JPS63295124A - Wire electric discharge machine - Google Patents

Abstract

PURPOSE:To improve the roughness of machining and its speed, by short circuiting a machining gap after the predetermined time from the time of starting voltage to be applied and turning off a switching element placing a resistor to be connected while shortening a pulse period when no-load voltage increases to a preset value. CONSTITUTION:A machine, which inputs a pulse from a pulse oscillator 21 to an AND gate 23 dividing no-load voltage by divider resistors 32, 33 to be input to a comparing amplifier 26, conducts by the output, when it is in a value of preset voltage E1 or less, a switching transistor 25 through the AND gate 23 and an amplifier 24, and the machine, charging a stray capacity 11 with voltage by a power source 22 not through a resistor 31, increases the voltage rapidly rising up. When the output reaches the preset voltage E1, the machine, closing the AND gate 23, placing the switching transistor 25 in a no-conduction condition and applying DC voltage E0 through the resistor 31, increases no-load voltage moderately rising. While when the no-load voltage increases to E1 or more, an output of the comparing amplifier 26 is given to a monostable multivibrator 27, and the machine generates a pulse, determining machining gap short circuit timing, and a machining gap short circuit pulse by a monostable multivibrator 28, enabling a pulse width to be shortened.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a wire electrical discharge machine that processes a workpiece by intermittently generating electrical discharge between a wire electrode and a workpiece. be.

[Conventional technology]

A conventional wire electric discharge machine was constructed as shown in FIG. In the figure, 1 is a wire electrode, 2 is a workpiece, 3 is a processing pulse power source, and 4 is a current limiting resistor.

5 is a feeder, 6.7 is a roller that guides the wire electrode 1, 8.9 is a guide for supporting the wire electrode 1, and 10 is a space between the wire electrode 1 and the workpiece 2 (hereinafter referred to as
This is a machining fluid supply nozzle for supplying an insulating machining fluid 10a to a machining gap (referred to as a machining gap).

During processing, the wire electrode 1 is caused to run through the roller 6, the feeder 5, the guide 8, the workpiece 2, the guide 9, and the roller 7 by a wire electrode supply device (not shown). At the same time, the machining fluid supply nozzle 10 supplies an insulating machining fluid 10a such as ion-exchanged water to the machining gap, and the pulse voltage generated from the machining pulse power source 3 is applied to the wire electrode via the current limiting resistor 4 and the feeder 5. 1 and workpiece 2
The workpiece 1 is cut by generating an intermittent arc discharge between them, that is, in the machining gap.

Pulse voltage (P, G
) is a rectangular wave as shown in waveform A in FIG. As shown in B1, the curve has a gentle rise. Furthermore, when no discharge occurs, the floating capacitance 11 is charged with a voltage, so that a DC voltage B2 is applied to the machining gap.

When a discharge occurs, as shown in waveform C, the peak value ■2 and the pulse width t1. I
A current determined by (discharge current) flows into the machining gap, and electrical discharge machining progresses.

Now, as is well known, the machining surface roughness is determined by the discharge energy, but since the arc voltage is almost constant (approximately 15 V when the machining fluid 10a is water), it can be simply expressed as the pulse width of the discharge R flow x the peak current (twxtr ) can be considered to be proportional to Furthermore, since the stray capacitance 〒11 is determined by the above-mentioned current-carrying cable and the mechanical structure of the electric discharge machine, the pulse width t8 of the pulse voltage released from the above-mentioned stray capacitance 11 is determined by the time constant of the circuit and is a constant value. It is.

Therefore, if it is assumed that the stray capacitance 11 cannot be reduced in the conventional processing machine described above, it is necessary to reduce the no-load voltage VGiP in order to reduce the roughness of the machined surface.

As a result, the peak current {circle around (2)} decreases.

FIG. 7 shows the relationship between no-load voltage V(, Hp) and machined surface roughness in a conventional processing machine, and it can be seen that reducing the no-load voltage V(, Hp) significantly improves the machined surface roughness.

[Problem that the invention seeks to solve]

However, in this method, when the no-load voltage vGaP is lowered as shown by the dotted lines (a) or (tl) in FIG. However, this may cause waviness on the machined surface,
One problem was that streaks were generated in the running direction of the wire electrode 1, which worsened the roughness of the machined surface.

Furthermore, as can be seen from Fig. 8, which shows the relationship between the pulse period T and the machining amount δ (although the dotted line in Fig. 8 is an imaginary extension), the pulse period T can be shortened (if the machining amount δ is In other words, the machining speed improves.However, in the conventional method, as shown in waveform B in FIG. The second problem was that it was slow.

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a wire electric discharge machine that can improve both the roughness of the machined surface and the machining speed.

Measures to solve problem C] Regarding the first problem when machining with a conventional electric discharge machine, which is the cause of the wire electrode adhering to the workpiece, the following is as follows.
After conducting various experiments and other studies, we found that the no-load voltage VGmF waveform was determined by the set off-time T as shown in FIG. At the time of FF, the actual applied voltage is also o■, and the pulse duty factor τ('rON/'
It has become clear that the problem can be solved by reducing r) to 50% or less.

The reason for this is unclear in many ways, but it is probably due to the no-load voltage ■6. ．． However, it is assumed that this is because the first problem occurs due to a type of plating action, since it is almost a direct current when no discharge is generated in the machining gap. Therefore, in the present invention, the machining gap is short-circuited after a predetermined time from the start of voltage application to the machining gap.

Regarding the second problem, B in waveform B in Fig. 6,
No-load voltage V. In order to increase the rising speed of P, as shown in FIG. 4, the value of the DC power supply voltage E0 is made sufficiently high, and the voltage is applied to the machining gap without passing through a resistor such as a current limiting resistor.

Then, when the no-load voltage VGaP reaches the set value E1, the switching element is turned off and a resistor is inserted to shorten the pulse width T. M is obtained, and the pulse period T can be shortened.

[Effect]

If the machining gap is short-circuited after a predetermined period of time after the voltage is applied to the machining gap, the no-load voltage VGmF is forced to 0■, and no direct current voltage is applied. Therefore, the duty factor τ of the applied pulse can be made sufficiently small, and the roughness of the machined surface can be improved.

Furthermore, if the value of the DC power supply voltage E0 is set sufficiently high and the voltage is applied to the machining gap without any resistance (especially current limiting resistance), the rise speed of the no-load voltage VGaF can be increased. In turn, the pulse width T. N can be shortened, and the pulse period T can be shortened to increase the machining speed. By increasing the DC power supply voltage E0, the no-load voltage v GaP
The surge generated at the upper part of the riser can be prevented by inserting a vibration suppressing resistor and applying a voltage in the latter half of the rising portion.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a configuration diagram showing an embodiment of a wire electric discharge machine according to the present invention. In FIG. 1, the same or equivalent parts as in FIG.

21 is a pulse oscillator, the output of which is given to one input of a two-manual AND gate 23. On the other hand, in the machining gap,
Voltage dividing resistors 32 and 33 are connected to detect the no-load voltage V GmP, and the divided voltage is applied to the inverting input of the comparison amplifier 26. A set voltage E for setting the no-load voltage VGmF is applied to the non-inverting side input of the comparison amplifier 26. The output of the comparison amplifier 26 is applied to the other input of the AND gate 23.

The output of the AND gate 23 is applied to the input of an inverting amplifier 24, and the output of the amplifier 24 is input to the base of the first switching transistor 25. The first switching transistor 25 has a collector connected to the feeder 5 in contact with the wire electrode 1, and an emitter connected to the positive electrode of the DC power supply 22, respectively. The negative electrode of the DC power source 22 is connected to the workpiece 2. In addition, the wire electrode 1 and the DC power source 2
A resistor 31 for suppressing vibration of no-load voltage is connected between the positive electrode of No.
is connected.

The pulse width T is determined by the circuit configuration described above. H is determined.

On the other hand, the output of the comparison amplifier 26 is also given to the input of the first monostable multi-bi break 27, and the output of the monostable multi-bi break 27 is given to the input of the second monostable multi-bi break 28. The output of the monostable multivibrator 2 is power amplified by the amplifier 29 and applied to the base of the second switching transistor 30.

The second switching transistor 30 has a collector connected to the wire electrode 1 through the feeder 5, and an emitter connected to the workpiece 2.

The above-mentioned circuit configuration has an off-pulse T having the waveform shown in FIGS. 3 and 4. It functions to specifically set the no-load voltage VGaP in the F1 section to OV.

Next, the operation of the above-mentioned electric discharge machine of the present invention will be explained with reference to FIG. 2. First, the wire electrode 1 is made to run as in the conventional case, and the machining liquid 10a is supplied to the machining gap by the nozzle 10. Further, a pulse having a period T as shown in waveform C in FIG. 2 is generated from the pulse oscillator 21. The pulse is applied to one input of AND gate 23. On the other hand, the no-load voltage VGmP is divided by the voltage dividing resistors 32 and 33 to a number of volts that will not damage the transistors in the comparator amplifier 26, and is applied to the inverting input of the comparator amplifier 26. Further, a set voltage E+ is applied to the non-inverting side input of the comparison amplifier 26.

In this state, at time T2 in FIG. 2, the no-load voltage vG,P is below the level E, so the comparator amplifier 2
The output signal of No. 6 is at a logical "1" level as shown in the waveform. Therefore, the output signal is given to the AND gate 23, and the output signal of the AND gate 23 is at the "1" level as shown in waveform F, and the output signal passes through the amplifier 24 and makes the first switching transistor 25 conductive. . As a result, the DC power supply 22 quickly charges the stray capacitance 11 through the first switching transistor 25 without passing through the resistor 31, and therefore the no-load voltage vG
The rising edge of , P becomes rapid as shown in (c) of the waveform. When the no-load voltage vG, , reaches the set voltage E1, the output of the comparator amplifier 26 is inverted to "O" level, so the AND gate 23 is closed and the waveform F becomes "
0'' level and the first switching transistor 2
5 is in a non-conductive state. On the other hand, the resistor 31 is connected to the DC power supply 22
and the feeder 5, so the DC voltage E. is applied to the machining gap through the resistor 31, and as shown in the wavy slope part (d), the rising part (c)
Compared to , the no-load voltage VGsP
increases, thereby suppressing surges caused by vibrations that occur at the top of the voltage.

Further, the output of the comparison amplifier 26 is also given to the first monostable multipipe lake 27, and the no-load voltage VGa
P becomes equal to or higher than the level E, and the output of the comparator amplifier 26 becomes “
At the time when the monostable multivibrator 27 is reversed to O'' level, the monostable multivibrator 27 generates a pulse having a predetermined pulse width T. This pulse width T11 determines the timing to short-circuit the machining gap. vibrator 27
The output of is given to the second monostable multi-by-break 28, which generates a pulse with a predetermined pulse width Ts. This pulse, width T, short-circuits the machining gap and increases the no-load voltage V G,
It is sufficient if there is a time span required for , to become OV.

Here, as shown in FIG. 4, the voltage Eo of the DC amount a22
If, for example, the value of the set value E is set to 300V and the value of the set value E is set to 50V, the pulse width ToN of the no-load voltage VG, , can be reduced to 1/6 of the conventional value. In addition, in the electrical discharge machine of the present invention, since there is no current limiting resistor 4 (see Fig. 5) as in the conventional case, the time to charge the stray capacitance 11 is shortened, and the no-load voltage V
Since the rising speed of 6 mF becomes faster, the pulse width T. According to experiments conducted by the inventors, the pulse width TON can be reduced to approximately 50 ns.

Therefore, the pulse period T can be shortened to about 150 ns to 100 ns.

Specific machining examples using the electric discharge machine of the present invention are listed below.

Wire electrode 1: Material brass, diameter 0.25mφ Workpiece 2:
Material: 5KDII, plate thickness: 70m Processing method: The rough processed (first cut) surface was second cut.

Pulse conditions: TON: 50ns T: 140ns VG-P: 50V Ip: 0.5A jw: 50ns As a result of processing under the above conditions, the processed surface was free of deposits and had no streaks in the wire running direction. , the surface roughness was 0.2 μm or less than Rmax.

Furthermore, since the pulse period can be shortened, the processing efficiency can be increased by about 5 times or more compared to the conventional method, which is a great industrial effect.

〔Effect of the invention〕

As described above, according to the present invention, off-pulse (TOF)
When F), the duty factor τ of the no-load voltage V, , , can be reduced by short-circuiting the machining gap, so that V, , ,
Even if the surface temperature is lowered, a good processed surface roughness with no deposits on the processed surface can be obtained. Furthermore, since the rise time of the no-load voltages (G and P) can be made faster, the pulse period T can be shortened, and the machining speed can be increased.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram showing an embodiment of the electric discharge machine of the present invention, Fig. 2 is a signal waveform diagram of each part of the same electric discharge machine, and Figs. 3 and 4 are for explaining the principle of the above electric discharge machine. Figure 5 is a configuration diagram of a conventional electric discharge machine, Figure 6 is a signal waveform diagram of each part of the same electric discharge machine, and Figures 7 and 8 are for explaining the problems of the same electric discharge machine. This is a graph of ■...Wire electrode, 2...Workpiece, 5...Electron feeder, 10a...Working fluid, 21...Pulse oscillator, 2
2...DC power supply, 23...AND gate, 25.3
0... Switching transistor, 26... Comparison amplifier, 27.28... Monostable multivibrator, 3
1... Resistor for vibration suppression, 32.33... Voltage dividing resistor (
machining gap voltage detection circuit). Patent Applicant Hitachi Seiko Co., Ltd. Agent Patent Attorney Tadashi Akimoto Figure 1 f Figure 2 Figure 3 Figure 4 Figure 6

Claims (1)

[Claims] In a wire electrical discharge machine that cuts the workpiece by supplying an insulating machining fluid between the wire electrode and the workpiece (machining gap) and generating intermittent arc discharge, the workpiece is cut at a certain period. a pulse oscillator that generates a pulse of a first switching circuit that applies a DC voltage to the machining gap through the resistor after reaching the set value without using the DC voltage;
A wire electric discharge machine comprising: a second switching circuit that short-circuits the machining gap after a predetermined time from the start of applying a DC voltage to the machining gap.