JPS61260921A - Power source for electric discharge machining - Google Patents

Abstract

PURPOSE:To stabilize an output voltage with respect to the variation of a floating capacitance and obtain a good-quality and uniform machining surface by switching the inductance of a variable-inductance coupling coil, within a proper range by a switching means. CONSTITUTION:When the on-off control of a switching element 2 is repeated at a frequency of several MHz by means of a driving circuit 3, the both-end voltage of a floating capacitance 8, i.e., a high-frequency AC voltage is generat ed across poles 6, to carry out electric discharge machining. In order to obtain a uniform machining surface, it is necessary to restrain the variation in the output voltage with respect to the changes in a floating capacitance 8 and a floating inductance 7. Thereupon, by properly switching the inductance of a variable-inductance coupling coil 10 which is sufficiently larger than the induct ance of the floating inductance 8, the output voltage can be stabilized. According ly, an extremely good-quality and uniform machining surface can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power source for electric discharge machining that can obtain a finished surface with a surface roughness of 1 μmRmax or less, which has been considered difficult in the past.

[Prior art] In general, electric discharge machining using AC high frequency has an average machining voltage of 0.
Therefore, chipping (missing phenomenon) due to electrolytic action does not occur, and the polarity changes every - half-wave discharge, and the discharge point is different, so it has excellent machining characteristics such as being able to obtain a high-quality machined surface at fi. have. FIG. 7 is a circuit diagram of a conventional AC high frequency power source for electrical discharge machining. In Figure 7,
(1) is a DC power supply, (2) is a switching element, (3)
is a switching element (drive circuit for driving 21,
(4) is a current limiting resistor, (5) is a coupling transformer, (
6) is the gap formed between the machining electrode and the workpiece, (
7) is a floating inductance that exists between the current supply line and the gap (6), and (8) is a floating capacitance that also exists between the current supply line and the gap (6).

Next, the operation of the conventional AC high frequency source for electric discharge machining shown in FIG. 7 will be explained. When the switching element (2) performs a switching operation at a frequency of several hundred to several MHz by the drive circuit (3), an alternating current pulse is generated on the primary side (direct current side) of the coupling transformer (5). When the current pulse generated on the first arrow side is induced to the secondary side (vl, between (6) side) of the coupling transformer (5), a current pulse exists between the coupling transformer (5) and the between poles (6). A current high frequency voltage determined by a resonant circuit of stray inductance (7) and stray capacitance (8) is supplied between the poles (6), and between the other poles 6
), an electrical discharge is generated between the machining electrode and the workpiece, and the relative position between the machining electrode and the workpiece is moved three-dimensionally, thereby moving the workpiece to the desired position. Processed into a processed shape. In this case, the characteristics of the machined surface are greatly influenced by the voltage supplied between the electrodes (6), and this voltage is determined by the stray inductance (7) and the stray capacitance (8). ) is 0.1 to several μH1 There is variation.Also, stray capacitance (8)
varies greatly depending on changes in the electrode during processing, the distance between workpieces, the facing area, etc.

[Problem that the invention seeks to solve]

In the conventional AC high frequency power supply with the above configuration, the voltage supplied between the electrodes (6) fluctuates greatly due to stray inductance (7) and stray capacitance (8), so it is difficult to maintain stable processing characteristics at all times. The problem was that it was difficult. In order to improve these problems, it is possible to make one frequency variable, tune it, and supply the desired voltage between the poles (6) VcFh, but t' during machining? M, is completely powerless against fluctuations in stray capacitance (8) caused by changes in the distance between workpieces and opposing areas;
The processing power source becomes extremely expensive, and furthermore, the operation by the operator becomes complicated. In addition, the coupling transformer (5)
There is also a problem in that it is difficult to reduce variations in characteristics and it is difficult to ensure stable power supply characteristics.

The present invention was made to solve the above problems, and
The purpose is to obtain a power source for electrical discharge machining that can always obtain a high-quality machined surface with a small degree of surface assemblage against fluctuations in stray capacitance peculiar to electric discharge machines, and is inexpensive and has a wide range of machining applications. .

[Failure to solve the problem]

Therefore, in the present invention, an electrode and a workpiece are arranged facing each other, and an electric discharge is generated between the electrodes. A DC power supply for voltage application, a switching element connected between the poles and the DC power supply in parallel to the poles and the DC power supply, and a current voltage generated between the poles by controlling the switching element on and off. a current-limiting resistor connected between the DC power supply and the switching element, a coupling capacitor connected between the switching element and the electrode gap, and a coupling capacitor and the electrode gap connected to each other; The variable inductance coupling coil is connected between the variable inductance coupling coil and the switching means for switching the inductance of the variable inductance coupling coil.

[For production]

The electrical discharge machining power supply having the above configuration performs electrical discharge machining by controlling the switching elements on and off using the drive circuit and applying a high frequency voltage between the electrodes. At this time, the output voltage is stabilized by appropriately switching the inductance of the variable inductance coupling coil using the switching means.

〔Example〕

Hereinafter, one embodiment of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a power source for electric discharge machining according to the present invention.

In Figure 1, (1) is a DC power supply, (2) is a switching element, (3) is a drive circuit for driving the switching element (2), (4) is a resistor for current limiting, (6)
is the gap formed between the machining electrode and the workpiece, (7) is the stray inductance that exists between the current supply line and the gap (6), etc., and (8) is the stray inductance that exists in the current supply line and the gap (6), etc. The stray capacitance that exists, (9) is the switching element (
2) and a coupling capacitor provided between the poles (6).

(1υ is a variable inductance coupling coil provided between the coupling capacitor (9) and the pole gap (6), and C11l is a relay contact (switching means) for switching the variable inductance coupling coil (Lol).

Next, the overall operation of the electric discharge machining power supply according to the present invention will be explained. Note that the inductance of the variable inductance (lO1 coupling coil 0α) is sufficiently larger than the inductance of the floating inductance (8).

First, when switching element (2) is turned off, the second
As shown in the figure, DC power supply (1) (El, resistor (4)
(R1), a coupling capacitor (91 (Cs)), a variable inductance coupling coil 0α (Ll), and a floating capacitance (81 (Cz)). (9) and the stray capacitance (8) are charged.Next, when the switching element (2) is turned on, the stray capacitance (3) (Cz) and the variable inductance coupling coil (10) are charged as shown in FIG. (Lt) and the coupling capacitor (91 (C+)) to the series circuit formed by I11, 11 currents flow in the direction shown by the arrow in the figure, and the coupling capacitor (91 (C+)
) and the stray capacitance (8) are discharged. Therefore, when the drive circuit (3) repeats on/off control of the switching element (2) at a switching speed of several MHz, the voltage across the floating capacitance (8), that is, the variable current high-frequency voltage, appears between the electrodes (6). is generated, and this voltage causes electrical discharge to occur in the gap (6), resulting in electrical discharge machining.

As mentioned above, the electrical circuit of the electrical discharge machining device includes the machine body and the machining gap, and there are differences in the mechanical structure of the electrical discharge machining device or the distance and opposing area between the electrode and the workpiece. Due to changes etc.

The capacitance of the floating capacitance (8) varies greatly.

Also, depending on the method of terminal treatment of the current supply line, etc.

The inductance of the stray inductance (7) will also vary greatly. In order to obtain a uniform machined surface, it is necessary to suppress fluctuations in the output voltage with respect to such changes in the floating capacitance (8) and the floating inductance (7). Figure 4 shows the stray capacitance (8) with the variable inductance coupling coil (10) as a parameter.
) is a diagram showing changes in output voltage with respect to fluctuations in
In the same figure, A, B, and C represent the inductance of the inductance fiO between the variable inductance coupling coils at 50 [μH].
], 10 [μH] and 1 [μH]. As is clear from the figure, the output voltage is determined by changing the inductance of the variable inductance coupling coil (1
μH], at least the stray capacitance (8)
It is stable within a fluctuation range of about 500 to 1000 [:pF].

FIG. 5 is a diagram showing changes in output voltage when the inductance of the variable inductance coupling coil (11) shown in FIG. 1 can be switched to two stages of 20 [μH] and 5 [μH]. , the inside of the figure is 20CμHIB is 5 [
μH]. As is clear from the figure, regardless of whether the inductance of the variable inductance coupling coil (11 is 20 [μH] or 5 [μH]), the variation range of the stray capacitance (8) is 500 to 500 [μH].
The output voltage becomes stable at 1000 [pH]. Therefore, by appropriately switching the relay contact αD according to the machining conditions, the cutting voltage is switched by 7 to perform electrical discharge machining.

Note that in finishing machining in ordinary electric discharge machining, the electrical conditions are switched as the machining progresses to ultimately obtain a high-quality machined surface and desired machining accuracy. Therefore,
In this embodiment, switching the voltage of the DC source (1) and switching the inductance of the variable inductance coupling coil 00) are combined to widen the output voltage range and enable more detailed selection of electrical conditions.

Next, FIG. 6 is a circuit diagram of a power source for electrical discharge machining according to another embodiment of the present invention. Note that in FIG. 6, parts that perform the same functions as those in FIG. In the above embodiment, two coils with different inductances were connected in parallel as the variable inductance coupling coil 01, and a relay contact Ql) connected in series with each of these two coils was used as the switching means. In this case, a variable inductance coupling coil σ (two coils connected in series as a force and a relay contact (1) connected in parallel to each of the two coils as a switching means) is used.

Note that in the embodiments shown in FIGS. 1 and 6, a relay contact (11) was used as the switching means, but other switching means,
For example, a rotary switch may be used.

〔Effect of the invention〕

As explained above, according to the present invention, the electrical discharge machining power supply of the apparatus for electrical discharge machining of the workpiece is made extremely efficient by generating electrical discharge between the poles formed by arranging the electrode and the workpiece facing each other. A DC power supply for applying a voltage between the poles, a switching element connected between the poles and the DC power supply in parallel with the DC power supply, and a switching element connected in parallel to the DC/current power supply between the poles and the poles by controlling on/off of the switching elements. A drive circuit that generates an alternating current voltage between the two, a current limiting resistor connected between the direct current power supply and the switching element, a coupling capacitor connected between the switching element and the pole, and a coupling capacitor and It is composed of a variable inductance coupling coil connected between the poles and a switching means for switching the inductance of the variable inductance coupling coil, and the switching means switches the inductance of the variable inductance coupling coil within an appropriate range. As a result, it is possible to stabilize the output voltage against fluctuations in stray capacitance peculiar to electric discharge machines, so it is possible to obtain an extremely high-quality and uniform machined surface.

Furthermore, since the output voltage can be changed by switching the inductance of the variable inductance coupling coil, the range of processing applications is widened.

Furthermore, since there is no need to change the switching frequency as in the conventional case, a tuning circuit is not required, and an extremely inexpensive power source for electrical discharge machining can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power source for electrical discharge machining according to the present invention. Figure 2 and! Figure 3 is an explanatory diagram of the operation of the electric discharge machining power supply shown in Figure 1, and Figures 4 and 5 are characteristic diagrams showing the characteristics of the output voltage with respect to fluctuations in stray capacitance of the electric discharge machining power supply shown in Figure 1. , FIG. 6 is a circuit diagram of a power source for electric discharge machining according to another embodiment of the present invention, and FIG. 7 is a circuit diagram of a conventional power source for electric discharge machining. In the figure, 1 is a DC power supply, 2 is a switching element, 3 is a drive circuit, 4 is a resistor, 6 is a gap between electrodes, 7 is a floating inductance, 8 is a floating capacitance, 9 is a coupling capacitor, 10
1 is a variable inductance coupling coil, and 11 is a relay contact. Note that the same reference numerals in each figure indicate the same or corresponding parts. Agent: Patent Attorney Tadashi Sato Figure 2 1. DC power supply 7: N-shape 1 Inductance 8: 5 Kizo 1: V-no power supply Figure 3 Figure 9: Clamping capacitor Figure 4 Figure 5 Figure 6 Figure 7 Procedural amendment (voluntary) January 13, 1985

Claims (4)

[Claims] (1) A voltage is applied between the electrodes in the electric discharge machining power supply of the apparatus for electrical discharge machining the workpiece by generating an electric discharge between the electrodes formed by arranging the electrodes and the workpiece so as to face each other. a switching element connected between the electrode gap and the DC power source in parallel to the electrode gap and the DC power source; and a switching element connected between the electrode gap and the DC power source in parallel to the electrode gap and the DC power source; a drive circuit that generates a voltage; a current-limiting resistor connected between the DC power supply and the switching element; a coupling capacitor connected between the switching element and the pole; and the coupling capacitor. A power source for electric discharge machining, comprising: a variable inductance coupling coil connected between the electrodes; and switching means for switching the inductance of the variable inductance coupling coil. (2) The electric discharge machining power supply according to claim 1, wherein the variable inductance coupling coil has an inductance that is sufficiently larger than the inductance of the stray inductance between the poles. (3) A variable inductance coupling coil is a combination of multiple coils with different inductances connected in parallel.
2. The electric discharge machining power supply according to claim 1, wherein the switching means is a relay contact connected in series to each of the plurality of coils. (4) A variable inductance coupling coil is a combination of multiple coils with different inductances connected in series.
2. The electric discharge machining power supply according to claim 1, wherein the switching means is a relay contact connected in parallel to each of the plurality of coils.