.

Claims (12)

1. A method of cutting off a portion in wire electric discharge machining,

a wire electrode fed from a source wire bobbin provided in an apparatus main body is supplied to a workpiece mounted below an upper head and a lower head arranged below the workpiece and facing the upper head, and the wire electrode is discarded via a guide member arranged below the lower head,

the method includes changing an electrical machining condition applied between the wire electrode and the workpiece from a machining cycle to a welding cycle at least one position of a predetermined machining shape of the workpiece, melting a part of the wire electrode, and welding the workpiece and a cut-out portion cut out from the workpiece with the wire electrode melt at a welded portion located at a predetermined position, thereby holding the cut-out portion on the workpiece by the welded portion and preventing the cut-out portion from falling off from the workpiece.

2. A method of cutting off a portion to be machined in wire electric discharge machining according to claim 1, wherein a current flowing through the wire electrode for welding the workpiece and the cut-off portion by the welding portion has a current peak value smaller and a pulse length longer than a current for wire electric discharge machining of the workpiece, changes from machining discharge to arc discharge, and welds the cut-off portion to the workpiece at the welding portion by welding using the wire electrode melt.

3. The method of cutting away a portion in wire electric discharge machining according to claim 1, wherein the welding cycle is performed under the machining conditions of: and welding the workpiece and the cut-out portion by using a part of the workpiece and a part of the cut-out portion facing each other as the welded portion while cutting the workpiece.

4. The method of processing a cut-away portion in wire electric discharge machining according to claim 1, wherein the cut-away portion is separated from the workpiece by breaking the welded portion by an external force after the electric discharge machining is performed on the workpiece with respect to the workpiece and the welded portion of the cut-away portion.

5. A method of cutting off a portion in wire electric discharge machining according to claim 1, wherein the electric machining condition is changed by connecting a 1 st circuit, a 2 nd circuit, and a 3 rd circuit in parallel between the wire electrode and the workpiece, and controlling on/off of the 1 st switch, the 2 nd switch, and the 3 rd switch, wherein the 1 st circuit is a circuit in which a low voltage load with a resistance for checking an inter-electrode state and the 1 st switch are connected in series, the 2 nd circuit is a circuit in which a high voltage load for electric discharge machining and the 2 nd switch are connected in series, and the 3 rd circuit is a circuit in which a 1 st diode and the 3 rd switch are connected in series.

6. A method of cutting away a portion in wire electric discharge machining according to claim 1, wherein the machining cycle of the workpiece is executed by 1 st specific control, the 1 st specific control being: the 1 st switch is turned on to apply the low voltage load between the wire electrode and the workpiece, and the 1 st switch is turned off to turn on the 2 nd switch to apply the high voltage load between the wire electrode and the workpiece, thereby performing electric discharge machining on the workpiece by the wire electrode.

7. A cut-away portion processing method in wire electric discharge machining according to claim 5, wherein the welding cycle of the work is performed by 2 nd specific control, the 2 nd specific control being: turning on the 1 st switch and the 3 rd switch to apply the low voltage load between the wire electrode and the workpiece, continuing the on state of the 3 rd switch, turning off the 1 st switch and turning on the 2 nd switch to apply the high voltage load between the wire electrode and the workpiece, and finally turning off the 2 nd switch to continue the on state of the 3 rd switch to release the high voltage load from the applied state, and passing a circulating current between the wire electrode and the workpiece to generate a current having a large pulse width, thereby welding the cut-off portion to the workpiece.

8. The cut-away portion processing method in wire electric discharge machining according to claim 1, in a circuit in which a 1 st circuit, a 2 nd circuit, a 3 rd circuit and a 4 th circuit are connected in parallel between the wire electrode and the workpiece, the 1 st switch, the 4 th switch and the 5 th switch are controlled to be turned on/off to change the electric machining condition, wherein the 1 st circuit is a circuit in which a low-voltage load with a resistor for checking an inter-electrode condition and the 1 st switch are connected in series, the 2 nd circuit is a circuit in which a high-voltage load for electric discharge machining, the 4 th switch, and the 5 th switch are connected in series, the 3 rd circuit is a circuit formed by connecting a 2 nd diode and the 5 th switch in series, and the 4 th circuit is a circuit formed by connecting a 3 rd diode and the 4 th switch in series.

9. A cut-away portion processing method in wire electric discharge machining according to claim 8, wherein the machining cycle of the workpiece is executed by 3 rd specific control, the 3 rd specific control being: the 1 st switch is turned on to apply the low voltage load between the wire electrode and the workpiece, and the 4 th switch and the 5 th switch are turned off to apply the high voltage load between the wire electrode and the workpiece, thereby performing electric discharge machining on the workpiece by the wire electrode.

10. A cut-away portion processing method in wire electric discharge machining according to claim 8, wherein the welding cycle of the work is performed by 4 th specific control, the 4 th specific control being: the method includes turning on the 1 st switch to apply the low voltage load between the wire electrode and the workpiece, turning off the 1 st switch and turning on the 4 th and 5 th switches to apply the high voltage load between the wire electrode and the workpiece, continuing the on states of the 4 th and 5 th switches to continue the high voltage load, and finally turning off the 4 th switch and continuing the on state of the 5 th switch to release the high voltage load, and circulating current is passed between the wire electrode and the workpiece to generate a current having a large pulse width, thereby welding the cut-off portion to the workpiece.

11. A cut-off portion processing method in wire electric discharge machining according to claim 1, wherein the portion of the wire electrode melted to weld the workpiece and the cut-off portion is a wire peripheral portion of the wire electrode, and when the cut-off portion and the workpiece are welded by melting the portion of the wire electrode, the wire electrode does not break, and a feeding state of the wire electrode can be maintained.

12. The method of cutting off a cut-off portion in wire electric discharge machining according to claim 1, wherein in the step of welding the cut-off portion and the workpiece by melting the portion of the wire electrode, when the wire electrode is broken, the wire electrode is fed to a machining seam at a wire breakage point, and the welding step or the machining step is continued.