JPH07266138A - Wire electric discharge machining method and power supply circuit for wire electric discharge machining - Google Patents

Abstract

PURPOSE:To finish the surface with finer surface roughness at a high speed by switching the machining voltage to high-frequency alternating voltage on a designated condition obtained by a high-frequency coupling transformer interposed between a voltage pulse supply source and a discharge gap to perform finishing electric discharge machining improved in surface roughness. CONSTITUTION:A circuit device 12 comprising a high frequency coupling transformer 12 interposed between a high frequency pulse generating circuit 10 and a discharge gap, and a circuit switching open-close switch 14 for the time of transition from a first machining process of working on dimensions, shape and accuracy to a second machining process of finishing such as machined surface roughness or the like is stored in a box. When open-close switches 14A, 14B of the feeder circuit 14 are off, and the primary and secondary coil open-close switches 14C, 14D are on, a power supply circuit for finish machining by high frequency a.c. voltage used in the second machining process is formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a wire electric discharge machining method,
In particular, from rough machining (first cut machining) to finish machining by the wire electric discharge machining, high machining speed (mainly short machining time) and excellent machining surface roughness (smaller machining surface roughness) Furthermore, the present invention relates to a processing method capable of finishing to a predetermined dimensional accuracy, and a processing power supply circuit suitable for carrying out the processing method.

[0002]

2. Description of the Related Art Conventionally, this type of wire electric discharge machining has a method in which a wire electrode stretched in a predetermined state between a pair of guides spaced apart from each other is axially renewedly fed and moved while being substantially perpendicular to the axial direction. The workpiece is made to face each other through a minute gap, and machining is performed by an electric discharge pulse generated by applying an intermittent voltage pulse between the two with the machining liquid supplied to the gap. By providing a relative machining feed along a predetermined machining contour line shape on the plane in the right-angled direction between the workpieces, the workpieces are cut and cut.

In order to machine and finish various molds, members, parts and the like by such a wire electric discharge machining method, first, the wire electric discharge machining is carried out by the material of the object to be machined,
Depending on the plate thickness, the purpose of processing, etc., the material of the wire electrode,
Select and set the wire diameter, tension applied to the processing section tension, renewal feed rate, etc., as well as the type and properties of the working fluid, and especially the electrical conductivity, as well as the intervening supply method such as jetting and dipping of the working fluid. And its machining conditions, etc. are selected and set, and machining feed conditions such as machining feed speed and servo control, and voltage or discharge pulse voltage value for machining, discharge pulse width, pause width, discharge current amplitude, etc. Select and set the electrical machining conditions, and give the first machining groove while controlling the machining feed along the locus offset by the predetermined amount from the predetermined machining contour line shape between the wire electrode and the workpiece while controlling it with the numerical controller. First cut processing (normal rough processing) is carried out.
Next, after the first cut processing, the setting of each of the various set processing conditions is switched to a predetermined second cut (medium processing) processing condition, and the offset of the processing feed path with respect to the predetermined processing contour line shape is switched and set to perform processing. Usually, from the first cut processing (rough processing), as it is performed, and then the third cutting processing of the next processing step is sequentially performed,
The object to be processed is finished to have a predetermined dimensional accuracy and surface roughness by 3 to 7 steps such as intermediate processing, semi-finishing processing, finishing processing, and final finishing processing (for example, JP-A-57-57). No. 102724, JP-A-1-45523.
No.

[0004]

In the processing of the first cut processing step, the work piece is made of an iron-based material and has a normal plate thickness (for example, about 20 to 90 mmt) and a wire electrode of about 0. When a brass-based wire of about 2 to 0.3 mmφ is used and a conventional water-based working fluid is used as the working fluid, there are various types of working power supplies or power supply circuits for the working. The processing performance is about 20 to 35 μmRmax for the processed surface roughness and about 150 to 300 mm ² for the processing speed, and there is no significant difference because the upper limit of the average processing current is restricted. However, in the finishing process after the second cut, especially in the finishing process,
When the demand for processing performance becomes strict, as the shape accuracy is about 1 to 2 μm or less, or the final finished surface roughness is about 1 to 3 μm Rmax or less, intermediate processing after the second cut, For example, 6 to 7 as processing steps such as intermediate finishing and finishing.
In many cases, more or more processing steps are required, a long processing time is required, and the processing efficiency is significantly reduced.

Considering this point, most of the conventional machining power supplies have a machined surface roughness of about 3 to 5 μm.
It is not suitable for finishing more than around mRmax,
It is unavoidable that long-time machining due to a large number of machining steps will be unavoidable only by changing and setting the machining conditions, while the machining surface (about 3 to 5 μmRmax) of the conventional machining power source.
Under the set processing conditions for finishing, it is quite difficult to perform dimensional and shape precision processing for drums or straightness of the work piece, leftovers, etc. It is known that it is difficult to finish the processed surface roughness to about 3 to 5 μRmax or more under the set processing conditions.

That is, a conventional wire electric discharge machining method and a machining power supply circuit or power supply device for the machining method are:
In particular, there was a problem in finally improving the finished surface roughness. Recently, for example, it has been attempted to apply a high frequency power source or a high frequency AC voltage to the discharge gap for finishing (for example, Japanese Patent Laid-Open No. 5-1774).
No. 35 and Japanese Patent Application Laid-Open No. 6-8049) could not be configured as a power supply circuit for wire electric discharge machining so that those performances could be sufficiently and reliably exhibited.

Therefore, an object of the present invention is to reduce the number of processing steps as small as possible, for example, preferably within the range from the first cut processing step to the force or fifth cut processing step, and more preferably to the third or force cut processing step. Through processing of about 5 to 5 processing steps, the workpiece is processed within a range of about 2 to 3 μm, preferably within a range of about 1 to 2 μm with a predetermined dimension and shape accuracy, within a range of about 3 to 5 μm Rmax,
It is preferable to provide a wire electric discharge machining method for finishing to a predetermined surface roughness within about 1 to 2 μm Rmax, and a power supply circuit for wire electric discharge machining therefor.

[0008]

The above-mentioned objects of the present invention are as follows. (1) The wire electrode stretched in a predetermined state between a pair of guides arranged at intervals is renewed while being moved in the axial direction. The workpiece is made to face each other through a minute gap in a direction substantially perpendicular to the axial direction, and a machining voltage is applied between the two with a machining liquid being supplied to the gap to perform machining by the generated electric discharge. In wire electric discharge machining for providing relative machining feed along a predetermined contour line shape to be machined on the plane in the perpendicular direction between the electrode and the workpiece, the wire electric discharge machining is performed as follows: (a) the machining voltage As the DC voltage source, an intermittent voltage pulse having a dwell time obtained by turning on / off the switching element is used, and the working fluid to be used, the material of the electrode / workpiece, the combination, the plate thickness, and the purpose of the working In the set processing conditions in accordance with,
A first machining step for machining and forming the contour-shaped machining groove with a predetermined dimensional accuracy; and (b) after the machining in the first machining step, the machining voltage is discharged to the voltage pulse supply source and the discharge. A wire electric discharge machining method is provided in which a second machining step of switching to a high frequency AC voltage of a predetermined condition obtained by a high frequency coupling transformer inserted between the gap and a finish electric discharge machining for improving surface roughness is sequentially performed. By

(2) In the processing method according to (1), the first processing step is a first-cut processing step of first processing and forming the contoured groove.
By providing a wire electric discharge machining method comprising a second cut machining step in which the machining conditions after the machining step are switched to perform machining with predetermined dimension and shape accuracy,

(3) In the processing method of (2), the wire electrode in the first cut processing step is
Servo feed control method between workpieces is zero method servo control method that feed rate becomes zero when deviation of discharge gap voltage with respect to servo reference voltage is zero, servo feed control method in the second cut machining process is deceleration servo By setting the control method and performing the wire electric discharge machining method for machining each machining step,

Further, (4) the above (1), (2) or (3)
In the machining method according to the first aspect of the present invention, an intermittent voltage pulse source having a dwell time obtained by turning on / off the switching element is used to turn on / off the DC voltage source in the first processing step. A resistor is inserted in the normal voltage pulse supply circuit in which a specified current limiting resistor is inserted in the series circuit that forms the voltage pulse when turned off, and in the series circuit that forms the current pulse by turning the DC voltage source on and off. Not installed, or with a non-resistive current pulse supply circuit in which a current limiting resistance other than a small resistance for current detection is not installed, and the switching element of the current pulse supply circuit is the normal voltage By providing a wire electric discharge machining method in which the electric discharge is applied by the voltage pulse applied to the electric discharge gap of the pulse supply circuit and the electric current is controlled to be turned on for a predetermined time width,

Further, (5) the above (1), (2) or (3)
In the machining method according to the present invention, in the second machining step, machining conditions for finishing the workpiece to a predetermined surface roughness after the machining of the first machining step are sequentially switched or not switched. By using a wire electric discharge machining method that includes one or more machining steps,

Further, (6) the above (1), (2) or (3)
In the machining method according to the second aspect, by setting the servo feed control method between the wire electrode and the workpiece in the second machining step to a deceleration servo control method to perform machining,

Further, (7) the above (1), (5) or (6)
In the processing method according to the present invention, in order to output and supply a high-frequency AC voltage from the secondary winding of the high-frequency coupling transformer to the discharge gap, the intermittent winding having a dwell time supplied to the primary winding of the transformer. This is achieved by an electric discharge machining method in which switching and connection are controlled so that current pulses are supplied from the resistanceless current pulse supply circuit.

Further, the above-mentioned object of the present invention is (8) voltage pulse supply in which a DC power source, a current limiting resistor and an ON / OFF switch element are connected in series to a discharge gap formed by a wire electrode and a workpiece. The circuit is connected in parallel, and a current pulse supply circuit having no current limiting resistance is connected in parallel in a series circuit in which a second DC power source and a second on / off switch element are connected in series, In the power supply circuit for wire electric discharge machining, which supplies an ON signal of a predetermined time width to the second ON / OFF switch element in response to the start of discharge in the discharge gap after the ON / OFF switch element 1 is turned on, A high-frequency on / off gate signal circuit is provided so as to be switchably connectable to the gate input of the second on / off switch element, and is wound between the output of both ends of each of the voltage and current pulse supply circuits and the discharge gap. A high-frequency coupling transformer of a ring core having a primary winding and a secondary winding, the output can be switched to a connection between the discharge gap and the primary winding, and the discharge gap can be connected to the output and the secondary winding. A changeover switch capable of changing over to the connection is provided, and in the finishing process after the roughing process and the dimension / shape accuracy producing process by the machining power source circuit,
The gate input of the ON / OFF switch element is switched and connected to the high-frequency gate signal circuit, and the output of the current pulse supply circuit and the discharge gap are connected to the primary winding and the secondary winding by the switching operation of the changeover switch. Connect to the output,
By providing a power supply circuit for wire electric discharge machining configured to supply a high frequency AC voltage to the electric discharge gap for finish electric discharge machining,

(9) In the processing power supply circuit according to (8), the high frequency coupling transformer is integrally coupled with the changeover switch and is housed in a box.
By setting the box as a power supply circuit for wire electric discharge machining provided in or near the machining tank near the electric discharge gap,

(10) In the processing power supply circuit according to (8) or (9), the high-frequency coupling transformer has a ferrite ring core, and the output is more than the number of windings of the input primary winding. By using a power supply circuit for wire electric discharge machining with a configuration in which the number of turns of the secondary winding is increased,

(11) In the processing power supply circuit of (9), the box is a transformer chamber for housing a high frequency coupling transformer, and a switch box for a power supply circuit opening / closing switch provided at both ends of the transformer chamber. And a switch box of a primary winding and a secondary winding opening / closing switch, and further, a side wall surface provided with a connection terminal to a work stand in the switch box is formed of a terminal metal plate or a terminal metal plate is attached. This is achieved by providing a power supply circuit for wire electric discharge machining, which is configured to electrically and mechanically connect and attach the terminal metal plate to the work stand.

[0019]

Since the wire electric discharge machining method of the present invention has the above-mentioned structure, the first cut machining step and / or the second machining step as the first machining step of the present invention by the intermittent voltage pulse having the down time. The cutting process can be performed efficiently and at high speed to ensure the predetermined size and shape accuracy, and the third process as the second process that is performed subsequent to the first process described above. Since the processing of the finishing processing step such as cutting and / or force cutting is preferably performed by applying a high frequency AC voltage capable of having a dwell time for each cycle,
The surface roughness can be finished more finely at high speed,
Fine and high-precision wire electric discharge machining can be efficiently performed by reducing the machining time as a whole.

Further, since the power supply circuit for wire electric discharge machining of the present invention has the above-mentioned structure, the first machining process such as the rough machining or the second cut machining step for obtaining the above-mentioned dimension and shape accuracy is the conventional type. The high-speed machining and dimension / shape accuracy machining are performed by using the machining power supply circuit of this wire electric discharge machine as it is, and mainly during the second machining process, which is finish machining to improve surface roughness. Since a high frequency AC voltage is obtained by combining a current pulse supply circuit in which a current limiting resistor in the voltage pulse power source used for the rough machining is not inserted and a high frequency coupling transformer having a separately provided changeover switch, With the effective use of circuit elements and equipment, it is now possible to perform finishing with a high-frequency AC voltage that is effective for surface roughness improvement.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a combination of the power supply circuit for wire electric discharge machining according to the present invention with a conventional power supply circuit for wire electric discharge machining, and a part of the power supply circuit of the conventional example is used and a part of the power supply circuit is switched. 1 shows a schematic configuration of one embodiment in which the wire is reciprocally fed and moved in the axial direction while a predetermined tension is applied between the pair of positioning guides 2A and 2B arranged at a distance. Electrodes 3 are work stands 4 placed on an xy cross table (not shown)
A workpiece to be machined, which is opposed to the wire electrode axial direction from a direction substantially perpendicular to the wire electrode axial direction through a minute discharge gap, and is intermittently applied between the two under a machining liquid supply intervention by a machining liquid supply means (not shown). The machining is performed by causing an electric discharge by a machining voltage such as a voltage pulse.

The machining voltage for machining in the first machining step of the present invention, that is, the intermittent voltage pulse, is supplied from the wire discharge machining power source circuit 5 of the embodiment shown in FIG. Supply is applied between the wire electrode 1 and the work piece 3 via a coaxial or shield wire as 11B, or to the lead wire near the discharge gap, preferably using a twisted wire. The power supply circuit 5
Is an electronic switch element 6B such as a MOS-FET transistor in which a plurality of DC voltage sources 6A and a current capacity are connected in parallel, a current limiting resistor 6C, and a reverse voltage prevention rectifier 6D.
The most conventional intermittent voltage pulse generation / supply circuit 6 composed of a series circuit of is connected to the power supply connection lines 11A and 11B in parallel with the discharge gap, and the intermittent voltage pulse is pulse-controlled. It is generated as desired by controlling the switch element 6B by the device 7. That is, the control device portion of the switch device 6B of the control device 7 is provided with a constant on-time signal τ _ON and OFF which is previously selected and set, except when the switch device 6B is controlled to be changed by the discharge state detection information of the discharge gap. When the voltage pulse is supplied and controlled by regularly and alternately repeating the time signal τ _OFF, and when the ON time signal of the switch element 6B is applied to the discharge gap from when the voltage pulse is applied to when the discharge is started in the discharge gap. It increases as a function of the discharge start delay period, that is, the measurement of the on-time signal is started from the start of discharge in the discharge gap after the start of the voltage pulse application so that the discharge duration of each discharge pulse becomes a set constant value, There is a control for turning off the switch element 6B upon completion and shifting it to the off time. In the following description, the latter case will be mainly described. Obtain, but the present invention is not construed as being limited thereto.

The power supply circuit 5 includes the switch element 6
In addition to the machining voltage pulse supply circuit 6 by turning on / off B, the discharge current amplitude Ip of the discharge pulse by the circuit 6 is increased, and thus the machining average current is increased to further increase the machining speed. A pulse current amplifier circuit or a current pulse supply circuit 8 is provided in parallel with the circuit 6 as a series circuit including a variable DC voltage source 8A, a switch element 8B, and a reverse voltage prevention rectifier 8C. In order to output a high current with a steep rise when the switching device 8B is turned on by the control device 7, a so-called current limiting resistor is a non-resistance circuit in its series circuit, or a control device for preventing damage to the switching device 8B. A circuit 8 in which a current limiting resistor is not inserted in addition to a minute detection resistor for operating the current controller 7A of the switch element 8B provided in 7. The on-time signal of the switch element 6B or the on-time signal from the start of the discharge is within several tens of μS at the maximum in wire electric discharge machining, and usually within several μS. Even when the discharge start in the gap is detected by a pulse and the switch is turned on during the on-time signal that operates, damage can be avoided from the relation of the switch element 8B or at least the transition time to the saturation region operation of the circuit 8 or the like. However, the operating region of the switch element 8B is set as an unsaturated region, or at least the range in which the current of the circuit 8 is sufficiently smaller than the saturation current value of the switch element 8B (usually a fraction) is set as the operating region. If the conditions are set, there is no problem of damage to the switch element 8B, and the current off cutoff characteristic of the switch element 8B or the circuit 8 is sharp and steep, which is preferable. It is the casting.

In the illustrated embodiment, in the power supply circuit 5,
There is provided another, ie, second voltage pulse supply circuit 9 consisting of a series circuit of a variable DC voltage source 9A, a switch element 9B, a current limiting resistor 9C and a reverse voltage prevention rectifier 9D. The voltage pulse supply circuit 9 is used as desired by the open / close switch 9E.
For example, the direct-current voltage source 9A is variable and has a voltage value equal to or higher than the direct-current voltage source 6A (about 80 to 120 V) whose output voltage is usually constant (about 80 to 280 V), and the current limiting resistor 9C is a resistor. 6C is set to be large, the current capacity of the circuit 9 is set to be small, and the switch element 9B is controlled by the pulse controller 7 such as ON / OFF synchronous application with the switch element 6B. It is a sub-power supply that not only is essential to the practice of the present invention, but also serves to accelerate the discharge start by increasing the machining voltage and to maintain a wide discharge gap by servo control by detecting the gap voltage.

The above-mentioned current pulse supply circuit 8 together with the voltage pulse supply circuit 6 and the normal circuit 9 serves as the power supply circuit 5.
A first-cut processing step for performing a first-cut processing step for the workpiece 3 and a second-cut processing step for performing dimension / shape accuracy processing of the processing after the first-cut processing step, that is, the first aspect of the present invention in which an intermittent voltage pulse is used as a processing voltage. It is used in the machining process, and the gate input is the changeover switch 8
It is connected to the control device 7 by E, and the related control with the circuit 6 as described above is performed, for example, but after the processing of the second cutting processing step which is the first processing step is finished, the present invention In the second processing step, the voltage pulse supply is performed when shifting to the finishing processing step 1 or 2 (for example, the third cut processing step or the force cut processing step) of the surface roughening processing using the high frequency AC voltage. Circuits 6 and 9 are provided with open / close switches 6E and 9 as required.
At the same time as disconnecting at E, the changeover switch 8E is switched to the gate signal circuit 8D side of the intermittent pulse so that the current pulse supply circuit 8 functions as the high frequency pulse (current) generation circuit 10.

At that time, a high frequency coupling transformer 1 provided between the high frequency pulse generating circuit 10 and the discharge gap.
3 and a circuit changeover opening / closing switch 14 for shifting from the first processing step for obtaining the above-mentioned dimension / shape accuracy to the second processing step for finishing such as processing surface roughness. The circuit device 12 is configured and switched as follows. High frequency coupling transformer 13
Is for converting each intermittent high-frequency pulse current output from the high-frequency pulse generation circuit 10 into a high-frequency AC voltage for one cycle, which is wound around a high-permeability ring core 13A made of high-frequency ferrite or the like. The wire 13B and the secondary winding 13C have a winding ratio of 1: 1 to 3, preferably 1: 1 to
2. The number of turns is 1 to 5 turns of the primary winding, preferably 1 to 2
Turn, secondary winding 1 to 12 turns, preferably 1 to 4 turns, so that a high frequency response can be achieved with a small number of turns.
Moreover, in order to obtain a high-frequency AC voltage for finishing, which is rather high in voltage and low in current, it is wound so that the number of turns of the secondary winding is equal to or more than that of the primary winding. is there.

Next, description will be made regarding the connection and switching configuration of the output of the high-frequency pulse generation circuit 10 and the power supply connection lines 11A and 11B between the discharge gap composed of the wire electrode 1 and the workpiece 3 and the circuit device 12. Then, the open / close switch for connecting / disconnecting the primary winding 13B to / from the output of the high-frequency pulse generating circuit 10 and the open / close switch for connecting / disconnecting the secondary winding 13C to / from the discharge gap are discharged to both ends of the output of the high-frequency pulse generating circuit 10. The power supply circuit opening / closing switches 14A and 14B provided in the circuit portions of the power supply connection lines 11A and 11B connected between the wire electrode 1 in the gap and the workpiece 3 and the input ends of the primary winding are connected to the power supply circuit to open / close. A primary winding opening / closing switch 14C inserted in one or both connection circuits while connecting to both of its output lines on the high-frequency pulse generation circuit 10 side of the switches 14A and 14B, And a secondary winding inserted in one or both connection circuits while connecting both ends of the output of the secondary winding to both the wire electrode 1 and the workpiece 3 on the discharge gap side of the power supply circuit opening / closing switches 14A and 14B. A winding opening / closing switch 14D, and the two feeding circuit opening / closing switches 14A, 1
4B, primary winding and secondary winding open / close switches 14C, 1
The 4D is for achieving the object by opening and closing the former open / close switches 14A and 14B so that the latter open / close switches 14C and 14D are turned off when the former open / close switches 14A and 14B are turned on. Switch 14
A and 14B are off, primary and secondary winding open / close switch 1
When 4C and 14D are turned on, the finishing machining power supply circuit using the high-frequency AC voltage used in the second machining step, which is the object of the present invention, is configured. In addition, in the figure, 1
1 for each open / close switch for the secondary and secondary windings
This is a case in which the number of changeover switches provided is one and the number of changeover switches provided is the smallest, but it goes without saying that various changeover circuit configurations can be made depending on the number of switches.

FIG. 2 shows that the machining power supply circuit of FIG. 1 is used as a power supply circuit for finishing in the second machining step of the present invention, that is, the open / close switches 6E and 9E are turned off as necessary, and a gate signal is output by the changeover switch 8E. A timing chart when the circuit 8D is turned on to cause the high-frequency pulse generation circuit 10 to function, the power supply circuit opening / closing switches 14A and 14B are turned off, and the transformer primary and secondary winding opening / closing switches 14C and 14D are turned on respectively, is shown. It is shown as an almost ideal waveform for two cycles, where a is a high frequency gate signal output from the intermittent pulse gate signal circuit 8D to turn on / off the switch element 8B, and b is a high frequency gate signal based on the gate signal. A current pulse output from the pulse generation circuit 10 and supplied to the primary winding 13B of the transformer 13, c is based on the pulse current A high-frequency AC voltage induced in the secondary winding 13C and applied to the discharge gap, and a discharge gap voltage waveform when discharge is generated in the discharge gap based on the high-frequency AC voltage application, and d is an example of discharge current in the discharge gap. is there.

In the finishing process to which the present invention is applied, the gate signal of the intermittent pulse output from the gate signal circuit 8D is T _ON = 100 nS, T in the drawing.
_OFF = 1.0 μS, approximately T _ON = 50 nS to 10
T _OFF = 500n below μS order of about 00nS
S to 10 μs or several tens of μS, and is preferably AT _OFF , with the limit that the AC voltages of c are mutually connected.
The condition is set so that ≧ 0. Further, the output current pulse waveform b of the high frequency pulse generation circuit 10 shows that the switching element 8B, or at least the current of the circuit 8 is in the saturation region operating state of the rising current sufficiently smaller than the saturation current value of the switching element 8B. The gate signal a is turned off, and the current of the switch element 8B or the circuit 8 is cut off at high speed.

Further, the high-frequency AC voltage of the secondary winding 13C shown in FIG. 7C is about 55 mmφ in outer diameter according to the recent test.
High permeability Mn-Zn ferrite or Ni-Zn ferrite or other ferrite toroidal core (for example, PC50T40 × 16 × 24 made by TDK) having an inner diameter of about 30 mm is double-stacked on a core 13A having a cross section of about 3.5 mm ² . When the primary winding 13B: 1 turn and the secondary winding 13C: 2 turns of the Teflon-based resin-coated conductor, the output of the DC voltage source 8A is about 60V, and the positive and negative voltages are about 150 to 170V, respectively, and the voltage source 8A.
With an output of about 25 V and positive and negative of about 60 to 65 V, respectively, it is applicable to the finishing processing (third cut and force cut) for improving the surface roughness, which is the second processing step of the present invention.
A high-frequency high-frequency AC voltage is preferably obtained, and as shown in the discharge current waveform d, when discharge is generated in the first half wave of one cycle of the AC voltage, the discharge is continued in the next half wave of the opposite polarity. Although it will occur, the finishing process can be advanced at an average processing current value smaller than about 1 A. For example, the positive-negative about 150 to 170 V, high-frequency AC voltage of about 1 MHz, the machined surface finished to about 10 to 13 μm Rmax until the second cut processing of the first processing step is subjected to the third cutting of the second processing step of the present invention. By processing, it can be finished to about 3.5 μm Rmax,
Further, by force-cutting with the high-frequency AC voltage of about 60 V positive and negative, the finish is about 1.5 μm Rmax.

The rest time A between the high frequency AC voltage c
When T _OFF is smaller, or even near continuous, when the average voltage in the discharge gap becomes a voltage below a predetermined level, or when a predetermined cycle (100 μS to 1 μS) is reached.
It is natural for safety that it is necessary to stop the on / off of the switch element 8B for every 0 mS), for example, for about 10 to 100 μS.

FIG. 3, FIG. 4 and FIG. 5 show the circuit device 1
2 is a schematic outline view of FIG. 2, an internal layout diagram, and an explanatory view of a configuration example of the opening / closing switch 14. In FIG. 3, the work stand 4 is
The circuit device 12 is located adjacent to the work stand 4 and is located in a machining liquid receiving pan or a machining tank on an xy table (not shown) orthogonal to the axis (Z axis) of the wire electrode 1.

The circuit device 12 is composed of a rectangular parallelepiped box-shaped body, and a transformer chamber 12A portion for accommodating the high frequency coupling transformer 13 in the center thereof, as shown in FIG. The switch boxes 12B and 1 of the power supply circuit opening / closing switches 14A and 14B are provided at opposite ends thereof.
Open / close switches 14C and 14D for the secondary and secondary windings
Switch box 12C of is provided, and both end surfaces are
Connection terminals 15A, 15B to which the output of the high frequency pulse generation circuit 10 is connected, and connection terminals 15C, 15D, 15E for connecting the output of the transformer secondary winding 13C to the discharge gap between the wire electrode 1 and the workpiece 3. And are provided. The output of the high frequency pulse generation circuit 10 in the power supply circuit 5 is connected to the terminals 15A and 15B via a coaxial or shielded wire 16 with reduced inductance, and the terminal 15C is connected to the positioning guides 2A and 2B. Required for mutual movement between the upper and lower guide blocks 18A and 18B or one of the guide blocks 18B (the lower one in the figure) that is closer to the wire electrode 1 (not shown) accommodated therein. It is connected by the shortest length, preferably the twisted wire 16A, and between the terminals 15D, 15E and the work stand 4,
The terminals 15D and 15E are short-circuited and connected with one output line or with two output lines 16B as shown, preferably using the shortest twisted wire.

Then, in the circuit device 12, the output of the high frequency pulse generating circuit 10 is changed to the high frequency coupling transformer 1.
Although it is relatively easy to supply the high frequency pulse current having the sharp and sharp rising and falling characteristics shown in FIG. 2B to the primary winding 13B of No. 3, it is induced in the secondary winding 13C at that time. Steep high-voltage high-frequency AC voltage c
Is difficult to supply and apply to the discharge gap as it is. In order to solve such a problem, the circuit device 12 is formed into one box-shaped body and the circuit device 12 is arranged at a position closer to the discharge gap. Adjacent to the work stand 4 of, or the side wall of the processing tank or the surface of the column on the processing tank side,
Alternatively, connecting wires 16A, 16 using twisted wires or the like are arranged at a position closer to a processing portion that does not interfere with processing of a processing head or the like that holds the guide blocks 18A, 18B, etc.
B is intended to be shorter. This connecting line 16A, 16
The former connecting wire 16A in B requires a certain length for mutual movement for machining, while the latter connecting wire 16B has a switch box 1 provided with terminals 15D and 15E.
2C end surface (surface in which terminals 15D and 15E are provided in FIG. 3 or surface facing the front surface of the work stand 4)
A part or the whole of which is used as a terminal metal plate having the terminals 15D and 15E provided therein, and the terminal metal plate is screwed to, for example, the front edge of the work stand 4, or may be attached by welding in some cases. Electrical and mechanical connections may be measured.

FIG. 5 shows a cross section of the secondary winding opening / closing switch 14D as an example for explaining the structure of the opening / closing switch 14. The structure is a butt contact type opening / closing switch as a whole. The switch box 12C has a fixed contactor 14DS connected to an external connection terminal 15D and a movable contactor 14DM that faces the fixed contactor 14D and moves back and forth in the opposite direction. The forward / backward movement of is performed by switching control of a fluid pressure source (not shown) connected to the pressure fluid supply / discharge holes 20A and 20B penetrating the wall of the box 12C. Each of the above contacts 1
4DS and 14DM are adjusted such that the butt contact surface 21 thereof maintains good conduction of high frequency power,
Also, seals 19A such as O-rings for fluid pressure operation, 1
It is equipped with 9B and 19C. In order to drive the movable contactor 14DM to move back and forth, in addition to the above fluid pressure source, various things such as a combination of electromagnetic force, spring, motor and link, rack, crank or the like can be used.
In the case of using the electromagnetic force described above, problems such as adsorption of machining waste may occur, and it may be necessary to take appropriate measures.

Next, a description will be given of a machining feed and its feed control method which are effectively applied when the wire electric discharge machining method of the present invention is carried out. FIG. 6 shows a conventional normal servo control, a so-called zero method type servo. In the explanatory diagram of control and operation characteristics, the vertical axis is the servo feed speed (Fmm / min), and the horizontal axis is the servo control reference voltage (SV) or the average gap length or the average gap voltage (Vgap). ,
SV is a servo reference voltage that is selectively set during the machining, ± SF is a feed rate that is selectively set to NC (maximum forward and backward), and LS is an operating characteristic curve. As long as there is no change setting, the gap length is controlled by feeding so that the average voltage (Vgap) of the discharge gap during machining matches the reference voltage (SV), and when it matches, feed is stopped, that is, the servo feed speed becomes zero. However, during so-called machining, that is, when the machining state is stable and machining is in progress, the servo feed speed is not zero and the feed speed MF is a certain value, and the average gap voltage (Vgap) is It is considered that the value is maintained at a value higher than the servo reference voltage SV by ΔV.

This servo control system is suitable as a servo feed control system for the machining of the first machining process of the present invention by intermittent voltage pulses, especially the first cut machining process for forming a machining groove first. Although it seems like a thing, in the first processing step, the processing of the second cut processing step for finishing the size and shape accuracy of the cutting side surface and the processing surface,
And, as a servo control method of the second machining step of the present invention for finishing the surface roughness of the machined surface in particular, although the ratio (gain) of the change in the servo feed speed to the gap change (especially in the vicinity of the stop position) is small, The range is large, and it is said that it is not suitable because it slowly moves back and forth over a wide range and the movement is large, or the change is large, or it seems that the purpose is not sufficiently achieved. That is, the reference voltage S of the above-mentioned gap voltage
Although the deviation ΔV corresponding to V is actually a relatively large value, the value of the feed speed MF with respect to the change is small, and the inclination angle α of the curve LS is relatively small in the vicinity of SV. This is because the setting had to be set so that the distance would suddenly increase. Further, further, this zero method (the deviation between the set servo reference voltage SV and the average machining voltage Vgap of the discharge gap is set to zero).
In the servo control method, the discharge gap is the target value for control,
When the gap length is reached, the average feed rate should be the above MF, but the feed rate is stopped. If the feed rate deviates from that position by a little larger or smaller, the feeds in the opposite directions are caused. Therefore, before and after the vicinity of the control position where the discharge gap is the target of control,
On the contrary, the width changes irregularly, so that so-called streaks or streaks of minute projections or depressions occur in the axial direction of the wire electrode, which is perpendicular to the progress of processing, on the machined surface of the workpiece, impairing the shape and surface accuracy. It was.

On the other hand, FIG. 7 shows a drum (straightness) of the machined surface which is adopted in the machining after the second cut machining step.
Of the conventional servo control, which is considered to be effective in improving the discharge and preventing streaking, when the average gap voltage Vgap of the discharge gap during machining is equal to the reference voltage SV, the above-mentioned conventional example is used. Instead of setting the machining feed rate F = 0 as in the control method of FIG. 6, the actual average machining feed rate CF = MF in the case where the feed rate F is based on the machining data based on the experiment or the like in advance, or If the gap voltage is set to a value in the vicinity of the reference voltage SV, the speed C
While the speed is increased from F to the maximum speed F of the machine, or to the set speed SF, for SV or less, it is a feed operation characteristic that becomes deceleration servo until it decreases to a predetermined gap value (for example, about 10V). A curve LD is drawn, and the backward feed is performed at a predetermined speed SF when the predetermined gap voltage is about 10 V or less.

Then, the feed rate CF in the above case is set by experimentally selecting the feed rate at which the drum (straightness) is the smallest or is not formed under the processing conditions. The speed CF is a value that is slightly lower than the average machining feed speed under the set machining conditions that are usually referred to for the set machining conditions, and is the inclination angle β of the curve LD with respect to the inclination angle of the characteristic curve LS. Is set to α <β to α << β in the vicinity of the SV, and α> β to α >> β when the SV is positively or negatively separated by a predetermined value or more.

The feed rate CF at which the drum is not formed means that the reference voltage SV is set to a low value under a certain set machining condition so that the gap is narrow, the discharge repetition frequency is high, and the machining is in a fast feed state. Then, mainly due to the discharge pressure, a (positive) drum-like shape protruding toward the wire electrode in the machining feed direction in the case of the first-cut machining step and in the offset direction with respect to the machining contour line in each of the machining steps after the second cut. On the other hand, when the reference voltage SV is set to a high value and the machining is performed with a wide gap, a low discharge repetition frequency, and a slow feed state, the feed is slow, the wire electrode vibrates between the guides, and the discharge pressure is increased. From the small size, the offset direction to the processing wheel in the above-mentioned processing feed direction in the case of the first cut processing step and the above-mentioned processing wheel in each processing step after the second cut In, which the wire electrode and the drum-shaped convex (reverse) on the opposite side, in which feed rate shape of drums during the two machining feedrate becomes substantially zero is present.

The target feed rate CF is substantially inversely proportional to the discharge gap length Gl and the machining feed rate under a certain set machining condition within a certain range. The feed rate can also be obtained from experimental data or theoretical formulas. Then, as will be described later in detail in Experimental Examples, dimensions and shapes except for the first cut processing step of creating a processing groove in the first processing contour processing shape of the first processing step of the present invention. During the second cut processing step for accuracy, and in the second processing step of the present invention, where the surface roughness is processed in one or more steps such as third cut and force cut, the feed rate is small and almost constant as a whole. By applying the deceleration servo control method, which is stable, the machining feed rate is constantly increased or decreased at a predetermined rate with respect to the change in the unit amount of the average machining voltage of the discharge gap, and the machining feed is continued. As long as there is no special accident such as a short circuit, there is no change in direction of forward and backward movement, and processing can be carried out while always feeding in one direction, so the movement of the feed is stable and almost no irregularity. Without the occurrence of streaks on the machined surface, the dimension and shape accuracy such as drum (straightness) and shape correction, and the minute surface roughness can be reliably obtained in a stable state. Is.

FIG. 8 shows the zero method servo control system of FIG. 6 and the deceleration servo control system of FIG. 7 on the same operational characteristic diagram, the contents of which are as described above, and the characteristic The curve LC1 is a constant speed servo control method that retracts only when the gap voltage is below a predetermined value and is regarded as a short circuit, and the characteristic curve LC2 is a so-called constant speed servo control method that decelerates at a constant speed above the reference voltage and decelerates below that. belongs to. Next, the wire electric discharge machining method and the machining power supply circuit of the present invention will be described based on specific experimental examples.

[Experimental Example 1] [Processing conditions] Workpiece material SKD-11 Plate thickness 40 mm Wire electrode material 35-65 Brass Wire diameter 0.2 mmφ Applied tension 1.2 kgf Renewal feed rate 9.5 m / min Processing fluid type Pure water specific resistance 10 × 10 ⁴ Ωcm Nozzle (upper and lower) Diameter 60 mmφ Discharge flow rate (upper and lower) 71 / min (source pressure about 12 kg / cm ² )

[First Cut Processing Setting Condition with Intermittent Voltage Pulse] Voltage pulse supply circuit Second voltage pulse supply circuit No load voltage 80V 80V Voltage pulse Positive polarity Positive polarity ON time (τ _ON ) 0.5 μs (Set discharge time ) 0.2 μs OFF time (τ _OFF ) 8.0 μs --- Current amplitude (Ip) 12 A (short current) 0.5 A (short) Current pulse supply circuit No load voltage 270 V Voltage pulse Positive polarity on time (τ _ON ) 0.5 μs OFF time (τ _OFF ) Current amplitude (ip) 500 A (during machining) Set machining feed rate (F) About 5 mm / min Servo voltage (average machining voltage) About 16 V Offset amount About 190 μm Servo control method Zero method control

According to the above processing conditions, in the first cut processing step, processing is performed at an average processing voltage of about 35 V, an average processing current of about 8.5 A and a processing speed of about 2.7 mm / min, and a processing time of about 41 minutes. , Surface roughness about 22-25μm
Rmax and straightness (taiko drum amount) were about 7 to 10 μm.

Next, the conventional second method, that is, the second cut processing step performed by the intermittent voltage pulse having the rest time as in the first cut processing step, and preferably the interval of 1 Hz is shortened. The case where processing is performed by applying a high-frequency AC voltage train that can cause a dwell time will be described below. In addition,
Regarding the described processing conditions, the processing conditions that are different from the set processing conditions of the previous processing step will be mainly described.

[Second Cut Processing Setting Condition by Intermittent Voltage Pulse] Conditions not described are the same as those in the case of the first cut processing. The same applies hereinafter to the second cut I. Machining liquid discharge rate (up and down) 11 / min (source pressure: about 1.5 kg / cm ² ) Voltage pulse supply circuit Second voltage pulse supply circuit No load voltage 80V 80V Voltage pulse Positive polarity Positive polarity ON time (τ _ON ) 0. 5μs (Set discharge time) 0.4μs Off time (τ _OFF ) 10μs Current amplitude (Ip) 12A 0.5A (Short) Current pulse supply circuit No load voltage 120V Voltage pulse Positive on-time (τ _ON ) 0.5μs Off Time (τ _OFF ) Current amplitude (ip) 320A (during machining) Set machining feed rate (F) About 20 mm / min Set servo voltage (average machining voltage) About 62 V Set offset amount About 130 μm Set servo control method Deceleration servo control

According to the above processing conditions, the second cut I is processed by the intermittent voltage pulse, the average processing voltage is about 65 V, the average processing current is about 1.2 A, and the processing speed is about 4.2 m.
Processing was performed at m / min, the processing time was about 26 minutes, the surface roughness was about 13 to 15 μm Rmax, and the straightness (taiko drum amount) was about 5 to 6 μm.

[Second Cut Processing Setting Condition by High-Frequency AC Voltage] Hereinafter referred to as Second Cut II. Wire electrode applied tension 1.4kgf Current pulse supply circuit No load voltage 280V Voltage pulse on time (τ _ON ) 0.6μs Off time (τ _OFF ) 11μs Current amplitude (Ip) 180A (during machining) High frequency coupling transformer Ferrite toroidal core outside Diameter 55mmφ Internal diameter 35mmφ Winding about 1.5mmφ copper wire coated with Teflon resin. Primary winding 5 turns Secondary winding 10 turns Set machining feed rate (F) Approx. 20 mm / min Set servo voltage (average machining voltage) Approx. 38 V Set offset amount Approx. 130 μm Servo control method Deceleration servo control

According to the above processing conditions, in the second cut II processing, the high frequency AC voltage is about 1.2 μs, except for the part of the damped oscillation after one cycle, and the voltage amplitude between the positive and negative is about 8.
0V, frequency about 86KHz, average processing current 0.2 ~
0.3A, processing speed is about 1.6 mm / min, processing surface roughness is about 11 to 12 μm Rmax, straightness (taiko) 6
Was about 7 μm.

When the second cuts I and II are compared and examined, the second cut II is excellent in terms of finished surface roughness, but the processing speed is remarkably slow and the straightness (the amount of drum) is hardly corrected. Not only that, but also the shape characteristics of the drum volume have hardly changed, that is, it is not suitable for the processing of dimension and shape accuracy because the processing amount is extremely small, whereas the second cut I is in terms of improving the surface roughness. Although it was inferior, it was found that the processing speed was high, and that it was easy to correct the amount of drums, and therefore it was suitable for processing to obtain dimensional and shape accuracy.

In order to further finish the work piece by the second cut I, the result of multi-step finish processing by the conventional example such as the third cut processing by the voltage pulse having the rest time like the second cut I and the force cut will be explained. Third cut processing setting conditions] Hereinafter, referred to as third cut I. Voltage pulse supply circuit Second voltage pulse No load voltage 80V 80V Voltage pulse Positive polarity Positive polarity On time (τ _ON ) 0.3 μs (Set discharge time) 0.4 μs Off time (τ _OFF ) 5.5 μs Current amplitude (Ip) 12A (Short current) 0.5A (Short) Current pulse supply circuit No load voltage 120A Voltage pulse Positive polarity ON time (τ _ON ) 0.3μs Off time (τ _OFF ) Current amplitude (ip) 320A (Processing) Speed Approx. 20 mm / min Servo voltage (average machining voltage) Approx. 62 V Offset amount Approx. 115 μm Servo control method Deceleration servo control

According to the above processing conditions, the third cut I
The average machining voltage is about 65 V and the average machining current is about 0.
9A, processing speed is about 9.1mm / min, processing time is about 12 minutes, surface roughness is about 10-12μmR
max, straightness (taiko amount) was about 4 to 5 μm.

[Force-cut processing conditions] Hereinafter referred to as force-cut I. Voltage pulse supply circuit Second voltage pulse supply circuit No-load voltage 80V 80V Voltage pulse Positive polarity Positive polarity ON time (τ _ON ) 0.1 μs (Set discharge time) 0.4 μs Off time (τ _OFF ) 5.5 μs Current amplitude ( Ip) 12A (short current) 0.5A (short) current pulse supply circuit no-load voltage 120V voltage pulse positive polarity on time (τ _ON ) 0.1 μs off time (τ _OFF ) current amplitude (ip) 180A set machining feed rate Approx. 20 mm / min Set servo voltage (average machining voltage) Approx. 62 V Set offset amount Approx. 105 μm Servo control method Deceleration servo control

According to the above processing conditions, the force cut I is processed at an average processing voltage of about 65 V, an average processing current of about 0.5 A, and a processing speed of about 10 mm / min. Processed surface roughness about 4.5-5.0μ
mRmax, straightness (amount of drum) about 2-3 μm.

Next, the above-mentioned power circuit 5 is applied to the work piece that has been processed by the force cut I by a conventional method.
Mainly, the electrical conditions such as the voltage pulse were finely changed and adjusted, and the processing after the (fifth cut) processing process was tried in multiple stages, but the size and shape ditching processing for correcting the drum (straightness) and the shape was performed. Then, the machined surface roughness becomes rather large, and conversely, when machined surface roughness improvement processing is performed, the drum (straightness) and shape are not corrected or improved, and various measures and a great deal of effort are required to achieve the purpose of processing and finishing. It took time.

Next, in order to compare the processing results of the third cut I and / or the force cut I, the processing of the second cut I, that is, the processed workpiece of the first processing step of the present invention, is performed. When the processing with the high frequency AC voltage (processing of the second processing step of the present invention) was performed, the results were as follows. The second cut in this case is according to the present invention as described above. In order to obtain the dimensional and shape accuracy, the setting processing conditions of the second cut I were carried out with some changes as follows.

Machining liquid (pure water) discharge rate (up and down) 1.5 l / min each Voltage pulse supply circuit Second voltage pulse supply circuit No load voltage 80V 80V Voltage pulse Positive polarity Positive polarity ON time (τ _ON ) 0.35 μs (Set discharge time) 0.4 μs Off time (τ _OFF ) 3 μs Current amplitude (Ip) 12 A (Short current) 0.5 A (Short) Current pulse supply circuit No load voltage 120 V Voltage pulse Positive polarity on-time (τ _ON ) 0 0.5 μs OFF time (τ _OFF ) Current amplitude (ip) 180 A Set machining feed rate About 20 mm / min Set servo voltage (average machining voltage) About 57 V Set offset amount About 130 μm Servo control method Deceleration servo control

The second cut I-1 under the above set machining conditions has an average machining voltage of about 57 V and an average machining current of about 0.
5A, processing is performed at an average processing speed of about 4.1 mm / min, processing time is about 29 minutes, and processing surface roughness is about 13 to 14 μm.
Rmax and straightness (amount of drum) were finished within about 2 to 3 μm.

[Setting Conditions for Third-Cut Processing by High-Frequency AC Voltage] Hereinafter, it is referred to as a third-cut II. Current pulse supply circuit Voltage pulse ON time (τ _ON ) 0.1 μs Off time (τ _OFF ) 1.5 μs Current amplitude (Ip) 180 A (during machining) High frequency coupling transformer (same as the second cut II) Set machining feed rate approx. 7mm / min Set servo voltage (average machining voltage.) About 21V Set offset amount About 115μm Servo control system Deceleration servo control

According to the above processing conditions, the third cut I
In the processing of I, the high-frequency AC voltage has a frequency of about 100 KHz or more, the voltage amplitude between positive and negative voltages is about 80 V, and the average processing current is about 0.2 to
Machining is performed at 0.3 A, machining feed rate of about 6.7 mm / min, machining time of about 17 minutes, and machined surface roughness of about 3.0 to
The finish was 3.5 μm Rmax and straightness (amount of drum) of about 1 to 2 μm. Comparing this result with the result of the force cut I described above, it can be seen that the required machining time is approximately equal to or more than the above, the surface roughness is excellent, and the straightness (amount of drum) is also equal to or more than that.

Next, examples of experiments based on the improved specifications and set machining conditions thereafter will be given. The improved specifications and the like are mainly the high-frequency coupling transformer 13 and its surroundings, as described in paragraphs [0026] and [0030]. [Examples 2 and 3] [Processing conditions] Workpiece material: SKD-11 Plate thickness: about 50 mm Processed shape: Punch (about 20 x 40) Wire electrode: Material: 35-65 Brass Wire diameter: about 0.2 mmφ Applied tension (separate sheet) Update Feed rate 9.5 m / min Type of processing liquid Pure water Specific resistance 5.0 × 10 ⁴ Ω · cm Nozzle (upper and lower) Diameter about 6 mmφ Discharge flow rate (separate description) Nozzle position Approximately 0.1 mm away from the top and bottom surfaces of the workpiece 2 High-frequency coupling transformer core material used in the processing process Double product of ferrite toroidal core Outer diameter approx. 55 mmφ Inner diameter approx. 35 mmφ Winding approx. 3.5 mm ² copper wire, Teflon resin covered primary winding 1 turn secondary Winding 2 turns

An experimental example 2 in which the first and second processing steps each have two steps under the above conditions is shown in Table 1 in FIG. In order to obtain the machining performance as shown in Table 1 above, the conventional 6 to 8 stages of machining processes are required, and the required machining time is at least 3 hours or more and near 4 hours.

Next, a processing experiment example 3 was carried out so that the surface roughness and the dimension / shape accuracy could be obtained as much as possible when the second high-frequency AC voltage processing in the second processing step was reduced to a single third-cut processing. Table 2 is shown in FIG. Since the number of processing steps is 3 in the above, the processing surface roughness was about 3.5 μm Rmax, the dimensional accuracy was ± 1 μm, and the processing time was further shortened. In Experimental Examples 2 and 3, the second voltage pulse supply circuit 9 equivalent to or less than the voltage pulse supply circuit 6 was not used, but there was no change in processing performance.

Further, although the above description has been made on the iron-based object to be processed, the second machining step of the present invention is the electric discharge machining by the high frequency AC voltage in which the average machining voltage of the discharge gap becomes substantially zero. Therefore, it is effective for the finish processing of cemented carbide such as WC-Co because there is no electrolytic corrosion dissolution of Co.
Processed surface roughness to about 1.0 μm Rmax,
In addition, the surface roughness of approximately 2.5 μm Rm
It is known to be finished in ax.

Further, in the finishing of the machined surface finished to about 3.5 to 5 μm Rmax by the first stage machining (third cut) of the second machining step, the secondary winding output and the discharge gap discharge circuit are provided. 1 to 10 μH, and under the above experimental conditions, preferably by inserting an inductance coil of about 2 to 5 μH in series, the secondary winding output AC voltage waveform of FIG. 2C becomes Waveform shaping into a clean sine wave was easily performed and the finish of the machined surface was improved, but it has not been quantified yet.

As described above, the embodiments of the present invention have been described with respect to the implementation of the processing method of the present invention and the processing power supply circuit of the present invention. However, the present invention is not limited to the spirit of the present invention described in the claims. The present invention can be implemented by making various changes to each part without departing from the above. For example, in the case of the power supply circuit for wire electric discharge machining in which the current pulse supply circuit 8 is not provided in FIG. 1, a resistance reduction circuit for short-circuiting the current limiting resistance 6D of the intermittent voltage pulse generation circuit 6 is attached. Then, the gate signal circuit 8 is added to the gate circuit of the switch element 6B.
Alternatively, the gate signal circuit 8D may not be built in the pulse controller 7 as a part of the pulse controller 7, and the gate signal circuit 8D may be stored in the controller 7. The switching control data can be read out so that the switching operation can be performed by software. Further, the high frequency AC voltage for finishing is further increased in frequency, for example, 2 MHz.
Therefore, for example, two sets of the current pulse supply circuits 8 are provided in parallel, and, for example, τ _ON = 100 nS for each, and τ
_{It is} sufficient to adjust two sets of 1 MHz high frequency (current) pulse generation circuits of _OFF = 900 nS with a phase difference of about 180 ° (π) so that one cycle of the high frequency AC voltage is completed within about 500 nS. This is also the case with respect to the connection of the power supply circuit device 12 used in the present invention, the number and arrangement of the open / close switches, the configuration of the open / close switches, and the like.

The high-frequency coupling transformer 13 seems to generate less heat as long as it is used for the finish machining with a small machining current as in the present invention. However, depending on the installation environment of the machine, air cooling, Cooling means such as water cooling can be taken.

[0069]

Since the wire-cut electric discharge machining method of the present invention is the above-described machining method, the first-cut machining step of the first machining step and / or Or, the processing of the second cut processing step is efficiently performed at high speed,
The shape accuracy can be reliably obtained, and the finishing processing step such as the third cutting and / or the force cutting as the second processing step that is performed subsequent to the above-mentioned processing step is preferably stopped every cycle. Since it is performed by applying a high-frequency high AC voltage that can increase the time, it is possible to finish the surface roughness more finely at high speed, reducing the time required for fine, high-precision wire electrical discharge machining as a whole. Therefore, it is possible to perform efficiently, and because the processing does not cause the risk of electrolytic corrosion, W
It is suitable for processing cemented carbide such as C-Co.

Since the power supply circuit for wire electric discharge machining according to the present invention has the above-mentioned structure, the rough machining or second cut machining step as the first machining step for obtaining the above-mentioned dimension and shape accuracy is performed by the conventional type. The high-speed machining and dimensional / shape precision machining are performed by using the machining power source provided by the wire electric discharge machine as it is, and mainly during the second machining step of finish machining to improve surface roughness. Is a combination of a non-resistive current pulse supply circuit in which a current limiting resistor in the voltage pulse power source used for roughing is not substantially provided, and a high frequency coupling transformer having a changeover switch which is separately provided. Since the voltage is obtained, it becomes possible to perform finishing with a high-frequency AC voltage, which is effective for surface roughness improvement, in the effective use state of circuit elements and equipment. It is extremely useful as preventing finish machining power source.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a power supply circuit of the present invention including a conventional power supply circuit for wire electric discharge machining.

FIG. 2 is a partial timing chart diagram when the circuit of FIG. 1 is operated as a finishing power supply circuit of the present invention.

FIG. 3 is a diagram showing an appearance, a layout, and a state of external connection of a part of the power supply circuit of the present invention.

FIG. 4 is a wiring diagram and a layout of a part of the power supply circuit of the present invention in a box.

FIG. 5 is a schematic configuration explanatory diagram of an opening / closing switch used in the power supply circuit of the present invention.

FIG. 6 is an explanatory view of operation characteristics of machining feed by a zero method servo control method.

FIG. 7 is an explanatory view of operation characteristics of machining feed according to the deceleration servo control method.

FIG. 8 is a characteristic diagram of operating characteristics comparison between a plurality of different servo control methods.

FIG. 9 is a diagram showing Table 2 as a typical processing experiment example 2 of the present invention together with processing conditions.

FIG. 10 is a diagram showing Table 3 as well as processing conditions of another processing example 3 of the present invention.

[Explanation of reference numerals] 1, wire electrodes 2A, 2B, positioning guide 3, workpiece 4, work stand 5, wire electric discharge power supply circuit 6, voltage pulse generation and supply circuit 6A, DC voltage source 6B, electronic switch element 6C, current limiting resistor 6D, backflow prevention rectifier 7, pulse control device 8, current amplification circuit 8A, variable DC voltage source 8B, electronic switch element 8C, backflow prevention rectifier 8D, gate signal circuit 8E, changeover switch 9, second voltage Pulse supply circuit 9A, variable DC voltage source 9B, electronic switch 9C, current limiting resistor 9D, backflow prevention rectifier 9E, open / close switch 10, high frequency pulse generation circuit 11A, 11B, power supply circuit connection line 12, circuit device 12A, transformer room 12B , 12C, open / close switch box 13, high frequency coupling transformer 13A, ring core 13B, Primary winding 13C, secondary winding 14A, 14B, 14C, 14D, open / close switch 15A, 15B, 15C, 15D, connection terminal 16, coaxial or shielded wire 16A, 16B, connection wire

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryusei Toyonaga 78 Nagaya, Sakai-cho, Sakai-gun, Fukui Prefecture Sodick Fukui Factory

Claims (11)

[Claims] 1. A wire electrode stretched in a predetermined state between a pair of guides arranged at a distance is renewedly fed and moved in the axial direction, and a workpiece is made to pass through a minute gap from a direction substantially perpendicular to the axial direction. Are made to face each other, and a machining voltage is applied between the two with the machining liquid being supplied to the gap to perform machining by means of an electric discharge that is generated. In the wire electric discharge machining for providing relative machining feed along the contour shape to be machined, the wire electric discharge machining is performed as (a) the machining voltage, and an electronic switch element connected in series to a DC voltage source is turned on.・ Using intermittent voltage pulses with a dwell time obtained by turning off, set according to the machining fluid used, the material of the electrode / workpiece, the combination, the plate thickness, and the purpose of machining. Under the machining conditions, a first machining step for machining the contour-shaped machining groove to a predetermined dimension and shape accuracy; and (b) the machining voltage after the machining in the first machining step, A second machining step of performing a final electric discharge machining for surface roughness improvement by switching to a high frequency AC voltage of a predetermined condition obtained by a high frequency coupling transformer inserted between the voltage pulse supply source and the discharge gap; A wire electric discharge machining method characterized by performing. 2. The first machining step is a first-cut machining step in which the contour-shaped machining groove is first machined to form, and a post-machining condition after the machining step is switched to a predetermined dimension / size.
The wire electric discharge machining method according to claim 1, further comprising a second cut machining step for machining the shape accuracy. 3. A servo feed control system between the wire electrode and the workpiece in the first cut machining step is a zero method servo control system in which the feed speed becomes zero when the deviation of the discharge gap voltage from the servo reference voltage is zero. The wire electrical discharge machining method according to claim 2, wherein the servo feed control method in the second cut machining step is set to a deceleration servo control method to perform machining. 4. An intermittent voltage pulse source having a dwell time obtained by turning on / off the DC voltage source in the first processing step by a switch element, and the DC voltage source is turned on / off by the switch element. A resistor is inserted in the normal voltage pulse supply circuit in which a specified current limiting resistor is inserted in the series circuit that forms the voltage pulse, and in the series circuit that forms the current pulse by turning the DC voltage source on and off. Or a non-resistive current pulse supply circuit in which a current limiting resistor other than a small resistance for current detection is not inserted, and the switch element of the current pulse supply circuit supplies the normal voltage pulse. 3. The circuit according to claim 1 or 2, wherein the start of discharge is detected by a voltage pulse applied to a circuit discharge gap, and ON control is performed for a predetermined time width. 3. The wire electric discharge machining method according to item 3. 5. The second processing step is performed once or a plurality of times at which the processing conditions for finishing the workpiece to a predetermined surface roughness after the processing of the first processing step are sequentially switched or not switched. 4. The wire electric discharge machining method according to claim 1, wherein the wire electric discharge machining method is performed by machining once. 6. The method according to claim 1, wherein the servo feed control method between the wire electrode and the workpiece in the second machining step is set to a deceleration servo control method to perform machining.
The wire electric discharge machining method according to 2, 3, or 5. 7. An intermittent current pulse having a dwell time supplied to the primary winding of the transformer for outputting and supplying a high frequency AC voltage from the secondary winding of the high frequency coupling transformer to the discharge gap. 7. The wire electric discharge machining method according to claim 1, 5 or 6, wherein the connection and the switching are controlled so that they are supplied from a non-resistance current pulse supply circuit. 8. A voltage pulse supply circuit in which a direct current voltage source, a current limiting resistor, and an on / off electronic switch element are connected in series is connected in parallel to a discharge gap formed by a wire electrode and a workpiece, and A current pulse supply circuit having no current limiting resistor is connected in parallel in a series circuit in which a second DC voltage source and a second on / off electronic switch element are connected in series, and the first on / off electronic switch is provided. In a power supply circuit for wire electric discharge machining, which supplies an ON signal of a predetermined time width to the second ON / OFF electronic switch element in response to the start of discharge in a discharge gap based on an applied voltage pulse after the element is turned on, A high frequency on / off gate signal circuit is provided so as to be switchably connectable to the gate input of the second on / off electronic switch element, and both ends of the voltage and current pulse supply circuits and a discharge gap are provided. A high frequency coupling transformer of a ring core having a primary winding and a secondary winding wound therebetween, the output can be switched to a connection between a discharge gap and the primary winding, and the discharge gap can be connected to the output. A switching switch that can switch the connection with the secondary winding is provided, and in the finishing process after the roughing process and the dimension / shape accuracy machining process by the machining power supply circuit, the gate of the second on / off electronic switch element. The input is switched and connected to the high-frequency gate signal circuit, and the output of the current pulse supply circuit is set to 1 by the switching operation of the changeover switch.
A power supply circuit for wire electric discharge machining, characterized in that a discharge gap is connected to a secondary winding output to a secondary winding, and a high-frequency AC voltage is supplied to the discharge gap for finish electric discharge machining. 9. The high-frequency coupling transformer and the changeover switch are integrally coupled and housed in a box, and the box is provided in or near a machining tank near the discharge gap. The power supply circuit for wire electric discharge machining according to claim 8. 10. The high-frequency coupling transformer comprises a ferrite ring core in which the number of windings of the output secondary winding is larger than the number of windings of the input primary winding. Or the power supply circuit for wire electric discharge machining according to any one of 9). 11. A transformer chamber for housing a high frequency coupling transformer, a switch box for a power supply circuit opening / closing switch, and a switch box for a primary winding and a secondary winding opening / closing switch provided at both ends of the transformer chamber. Further, the side wall surface provided with connection terminals to the work stand in the switch box is formed of a terminal metal plate or a terminal metal plate is attached, and the terminal metal plate is provided electrically and mechanically on the work stand. The power supply circuit for wire electric discharge machining according to claim 9, wherein the power supply circuit is configured to be connected and attached.