JPH071243A - Wire cut electric discharge device - Google Patents

Abstract

PURPOSE:To provide a smooth processed surface easily in a short time by a method wherein processing liquid mixed with semiconductive powder fine grain is used as processing liquid and processing is effected such that an output wire is varied to output a wire having inductance. CONSTITUTION:When a processing condition set signal is inputted to a source device 41 from a numerical control device, parameters, such as a given discharge ON time, a rest time, an applying time, and a current crest value, are set. Further, when powder-mixed processing liquid is selected by a processing liquid selecting means 43, a plurality of the electromagnetic on-off valves of a processing liquid feeding device 18 are switched and powder-mixed processing liquid is fed in a processing gap. An output wire through which the source device and a work 3 are interconnected is varied to an output wire having an inductance L. An electric discharge pulse produces a pulse having the gentle rise of a current and discharge dispersed through pulverized grains included in processing liquid fed in the processing gap is carried out to form a processed surface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire-cut electric discharge machine, and more particularly to a wire-cut electric discharge machine using an oil-based machining liquid, and more particularly to a wire-cut electric discharge machine capable of finishing a glossy surface on a workpiece.

[0002]

2. Description of the Related Art A wire cut electric discharge machine is 0.02
From 0.3 mm to a wire electrode made of a material such as brass or tungsten while being renewed and fed between a pair of wire guides, the intermittent electric pulse supplied from the electrical discharge machining power source is processed under the presence of machining fluid. The material is supplied to the object and the wire electrode, and electric discharge is generated in the minute gap between the object to be processed and the wire electrode for processing.

As the above-mentioned machining fluid, there are those which use an ion-exchanged water or an oil-based machining fluid like the die-sinking electric discharge machining apparatus, a water-machining fluid for rough machining, and an oil-based machining fluid for finishing. is there. The water-processing fluid is generally widely used because it has a higher processing speed with respect to the surface roughness than that of the oil-based processing fluid. Oil-based working fluids are often used when there is a problem of electrolytic corrosion of a workpiece such as a sintered alloy or when high working accuracy is required.

A conventional wire cut electric discharge machine will be described below with reference to FIG.

In FIG. 4, 4 is a wire electrode and 3 is a workpiece. The workpiece 3 is fixed to a work stand (not shown), and the work stand is fixed to the XY cross table 2 on which the processing tank 1 is placed. The XY cross table 2 is controlled by a known numerical controller 12, and the work 3 is paired with a wire electrode guide guide by the X-axis and Y-axis motors 8 and 7 and the motor drive circuit 15 attached to the XY cross table 2. 5a, 6
It can move relative to the wire electrode 4 guided and supported by ab. Also, the wire electrode 4
Is supplied from above by a wire electrode supply device (not shown) and is recovered by a recovery device, and is constantly renewed during electric discharge machining.

Reference numeral 70 is a machining fluid supply device, which is a clean machining fluid tank 7
It has a two tank structure of 0b and a pollution tank 70a. The clean machining liquid is supplied from the clean machining liquid tank 70b to the pair of upper and lower jet wire guide assemblies FGa and FGb through the flow rate adjusting valves 5e and 6e by the pump P1, and is supplied to the machining gap from the upper and lower jet nozzles 5c and 6c. It Further, the clean machining fluid is also supplied to the machining tank 1 through the pipeline P13, and the drain valve DV is closed so that the machining can be performed while the workpiece 3 is immersed in the machining fluid. There is. Furthermore, the processing liquid is returned from the conduit P14 to the pollution tank 70a to form a circulation circuit.
The collected polluted liquid is returned by the pump P2 through the filter F11 to the cleaning liquid tank 70b.

Next, reference numeral 41 denotes a main power supply device which is provided with a plurality of switching elements, a current limiting resistor, a variable voltage power supply, a pulse width control circuit for on-off controlling the switching elements, and the like, and has a discharge pulse width of It is a power supply that supplies a current pulse having a high current peak value in about 5 μsec or less. Four
Reference numeral 2 denotes a sub power supply device, which supplies a discharge pulse voltage from the suspension raising region to the finishing region. The main power supply device 41 and the sub power supply device 42 have a discharge on time, an electric discharge machining pause time, a current peak value, which are set by the machining condition setting means 19.
And a plurality of control signals necessary to generate electric discharge machining pulses for machining conditions such as applied voltage.
Receive from

The positive electrode and the negative electrode of the main power supply device 41 and the sub power supply device 42 are the positive electrode side output line 21 and the negative electrode output line 22.
Are connected to the work piece 3 and the power supply pieces 5b and 6b, respectively, and the voltage supplied from the power supply device is applied between the wire electrode 4 and the work piece 3 to generate an electric discharge in a minute gap therebetween. Processing is performed.

The positive electrode output line 21 and the negative electrode output line 22 are
Various measures are taken because the line inductance has a significant effect on EDM performance. In other words, wire-cut electric discharge machining is different from die-sinking electric discharge machining.
By supplying a machining pulse having a pulse width of μsec or less and a current peak value of 1000 A or more with a high peak value to the machining gap, the machining energy and the discharge frequency are increased to accelerate the machining speed. Even in the finishing process, the rise of the current has a great influence on the machining performance. Therefore, the output line with as much inductance as possible is used for the electric path for transmitting the electric discharge machining pulse. The main practice is to make the output line from the power supply device the coaxial line in the forward and return lines as much as possible, and to make the single wire part of the connection to the power feeding piece and the work piece as short as possible. It has become.

Further, in the finishing region, if the stray capacitance is large, there is a problem that the finished surface cannot be made fine enough. Therefore, measures are taken to prevent the stray capacitance from affecting the machining gap.

[0011]

In the wire-cut electric discharge machine constructed as described above, when finishing machining is performed by using an oil-based machining liquid, the machining time can be obtained under efficient machining conditions. The finished surface roughness is about 5 μRmax in the case of iron-based workpieces, and the machining speed is slower than that of the water-machining liquid. It takes considerable experience to set the surface roughness to about 3 μRmax, and if the processing area is large, it becomes difficult to obtain a uniformly processed surface. Further, since the processing time becomes very long, it is only used in the case of processing that requires high processing accuracy. Furthermore, when obtaining a finely machined surface, a special power supply circuit is newly required, and the machining time is further delayed.

Further, the machined surface obtained by the above-mentioned device is a satin surface, and when the machined surface requires a smooth machined surface close to a mirror surface, a polishing step is required, and the machined shape with high accuracy can be obtained with high accuracy. It took considerable skill and labor to polish without degrading.

The present invention has been made in view of the above problems. Even in the finishing process using an oil-based machining liquid with a surface roughness of 5 μRmax or less, the machining time is remarkably shorter than that of the conventional apparatus and a large machining area is required. However, it is an object of the present invention to provide a wire-cut electric discharge machine capable of easily forming a smooth machined surface of about 2 μRmax.

[0014]

According to the present invention, a wire electrode is axially renewed and moved between a pair of guides arranged at intervals so that a work piece is formed in a minute gap from a direction substantially perpendicular to the axial direction. A power supply device is provided so as to face each other to supply an intermittent voltage pulse to the gap, machining is performed by an electric discharge pulse generated through a machining fluid, and relative machining feed is applied between the wire electrode and the workpiece. In a wire cut electric discharge machine that processes a desired contour shape by
A power supply circuit for supplying a machining pulse of a machining parameter such as an electric discharge machining pause time to the machining gap, and a machining liquid for supplying an oil-based machining liquid and a machining liquid in which powder fine particles are mixed into the oil-based machining liquid to the machining gap. A supply device, a processing liquid selection means for selecting the processing liquid from the processing liquid supply device and supplying it to the gap, and a finishing process using a semiconductive powder mixed processing liquid from the processing liquid supply device. In this case, insertion means for inserting an inductance element into at least one of the electric discharge machining pulse output line connected between the power supply circuit and the workpiece side of the machining gap or the wire electrode side, or an output line having a sufficiently large inductance The wire-cut electric discharge machine has switching means for switching to the electric discharge pulse output line.

[0015]

When a machining condition setting signal from the numerical controller is input to the power supply device, machining parameters such as predetermined discharge on time, rest time, applied voltage, and current peak value are set.
Further, when the powder mixed processing liquid is selected by the processing liquid selection means, a plurality of electromagnetic on-off valves of the processing liquid supply device are switched to supply the powder mixed processing liquid to the processing gap,
The output line connecting the power supply device and the workpiece is changed to an output line having an inductance. The electric discharge machining pulse supplied from the power supply device is a pulse whose current rises gently, and is discharged through the fine powder particles that are supplied to the machining gap and are present in the machining fluid to form a smooth machining surface. It

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the wire cut electric discharge machine of the present invention will be described in detail below with reference to the accompanying drawings. Figure 1
FIG. 2 is a configuration diagram showing an embodiment of the present invention, and FIG. 2 is a detailed diagram showing an electric discharge machining power source portion shown in FIG. In FIG. 1, it is roughly divided into a machine device section 50 (central part in the figure) for performing electric discharge machining, and a machining fluid supply section 60 for supplying and switching a powder mixed machining fluid, an oil machining fluid and a water machining fluid. (Left side in the drawing), and a power supply unit 40 (right side in the drawing) that includes a power supply unit that generates an electric discharge machining pulse and a numerical control device that drives a machining table along a desired contour locus.

First, the mechanical device section 50 will be described. The processing tank 1 is placed on the XY cross table 2 for performing the processing by immersing the workpiece 3 in the processing liquid. The XY cross table 2 is a ball screw attached to the X-axis and Y-axis motors 7 and 8. It is composed of. When the motor drive circuit 15 receives the control signal from the numerical controller 12 and drives the XY axis motor, the workpiece 3 is moved relative to the wire electrode 4. Further, the detection device 20 for detecting the processing state sends the detection data to the numerical control device 12, and the numerical control device 12 gives a so-called servo control signal to the motor drive circuit 15 so that the workpiece 3 and the wire electrode 4 can be processed. The machining gap is maintained at a proper distance.

In the processing tank 1, a work piece 3 is fixed to a work stand (not shown).
An upper jet wire guide member 5 and a lower jet wire guide member 6 facing each other are provided above and below. The upper jet wire guide member 5 includes an upper wire guide 5a for guiding the wire electrode 4 renewed and fed during processing in the axial direction thereof, an upper power feeding piece 5b for supplying a processing pulse from a power supply device to the wire electrode 4, and It is composed of an upper nozzle 5c and the like for jetting the working liquid toward the working gap. The partition wall 5d is provided to prevent the powder-mixed processing liquid from entering the upper wire guide 5a and the upper power feeding piece 5b side when processing is performed using the powder-mixed processing liquid as described later. The lower jet wire guide member 6 also has the same configuration as the upper jet wire guide member 5, and thus the description thereof is omitted.

Next, the working fluid supply device 60 will be described. The working fluid supply device 60 is the water working fluid supply device 1
6, oil processing liquid supply device 17, powder mixed processing liquid supply device 1
8 and a plurality of control valves for switching the working fluid, a liquid feed pump,
It is composed of a filter and a conduit connecting them. First, regarding the water processing liquid supply device 16, it is used when performing roughing processing before using the processing device of the present invention, or when performing processing with only the water processing liquid.

The water processing liquid supply device 16 comprises two tanks, a clean water processing liquid tank 16a and a polluted water processing liquid tank 16b. A pump 16c for sending the water processing liquid to the processing gap in the clean water processing liquid tank 16a, an ion exchange for increasing the specific resistance value of the processing liquid when the specific resistance value of the processing liquid falls below a predetermined value. A pump 16e, which is controlled by the output of the device 16i and the specific resistance detector and sends the working fluid to the ion exchange device, is provided. Next, the processing liquid recovered from the processing tank 1 is returned to the polluted water processing liquid tank 16b, and a pump for filtering the used processing liquid polluted with processing wastes and returning it to the clean water processing liquid tank 16a. 16d and a filter 16h are provided.

The oil working liquid supply device 17 is used when the electromagnetic on-off valve is switched by a signal from a working liquid selecting means 19 described later to feed the oil working liquid to the working tank 1 and the working gap. The oil processing liquid supply device 17 is also similar to the water processing liquid supply device 16 in the clean oil processing liquid tank 17a and the polluted oil processing liquid tank 17.
It has a two tank structure of b. In the clean oil processing liquid tank 17a, the oil processing liquid is supplied to the processing tank 1, the upper jet wire guide member 5 and the lower jet wire guide member 6 and the flow rate adjusting valve 5e.
Pump 1 for feeding liquid through the flow rate control valve 6e
7c is provided. Further, the clean machining liquid from the pump 17c is separated from the flow rate adjusting valve 17i by the partition wall 5d of the upper jet wire guide member 5 to form the upper wire guide 5.
It is also connected to the side where a is arranged, and in order to prevent the powder particles from entering between the wire electrode 4 and the upper wire guide 5a, the hydraulic pressure slightly higher than the hydraulic pressure supplied to the upper nozzle 5c side. Liquid pressure gauge and flow control valve 17
It is adjusted by i. The same applies to the lower jet wire guide member 6. Next, in the polluted oil processing liquid tank 17b, a filter 17 for filtering the polluted processing liquid returned from the processing tank 1 and returning it to the clean oil processing liquid tank 17a.
h and pump 17d are provided.

The water-machining liquid supply device 16 and the oil-machining liquid supply device 17 have the same structure as the conventional wire-cut electric discharge machining device using a water or oil machining liquid, and of course, a water-oil separation device. Although not shown, they are provided in both working fluid supply devices. In the present invention, in addition to the above configuration, a powder-mixed working liquid supply device 18 is further provided. Similarly to the above, when the powder-mixed processing liquid is selected by the processing-liquid selecting means 19, the plurality of electromagnetic on-off valves are switched, and the powder-mixed processing liquid is supplied to the processing tank 1, the upper jet wire guide member 5, and the lower jet wire guide member 6. Supplied. The powder-containing processing liquid supply device 18 is also the powder-containing cleaning processing liquid tank 1
8a and a powder-mixed pollution processing liquid tank 18b,
The powder-mixed processing liquid is supplied to the processing tank 1, the upper jet wire guide member 5, and the lower jet wire guide member 6 by the pump 18c from the powder-mixed cleaning fluid tank 18a side.

The pump 18c has a path for returning only the oil processing liquid to the polluted oil processing liquid tank 17b, and a backwash filter 18i is provided in the path. This is because when the oil processing liquid is supplied from the clean oil processing liquid tank 17a to fill the processing tank 1, and the powder mixed processing liquid is supplied only from the upper nozzle 5c and the lower nozzle 6c for processing, the inside of the processing tank 1 Since the powder-containing processing liquid is mixed with the processing liquid of No. 1, the processing liquid in the processing tank 1 is once returned to the powder-containing polluted processing liquid tank 18b,
It is used when returning the working fluid which is insufficient in the oil working fluid supply device 17.

In the powder-contaminated processing fluid tank 18b, the powder-mixed processing fluid returned from the processing tank 1 is temporarily collected, and only the processing dust larger than the powder particles generated by the processing is removed to remove the powder-mixed cleaning fluid tank. A filter 18h for catching particles of 5 μm or more returned to the side of 18a is provided. Since the powder particles mixed in the powder-mixed working liquid are fine particles having a particle size of 2 μm or less, they are not captured by the filter 18h. Further, if the use of the powder-mixed machining liquid supply device 18 is limited to the finish machining, the mixture of large machining chips will be eliminated.
The structure of only the tank may be used.

Here, the control and operation of the electromagnetic opening / closing valve when switching and using the three kinds of working fluids will be described.
First, when using the water processing liquid, the electromagnetic opening / closing valve 18g,
The solenoid on-off valve 17g is closed and the solenoid on-off valve 16g is opened. The solenoid on-off valve 1a and the solenoid on-off valve 16f are opened.
f and the electromagnetic on-off valve 18f are closed. Next, the pump 16c is driven to deliver the liquid. The supplied water processing liquid is the solenoid on-off valve 16
It is supplied to the processing tank 1 through f and the electromagnetic opening / closing valve 1a. Here, although not shown, if the drain port on the drainage side is closed, the machining tank 1 is filled with the machining fluid and overflows when the fluid level exceeds the set level, and the machining fluid is contaminated through the electromagnetic opening / closing valve 16g. Water processing liquid tank 16b
Returned to. The jet flow to the machining gap is also adjusted by the flow rate adjusting valve 5e and the flow rate adjusting valve 6e. After the processing is completed, drainage is performed by opening the drain port.

Next, the operation of the oil processing liquid supply device 17 will be described. The electromagnetic opening / closing valve 16f, the electromagnetic opening / closing valve 16g, the electromagnetic opening / closing valve 18f and the electromagnetic opening / closing valve 18g are closed, the electromagnetic opening / closing valve 17f, the electromagnetic opening / closing valve 17g and the electromagnetic opening / closing valve 1a are opened to drive the pump 17c. By closing the drain in the same manner as described above, a working fluid can be supplied by forming a circulation circuit as in the case of the above-mentioned water working fluid.

In the powder-mixed working liquid supply device 18, the working liquid is supplied in the same manner as described above. When the powder-mixed working liquid is selected, the electromagnetic opening / closing valve 17f, the electromagnetic opening / closing valve 17g, the electromagnetic opening / closing valve 16f, and the electromagnetic opening / closing valve 16g are closed, and the electromagnetic opening / closing valve 1a, the electromagnetic opening / closing valve 18g, and the electromagnetic opening / closing valve 18f are opened to pump. When 18c is driven, the powder-mixed working liquid is supplied to the processing tank 1, the upper jet wire guide member 5, and the lower jet wire guide member 6, respectively. The overflowed powder-mixed working fluid is returned to the powder-mixed polluted working fluid tank 18b through the electromagnetic opening / closing valve 18g. Further, the pump 17c is also driven so that the clean oil processing liquid is sent to the wire guide sides of the upper jet wire guide member 5 and the lower jet wire guide member 6,
Prevents infiltration of powder-containing processing fluid. Further, the clean working fluid is also supplied to the rotating part or the sliding part of the supply / recovery mechanism of the wire electrode 4 used in the working tank 1, and is always processed when working with the powder mixed working liquid. In order to prevent the infiltration of powder particles, it is supplied to each of the above parts.

Next, the power supply unit 40 will be described in detail with reference to FIG. The power supply unit 40 is a main power supply unit 41 that outputs a current pulse having a high peak value in order to increase the processing speed, and 0.1 when performing processing from the intermediate finishing area to the finishing area.
The sub-power supply device 42 for supplying a current pulse of about 5 A to 100 A, the main power supply device 41 and the sub-power supply device 42, the upper power feeding piece 5b, the lower power feeding piece 6b, and the workpiece 3 are connected to the mechanical device section 50. The output line connecting portion 44 includes a working liquid selecting means 43 for switching and controlling the working liquid and for controlling switching of the output line electric circuit depending on the working liquid used. In addition, the same code | symbol has shown the same thing among the code | symbols used in the figure.

The sub power supply device 42 has two types of power supplies, HVP and MVP.
Have a VP, and each HVP is from 150V to 30
It is a variable voltage power source of 0V and MVP is 60 to 120V.
It is a power supply with a variable voltage. A backflow prevention diode Da, a variable resistance VR, and a switching element Tra are connected in series on the + side of the power supply HVP, and are connected to the workpiece 3 through the output line connection portion 44. The negative electrode side is connected to the upper and lower power feeding pieces 5b through the output line connecting portion 44. The variable resistor VR is a resistor of 500 to 1 K ohm, and the HVP power supply circuit is used to supply a high-voltage machining pulse. In the high-voltage power supply circuit of the HVP, the machining condition setting signal S1 set by the numerical controller 12 is input to the machining pulse controller 42a, and the machining pulse controller 42a is operated.
Performs conduction control of Tra with a signal of a predetermined ON time and rest time, sets HVP to a specified power supply voltage, and changes VR to a resistance value that is a set current peak value, thereby performing desired processing. Supply a pulse.

The power supply MVP is also constructed in substantially the same manner as the power supply HVP, and the first switching circuit is a diode D.
1, the current limiting resistors R1 and Tr1 are connected in series, and the second and third switching circuits are respectively connected in parallel below, and are connected to the workpiece 3 through the output line connecting portion 44. The machining pulse control device 42a selects MVP as the set power supply voltage by the machining condition setting signal S1 and further ON-OFF controls as many switching elements Tr1 to Trn as there are at the set current peak value. The machining pulse of is supplied to the machining gap. The ON and OFF times of the supplied processing pulse are 0.5 μSEC to 10 μSEC.

In the main power supply device 41, a resistance smaller than the current limiting resistance value used in the sub power supply device 42 is used, and the current peak value is from several hundred amps to 1000 amps and the pulse width is 0.1. Since the configuration is almost the same except that it can supply a high peak current of about 5 μSEC, description thereof will be omitted.

Next, the machining liquid selecting means 43 will be described. The machining fluid selection means 43 is provided with a machining fluid setting switch (not shown) (which may be a signal from the numerical controller 12) of a water machining fluid selection signal SW, an oil machining fluid selection signal SO, and a powder mixed machining fluid selection signal SOP. The signals are input in the following combinations. The LoFF signal is a signal that ignores switching for using the output line having an inductance,
It is used when only processing speed is improved with a powder mixed processing liquid. (A) SW-ON (b) SW-OFF SO-ON SOP-OFF (c) SW-OFF SO-OFF SOP-ON (d) SW-OFF SO-ON SOP-ON

First, when the water-working fluid of (a) is turned on, the water-working fluid is selected and the signal for controlling the electromagnetic on-off valve is sent to the machining-fluid supply device through the signal line S2 as described above. The circulation path of is switched to the water processing liquid. When the water processing liquid is selected and the SW is ON, other switching signals are ignored to prevent water and oil from being mixed with each other. Similarly, when the combination (b) is selected, a signal for switching to the oil processing liquid supply circuit is sent to the processing liquid supply device 60. The same applies to the case of (c), and the machining liquid supply path is switched as described above.

When (d) is selected, the solenoid opening / closing valve 1
a, only the electromagnetic on-off valve 17f is opened, the pump 17c is driven, the oil processing liquid is supplied to the processing tank 1 and the drain of the processing tank 1 is closed, so that the processing liquid is accumulated until a predetermined liquid level is reached. . Here, a liquid level sensor (not shown) detects that the machining fluid has reached the set value, and closes the electromagnetic on-off valve 1a and the electromagnetic on-off valve 17f to close the electromagnetic on-off valve 1.
8 g and the solenoid on-off valve 18 f are opened, and the pump 18 c is driven to drive the upper nozzle 5 c and the lower nozzle 6 c.
It becomes a circulation path for supplying the powder-mixed working liquid only.

Next, the machining liquid selecting means 43 is set to the above (c).
When the combination of (d) and (d) is selected, a control signal is sent to the output line connection section 44 through the signal line S3, and the output line is connected to
Control for switching the output lines 21 and 22 is performed as shown in FIG.
This will be described with reference to FIG. In the figure, the same reference numerals indicate the same parts. In FIG. 3A, the output lines on the positive electrode side and the negative electrode side output from the sub power supply device 42 are coaxial lines surrounded by the negative electrode side output line 22a with the positive electrode side output line 21 as the core wire, and the forward and return paths are provided. The inductance is infinitely reduced by the current flowing through the wire, and it is a low impedance wire manufactured so that the inductance and the capacitance cancel each other out, not having the capacitance like the usual shielded wire. The low impedance wire is connected to near the machining gap.

In the vicinity of the machining gap, the positive electrode side output line 21 and the negative electrode side output line 22 are again connected as a single line to the upper power feeding piece 5b, the lower power feeding piece 6b and the work piece 3, respectively.
An output line switching means 23a is provided between the positive electrode side output wire 21 guided from the power supply device to the vicinity of the machining gap and the single wire portion, and the powder mixed working fluid is selected by the working fluid selection means. The output line 21 on the positive electrode side becomes the connection shown in the figure, and serves as a path having an inductance of several ten μH to 30 μH. The value of the inductance should be selected according to the processing conditions such as the current value to be processed, but the processing ON time is 4.5 μSEC, the processing pause time is 1.5 μSEC, the current peak value is 1 ampere (at the time of short circuit), and the power supply voltage is 80V. , 2 under the condition of auxiliary power supply voltage 250V (current value at short circuit 0.3A)
About 0 μH was a preferable value for obtaining a good-quality smooth surface.

In FIG. 3B, two output lines are provided at the outlet of the sub-power supply device 42, and the low impedance line (22a, 21) is used in the preceding process, which requires a high processing speed. The output line (22b, 21a) of the present invention, which supplies a machining pulse and has an inductance, is used as another path, and the switching device 23b is switched by the selected machining liquid. In the embodiment, the path having the inductance on the side of the workpiece is shown, but the output wire 22 on the negative electrode side is provided.
May be inserted on the side.

Next, the powder-mixed working liquid used will be described. In the device of the present invention, a mineral oil-based hydrocarbon oil is used as the oil processing liquid, and in view of the danger of fire in particular, the fourth type third petroleum oil generally used for electric discharge machining is used as the processing liquid. , Semi-conductive powder, Gr,
A mixture of powders such as Al can be used. It is preferably a mixed liquid in which polycrystalline silicon powder is mixed at a ratio of 1 to 1.5 weight percent, and a powder particle size of 2 μm or less, more preferably 1 μm or less is suitable.
This is because when a machining liquid having a particle size of 5 μm or more as a main component is used, sagging occurs near the upper surface and the lower surface of the workpiece 3 or in the corner portion of the machining shape, and the machining gap becomes too wide. This is because it may damage the When the conductivity of the mixed particles is high, the concentration may be adjusted so that the resistance of the working fluid is at least 10,000 ohms per cm.

Finally, the overall operation and the result thereof will be described with reference to an experimental example using the apparatus of the present invention. [Experimental Example] An example is shown in which tungsten is used for the wire electrode and an iron-based workpiece is processed into a contour shape five times for finishing, and processing is performed using an oil-based processing liquid from the first processing step. Workpiece material SKD-61 Plate thickness 2 mm Electrode material and diameter 0.05 mm (i) First machining process Machining fluid selection SO (Oil-based machining fluid immersion machining) Machining condition setting No load voltage: 80 V Pulse width: On-time 2μSEC OFF time 11μSEC Current peak value: 2.4A Auxiliary power supply no-load voltage: 150V DC voltage Maximum current during short circuit: 0.15A (VR resistance value 1K ohm) Gap capacitor: 0.01μF Servo voltage: 95V Offset value: 45μm Processing State Average processing voltage: 105V Average processing current: Approx. 0.07A Processing movement speed: 0.8mm / min

(Ii) Second processing step Selection of processing liquid SOP (powder-mixed oil-based processing liquid immersion processing) Loff on (without using inductance) Processing liquid powder fine particles: polycrystalline silicon addition amount: 1.5% by weight addition Powder average particle size: 2 μm Processing condition setting No load voltage: 80 V Pulse width: On time 0.5 μSEC Off time 5 μSEC Current peak value: 4 A Auxiliary power source no load voltage: 150 V DC voltage Maximum current at short circuit: 0.15 A (VR resistance) Value 1K ohm) Gap capacitor: Not used Servo voltage: 100V Offset value: 45 μm Machining state Average machining voltage: 113V Average machining current: Approx. 0.7A Machining speed: 7mm / min

(Iii) Third Step Only parts different from the above second step will be described. Servo voltage: 90V Machining state Average machining voltage: 123V Average machining current: about 0.05A Machining speed: 7.4mm / min Machining surface roughness: About 5μRmax

(IV) Fourth Step Selection of Processing Liquid SOP (Powder-mixed oil-based processing liquid immersion processing) Processing liquid Powder fine particles: Polycrystalline silicon Addition amount: 1.5% by weight Additive powder average particle diameter: 2 μm Processing condition setting No-load voltage: 80V Pulse width: On-time 4.5μSEC Off-time 1.5μSEC Current peak value: 2.4A Auxiliary power source no-load voltage: 250V DC voltage Short-circuit maximum current: 0.25A (VR resistance value 1K ohm) Gap Capacitor: Not used Servo voltage: 200V Offset value: 70 μm Machining state Average machining voltage: 250 V Average machining current: Approx. 0.05 A Machining speed: 7.2 mm / min Machining surface roughness: Machining with machining settings of approximately 2 μRmax or more As a result, a smooth machined surface was obtained.

Next, the operation will be briefly described with reference to the above experimental example. First, in the first machining step, a machining program is input from an input device (not shown), and various machining parameters described in the program are supplied as various setting signals from the numerical controller 12 via the signal line S1 to the main power supply device 41. And machining pulse control device 4 for the sub-u power supply device 42
2a (the processing pulse control device of the main power supply device 41 is not shown) is sent to the plurality of switching circuits for conduction control, and the variable power supply and the variable resistance are set to predetermined values.

Further, in the first machining step, since SO is set in the machining fluid selecting means 43, the machining fluid selecting means 4
Reference numeral 3 sends a signal for switching the electromagnetic on-off valve to the working fluid supply device 60 through the signal line S3 so as to form an oil working fluid circulation circuit. The control state of the solenoid opening / closing valve is as described above. In addition, you may select SW by the working fluid selection means 43 and process with a water working fluid.

Next, when the first machining step is completed, the numerical controller 12 calls the following program and the machining parameters corresponding to the second machining step are sent to the auxiliary power supply device 42 in the same manner as described above, and machining is performed under the machining conditions of the second step. A pulse is delivered. Here, in the second machining step, since the selection of the machining fluid is SOP, the machining fluid selection means 43 sends the control signal of the electromagnetic opening / closing valve to the machining fluid supply device 60 so as to switch the machining fluid to the powder-mixed machining fluid. The working fluid is switched. Also, Lof
Since the f signal is also turned on, the output line switching signal is not sent to the output line connecting section 44. In the third machining step, since the servo voltage setting is only changed, the machining is continued without changing the remaining machining condition parameters.

Further, in the fourth processing step, the processing conditions are changed in the same manner as described above, and since there is no Loff signal, the positive side output line 21 of the output line connecting portion 44 is changed to a circuit having an inductance and processed. Is done. On this occasion,
As the working liquid, the powder-mixed working liquid is used as it is, and a smooth and fine working surface which is the object of the present invention is formed. It has been confirmed that a similar machined surface can be easily obtained up to a plate thickness of about 80 mm.

FIG. 5 shows 5 μRm obtained by conventional processing.
The state of the machined surface when the machined surface of ax and the machining fluid containing powder are used and an output pulse is further supplied through the output line having the inductance of 20 μH will be described. FIG. 5A is a machined surface obtained when machining is performed by the apparatus of the present invention, and FIG. 5b is a case where a discharge oil aging time of 0.
5 μSEC, discharge pause time 1 μSEC, current peak value 3.
It shows a machined surface obtained when machined at 2 A and a no-load voltage of 80 V.

[0048]

As described above, it is difficult to obtain the conventional method by using the working fluid in which the fine particles of powder such as semiconductivity are mixed in the working fluid and changing the output line to the output line having the inductance. The machined surface can be easily obtained in a short processing time. Even when a smooth surface is required, the apparatus of the present invention can minimize polishing, and in the case of an injection molding die or the like, a processed surface having excellent releasability can be obtained. be able to.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the present invention.

FIG. 2 is a detailed detailed configuration diagram of a power supply unit and a processing liquid selection unit.

FIG. 3 is a detailed partial view showing a switching connection of output lines.

[Fig. 4] Configuration diagram of conventional wire-cut electric discharge machining

FIG. 5 is a diagram in which unevenness of a machined surface of a workpiece machined using the apparatus of the present invention and a conventional machined surface are measured.

[Explanation of symbols]

 1 Processing Tank 2 XY Cross Table 3 Workpiece 4 Wire Electrode 5 Upper Jet Wire Guide Member 6 Lower Jet Wire Guide Member 5a, 6a Upper and Lower Wire Guides 5b, 6b Vertical Feeding Piece 12 Numerical Control Device 16 Water Processing Liquid Supply Device 17 Oil Processing liquid supply device 18 Powder mixed processing liquid supply device 16g, 16f Electromagnetic on-off valve 17g, 17f 18g, 18f 21 Positive side output line 21 22 Negative side output line 22 23a, b Output line switch 42 Sub power supply device 43 Processing liquid selection Means 44 Output line switching connection

Claims (1)

[Claims] 1. A wire electrode is axially renewedly moved between a pair of guides arranged at a distance, and a workpiece is made to face each other with a minute gap in a direction substantially perpendicular to the axial direction, and the gap is provided in the gap. Equipped with a power supply that supplies intermittent voltage pulses,
Machining is performed by the electric discharge pulse generated through the machining fluid,
In a wire cut electric discharge machine that gives a relative machining feed between the wire electrode and the work piece to machine a desired contour shape, a machining pulse of a machining parameter such as a desired discharge on time and an electric discharge machining pause time is set. A power supply circuit for supplying to the machining gap, a machining liquid supply device for supplying an oil-based machining liquid and a machining liquid obtained by mixing fine particles of powder in the oil-based machining liquid to the machining gap, and machining from the machining liquid supply device. A machining liquid selecting means for selecting and supplying a liquid to the gap, and a finishing liquid using a semiconductive powder-mixed machining liquid from the machining liquid supply device, the power circuit and the machining gap Insertion means for inserting an inductance element into at least one of the electric discharge machining pulse output lines connected between the workpiece side or the wire electrode side, or before the output line having a sufficiently large inductance A wire-cut electric discharge machine having a switching means for switching to the electric discharge pulse output line.